ICAM-related Protein

The present invention relates generally to cellular adhesion molecules and more particularly to the cloning and expression of DNA encoding a heretofore unknown human polypeptide designated "ICAM-R" which possesses structural relatedness to the human intercellular adhesion molecules ICAM-1 and ICAM-2.

Research spanning the last decade has significantly elucidated the molecular events attending cell-cell interactions in the body, especially those events involved in the movement and activation of cells in the immune system. See generally, Springer, Nature, 346:425-434 (1990). Cell surface proteins, and especially the so-called Cellular Adhesion Molecules ("CAMs") have correspondingly been the subject of pharmaceutical research and development having as its goal intervention in the processes of leukocyte extravasation to sites of inflammation and leukocyte movement to distinct target tissues. The isolation and characterizatiori of cellular adhesion molecules, the cloning and expression of DNA sequences encoding such molecules, and the development of therapeutic and diagnostic agents relevant to inflammatory processes, vital infection and cancer metastasis have also been the subject of numerous U.S. and foreign applications for Letters Patent. See Edwards, Current Opinion in Therapeutic Patents, 1 (11): 1617-1630 (1991) and particularly the published "patent literature references" cited therein.

Of fundamental interest to the background of the present invention are the prior identification and characterization of certain mediators of cell adhesion events, the "leukointegrins," LFA-1, MAC-1 and gp 150.95 (referred to in WHO nomenclature as CD18/CD11a, CD18/CD11b, and CD18/CD11c, respectively) which form a subfamily of heterodimeric "integrin" cell surface proteins present on B lymphocytes, T lymphocytes monocytes and granulocytes. See, e.g., Table 1 of Springer, supra, at page 429. Also of interest are other single chain adhesion molecules (CAMs) that have been implicated in leukocyte activation, adhesion, motility and the like, which are events attendant the inflammatory process. For example, it is presently believed that prior to the leukocyte extravasation which characterizes inflammatory processes, activation of integrins constitutively expressed on leukocytes occurs and is followed by a tight ligand/receptor interaction between the integrins (e.g., LFA-1) and one or both of two distinct intercellular adhesion molecules, (ICAMs) designated ICAM-1 and ICAM-2 which are expressed on blood vessel endothelial cell surfaces and on other leukocytes.

Like the other CAMs characterized to date, [e.g., vascular adhesion molecule (VCAM-1) as described in PCT WO 90/13300 published Nov. 15, 1990; and platelet endothelial cell adhesion molecule (PECAM-1) as described in Newman et al., Science, 247:1219-1222 (1990) and PCT WO 91/10683 published Jul. 25, 1991], ICAM-1 and ICAM-2 are structurally homologous to other members of the immunoglobulin gene superfamily in that the extracellular portion of each is comprised of a series of domains sharing a similar carboxy terminal motif. A "typical" immunoglobulin-like domain contains a loop structure usually anchored by a disulfide bond between two cysteines at the extremity of each loop. ICAM-1 includes five immunoglobulin-like domains; ICAM-2, which differs from ICAM-1 in terms of cell distribution, includes two such domains; PECAM-1 includes six; VCAM includes six or seven, depending on splice variations, and so on. Moreover, CAMs typically include a hydrophobic "transmembrane" region believed to participate in orientation of the molecule a the cell surface and a carboxy terminal "cytoplasmic" region. Graphic models of the operative disposition of CAMs generally show the molecule anchored in the cell membrane at the transmembrane region with the cytoplasmic "tail" extending into the cell cytoplasm and one or more immunoglobulin-like loops extending outward from the cell surface.

A variety of therapeutic uses have been projected for intercellular adhesion molecules, including uses premised on the ability of ICAM-1 to bind human rhinovirus. European Patent Application 468 257 A published Jan. 29, 1992, for example, addresses the development of multimeric configurations and forms of ICAM-1 (including full length and truncated molecular forms) proposed to have enhanced ligand/receptor binding activity, especially in binding to viruses, lymphocyte associated antigens and pathogens such as Plasmodium falciparum.

In a like manner, a variety of uses have been projected for proteins immunologically related to intercellular adhesion molecules. WO91/16928, published November 14, 1991, for example, addresses humanized chimeric anti-ICAM-1 antibodies and their use in treatment of specific and non-specific inflammation, viral infection and asthma. Anti-ICAM-1 antibodies and fragments thereof are described as useful in treatment of endotoxic shock in WO92/04034, published March 19, 1992. Inhibition of ICAM-1 dependent inflammatory responses with anti-ICAM-1 anti-idiotypic antibodies and antibody fragments is addressed in WO92/06119, published Apr. 16, 1992.

Despite the fundamental insights into cell adhesion phenomena which have been gained by the identification and characterization of intercellular adhesion proteins such as ICAM-1 and lymphocyte interactive integrins such as LFA-1, the picture is far from complete. It is generally believed that numerous other proteins are involved in inflammatory processes and in targeted lymphocyte movement throughout the body. Quite recently, for example, Springer and his co-workers postulated the existence of a third counter-receptor for LFA-1 [de Fougerolles et al., J. Exp. Med., 174:253-267 (1991)] and subsequently reported success in immunoprecipitating a "third" ICAM ligand, designated "ICAM-3"[de Fougerolles, et al., J. Exp. Med., 175:185-190 (1992)]. This molecule was reported to bind soluble LFA-1 and to be highly expressed by resting lymphocytes, monocytes and neutrophils. Unlike ICAM-1 and ICAM-2, however, the new ligand was not found to be expressed by endothelial cells. The immunoprecipitated product was noted to display a molecular weight of about 124,000 and to be heavily glycosylated, as revealed by a drop in apparent molecular weight to about 87,000 upon N-glyanase treatment. Even more recently, another research group described a cDNA sequence for a counter-receptor for LFA-1 which was also designated "ICAM-3" [see Fawcett et al., Nature, 360:481-484 (1992)].

There thus continues to be a need in the art for the discovery of additional proteins participating in human cell-cell interactions and especially a need for information serving to specifically identify and characterize such proteins in terms of their amino acid sequence. Moreover, to the extent that such molecules might form the basis for the development of therapeutic and diagnostic agents, it is essential that the DNA encoding them be elucidated. Such seminal information would inter alia, provide for the large scale production of the proteins, allow for the identification of cells naturally producing them, and permit the preparation of antibody substances or other novel binding proteins specifically reactive therewith and/or inhibitory of ligand/receptor binding reactions in which they are involved.

In one of its aspects, the present invention provides purified and isolated polynucleotides (e.g., DNA sequences and RNA transcripts thereof) encoding a novel human polypeptide, "ICAM-R," as well as polypeptide variants (including fragments and analogs) thereof which display one or more ligand/receptor binding biological activities and/or immunological properties specific to ICAM-R. ICAM-R-specific ligand/receptor binding biological activities encompass interactions of both the ICAM-R extracellular and cytoplasmic domains with other molecules (e.g., in processes of cell-cell adhesion and/or signal transduction). Preferred DNA sequences of the invention include genomic and eDNA sequences as well as wholly or partially chemically synthesized DNA sequences. Biological replicas (i.e., copies of isolated DNA sequences made in vivo or in vitro) of DNA sequences of the invention are contemplated. Also provided are autonomously replicating recombinant constructions such as plasmid and vital DNA vectors incorporating ICAM-R sequences and especially vectors wherein DNA encoding ICAM-R or an ICAM-R variant is operatively linked to an endogenous or exogenous expression control DNA sequence.

According to another aspect of the invention, host cells, especially unicellular host cells such as procaryotic and eucaryotic cells, are stably transformed with DNA sequences of the invention in a manner allowing the desired polypeptides to be expressed therein. Host cells expressing such ICAM-R and ICAM-R variant products can serve a variety of useful purposes. To the extent that the expressed products are "displayed" on host cell surfaces, the cells may constitute a valuable immunogen for the development of antibody substances specifically immunoreactive with ICAM-R and ICAM-R variants. Host cells of the invention are conspicuously useful in methods for the large scale production of ICAM-R and ICAM-R variants wherein the cells are grown in a suitable culture medium and the desired polypeptide products are isolated from the cells or from the medium in which the cells are grown.

Novel ICAM-R and ICAM-R variant products of the invention may be obtained as isolates from natural cell sources, but are preferably produced by recombinant procedures involving host cells of the invention. The products may be obtained in fully or partially glycosylated, partially or wholly de-glycosylated, or non-glycosylated forms, depending on the host cell selected for recombinant production and/or post-isolation processing.

Products of the invention include monomeric and multimeric polypeptides having the sequence of amino acid residues numbered -29 through 518 as set out in SEQ ID NO: 1 herein. As explained in detail infra, this sequence includes a putalive signal or leader sequence which precedes the "mature" protein sequence and spans residues -29 through -1, followed by the putative mature protein including, in order, five putalive immunoglobulin-like domains (respectively spanning residues 1 to 90, 91 to 187, 188 to 285, 286 to 387, and 388 to about 456), a hydrophobic "transmembrane" region extending from about residue 457 to about residue 481 and a "cytoplasmic" region constituting the balance of the polypeptide at its carboxy terminus. Based on amino acid composition, the calculated molecular weight of the mature protein lacking glycosylation or other post-translational modification is approximately 52,417. ICAM-R variants of the invention may comprise water soluble and insoluble ICAM-R fragments including one or more of the regions specified above and may also comprise polypeptide analogs wherein one or more of the specified amino acids is deleted or replaced: (1) without loss, and preferably with enhancement, of one or more biological activities or immunological characteristics specific for ICAM-R; or (2) with specific disablement of a particular ligand/receptor binding function. Analog polypeptides including additional amino acid (e.g., lysine or cysteine) residues that facilitate multimer formation are contemplated.

Also comprehended by the present invention are antibody substances (e.g., monoclonal and polyclonal antibodies, single chain antibodies, chimeric antibodies, CDR-grafted antibodies and the like) and other binding proteins (e.g., polypeptides and peptides which are specific (i.e., non-reactive with the ICAM-1 and ICAM-2 intercellular adhesion molecules to which ICAM-R is structurally related) for ICAM-R or ICAM-R variants. Antibody substances can be developed using isolated natural or recombinant ICAM-R or ICAM-R variants or cells expressing such products on their surfaces. Specifically illustrating antibodies of the present invention are the monoclonal antibodies produced by the hybridoma cell lines designated 26E3D-1, 26I8F-2, 26I10E-2, 26H11C-2 which were deposited with the American Type Culture Collection (ATCC), 12301 Parklawn Drive, Rockville, Md. 20852, on Jun. 2, 1992 as Accession Nos. HB 11054, HB 11056, HB 11053, and HB 11055, respectively; the hybridoma cell line designated 43H7C which was deposited with the ATCC on Dec. 16, 1992 as Accession No. HB 11221; the hybridoma cell lines designated 42C5H and 42D9B which were deposited with the ATCC on Jan. 15, 1993 as Accession Nos. HB 11235 and the hybridoma cell lines 46D7E and 46I12H which were deposited with the ATCC on Jan. 7, 1993 as Accession Nos. HB 11232 and HB 11231, respectively.

Binding proteins are useful, in turn,. in compositions for immunization as well as for purifying polypeptides of the invention and identifying cells displaying the polypeptides on their surfaces. They are also manifestly useful in modulating (i.e., blocking, inhibiting or stimulating) ligand/receptor binding biological activities involving ICAM-R, especially those ICAM-R effector functions involved in specific and non-specific immune system responses. Anti-idiotypic antibodies specific for anti-ICAM-R antibody substances and uses of such anti-idiotypic antibody substances in modulating immune responses are also contemplated. Assays for the detection and quantification of ICAM-R on cell surfaces and in fluids such as serum may involve a single antibody substance or multiple antibody substances in a "sandwich" assay format.

The scientific value of the information contributed through the disclosures of DNA and amino acid sequences of the present invention is manifest. As one series of examples, knowledge of the sequence of a cDNA for ICAM-R makes possible the isolation by DNA/DNA hybridization of genomic DNA sequences encoding ICAM-R and specifying ICAM-R expression control regulatory sequences such as promoters, operators and the like. DNA/DNA hybridization procedures carried out with DNA sequences of the invention and under stringent conditions are likewise expected to allow the isolation of DNAs encoding allelic variants of ICAM-R, other structurally related proteins sharing one or more of the biological and/or immunological properties specific to ICAM-R, and non-human species proteins (e.g., rodent) homologous to ICAM-R. DNAs of the invention are useful in DNA/RNA hybridization assays to detect the capacity of cells to synthesize ICAM-R. Also made available by the invention are anti-sense polynucleotides relevant to regulating expression of ICAM-R by those cells which ordinarily express the same. As another series of examples, knowledge of the DNA and amino acid sequences of ICAM-R makes possible the generation by recombinant means of ICAM-R variants such as hybrid fusion proteins (sometimes referred to as "immunoadhesions") characterized by the presence of ICAM-R protein sequences and immunoglobulin heavy chain constant regions and/or hinge regions. See, Capon et at., Nature, 337:525-531 (1989); Ashkenazi et al., P.N.A.S. (USAJ, 88:10535-10539 (1991); and PCT WO 89/02922, published Apr. 6, 1989. ICAM-R variant fusion proteins may also include, for example, selected extracellular domains of ICAM-R and portions of other cell adhesion molecules.

The DNA and amino acid sequence information provided by the present invention also makes possible the systematic analysis of the structure and function of ICAM-R and definition of those molecules with which it will interact on extracellular and intracellular levels. The idiotypes of anti-ICAM-R monoclonal antibodies of the invention are representative of such molecules and may mimic natural binding proteins (peptides and polypeptides) through which ICAM-R intercellular and intracellular activities are modulated or by which ICAM-R modulates intercellular and intracellular events. Alternately, they may represent new classes of modulators of ICAM-R activities. Anti-idiotypic antibodies, in turn, may represent new classes of biologically active ICAM-R equivalents.

Numerous other aspects and advantages of the present invention will be apparent upon consideration of the following detailed description thereof, reference being made to the drawing wherein:

FIG. 1(A through G) depicts an isolated cDNA clone insert (SEQ ID NO: 2) derived from HL60 cells encoding ICAM-R and the deduced amino acid sequence (SEQ ID NO: 1) of an open reading frame therein;

FIG. 2(A through B) comprises bar graphs illustrating the results of Northern blot hybridization of transfected L cells using ICAM-R and ICAM-1 DNA probes;

FIG. 3(A through F) presents photomicrographs depicting the results of in situ hybridizations of transfected L cells using ICAM-R or ICAM-1 RNA probes;

FIG. 4 illustrates in histogram format the results of FACS analyses of indirect immunofiuorescence staining of transfected L cells using monoclonal antibodies specific for ICAM-R, ICAM-1 or ICAM-2.

FIG. 5 diagrams three chimeric ICAM-R proteins utilized to map epitopes of anti-ICAM-R monoclonal antibodies of the invention.

FIG. 6(A through B) presents bar graphs depicting the results of actin-normalized Northern blot hybridization of human leukocyte cell lines and umbilical cord endothelial cells using ICAM-R of ICAM-1 DNA probes;

FIG. 7(A through B) are photographs of Western blots of immunoprecipitations of lysates from human ceils lines using ICAM-R specific monoclonal antibodies;

FIG. 8(A through G) presents photomicrographs of immunohistologic staining of various human tissues with an anti-ICAM-R monoclonal antibody.

FIG. 9 comprises bar graphs illustrating the effects of anti-ICAM-R monoclonal antibodies on superantigen-induced proliferation of human peripheral blood lymphocytes;

FIG. 10 is a bar graph depicting the effects of anti-ICAM-R monoclonal antibodies on alloantigen-induced T-cell proliferation; and

FIG. 11 comprises a bar graph illustrating that crosslinking distinct ICAM-R epitopes differentially affects ICAM-R association with the cytoskeleton.

The present invention is illustrated by the following examples relating to the isolation of a full length cDNA clone encoding ICAM-R from a cDNA library derived from human HL60 promyelocytic cells (ATCC CCL 240) and to the expression of ICAM-R DNA in L cells. More particularly, Example 1 addresses the design and construction of oligonucleotide probes for PCR amplification of ICAM related DNAs. Example 2 addresses the use of the probes to amplify a genomic DNA fragment homologous to, but distinct from, DNAs encoding ICAM-1 and ICAM-2. Example 3 treats the screening of cDNA libraries with the genomic fragment to isolate additional ICAM-R coding sequences. Example 4 refers to the further screening of eDNA libraries to isolate a full length human cDNA encoding ICAM-R. Example 5 provides a characterization of DNA and amino acid sequence information for ICAM-R and relates the structures thereof to ICAM-1 and ICAM-2. Example 6 describes the isolation of a DNA sequence encoding a rodent homologue of ICAM-R. Example 7 relates to the development of mammalian host cells expressing ICAM-R. Example 8 describes preliminary experiments indicating that ICAM-R may participate in intercellular adhesion events involving a .beta.2 integrin pathway. Example 9 relates to the construction and expression of a soluble variant of ICAM-R. Example 10 describes to the preparation of anti-ICAM-R antibodies. Example 11 relates to mapping of the ICAM-R epitopes recognized by the anti-ICAM-R monoclonal antibodies of the invention. Examples 12, 13 and 14 relate to assessment of the distribution and biochemical characterization of ICAM-R polypeptide and RNA encoding the same in normal cells and tissues as well as in various cell lines. Example 15 describes assays for the involvement of ICAM-R in homotypic cell-cell adhesion. Example 16 addresses preliminary experiments indicating that ICAM-R is involved in immune cell activation/proliferation. Example 17 describes experiments showing differential phosphorylation of and cytoskeletal associations with the cytoplasmic domain of ICAM-R.

Nucleic acid and amino acid alignments of individual sets of CAMs (e.g., ICAM-1 and ICAM-2) did not manifest sufficient conservation between molecules to yield information useful in the design of consensus-type probes for isolating related novel genes. The strategic focus of attempts to isolate unknown DNAs encoding cellular adhesion molecules therefore involved the development of degenerate consensus oligonucleotides representing putalive spaced apart DNA sequences of various known molecules and the use of these oligonucleotides as primers for polymerase chain reaction (PCR) amplification of DNA replicas of intermediate gene sequences which resemble, but are not identical to, the known DNAs. The starting point for oligonucleotide primer design was the notation that the amino acids in regions surrounding cysteines which form immunoglobulin-like loops of certain CAMs are somewhat conserved. At the amino terminal side of the motif, the sequence:

is found, while at the carboxy terminal side of the motif, the sequence:

is typical. [See Hunkapiller et al., Nature, 323:15-16 (1986); Williams et al, Ann. Rev. Immunol., 6:381-405 (1988); and Newman et al, supra.] In and of themselves the two amino acid motifs are much too general and do not allow the construction of degenerate sets of oligonucleotides useful as probes for unknown DNAs which might share the motif. In an attempt to solve this problem, each individual CAM sequence was split into a domain of sub files defined by the cysteine motif termini described above. Subfiles were generated for each of the seven domains of human vascular adhesion molecule (VCAM-1), the six domains of human platelet endothelial cell adhesion molecule (PECAM-1), the five domains of ICAM-1, the two domains of ICAM-2, three of the four domains of both human myeloglobin-related glycoprotein and human fibroblast growth factor receptor, and the five domains of mouse neural cell adhesion molecule (NCAM). All the sub files were pooled and segregated independently from the CAM of origin using a multialignment hornology computer algorithm designated "Multalin" [Corpet, Nucleic Acids Research, 16(22): 10881-10890 (1988)] providing a tree of alignment allowing the ascertainment of consensus sequences around cysteine motifs. A consensus sequence representing the amino terminal cysteine motif was determined to be:

while the carboxy terminal consensus sequence was determined to be:

Employing human preferences for codon usage to partially eliminate degeneracy, three separate sets of degenerate oligonucleotides totalling 1152 probes were generated for use as top strand PCR primers for amplification from a putative amino terminus of the motif. The specific degenerate sequences of the three pools are set out below in IUPAC nomenclature.

Each of the primers included a PstI restriction endonuclease recognition site (CTGCAG) to facilitate cloning of amplified products.

A total of 768 probes were designed as bottom strand primers as set out below in IUPAC nomenclature for amplification from a putative carboxy terminus of the motif. Each of these primers included an XbaI recognition site (TCTAGA) to facilitate cloning of amplified products.

Oligonucleotides were synthesized with an automated Applied Biosystems, Inc. (Foster City, Calif.) Model 394 DNA synthesizer using an 0.2 micromolar scale synthesis program and employing beta-cyanoethyl chemistry. Protective groups were then removed by heating at 55.degree. C. for in excess of six hours. Oligonucleotides were then lyophilized to dryness, rehydrated in TE (10 mM Tris, pH 7.0, 1 mm EDTA) and desalted in TE by size exclusion chromatography with G25-150 Sephadex.

The two sets of probes whose design and synthesis are described in Example 1 were employed in PCR amplification procedures applied to a human genomic DNA template. Briefly put, PCR-generated fragments of a size similar to that of the immunoglobulin-like loop regions of ICAM-1 and ICAM-2 were isolated, subcloned into Bluescript plasmid (Stratagene, LaJolla, Calif.) and screened both directly by sequencing and hybridization in arrays for homology to ICAM-2 DNA. Approximately 50% of the fragments were identical to ICAM-1 or ICAM-2 (except, of course, in the regions of the degenerate primer). One subclone, designated 13-3C7, was found to have an open reading frame homologous to ICAM-1 and ICAM-2 in the region of their respective second domains. It did not correspond to any known sequence present in the Genbank data base. The specific manipulations leading up to the isolation of subclone 13-3C7 were as follows.

The degenerate oligonucleotides were mixed to a final concentration of 10 .mu.g/ml in a PCR reaction to amplify human gertomit DNA obtained either from peripheral blood leukocytes or Hela cells. The DNA amplification was performed in PCR buffer (2 mM MgCl.sub.2, 25 mm KCl, 10 mM Tris pH 8.3) with 2 mM deoxynucleotides. After a 94.degree. C. denaturation for 4 minutes, 30 PCR cycles were performed with annealing at 60.degree. C. for 2 minutes, elongation at 72.degree. C. for 4 minutes and denaturation at 94.degree. C. for 1 minute. A DNA band migrating at about 0.2 kb was extracted from a 6% polyacrylamide gel by electroelution, digested by XbaI and Pst 1 restriction enzymes, and ligated into the Bluescript vector (Stratagene). The plasmid was electroporated into XL 1-blue strains of E. coIi (Stratagene) and colonies were selected on X-gal IPTG, carbenicillin agarose plates. Single strand templates were obtained from 6 white colonies after addition of M13K07 helper phage (Stratagene), carbenicillin, and kanamycin to a 2 ml culture of each colony. For sequence analysis, the single strand templates were then sequenced using the Sanger method both by DNA automatic sequencing (Applied Biosystems) and with a sequenase kit (UCB, Belgium). Four sequences (clones 1.1, 1.3, 1.4, 1.6) were obtained which were 184-185 base pairs (bp) long and were 92-95% homologous to the second domain of ICAM-2. In addition, a 182 bp long DNA sequence (clone 1.5) was obtained which contained a frameshift in the open reading frame of an ICAM-1-like domain along with a 66 bp DNA (clone 1.2) corresponding to a truncated immunoglobulin-like domain.

The sequence of clones 1.6, 1.5, 1.2 was used to design three oligonucleotide probes (RM 16, RM 15, RM 12) that were used in subsequent tests to eliminate from further consideration additional colonies containing cDNAs that were highly homologous to the previous isolated clones. The sequences of probes RM16, RM15 and RM12 are set out below.

In a second round of tests, new colonies were obtained from the original PCR products that had been XbaI and Pst1 digested and from additional PCR products that had been rendered blunt-ended by treatment with the Klenow fragment of polymerase I and subcloned by blunt-end ligation. The colonies containing the vector with an insert were selected on carbenicillin L broth agarose plates containing X-gal and IPTG. Single strand templates were then synthesized in 96-well plates by growing individual white colonies in 300 .mu.l L broth, to which was added M13K07 phage, carbenicillin and kanamycin. Ten .mu.l of each template was transferred with a pronging device to a nylon membrane, denatured and fixed with UV light. (Ten .mu.l of each template were transferred to three different nylon membranes for each 96-well plate.) Oligonucleotides RM16, RM15, RM12 were labelled by phosphorylation using [.lambda.-.sup.32 P]ATP. The nylon membranes were pre-hybridized in 20% formamide, 5X SSC, 5X Denhardt's solution and 0.5% SDS for 3 hours at 42.degree. C. then hybridized overnight with the different radiolabelled oligonucleotide probes under the same conditions. The membranes were then washed in 0.2X SSC, 0.5% SDS three times for 15 minutes each at room temperature then washed in the same buffer at 3.degree. C. for 15 minutes, rinsed in 2X SSC and exposed. Each template that did not hybridize with either of the three oligonucleotide probes was further sequenced using the Sanger technique by DNA automatic sequencing and by sequenase kit. Using this technique, the 170 bp DNA sequence of a clone designated 13-3C7 was determined.

The cDNA insert of subclone 13-3C7 isolated in Example 2 was used as a hybridization probe to screen four different lambda phage cDNA libraries prepared from human spleen, human placenta (two libraries) and human leukocyte cell line U937 (ATCC CRL 1593). Briefly summarized, one hundred and twenty positive clones were picked (from among the approximately 1.6 million clones screened), subcloned, rescreened with the 13-3C7 probe, and the rescreening positive were size selected for inserts of greater than approximately 500 bp by analytical PCR with primers corresponding to the plasmid DNA flanking the insertion for DNAs. A 1.3 kb clone derived from U937 cDNA, designated clone 19C, was sequenced and revealed DNA regions encoding two immunoglobulin-like domains separated by what appeared to be an intervening sequence (intron) resulting from improper or incomplete mRNA splicing prior to cDNA formation. The two regions displayed significant hornology, but overall distinctness, in comparison to domains 2 and 3 of ICAM-1 and less homology to domains 1 and 2 of ICAM-2.

The specific procedures leading up to isolation of clone 19C were as follows. The four libraries were constructed in lambda gt10 phage (.lambda.gt10) using cDNA obtained from the U937 cell line, from the spleen of a patient with chronic myelomonocytic leukemia and from human placenta. Exact match oligonucleotides designated 1 Hr-5' and 1Hr-3' were designed corresponding to the 5' and 3' sides of the domain-like region of subclone 13-3C7 (including bases attributable to incorporation of the original degenerate primer). The sequences of the 1 Hr-5' and 1 Hr-3' oligonucleotide primers are set out below.

Using these oligonucleotides in a PCR reaction with the 13-3C7 insert template and .sup.32 P-dCTP, a 148 bp long DNA probe was generated. The cDNA libraries were plated and transferred to nylon membranes. The membranes were pre-hybridized in 40% formamide, 5X SSC, 5X Denhardt's, 0.5% SDS at 42.degree. C. for at least 15 minutes, then hybridized overnight with the probe in the same buffer at 42.degree. C. The membranes were washed several times at room temperature in 2X SSC and exposed. Most of the phage plaques that hybridized with the probe were derived from the U937 cDNA library. These phages were further purified and tested by PCR (using 1 Hr-5' and 1 Hr-3' as primers) for the presence of the domain inside the cDNA clones. The phage were also tested by PCR to determine the length of the clones and the location of the domain within the cDNA fragment (using a combination of 13-3C7 specific primers and primers homologous to flanking .lambda.gt10 vector sequences). Two clones were selected. Clone 1F was 0.7 kb long and clone 19C was 1.3 kb long. These cDNAs were digested with EcoRI and subcloned in the Bluescript vector. In addition, the largest cDNA (clone 19C) was sonicated to obtain small pieces which were sub-cloned into Bluescript for sequencing. By homology with the ICAM-1 molecule, clone 19C cDNA contains 2 regions having homology to domains 2 and 3 of ICAM-1, respectively, with an intervening sequence of unrelated DNA. Hereinafter, these DNA regions are referred to as domains 2 and 3 of ICAM-R.

The 1.3 kb (clone 19C) DNA isolated in Example 3 and having regions encoding immunoglobulin-like loops resembling domains 2 and 3 of ICAM-1 was then employed to generate a probe for the screening of additional cDNA libraries in an attempt to isolate a full length cDNA clone. Briefly, the domain 2 and 3 regions within clone 19C were each amplified by PCR using unique probes designated to match respective amino (5') and carboxy (3') terminal portions of the domains. These amplified DNAs, in turn, provided probes for screening of eDNA libraries derived from: (1) the HL60 myelomonocytic cell line; (2) lipopolysaccharide-activated human monocytes; (3) HUT-78 T-cells (ATCC T1B161); and (4) activated peripheral blood leukocytes. The latter two libraries yielded no positive upon rescreening. Positives derived from HL60 and monocyte cDNA libraries were then screened with a probe representing domain 2 of ICAM-1 DNA (GenBank, Accession No. 22634) in order to eliminate ICAM-1 clones. A single phagmid clone derived from lambda 345 and designated pVZ-147, repeatedly tested positive for hybridization with the probe(s) based on the DNA isolated in Example 4 and negative for hybridization with the ICAM-1 DNA probe. The approximately 1.7 kb insert from clone pVZ-147 was isolated and sequenced to provide the 1781 bp sequence set out in SEQ ID NO: 2. The deduced amino acid sequence of the polypeptide encoded by this DNA is set out in SEQ ID NO: 1. The polypeptide was designated "ICAM-R" on the basis of its structural relatedness to ICAM-1 and ICAM-2. The DNA and deduced amino acid sequences of ICAM-R were published after the priority dates of this application in Vazeux et al., Nature, 360:485-488 (1992). The open reading frame of the DNA sequence of ICAM-3 published after the priority dates of this application in Fawcett et al., supra, differs at two nucleotide positions from the coding region of the DNA sequence of ICAM-R presented in FIG. 1(A through G) herein. (See nucleotide positions 194 and 1275.)

The specific manipulations involved in the isolation of lambda phage clone pVZ147 are as follows. All cDNA libraries were constructed in .lambda.gt10 except for the HL60 library which cloned into phage lambda 345. Oligonucleotides for use in library screening and rescreening had the following sequences.

Probes IHr 2-5' and IHr 2-3' were employed in a PCR amplification using .sup.32 P-dCTP on the clone 19C template to generate a domain 2 specific probe for cDNA screening. Likewise, probes IHr 3-5' and IHr 3-3' were employed to generate a domain 3 specific probe. Finally, probes Icam 1-5 and Icam 1-3 were employed to amplify an ICAM-1 segment probe corresponding to bases 440 through 609 of the ICAM-1 cDNA sequence (GenBank, Accession No. 22634), i.e., the ICAM-1 second domain.

The cDNA libraries were plated, transferred on nylon membranes, hybridized with the domain 2 probe (derived from clone 19C) in 40% formamide, 5X SSC, 5X Denhardt, 0.5% SDS and washed as described above. All the plaques that hybridized with the domain 2 probe were derived from the monocyte and HL60 libraries. These phage plaques were purified by dilution, plating, transfer and hybridization with the domain 2 probe. To further characterize the eDNA clones, each plaque that had hybridized with the domain 2 probe was grown on an array in triplicate, transferred to a nylon membrane and hybridized under higher stringency conditions (50% formamide, 5X SSC, 5X Denhardt, 0.5 % SDS) with three different probes: the domain 2 probe; the domain 3 probe, and the ICAM-1 second domain probe. Five clones were found in the HL60 library and 2 clones in the monocyte library which hybridized with both domain 2 and domain 3 probes and not with the ICAM-1 second domain probe. A sixth clone from the HL60 library hybridized only with domain 2 probe and did not hybridize with either domain 3 or with ICAM-1 second domain. The cDNAs of the 6 clones from the HL60 library were further analyzed. The phages were tested by PCR for the presence of properly spliced cDNA using oligonucleotide primers corresponding to the 5' extremity (IHr2-5') of domain 2 and to the 3' extremity (IHr3-3') of domain 3. The clones were also tested by PCR for length and location of the domains inside the clones. The cDNA plasmids were extracted and cyclized from phage lambda 345 by digestion with SfiI and self-ligation. To facilitate making single strand templates and sequencing in both orientations, each cDNA was also subcloned in Bluescript SK+vector (Stragene). Plasmid pVZ147 was determined to include the entire ICAM-R coding sequence in a single open reading frame.

A. Characterization of the ICAM-R Polypeptide

FIG. 1 (A through G) graphically illustrates the sequence of the human eDNA insert of the lambda phage clone pVZ 147 isolated in Example 4, above. The total of 1781 bp shown are as set out in SEQ ID NO: 2. The deduced amino acid sequence of the ICAM-R polypeptide as set out in SEQ ID NO: 1 is graphically subdivided in FIG. 1(A through G) into the following regions:

(1) A putative signal or leader sequence is illustrated preceding the sequence of the "mature" protein and spanning amino acids designated -29 through -1. Determination of whether the translation product is actually initiated at -29 or -26 will be provided by amino acid sequencing of intercellular expression products. The designation of the first residue of the mature protein was based on generalized analogy to amino acids (and corresponding bases) for residues of secreted human proteins in the region of the junction of the mature protein and leader sequences. Confirmation of the actual initial residue of the mature protein awaits sequencing of a secreted recombinant product or, e.g., an immunopurified natural product.

(2) Within the mature protein spanning residues +1 through 518, five putative immunoglobulin-like loop regions are shown (white on black) bounded by cysteines within the five putative immunoglobulin-like domains (shown in boxes). Note that in the first domain (residues 1 through 91), cysteine residues potentially significant to loop formation are present at positions 24, 28, 67 and 71. Each of the remaining putative loops has a single relevant cysteine at each of its ends.

(3) Also within the mature protein, a putative hydrophobic "transmembrane" region is illustrated with dashes connecting residues 457 through 481 which follow the fifth immunoglobulin-like domain. A putative carboxy terminal "cytoplasmic" region constitutes residues 482 through 518.

(4) Potential N-linked glycosylation sites [characterized by the consensus sequence, Aspargine-X-(Serine or Threonine)] are indicated with an asterisk. Potential O-linked glycosylation sites occur at any serine or threonine residue.

A comparison was made between the amino acid sequence (SEQ ID NO: 1) of ICAM-R and the published 537 residue amino acid sequence of ICAM-1 (GenBank Accession No. 22634; cf, FIG. 8 of European Patent Application 0 289 949 published Nov. 11, 1988). This comparison revealed 249 matches within the aligned 537 residues, indicating an overall amino acid identity of 48% between the two polypeptides. The highest percentage of matches was noted to be present between domains 2 and 3 of ICAM-1 and putative domains 2 and 3 of ICAM-R. Likewise the alignment of SEQ ID NO: 1 with the published 295 residues of the amino acid sequence of ICAM-2 (GenBank accession No. 22635; cf, FIG. 2 of European Patent Application 0 387 668 published Sep. 19, 1990) revealed 78 matches among the 282 aligned residues, for a 27% overall identity of amino acids in one possible alignment. The cytoplasmic domain of ICAM-R was found to be 20% identical to the cytoplasmic domain of ICAM-1 and 34% identical to the cytoplasmic domain of ICAM-2 in one possible alignment.

B. Characterization of ICAM-R DNA

A comparative alignment of the human ICAM-R DNA sequence (SEQ ID NO: 2) was made with the published DNA sequences of ICAM-1 and ICAM-2, supra. A total of 677 matches were noted among the 1623 aligned bases of ICAM-R and ICAM-1 providing an overall identity of 41%. A 42% identity (484 matches) between the aligned 1136 bases of ICAM-R and ICAM-2 DNAs was noted.

Reference points in the FIG. 1 (A through G) DNA having "historical" significance to the isolation of the ICAM-R gene include the following:

(a) bases 420 through 567 correspond to the subclone 13-3C7 isolated in Example 2;

(b) bases 373 through 663 correspond to the immunoglobulin-like domain 2 localized in clone 19C of Example 3 (with bases 418 through 435 and 561 through 578, respectively corresponding to probes IHr2-5' and IHr2-3' employed for PCR amplification of domain 2 to provide one of the oligonucleotide probes for use in Example 4); and

(c) bases 664 through 957 correspond to the immunoglobulin-like domain 3 localized on clone 19C of Example 3 (with bases 699 through 717 and 800 through 819, respectively corresponding to probes IHr3-5' and IHr3-3' employed for PCR amplification of domain 3 to provide another oligonucleotide probe for use in Example 4.

A rodent homologue of ICAM-R was isolated by low stringency hybridization using ICAM-R specific probes.

Adult Balb/c mouse PBL cDNA and rat PBC cDNA .lambda. phage libraries (Clonetech, La Jolla, Calif.) and .lambda. phage rat genomic DNA libraries made from rat liver DNA and C6VL lymphoblastoid cell DNA were screened with the full length human ICAM-R gene or fragments thereof. Library plaques were transferred to Hybond N+ nylon membranes (Amersham Corp., Arlington Heights, Ill.). All prehybridizations and hybridizations were carried out in a solution of 40-50 % formamide, 5X Denhardt's, 5X SSPE and 1.0 % SDS at 42.degree. C. .sup.32 P-radiolabelled probes were added at a concentration of 10.sup.5 -10.sup.6 cpm/ml of hybridization solution. Following hybridization, filters were washed extensively at room temperature in 2X SSPE/0.1% SDS and then exposed to X-ray film. Positive clones were plaque purified in another round of hybridization. Lambda DNA was prepaxed from lysates of each clone and digested with either HaelII or RsaI. Fragments of the genomic DNA were cloned into a sequencing vector for analysis. Approximately 2.5.times.10.sup.6 plaques from rodent cDNA libraries and 2.0 .times.10.sup.6 from genomic libraries were screened with the full length human ICAM-R probe. No ICAM-R related clones were identified. An additional 0.5.times.10.sup.6 plaques from rodent cDNA libraries and 1.0.times.10.sup.6 from rodent genomic libraries were screened with an ICAM-R domain 2 specific probe corresponding to nucleotides 372 to 663 of SEQ ID NO: 2. A genomic clone from rat was identified as a candidate for rodent homologue of ICAM-R. SEQ ID NO: 23 and 24 sets out sequence data (341 bp) for the rat domain 2 clone. Table 1 below indicates the DNA and amino acid sequence identity of the rat clone to corresponding regions of human ICAM-R, ICAM-1 and ICAM-2.

ICAM-R eDNA was transfected into L-M(TK.sup.-) mouse cells (ATCC CCL 1.3) and the cells were assayed for expression of ICAM-R by Northern blot and in situ hybridization.

A. Transfection of ICAM-R DNA

The full length ICAM-R cDNA insert of pVZ-147 and a small portion of the phagmid vector 3' to the cDNA insert was excised using restriction enzymes NotI and XbaI and ligated into commercial plasmid pCDNAl-neo (Invitrogen Inc., San Diego, Calif.) cut with NotI and XbaI. The resulting plasmid, designated pCDNAi-neo-ICAM-R, was transfected into mouse L cells by the calcium phosphate precipitation method described in Chen et al., Molecular and Cellular Biology, 7:2745-2748 (1987). ICAM-1 DNA (construct pCDNA-neo-ICAM-1) was also transfected into mouse L cells as a control. A cDNA fragment containing the complete ICAM-1 protein coding region was ligated into plasmid pCDNAl-neo and transfected into L cells by the calcium phosphate precipitation method. Following selection for neomycin resistance, individual ICAM-R or ICAM-1 transfectants were subcloned using cloning cylinders (Bellco Glass Inc., Vineland, N.J.). The clones expressing the highest level of ICAM-R and ICAM-1 protein were then sorted on a cell-sorter.

Constructs pCDNA-neo-ICAM-R and pCDNA-neo-ICAM-1 were also transfected into CV-1 cells by the calcium phosphate precipitation method. The clones expressing high levels of ICAM-R and ICAM-1 were selected as described above for L cell tranfectants. Based on FACs analysis with ICAM-R and ICAM-1 specific antibodies the level of protein expression was higher with CV-1 transfectants then with the mouse LTK transfectants.

B. Northern Blot Hybridizations

Following transfection of full length ICAM-R or ICAM-I cDNAs into mouse L ceils, specific expression of the corresponding mRNAs in transfected and untransfected L cells was determined by Northern blot hybridization with .sup.32 P-labelled ICAM-R or ICAM-1 DNA probes. Transfectants were grown in log phase, then centrifuged and washed two timds with 150 mM NaCl. The pellet was resuspended in 3.5 ml GIT (guanidinium isothiocyanate) buffer, then sheared in a polytron mixer for 20 seconds. After adding 1.7 ml CsCl buffer to an ultracentrifuge tube, the GIT/RNA mix was layered on top. Samples were spun at 35 K (179,000 x g), 20.degree. C., for 21 hours. All liquid was removed and the pelleted RNA was resuspended in 300 .mu.l 0.3M sodium acetate pH 5.2, then precipitated with 750 .mu.l EtOH at -20.degree. C. The precipitate was resuspended in H.sub.2 O, then treated with Proteinase K to remove any RNAses. After a phenol/chloroform extraction, the RNA was re-precipitated, resuspended in H.sub.2 O and the OD of the sample at 260 nm was measured.

The RNAs were electrophoresed in 1% formaldehyde agarose gels, prepared with diethyl pyrocarbonate (DEPC) treated solutions. Ten .mu.g of each total RNA sample was loaded per lane. RNA was electrophoresed at 30 V for approximately 18 hours with continuous circulation of buffers accomplished with a peristaltic pump. Each resulting gel was soaked two times in 20X SSPE for 20 minutes each at room temperature. Transfer of RNA to Hybond-C membranes (Amersham Corp., Arlington Heights, Ill.) was accomplished by capillary action overnight in 20X SSPE. Using a Stratagene stratalinker, RNA was stably crosslinked to each membrane by exposure to ultraviolet light.

To generate ICAM-1 DNA probes, 100-200 ng template DNA (a 1.8 kb Xba/Kpn fragment incorporating the entire ICAM-1 coding sequence) was mixed with H.sub.2 O and random hexamer, boiled for 5 minutes, and then incubated 5 minutes on ice. To the template DNA were added: .sup.32 P-dCTP and .sup.32 P-dTTP, 10.sup.-4 M dGTP/dATP, 10X Klenow Buffer (Boehringer Mannhelm Biochemicals, Indianapolis, Ind.) and Klenow enzyme, and the mixture was left at room temperature for 1 hour. Samples were passed over a Quickspin G25 DNA column (Boehringer) to separate incorporated from unincorporated label.

To generate ICAM-R DNA probes, 200 pg of DNA tempIate (a 1.4 kb fragment of clone pVZ-147 truncated to remove the poly-A tail) was amplified by PCR primed with oligonucleotides complimentary to the 5' and 3' extremities of domain 1. .sup.32 P-dCTP was added to the reaction mixture. Samples were held at 94.degree. C. for 4 minutes then run through 30 cycles of the temperature step sequence (94.degree. C., 1 minute; 50.degree. C., 2 minutes; 72.degree. C., 4 minutes) Samples were then run over a Quickspin column and incorporation of label was assessed by scintillation counting of 1 .mu.l aliquots.

The DNA probes were denatured with 5M NaOH, then neutralized with 1M Tris. The Hybond-C membranes were prehybridized at 50.degree. C. for 30 minutes in a 50% formamide pre-hybridization mix. Probe was added to each membrane to a concentration of 1.times.10.sup.6 cpm/ml hybridization mix (50% formamide, 5X Denhardt's solution, 5X SSPE, 1% SDS), and the membranes were incubated overnight at 42.degree. C. Each membrane was then washed 5 times in 2X SSPE/0.1% SDS at room temperature for 10 minutes each wash. One 10 minute wash was done at 50.degree. C. in 0.5X SSPE/0.1% SDS, with an additional rinse in 2X SSPE. Hybridization with the major RNA transcript was quantitated using a Molecular Dynamics (Sunnyvale, Calif.) Model 400A PhosphoImager.

Results of the northern blot hybridizations are presented in bar graph form in FIG. 2(A through B). FIG. 2A illustrates specific hybridization of the ICAM-R probe with RNA extracted from ICAM-R transfectants, but not with RNA from ICAM-1 transfectants or untransfected L cells. Reciprocally, FIG. 2B indicates hybridization of the ICAM-1 probe with RNA extracted from ICAM-1 transfectants, but not with RNA from ICAM-R transfectants or parental L cells.

C. In situ Hybridizations

L cells and L cells transfected as described above with either ICAM-R or ICAM-1 cDNAs were hybridized in situ with radiolabelled single-stranded RNA probes derived from ICAM-R or ICAM-1. Single-stranded RNA probes were generated from DNA templates corresponding to the first (i.e., N- terminal) immunoglobulin-like domain of ICAM-R or ICAM-1 by in vitro RNA transcription incorporating .sup.35 S-UTP. Probes were chemically hydrolyzed to approximately 200 bp.

Transfected and untransfected L cells were layered onto Vectabond (Vector Laboratories, Inc., Burlingame, Calif.) coated slides and stored at -70.degree. C. Prior to use, slides were removed from -70.degree. C. and placed at 55.degree. C. for 5 minutes. Sections were then fixed in 4% paraformaldehyde for 20 minutes at 4.degree. C., dehydrated in 70-95-100% EtOH for 10 minutes at room temperature, and allowed to air dry for 30 minutes. Sections were denatured for 2 minutes at 70.degree. C. in 70% formamide/2X SSC, rinsed in 2X SSC dehydrated and then air dried for 30 minutes. Prehybridization for 2 hours at 42.degree. C. with a mixture containing 50 % formamide, 0.3M NaCl, 20mM Tris pH 8.0, 10% dextran sulfate, 1X Denhardt's solution, 100 mM dithiothreitol (DTT) and 5 mM EDTA was performed. Hybridization was carried out overnight (12-16 hours) at 50.degree. C. in the same mixture additionally containing either .sup.35 S-labelled ICAM-1 or .sup.35 S-labelled ICAM-R RNA probes (6.times.10.sup.5 cpm/section). After hybridization, sections were washed for 1 hour at room temperature in 4X SSC/10mM DTT, then for 40 minutes at 60.degree. C. in 50% formamide/1X SSC/10mM DTT, 30 minutes at room temperature in 2X SSC, and 30 minutes at room temperature in 0.1X SSC. The sections were alcohol dehydrated, air dried for 30 minutes, developed (after storage at 4.degree. C. in complete darkness) and counterstained with hematoxylin/eosin.

Photomicrographs of the in situ hybridizations are set out in FIG. 3(A through F) wherein photomicrograph 3A is of parental L cells probed with ICAM-R RNA; 3B is of ICAM-R transfected L cells probed with ICAM-R RNA; 3C is of ICAM-1 transfected L cells probed with ICAM-R RNA; 3D is of parental L cells probed with ICAM-1 RNA; 3E is of ICAM-R transfected L cells probed with ICAM-1 RNA; and 3F is of ICAM-1 transfected L cells probed with ICAM-1 RNA. The photomicrographs demonstrate specific hybridization of each RNA probe only with L cells transfected with a homologous cDNA.

Experiments testing the adhesion of leukocytes to transfected L cells expressing ICAM-R on their surface indicate that ICAM-R is a ligand/receptor for an adhesion molecule or molecules on leukocytes. SKW3 cells (T lymphoblastoid cells) were pretreated with phorbol ester to activate LFA-1-dependent adhesion as described in Dustin et at., Nature, 341:619-624 (1989) and were assayed for binding to ICAM-R and ICAM-1 transfectants.

Untransfected L cells or L cells transfected with either ICAM-R or ICAM-1 (see Example 7) were seeded in 24-well tissue culture plates (3.times.10.sup.5 cells per well) 24-48 hours prior to the adhesion assay. SKW3 cells were washed in serum-free RPMI (Gibco, Canada), labelled with Calcein-AM (Molecular Probes Inc., Eugene, Oreg.), and stimulated with 10 ng/ml phorbol myristylacetate (PMA) for 20 minutes at 37.degree. C. Selected stimulated SKW3 cells were then pretreated with anti-CD18 (TS1/18, ATCC HB203), anti-CD11a (TS1/22, ATCC HB202) hybridoma supernatant or control anti-CD2 (ATCC HB195) purified monoclonal antibody for 30 minutes at room temperature before incubation with adherent, transfected L cells. Antibody-treated and non-antibody-treated, calcein-labelled SKW-3 cells were added (5.times.10.sup.5 cells per well) to confluent monolayers of ICAM-R or ICAM-1 transfectants and incubated for 30 minutes at 37.degree. C. in RPMI/1% fetal calf serum (FCS, Hyclone Laboratories Inc., Logan, Utah) Unbound cells were aspirated and wells were filled with RPMI-FCS. Plates were sealed, centrifuged in an inverted position at 200 rpm for 4 minutes and aspirated. The plates were then washed with RPMI-FCS and scanned with an automatic fluorescence reader.

Adhesion of stimulated SKW3 cells to both the ICAM-R and the ICAM-1 transfectants was inhibited by monoclonal antibodies against either the .alpha. (CD 11a) or .beta. (CD18) chains of LFA-1 indicating that ICAM-R may participate in intercellular adhesion events involving a .beta.2 integrin pathway. Intracellular adhesion was unaffected by the control anti-CD2 reagent.

A water soluble variant of ICAM-R was constructed and expressed as follows.

The cDNA for ICAM-R was altered by standard procedures of site-directed mutagenesis [see, e.g., Kunkei et al., Proc. Natl. Acad. Sci. USA, 82: 488-492 (1985)] in order to truncate the protein coding sequence at the predicted junction (amino acid 457) of its extracellular and transmembrane domains as determined by a computer algorithm that predicts hydropathy [Kyte et al., J. Mol. Biol., 157:105-132 (1982)]. The DNA sequence of ICAM-R was cut from pVZ147 (Example 4) with restriction enzymes SalI and NotI. The resulting fragment included the complete ICAM-R coding sequences beginning at the 5' end of the coding strand and also included at the 3' end a short segment of the multiple cloning sites. This fragment was subcloned into the M13 BM21 vector (Boehringer) linearized with SalI and NotI resulting in a molecule called M13 BM21ICAM-R.

A mutagenizing oligonucleotide was synthesized with the sequence below.

The oligonucleotide changes the phenylalanine at position 457 of ICAM-R to a stop codon. The oligonucleotide was utilized as described in Kunkel et aI., supra, to generate from M13 BM21ICAM-R six M13 phage isolates encoding a stop codon at position 457. An isolate designated BM21ICAM-Rt1 was chosen for further study.

This single strand template was converted to a double strand DNA molecule by primer extension using Klenow DNA polymerase as follows. Ten .mu.g of purified single strand M13 BM21ICAM-Rt1 DNA was annealed to 50 ng Lac Z universal -20 primer (GTAAAACGACGGCCAGT, SEQ ID NO: 26) in 1X Klenow DNA polymerase buffer (10mM Tris-Cl pH 7.5, 5mM MgCl.sub.2, 7.5mM dithiothreitol) by incubating the mix at 65.degree. C. for 5 minutes and then 25.degree. C. for 5 minutes. The following mixture was then added to the annealing reaction: 33 xM final concentration dATP, dGTP, dCTP, dTTP; 4 units of Klenow DNA polymerase (Boehringer), and 1X Klenow buffer. The primer extension reaction was allowed to incubate at 37.degree. C. for 45 minutes prior to being stopped by a single phenol/chloroform (1: 1) extraction and ethanol precipitation. A portion of the cDNA insert was released from the M13 BM21ICAM-Rt1 phage by restriction digest using restriction enzymes EcoRV and NcoI. The fragment of DNA released contained the complete coding sequence for the truncated ICAM-R protein, the 3' untranslated region and a small segment of polylinker sequence from the M13 BM21 phage. After agarose gel purification the fragment was ligated to linearized vector Bluebac III (Invitrogen Corp., San Diego, Calif.), a transfer vector containing genomic baculovirus sequences for homologous recombination that flank the ETL promoter driving expression of the E. coli beta-galactosidase gene and the polyhedron promoter driving expression of the gene of interest, in this case ICAM-Rt1.

The Bluebac III vector had been prepared in the following way prior to ligation. Three .mu.g of supercoiled plasmid DNA was digested with 20 units HinDIII endonuclease (Boehringer). After a phenol/chloroform extraction and ethanol precipitation the DNA pellet was resuspended in 1X Klenow DNA polymerase buffer; 33 .mu.M final concentration dATP, dGTP, dCTP, dTTP; 2 units of Klenow DNA polymerase (Boehringer) and incubated at 37.degree. C. for 60 minutes to fill in the termini of the molecule. The fill-in reaction was terminated by phenol/chloroform extraction and precipitation with ethanol. The blunt-ended DNA was resuspended in 1X NcoI buffer, 20 units of NcoI endonuclease were added and incubated at 37.degree. C. for 60 minutes.

A portion of the ligation reaction of the ICAM-Rt1 insert and linearized plasmid was used to transform electro-competent XL-1 E. coli (Stratagene) and individual colonies were selected on LB plates supplemented with 60 .mu.g/ml carbenicillin. Twelve individual isolates were analyzed by digestion of mini-prep DNA using PstI or EcoRI for diagnostic purposes. One isolate that exhibited the expected band pattern was designated pBBIII.ICAM-Rt1.

Sf-9 cells (Invitrogen) to be transfected or infected with pBBIII ICAM-Rt1 DNA were maintained in spinner flasks in TNM-FH [Grace's medium (Gibco, Grand Island, N.Y.) supplemented with 10% heat inactivated fetal bovine serum and gentamycin at 10 .mu.g/ml] at 27.degree. C. in a forced draft incubator. Spinner flask impellets were rotated at 60 rpm on an insulated five place stir plate. Log phase Sf-9 cells (1.5-2.5.times.10.sup.6 /ml) with greater than 90% viability were routinely subcultured twice weekly.

Sf-9 cells at log growth phase were plated (2.times.10.sup.6 cells/60 mm dish) in TNM-FH medium and allowed to attach for 1 hour at 27.degree. C. After this time the following mixture was made up in a sterile polystyrene tube and incubated at room temperature for 15 minutes: 1 ml TMN-FH medium, 1 .mu.g linear Autographa caIifornica nuclear polyhidrosis virus (AcNPV, baculovirus) genomic DNA (Invitrogen), 3 .mu.g of pBBIII.ICAM-Rt1 DNA and 20 .mu.l of a stock cationic liposome solution (Invitrogen). Two other independent mixtures were made up with or without pBluebac III substituted for pBBIII.ICAM-Rt1 DNA as controls. The media was removed from the seeded plates, replaced with 2 ml of Grace's medium and allowed to incubate for 2 minutes. All media was removed from the plates and the DNA/liposome mixtures were added dropwise on the cells of individual plates. One plate received TNMoFH medium alone as a mock transfection control. The plates were then incubated at 27.degree. C. for 4 hours with occasional rocking. Following this incubation, 1 ml of TNM-FH medium was added to the plates. After further incubation for 48 hours, the transfection media containing virus was removed and these viral stocks were used to infect plates of Sf-9 cells for plaque identification.

Sf-9 cells were seeded at 2.times.10.sup.6 cells/60 mm dish in TNM-FH medium and allowed to attach for approximately 1 hour at 27.degree. C. The media was removed. Several 10-fold serial dilutions were made from each vital stock and 1 .mu.l of each dilution was added to a single dish of adherent Sf-9 cells and incubated for 1 hour at 27.degree. C. Following removal of the virus inoculum, each dish of cells was overlayed with 3 ml of a mixture of TNM-FH medium, 0.625 % low melting point agarose (BRL, Gaithersburg, Md.) and 300 .mu.g/ml halogenated idolyl-beta-D-galactosidase (Bluo-gal, BRL) that had been previously equilibrated to about 30.degree. C. and allowed to solidify at room temperature for 1 hour. The plates were then incubated until blue color developed (typically 4-5 days). Twenty-four plaques of recombinant viruses (identified due to their expression of beta-galactosidase and conversion of the chromogenic substrate, Bluo-gal to a blue precipitate in infected cells) were transferred to individual wells of a 24-well cell culture plate that had been seeded with 1 ml of Sf-9 cells (2.times.10.sup.5 /ml) in TNM-FH. After 5 days at 27.degree. C. the media was harvested, microfuged at 1,000 rpm for 5 minutes at 4.degree. C. and the resulting supernatant was transferred to a fresh tube. These stocks were designated as BacR.P1 stocks with their respective isolate number.

BacR.P1 stocks were assayed for the production of ICAM-R by an antigen capture (ELBA) assay. Anti-ICAM-R monoclonaI antibody 26I10E-2 (see Example 10) was biotinylated as follows. A tenth volume of 1M NaCO.sub.3 was added to monoclonal antibody 26I10E at 1 mg/ml. NHS-biotin (Sigma Chemical Co., St. Louis, Mo.) was dissolved into dimethyl sulfoxide (DMSO, Mallinckrodt, Paris, Ky.) at 1 mg/ml. One hundred eighty .mu.l biotin solution was added to each 1 mg antibody and rotated at 4.degree. C. overnight. The biotinylation reaction was terminated by dialysis against PBS for 16 hours with 3 changes at 4.degree. C. For the assay of BacR.P1 stocks, each well of a ninety-six well plate was coated with monoclonal antibody 26E3D (50 .mu.l at 10 .mu.g/ml) for either 2 hours at 37.degree. C. or 16 hours at 4.degree. C. The coating was then aspirated and the wells were rinsed 2 times with PBS. Wells were blocked with 200 .mu.l of 1% BSA in PBS for 30 minutes at 37.degree. C. Two ten-fold serial dilutions of BacR.P1 stocks were made in PBS. Fifty .mu.l from the BacR.P1 stocks (neat) or the dilutions were added to the wells and incubated for 30 minutes at 37.degree. C. After 2 washes with PBS, 50 .mu.l for a 1:250 dilution of biotinylated 26I10E in 1% BSA/PBS was added to the wells and incubated for 30 minutes at 37.degree. C. After 3 washes with PBS, 50 .mu.l/well of horseradish peroxidase conjugated to streptavidin (Zymed Laboratories Inc., San Francisco, Calif.) diluted in 1% BSA/PBS to 1:4000 was added and incubated for 30 minutes at 370.degree. C. After 2 washes with PBS, 200 .mu.l/well substrate buffer with ABTS (Zymed) was added and incubated at room temperature until a color reaction developed. The plate was read in an automated plate reader at a wavelength of 410 nm.

Four of the highest expressors of soluble ICAM-R as determined by the above antigen capture assay were chosen for plaque purification and BacR.P1 stocks of those isolates were diluted by 10-fold serial dilutions and plated with an agar overlay. A single blue plaque from the highest dilution was isolated and placed in 1 ml of TNM-FH medium, vortexed vigorously and serially diluted for one more round of plaque isolation. A final plaque isolate was chosen that was clear of all wildtype baculovirus and removed to a T-25 flask that has been seeded with 2.times.10.sup.6 Sf-9 cells in TNM-FH media. After 5 days incubation at 27.degree. C., the media was harvested by centrifugation at 1200 rpm for 5 minutes and 4 ml of the supernatant (designated BAC-R.P2 stock) was transferred to a 1 liter spinner flask containing 500 ml of TNM-FH seeded with 2.times.10.sup.6 cells/ml. After another 5 days incubation at 27.degree. C., the infection media was harvested by centrifugation at 1000 rpm for 5 minutes. The supernatant was stored at 4.degree. C. and was designated BAC-R.P3 stock. The BAC-R.P3 stock was titered by plating aliquots of ten fold serial dilutions onto adherent Sf-9 cells and overlaying with 0.625% agarose in TNM-FH supplemented with 300 .mu.g/ml Bluo-gal (BRL). After 4 days incubation at 27.degree. C., the number of plaques was counted and a titer determined.

Infections for expression of soluble ICAM-R protein were carried out in 3 liter flasks containing 1.5 L of EX/Cell 401 medium (JRH Biosciences, Lenexa, Kans.). Sf-9 cells dividing at log phase (2.times.10.sup.6 /ml) were infected at a multiplicity of infection (moi) of 5 with BAC-R.P3 virus stock. After 4 days, the media was harvested and was separated from the cells by centrifugation. Soluble ICAM-R protein was purified from the insect cell media as follows. Four ml 1M Tris-Cl pH 7.5 was added to each 200 ml of insect cell supernatant and was pumped at about 35 ml/hour at 4.degree. C onto a .about.3.5 ml column of Lentil Lectin Sepharose (Pharmacia, Uppsala, Sweden) previously equilibrated with 20 mM Tris-Cl pH 7.5/0.1M NaCl (equilibration buffer). After loading, the column was washed with 25 ml equilibration buffer. The column was then eluted with 11 ml equilibration buffer containing 0.2M methyl .alpha.-D-mannnopyranoside. The eluate contained soluble ICAM-R.

The partially purified soluble ICAM-R protein was assayed for binding to SKW3 cells that were pretreated with phorbol ester as described in Example 8 to activate LFA-1-dependent adhesion. The ICAM-R protein was coated onto 96-well Immulon 4 (Dynatech) plates after adjusting the leetin eluate to 25 mM carbonate pH 9.6 and incubated overnight at 4.degree. C. The plates were washed two times with PBS, blocked for 30 minutes at 37.degree. C. with 200 ul/well PBS, 1% BSA, and washed again with PBS before adding cells. SKW3 cells were washed in serum-free RPMI (Gibco), labelled with Calcein-AM (Molecular Probes), and stimulated with PMA. In monoclonal antibody blocking experiments, the cells were treated (before stimulation with PMA) with appropriate purified monoclonal antibodies for 20 minutes at room temperature as described in Example 8 before incubation with the plate-bound ICAM-R protein. Cells were then added to the plates and incubated for 1 hour at 37.degree. C. Hates were sealed, centrifuged in an inverted position at 200 rpm for 4 minutes and aspirated. The centrifugation was followed by washes with RPMI/1% FCS. The plates were then scanned with a fluorescence microscope and an automated fluorescence reader. Preliminary data demonstrate adhesion of phorbol ester-activated lymphocytes to the plate bound ICAM-R protein.

Monoclonal antibodies specific for ICAM-R were generated from the fusion of NS-1 myeloma cells with spleen cells of Balb/c mice immunized with human cell lines that express ICAM-R. Monoclonal antibodies were generated from four different fusions designated fusions 26, 42, 43, and 46.

A. Immunization of Mice

For fusion 26, five 6 to 12-week old Balb/c mice (Charles River Bioteehnical Services, Inc., Wilmington, Mass., IACUC #901103) were immunized with HL-60 cells to generate anti-ICAM-R monoclonal antibodies. Two Balb/c mice were bled retro-orbitally for the collection of pre-immune serum on day 0. On day 2, each animal received a total of 6.times.10.sup.6 HL-60 cells in 0.5 ml PBS (0.1 ml s.c. and 0.4 ml i.p.). A second immunization with 9.5.times.10.sup.6 HL-60 cells was administered on day 28 in the same manner. Immune serum was collected via retro-orbital bleeding on day 35 and tested by FACS (FACS screening is described in detail in Section C below) to determine its reactivity to ICAM-R transfectants. Based on these results, both animals were immunized a third time on day 51 with 6.5.times.10.sup.6 HL-60 cells and a fusion was performed with spleen cells sterilely removed from one animal (#764) on day 54.

For fusion 42, on day 0 each of five mice was prebled and then immunized j.p. with 5.times.10.sup.6 SKW3 cells in 0.5 ml PBS containing 50 .mu.g adjuvant peptide (Sigma). The mice were boosted in the same manner on days 21 and 42. Ten days after the third injection, the mice were bled and immune sera was tested by FACS. Mouse #843 was given a final boost of SKW3 cells on day 64. The spleen was sterilely removed three days later.

For fusion 43, on day 0 each of five mice was prebled and then immunized i.v. with 5 x 106 cells from the erythroleukemic cell line K562. Each mouse was given a daily i.p. injection of 1.5 mg cyclophosphamide in 150 .mu.l for the next two days. On day 10, SKW3 cells plus adjuvant peptide were injected as in Fusion 42. On day 30, mice were given another cycle of K562 cells followed by cyclophosphamide. On day 42 mice were boosted with SKW3 cells with adjuvant peptide. Mice were bled on day 56 and immune sera was tested by FACS. Mouse #1021 was given a final boost of SKW3 cells and adjuvant peptide on day 78. The spleen was sterilely removed three days later.

For fusion 46, a mouse (#900) was immunized as for fusion 42. On day 128, the mouse was given a final boost of approximately 4.times.10.sup.6 Macaca nernestrina spleen cells. The single cell suspension of monkey spleen was prepared as described below in the following paragraph. The monkey cells were pelleted and resuspended in erythrocyte lysis buffer: 0.15M NH.sub.4 Cl, 1M KHCO.sub.3, 0.1lmM Na.sub.2 EDTA, pH 7.2-7.4. After lysing the erythrocytes, the splenocytes were washed twice in RPMI and once in PBS. Finally, the cells were resuspended in 400 .mu.l PBS containing 50 .mu.g adjuvant peptide and injected. The mouse spleen was removed sterilely three days later.

B. Fusions

Briefly, a single-cell suspension was formed from each mouse spleen by grinding the spleen between the frosted ends of two glass microscope slides submerged in serum free RPMI 1640 (Gibco), supplemented with 2mM L-glutamine, lmM sodium pyruvate, 100 units/ml penicillin, and 100 .mu.g/ml streptomycin (Gibco). The cell suspension was filtered through sterile 70 mesh Nitex cell strainer (Becton Dickinson, Parsippany, N.J.), and washed twice by centrifuging at 200 g for 5 minutes and resuspending the pellet in 20 ml serum free RPMI. Thymocytes taken from three naive Balb/c mice were prepared in a similar manner.

NS-1 myeloma cells, kept in log phase in RPMI with 11% fetal bovine serum (FBS) or Fetalclone (Hyclone) for three days prior to fusion, were centrifuged at 200 g for 5 minutes, and the pellet was washed twice as described in the foregoing paragraph. After washing, each cell suspension was brought to a final volume of 10 ml in serum free RPMI, and 10 .mu.l was diluted 1:100. Twenty/xl of each dilution was removed, mixed with 20 .mu.l 0.4% trypan blue stain in 0.85 % saline (Gibco), loaded onto a hemacytometer (Baxter Healthcare Corp. Deerfield, Ill.) and counted.

A sample of 2.times.10.sup.8 spleen cells was combined with 4.times.10.sup.7 NS-1 cells, centrifuged and the supernatant was aspirated. The cell pellet was dislodged by tapping the tube and 2 ml of 37.degree. C. PEG 1500 (50% in 75ram Hepes, pH 8.0) (Boehringer) was added with stirring over the course of 1 minute, followed by adding 14 ml of serum free RPMI over 7 minutes. An additional 16 ml RPMI was added and the cells were centrifuged at 200 g for 10 minutes. After discarding the supernatant, the pellet was resuspended in 200 ml RPMI containing 15% FBS or Fetalclone, 100 .mu.M sodium hypoxanthine, 0.4 .mu.M aminopterin, 16 .mu.M thymidine (HAT) (Gibco), 25 units/ml IL-6 (Boehringer) and 1.5.times.10.sup.6 thymocytes/ml. The suspension was dispensed into ten 96-well flat bottom tissue culture plates at 200 .mu.l/well. Cells in plates were fed three times typically on 2, 4, and 6 days post fusion by aspirating approximately 100 .mu.l from each well with an 18 G needle (Becton Dickinson), and adding 100 .mu.l/well plating medium described above except containing 10 units/ml IL-6 and lacking thymocytes.

C. Screening

When cell growth reached 60-80% confluency (day 8-10), culture supernatants were taken from each well of Fusions 26 and 42, pooled by column or row and analyzed by FACS on parental L cells (Fusion 26) or parental CV-1 cells (Fusion 42); (negative control) and on L cells (Fusion 26) or CV-1 cells (Fusion 42) transfected with ICAM-R DNA. Briefly, transfected and nontransfected L cells or CV-1 cells were collected from culture by EDTA (Versene) treatment and gentle scraping in order to remove the cells from the plastic tissue culture vessels. Cells were washed two times in Dulbecco's PBS with Ca.sup.2+ and Mg.sup.2+, one time in "FA Buffer" (either D-PBS or RPMI 1640, 1% BSA, 10 mM NaN.sub.3), and dispensed into 96-well round bottomed plates at 1.5-2.0 .times.10.sup.5 cells/100 .mu.l FA Buffer per well. At this point, the assay was continued at 4.degree. C. Cells were pelleted by centrifugation in a clinical centrifuge at 4.degree. C. The supernatant from each well was carefully suctioned off, the pellets were broken up by gently tapping all sides of the assay plate. One hundred .mu.l of hybridoma supernatant pool was added per well using a 12-channel piperman. Each monoclonal antibody-containing supernatant pool was incubated for 1 hour on both parental and transfected cells at 4.degree. C. Assay plates were then washed 2 times with FA Buffer as above. The last wash was replaced with a 50 .mu.l/well of a 1:100 dilution of a F(ab').sub.2 fragment of sheep anti-mouse IgG (whole molecule)-FITC conjugate (Sigma) prepared in FA Buffer. Assay plates were incubated at 4.degree. C. protected from light for 45 minutes. The assay plates were then washed 2 times with D-PBS containing NaN.sub.3 only (i.e., no BSA) in the same manner as before and the last wash was replaced with 200 .mu.l/well 1% paraformaldehyde in D-PBS. Samples were then transferred to polystyrene tubes with the aid of a multichannel pipet for flow cytometric analysis (FACS) with a Becton Dickinson FACscan analyzer.

Fusions 43 and 46 were screened initially by antibody capture ELISA, testing for the presence of mouse IgG in hybridoma supernatants. Immunlon 4 plates (Dynatech, Cambridge, Mass.) were coated at 4.degree. C. with 50 .mu.l/well goat anti-mouse IgA, IgG or IgM (Organon Teknika Corp., Durham, N.C.) diluted 1:5000 in 50 mM carbonate buffer, pH 9.6. Plates were washed 3 times with PBS with 0.05 % Tween 20 (PBST) and 50 .mu.l culture supernatant was added. After incubation at 37.degree. C. for 30 minutes, and washing as above, 50 .mu.l of horseradish peroxidase conjugated goat anti-mouse IgG(fc) (Jackson ImmunoResearch, West Grove, Pa.) diluted 1:3500 in PBST was added. Plates were incubated as above, washed 4 times with PBST and 100 .mu.l substrate, consisting of 1 mg/ml o-phenylene diamine (Sigma) and 0.1 .mu.l/ml 30% H.sub.2 O.sub.2 in 100 mM Citrate, pH 4.5, was added. The color reaction was stopped in 5 minutes with the addition of 50 .mu.l of 15 % sulfuric acid. A.sub.490 was read on an automatic plate reader.

D. Subcloning

Supernatants from individual wells representing the intersection points of positive columns and rows (Fusion 26 and 42), or individual wells producing IgG (Fusions 43 and 46) were rescreened by FACS the following day. L cells or L cells transfected with ICAM-R DNA were used for screening Fusion 26 antibodies and CV-1 cells or CV-1 cells transfected with ICAM-R DNA were used for screening antibodies from Fusions 42, 43 and 46. Twelve wells (designated 26E3D-1, 26E3E, 26H3G, 26H11C-2, 2618F-2, 26I10E-2, 26I10F, 42C5H, 42D9B, 43H7C, 46D71E, and 46I 12H) showed preferential staining of the ICAM-R transfectants vs. the control cells. These wells were subcloned two to three times, successively, by doubling dilution in RPMI, 15% FBS, 100 .mu.M sodium hypoxanthine, 16 .mu.M thymidine, and 10 units/ml IL-6 (Boehringer). Wells of subclone plates were scored visually after 4 days and the number of colonies in the least dense wells were recorded. Selected wells of the each cloning were tested by FACS after 7-10 days. Activity was retained in nine lines [26E3D-1 (ATCC HB 11053), 26H11C-2 (HB 11056), 26I8F-2 (HB 11054), 26I10E-2 (ATCC HB 11055), 42C5H (ATCC HB 11235), 42D9B (ATCC 11236), 43H7C (ATCC 11221), 46D7E (ATCC HB 11232) and 46I12H (ATCC HB11231)]. In the final cloning, positive wells containing single colonies were expanded in RPMI with 11% FBS.

E. Characterization

The monoclonal antibodies produced by above hybridomas were isotyped in an ELISA assay. Immulon 4 plates (Dynatech) were coated at 4.degree. C. with 50 .mu.l/well goat anti-mouse IgA, IgG or IgM (Organon Teknika) diluted 1:5000 in 50 mM carbonate buffer, pH 9.6. Plates were blocked for 30 minutes at 37.degree. C. with 1% BSA in PBS, washed 3 times with PBS with 0.05% Tween 20 (PBST) and 50 .mu.l culture supernatant (diluted 1:10 in PBST) was added. After incubation and washing as above, 50 .mu.l of horseradish peroxidase conjugated rabbit anti-mouse IgG.sub.1, G.sub.2a, G.sub.2b, or G.sub.3 (Zymed) diluted 1:1000 in PBST with 1% normal goat serum was added. Plates were incubated as above, washed 4 times with PBST and 100 .mu.l substrate, consisting of 1 mg/ml o-phenylene diamine (Sigma) and 0.1 .mu.l/ml 30% hydrogen peroxide in 100 mM Citrate, pH 4.5, was added. The color reaction was stopped in 5 minutes with the addition of 50 .mu.l of 15% sulfuric acid. A.sub.490 was read on a plate reader. Results showed that the monoclonal antibodies produced by hybridomas 26E3D-1, 42C5H and 46I12H were IgG.sub.2a while the other six monoclonal antibodies were IgG.sub.1.

FACS analyses of indirect immunofluorescence staining of control cells and cells transfected with ICAM-R or ICAM-I DNA using monoclonal antibodies against ICAM-R, ICAM-1 and ICAM-2 were performed. Staining was carried out as described for FACS analyses in Example 10C using either 0.1 ml hybridoma culture supernatant (anti-ICAM-R) or 1 .mu.g pure monoclonal antibody (anti-ICAM-1 or ICAM-2) per 5.times.10.sup.5 cells. Results of the analyses are presented as histograms (representing 10.sup.4 cells analyzed) in FIG. 4. Anti-ICAM-R antibody 26H11C-2 specifically bound to L cells transfected with ICAM-R cDNA, but not to parental or ICAM-1 transfeeler L cells. ICAM-R did not react with antibodies against ICAM-1 (Mab LB2 from Edward Clark, University of Washington) or ICAM-2 (IC2/2, Biosource Genetics Corp., Vacaville, Calif.). In parallel experiments, anti-ICAM-R monoclonal antibodies 26E3D-1, 26I10E-2, and 26I8F-2 exhibited the same reactivity on transfectants as monoclonal antibody 26H11C-2. Anti-ICAM-R antibodies 42C5H, 42DF9B, 43H7C, 46D7E, and 46I12H antibodies also reacted specifically with ICAM-R transfected cells but not with parental CV-1 cells or to ICAM-1 transfected CV-1 cells.

FACS analysis of indirect immunofluorescence of Macaca fascicularis or dog peripheral blood leukocytes was performed using the nine anti-ICAM-R monoclonal antibodies. Twenty ml of heparinized Macaca fascicularis blood was diluted with 280 ml of erythrocyte lysis buffer, incubated 3-5 minutes at room temperature, and centrifuged at 200 g for 5 minutes. The supernatant was discarded. The pellet was washed once in cold D-PBS containing 2 % fetal bovine serum and the cells were counted by hemacytometer. Twenty ml of heparinized dog blood was diluted in two volumes of Waymouth's medium (Gibco) plus 2 % nonessential amino acids (NEAA). Each 5 ml of blood solution was layered over 4 ml of histopaque and centrifuged at 1000 g for 20 minutes at room temperature. Cells were collected from the interface, washed once in Waymouth's medium plus 2% NEAA, and counted as above. Each cell population was stained as described previously in Example 10C and analyzed by FACS. Anti-ICAM-R antibodies 26I10E and 46I12H specifically stained monkey PBL while the other seven antibodies did not. None of the antibodies specifically stained dog PBL.

F. Purification

Hybridoma culture supernatant containing anti-ICAM-R monoclonal antibody 26E3D-1 or 26I10E-2 was adjusted to 1.5M glycine, 3.0 M NaCl pH 8.9, and put over a 2 ml bed volume protein A column (Sigma). After washing with 1.5M glycine, 3M NaCl, pH 8.9, the column was eluted with 100 mM sodium citrate, pH 4.0. One ml fractions were collected into 100 .mu.l of 1.5M Tris, pH 8.8. Fractions containing antibody as determined by A.sub.280 were pooled and dialyzed against PBS.

FACS-based competition assays utilizing human peripheral blood leukocytes or SKW3 cells (both ICAM-R expressing cells) indicate that monoclonal antibodies 26I10E and 26E3D are immunologically reactive with distinct epitopes of ICAM-R. In the assays, human peripheral blood leukocytes (PBL) obtained by Ficoli Hypaque centrifugation of normal peripheral blood were washed twice in ice cold FACS buffer (PBS containing 0.1% sodium azide and 1% bovine serum albumin) and 2.times.10.sup.5 cells were incubated in triplicate polypropylene tubes with 5 .mu.g of each of the following antibodies 26E3D-1, 26I10E-2, and control isotype IgG (Sigma). All tubes containing the first stage antibodies were then incubated for 30 minutes at 4.degree. C. and washed twice in cold FACS buffer. To each triplicate tube, 5 .mu.g of each of the following second stage antibodies were added: biofinylated-26E3 D- 1, biotinylated-26I10E-2, biotinylated-anti-rat CD4 (negative control). All second stage antibodies were biotinylated according to standard procedures as described in Example 9 and all tubes were then incubated for an additional 30 minutes at 4.degree. C. before washing twice in FACS buffer. Five ul of a 1:10 dilution of Strepavidin-phycoerythrin (Southern Biotechnology, Birmingham, Ala.) was then added to each tube containing 50 .mu.l FACS buffer and all tubes were incubated for 30 minutes at 4.degree. C. Finally, all tubes were washed twice in FACS buffer and analyzed by flow cytometry (FACScan, Becton-Dickinson). While monoclonal antibody 26I10E-2 blocked binding of biotinylated-26I10E-2 to ICAM-R on PBL, it did not block binding of monoclonal antibody 26E3D-1. Similarly, monoclonal antibody 26E3D-1 did block binding of biotinylated-26E3D-1 but did not block binding monoclonal antibody 26I10E-2, These results indicate that the two antibodies recognize distinct epitopes on ICAM-R. Equivalent results were obtained when using the human cell line SKW3 as follows. SKW3 cells were labelled with either 1 .mu.g of antibody 26E3D-1 or 26I10E-2, washed in FACS buffer and incubated with 1 .mu.g biotinylated-26E3D-1 or biotinylated 26I10E-2. All tubes were then washed in FACS buffer, incubated with Strepavidin-phycoerythrin for an additional 30 minutes at 4.degree. C. and analyzed by FACScan. In the assays, if an unlabelled antibody (the "blocking" antibody) prevented the labelled antibody from binding to ICAM-R, it indicates that the unlabelled antibody "competes" with the labelled antibody for binding to ICAM-R and that the two antibodies recognize the same epitope on ICAM-R. A variation of the competition assay in which unlabelled antibody is used to "compete away" binding of a labelled antibody may also be utilized to determine if two antibodies recognize the same epitope.

The specific ICAM-R epitopes recognized by the various monoclonal antibodies of the invention can be mapped by three different methods.

A. Epitope Mapping Using The Multipin Peptide Synthesis System

The first method for mapping linear epitopes recognized by the ICAM-R specific antibodies of the invention utilized the Multipin Peptide Synthesis System (Chiron Mimotopes Pty. Ltd., Victoria, Australia) which places ten amino acid peptides representing overlapping segments of the protein of interest on the surface of a series of plastic pins. A modified ELISA test is performed to determine binding of a monoclonal antibody to each peptide.

The ELISA to determine binding of the monoclonal antibodies to ICAM-R peptides was run as follows. The pins were placed in five 96-well plates containing 200 .mu.l per well blocking buffer (2% weight/volume BSA, 0.1% volume/volume Tween 20, 0.01M PBS, pH 7.2) and incubated for one hour at 20.degree. C. with agitation. The pins were transferred to plates with 175 .mu.l per well of undiluted anti-ICAM-R monoclonal antibody supernatant and incubated overnight at 4.degree. C. with agitation. The pins were then washed four times with 0.01M PBS, pH 7.2 (10 minutes/wash at 20.degree. C. with agitation) and placed in plates containing 175 .mu.l per well HRP-Goat anft-mouse IgG (H+L) (Kirkegaard and Perry Laboratory Inc., Gaithersburg, Md.) diluted to an appropriate concentration in conjugate diluent (1% volume/volume sheep serum, 0.1% volume/volume Tween 20, 0.1% weight/volume sodium caseinate and 0.01M PBS). The plates were agitated for one hour at 20.degree. C., and washed four times with 0.01M PBS. The pins were transferred to plates containing ABTS substrate solution [0.5 mg/ml ABTS, 0.01% weight/volume H.sub.2 O.sub.2 in substrate buffer (17.9 g/L Na.sub.2 HPa.sub.4 H.sub.2 O, 16.8 g/L citric acid monohydrate, pH 4.0)] for 45 minutes at 20.degree. C. with agitation and then the plates were read at 410/495 nm.

Relative reactivity with individual pins was determined after normalizing results for differences in immunoglobulin concentrations in anti-ICAM-R and control hybridoma supernatants and reactivities of positive controls between assays. Mouse IgG levels for each supernatant had been determined by antibody capture ELISA as follows. Iratoulon 4 plates were coated and washed as described in Example 10C. Fifty .mu.l/well of culture supernatant diluted in PBST [or known concentrations in doubling dilutions in PBST of mouse IgG.sub.1 and IgG.sub.2a (MOPC-21, and UPC-10) (Sigma)] was added to the plate. After incubating for 1 hour at room temperature and washing 3 times with PBST, horseradish peroxidase conjugated goat anti-mouse IgG(fc) (Jackson ImmunoResearch, West Grove, Pa.) was diluted 1:2000 for mouse IgG.sub.1 and 1:1000 for IgG.sub.2a, and added 50 .mu.l/well. After the plate was incubated for 1 hour at room temperature and washed 4 times in PBST, the remainder of the assay was conducted as described in Example 10C. Antibody concentrations of culture supernatant were determined by fitting measured optical densities to the standard curve of the isotype matched control.

Strong reactivity of monoclonal antibody 26E3D-2 was noted with two overlapping peptides spanning amino acids 13.gtoreq.23, as illustrated below:

Regions reactive with anti-ICAM-R antibodies can also be defined and/or verified using the following methodologies.

B. Epitope Mapping Using A Library of Bacterial Clones

Epitope mapping with the anti-ICAM-R antibodies was also performed using the Novatope Library Construction and Screening System (Novagen, Madison, Wis.). Using this method, a library of bacterial clones is generated wherein each clone expresses a polypeptide including a small peptide derived from the protein being examined. The library is then screened by standard colony lift methods using monoclonal antibodies as probes.

Double-stranded DNA encoding the external domain of ICAM-R (amino acids 1 to 487) from pVZ147 (See Example 4) was cut with different amounts of DNAseI in the presence of 10 mM manganese for 10 minutes at 21.degree. C. The reaction was stopped with EDTA and 1/10 of the reaction was electrophoresed on a 2% agarose gel with ethidium bromide and appropriate markers. Those reactions containing fragments in the 50-150 bp range were pooled and electrophoresed on another 2% gel. The area of the gel between 50-150 bp was excised, the fragments contained therein were electroeluted into dialysis tubing (SP Brand Spectra/Por 2, MWCO 12-14,000), and then phenol/chloroform extracted and ethanol precipitated.

One .mu.g DNA was blunted according to the manufacturer's protocol, using T4 DNA polymerase and all four dNTPs. The reaction was stopped by heating to 75.degree. C. for 10 minutes, then a single 3' dA residue was added by using Tth DNA polymerase (Novagen). The reaction was stopped by heating to 70.degree. C. for 15 minutes and extracted with chloroform. When starting with 1 .mu.g of DNA, the final concentration was 11.8 ng/.mu.l in 85 .mu.l. The dA tailed fragments are ligated into the pTOPE T-vector (Novagen) which is designed for the expression of inserts as stable fusion proteins driven by T7 RNA polymerase (the structural gene for which is carried on a replicon in the host cell). Using 6 ng of 100 bp DNA (0.2 pmol), the ligation reaction was run at 16.degree. C. for 5 hours. NovaBlue(DE3) (Novagen) cells were transformed with 1 .mu.l (1/10) of the reaction mix, and spread on LB agar (carbenicillin/tetracycline) plates to obtain an initial count of transformants. The remainder of the ligation reaction was put at 16.degree. C. for an additional 16 hours. Based on the initial plating, 2 .mu.l of the ligation reaction was used to transform 40 .mu.l of competent NovaBlue(DE3) cells, then 8 plates were spread at a density of approximately 1250 colones/plate for screening with antibody.

Colonies were screened using standard colony lift methods onto nitrocellulose membranes, lysed in a chloroform vapor chamber and denatured. Using anti-ICAM-R monoclonal antibody 26E3D-1 at a 1:10 dilution in TBST (Tris-buffered saline/Tween) as a primary antibody, the assay was developed using an alkaline phosphatase-coupled secondary reagent. The substrate mix was incubated for 30 minutes. One isolated colony gave a strong positive reaction. Three others areas (not isolated colonies) gave weak positive reactions. Streaks were made from a stab of the isolated colony or colony areas for re-screening. Upon re-probing with 26E3D-1, the streak from the isolated colony had positive reactive areas after a 20 minute incubation with substrate. The other three colony area samples were negative. A stab from the ICAM-R reactive area was re-streaked, incubated overnight at 37.degree. C. and re-probed incubating with substrate for 10 minutes. Many 26E3D-1 reactive colonies resulted. Plasmid DNA recovered from these colonies can be sequenced and the amino acid sequence corresponding to the 26E3D-1 reactive epitope can be determined.

C. Epitope Mapping by Domain Substitution

Conformational epitopes of ICAM-R recognized by the monoclonal antibodies of the invention may be mapped by domain substitution experiments. In these experiments, chimeric variants of ICAM-R are generated in which selected immunoglobulin-like domains of ICAM-R are fused to portions of ICAM-1 and assayed for binding to the monoclonal antibodies of the invention by FACS.

FIG. 5 is a diagram of the chimetic proteins whose construction is outlined below. Protein number 1 contains the amino-terminal immunoglobulin-like domain of ICAM-R (residues 1 to 93) fused to ICAM-1 (residue 117 to 532). Protein number 2 contains the first two amino terminal immunoglobulin-like domains of ICAM-R (residues 1 to 190) fused to ICAM-1 (residues 118 to 532). Protein number 3 contains the first three immunoglobulin-like domains of ICAM-R (residues 1 to 291) fused to ICAM-1 (residues 317 to 532).

Protein number 1 was made by engineering a unique Nhe I site into the coding sequences of ICAM-R and ICAM-1 at the junction of immunoglobulin-like domains 1 and 2 of each. The DNA sequence of ICAM-R was subcloned into the M13 BM21 vector (Boehringer) as described in Example 9 resulting in a molecule called M13 BM21ICAM-R. The entire coding sequence of ICAM-1 [Simmons et al., Nature, 331:624-627 (1988)] was subcloned into the plasmid pBSSK(+) (Invitrogen). The resulting plasmid, pBSSK(+)ICAM-1 was cut with SalI and KpnI to release the ICAM-1 coding sequence along with a short segment of the multiple cloning sites and ligated to M13 BM21 cut with restriction enzymes SalI and KpnI resulting in a molecule called M13 BM21ICAM-l. M13 phage isolates were verified by DNA sequence analysis.

Mutagenizing oligonucleotides ICAM 1. D 1. Nhe 1 (corresponding to nucleotides 426 to 393 of ICAM-1) and ICAMR.D1Nhe 1 (corresponding to nucleotides 367 to 393 of ICAM-R) having the following sequences were synthesized by routine laboratory methods:

Nucleotides 16 and 19 of ICAM 1. D 1. NheI and nucleotide 15 of ICAMR. D 1. NheI form mismatch base pairs when the oligos are annealed to their respective complementary DNA sequences. Both oligonucleotides introduce a recognition site for endonuclease Nhe. I. Site-directed mutagenesis with the oligonucleotides was employed to introduce the sequences of these oligos into the respective ICAM-1 and ICAM-R target DNA sequences M13 BM21ICAM-1 and M13 BM21ICAM-R. Several phage isolates from each mutagenesis reaction were sequenced to verify that the correct DNA sequence was present. These isolates were designated M13 BM21ICAM-R.NheI and M13 BM21ICAM-1.NheI.

The coding region for the ICAM-R signal peptide and immunoglobulin-like domain 1 was isolated from M13 BM21ICAM-R.NheI by the following method. Ten .mu.g of purified single strand M13 BM21ICAM-R.NheI phage DNA was annealed to 50 ng Lac Z universal -20 primer (SEQ ID NO: 26) in 1X Klenow DNA polymerase buffer (10ram Tris-C1 pH 7.5, 5 mM MgCl.sub.2, 7.5 mM dithiothreitol) by incubating the mix at 65.degree. C. for 5 minutes and then 25.degree. C. for 5 minutes. The following mixture was then added to the annealing reaction: 33 .mu.M final concentration dATP, dGTP, dCTP, dTTP; 4 units of Klenow DNA polymerase (Boehringer), and 1X Klenow buffer. The primer extension reaction was allowed to incubate at 37.degree. C. for 45 minutes prior to being stopped by a single phenol/chloroform (1: 1) extraction and ethanol precipitation. The dried pellet was resuspended in 1X EcoRI buffer and 20 units each of EcoRI and NheI endonucleases were added prior to a 60 minute incubation at 37.degree. C. A 412 bp fragment containing the coding sequence for ICAM-R signal peptide and immunoglobulin-like domain 1 was agarose gel purified.

The DNA sequence of ICAM-1 containing the coding region for immunoglobulin-like domains 2 through 5, the transmembrane and cytoplasmic domains was isolated by restriction enzyme digest. Ten .mu.g of primer extended M13.BM21ICAM-1.NheI were cut with NheI and NotI. This resulted in the release of a DNA fragment of 1476 bp which was agarose gel purified.

Five .mu.g of the mammalian expression plasmid pCDNAIAmp (Invitrogen) was digested with EcoRI and NotI and purified by spin column chromatography. A 20 .mu.l ligation mix was assembled containing the following components: 50 ng linear pCDNA1Amp with EcoRI and NotI termini, 100 ng of the 412 bp ICAM-R fragment, 100 ng of the 1476 bp ICAM-1 fragment, 1X ligase buffer and 1 unit of T4 DNA ligase (Boehringer). The reaction was incubated at 25.degree. C. for 16 hours and used to transform competent XL-1 cells (Biorad). Transformants were selected on LB plates supplemented with carbenicillin at a final concentration of 100 .mu.g/ml. Transformants were analyzed using a standard mini DNA prep procedure and digestion with diagnostic endonucleases. Isolates designated pCDNA1Amp. RD1.ID2-5 were chosen for expression studies.

To construct coding sequences for proteins 2 and 3, engineered versions of M13 BM21ICAM-1 and M13 BM21ICAM-R in which a unique NheI site was created between immunoglobulin-like domains 2 and 3 or a unique AflII site was created between immunoglobulin-like domains 3 and 4 were generated by methods similar to those described in the foregoing paragraphs. Four oligonucleotides (ICAM-1.D2.NheI corresponding to nucleotides 686 to 713 of ICAM-1, ICAM-R.D2.NheI corresponding to nucleotides 655 to 690 of ICAM-R, ICAM-1.D3.AflII corresponding to nucleotides 987 to 1026 of ICAM-1, and ICAM-R.D3 .AflII corresponding to nucleotides 962 to 993 of ICAM-R) with the sequences set out below were synthesized for this purpose.

Nucleotide 13 of ICAM1.D2NheI; nucleotides 17, 18 and 20 of ICAMR.D2.NheI; nucleotides 17, 18, 20 and 22 of ICAM-1.D3. AflII; and nucleotides 15 and 17 of ICAM-R.D3.AflII form mismatch base pairs when the oligonucleotides are annealed to their respective complimentary DNA sequences. The appropriate coding sequences of ICAM-R and ICAM-1 (sequences encoding the first two amino terminal immunoglobulin-like domains of ICAM-R fused to sequences encoding ICAM-1 residues 118 to 532 for protein 2 and sequences encoding the first three immunoglobulin-like domains of ICAM-R fused to sequences encoding ICAM-1 residues 317 to 532 for protein 3) were then subcloned into expression plasmid pCDNA 1 Amp (Invitrogen) to generate isolates pCDNA 1 Amp. RD 1-2.1 D3 -5 and pCDNAAmp. RD 1-3.1 D4-5 respectively encoding ICAM-R variant proteins 2 and 3.

Control plasmids containing the full length ICAM-R or ICAM-1 cDNA sequences were generated by ligating gel-purified eDNA fragments to plasmid pCDNA1Amp. The two plasmids pCDNA1AmpICAM-1 and pCDNA1AmpICAM-R express the full length ICAM-1 and ICAM-R proteins, respectively, so that monoclonal antibody binding to native protein in equivalent cellular contexts can be assessed.

These constructs can be used to transfeet rat L cells by a calcium phosphate co-precipitate protocol using 10 .mu.g of 2X CsCl-banded pCDNA1Amp. RD1.1D2-5 (protein 1), pCDNA1Amp. RD1-2.1D3-5 (protein 2), pCDNAAmp. RD1-3.1D4-5 (protein 3), pCDNA1AmpICAM-1, pCDNA1AmplCAM-R or pCDNA1Amp. In this protocol, forty-eight hours post-transfection the cells are released from the dishes by mild trypsinization. The cells are divided and incubated on ice with the monoclonal antibodies 26E3D-1, 26HIIC-2, 26I8F-2, and 26I10E-2 or a control isotype matched monoclonal antibody at a concentration of 10 .mu.g/ml or no monoclonal antibody for 1 hour. The cells are then processed for FACS analysis as previously described in Example 10C.

Differential reactivity of an anti-ICAM-R antibody of the invention with the ICAM-R variant proteins is indicative of reactivity with a specific domain of ICAM-R. Once particular domains are identified that reacted with specific anti-ICAM-R monoclonal antibodies, individual residues within those domains are changed by oligo-directed site specific mutagenesis to determine their relative effects on monoclonal antibody binding. Based on computer algorithms that predict protein hydropathy and secondary structure (Kyte et at., supra), particular residues that have the potential for antibody interactions are targeted for mutagenesis.

The distribution of ICAM-R protein and the expression of ICAM-R RNA in various cells and cell lines were respectively assayed by FACS analysis and Northern blot hybridization.

A. FACS Analyses of ICAM-R Protein Distribution

In Leukocytic Cell Lines and Normal Leukocytes

FACS analyses carried out as described in Example 10C on leukocyte cell lines using anti-ICAM-R monoclonal antibody 26HIIC-2, anti-ICAM-1 antibody (LB2) and anti-CD18 antibody (TS1/18, ATCC HB203) illustrated that ICAM-R is expressed on a wide variety of in vitro propagated cells lines representative of the major leukocyte lineages: T lymphocytes, B lymphocytes, and myeloid cells. Surface expression of ICAM-R was not detected on the primitive erythroleukemic line, K562. Further, ICAM-R was not expressed detectably by cultured human umbilical vein endothelial cells (HUVECS) either before or after stimulation with tumor necrosis factor which did upregulate expression of ICAM- 1. This pattern of expression is also distinct from that observed for ICAM-2 which is expressed on endothelium. Table 1 below provides the mean fluorescence of each cell sample and the percent positive cells relative to a control in each cell sample (e.g., mean fluorescence of 13/11% positive cells).

FACS Analysis of ICAM-R Distribution

On Human and Macaque Leukocytes

FACS analyses performed as described in Example 10C on normal human and macaque peripheral blood leukocytes showed that the anti-ICAM-R monoclonal antibody 26HIIC2 reacted with the three major human leukocyte lineages: lymphold, monocytoid and granulocytoid. See the final six entries of Table 1. In addition, monoclonal antibodies 26I10E-2 and 46I12H cross-reacted with macaque leukocytes (Table 1 and Example 10E) indicating that these monoclonal antibodies may be useful in monitoring the expression of ICAM-R in disease models executed in this animal.

Human bronchiolar aveolar lavage cells (primarily macrophages) were stained with five anti-ICAM-R antibodies (26H11C-2, 26I8F-2, 26I10E-2, 42D9B, and 43H11C) as described in Example 10 and analyzed by FAGS. None of the antibodies specifically stained these cells. (See Example 14, where the expression of ICAM-R in lung tissue is described.)

C. Northern Blot Analyses of ICAM-R RNA Expression in Leukocytic Cell Lines and HUVECS

RNA was extracted from human leukocyte cell lines and from HUVECS as described in Example 7, and was analyzed by Northern blot hybridization (also as described in Example 7) by probing with either ICAM-R or ICAM-1 cDNA. After phosphorimaging of the initial hybridization, blots were stripped and reanalyzed using a human actin probe. The results of the actin normalized Northerns of ICAM-R and ICAM-1 probed blots are presented in FIG. 6(A through B) as bar graphs. At the RNA level, ICAM-R was expressed in a variety of leukocytic cell types. ICAM-R RNA expression was not necessarily concomitant with the expression of ICAM-1 RNA. For example, unstimulated HUVECS express low levels of ICAM-1 and expression is upregulated following TNF stimulation (FIG. 6B). In contrast, detectable levels of ICAM-R message were not observed in unstimulated or stimulated HUVECS (FIG. 6A).

Immunoprecipitations of detergent solubilized lysates of surface biotinylated human cell lines KG1a, K562 and CEM were performed using the four anti-ICAM-R monoclonal antibodies: 26H11C-2, 26E3D-1, 26I10E-2, and 26I8F-2.

Cell surface proteins on human leukocyte cell lines KG1, K562, and CEM were labelled by reaction with sulfo-NHS-biotin (Pierce Chemical Company, Rockford, Ill.) as follows. For each reaction 0.5-1.times.10.sup.7 cells were washed twice in phosphate buffered saline (PBS), resuspended in 1 ml PBS and 10 .mu.l of 100 mM sulfo-NHS-biotin diluted in PBS was added. Following incubation for 10 minutes at 37.degree. C. the cells were washed once with PBS, and 4 ml of 10 mM Tris pH 8.4, 0.25M sucrose was added and the cells were then incubated for 30 minutes at 4.degree. C. with gentle mixing. The cells were pelleted by centrifugation, the supernatant was aspirated and the pellet was solubilized with 300 .mu.l of 10 mM Tris pH 8, 50 mM NaCl, 1% Triton X-100, 1 mM phenylmethylsulfonyl fluoride, 1 mM EDTA by incubating on ice for 15 minutes. The lysate was clarified by centrifugation and the supernatant was precleared by addition of 25 .mu.l normal mouse serum and incubation for 1 hour at 4.degree. C. This step was followed by the addition of 20 .mu.l of a 50/50 (v/v) solution of protein-A sepharose beads (Sigma) that had been preincubated with 20 .mu.g of affinity purified rabbit anti-mouse Immunoglobulin (Zymed). After incubation for 30 minutes at 4.degree. C., the sepharose beads were removed by centrifugation.

Specific immunoprecipitations were then performed by addition of 20 .mu.l of sepharose beads that had been prearmed by sequential incubation with rabbit anti-mouse immunoglobulin and either anti-ICAM-R or control IgG.sub.1 or IgG.sub.2a monoclonal antibodies. Following overnight incubation at 4.degree. C. with agitation, sepharose beads were pelleted in a microcentrifuge and washed sequentially 2 times with 1 ml 10 mM Hepes pH 7.3, 150 mM NaCl, 1% Triton X-100; lx with 0.1M Tris pH 8, 0.5 M LiCl, 1% beta mercaptoethanol; and 1x with 20 mM Tris pH 7.5, 50 mM NaCl. 0.5% NP-40. Beads were then eluted with 50 .mu.l 150 mM Tris pH 6.8, bromphenol blue, 20% beta mercaptoethanol, 4% SDS and 20% glycerol; boiled for 5 minutes; and pelleted by centrifugation. Thirty-five .mu.l of the resulting eluate was then analyzed by SDS-PAGE (10% acrylamide). After electrophoresis, proteins were electroblotted onto Immobilon-P membranes (Millipore, Bedford, Mass.) and incubated in 2% bovine serum albumin diluted in Tris-buffered saline containing 0.2 % Tween-20 for 20 minutes at 4.degree. C. Blots were then incubated with horseradish peroxidase coupled to streptavidin (Vector) in TBS-Tween at room temperature for 20 minutes. Following 3 rinses in TBS-Tween, ECL western blotting detection reagents (Amersham) were added and chemiluminescent bands were visualized on Kodak X-OMAT-AR film.

FIG. 7(A through B) shows the resulting Western blots. A single specifically precipitated species of 120 kD was observed in immunoprecipitates with monoclonal antibody 26H11C-2 from KG 1 cells, but not from K562 cells (See FIG. 7A).

A 120 kD band was also resolved in immunoprecipitates of the T cell line CEM (FIG. 7B, wherein Lane A was reacted with monoclonal antibody 26H11C-2; Lane B, monoclonal antibody 26I110E-2; Lane C, monoclonal antibody 2618E; Lane D, monoclonal antibody 26E3D-1; and Lane E, a negative control antibody). The size of the ICAM-R species resolved in other immunoprecipitations varied slightly depending on the cellular source. Species ranging from .about.116 kD on some lymphold cells to .about.140 kD on some myeloid cells were observed. Given the predicted size (about 52 kD) of the core peptide based on the nucleotide sequence of the ICAM-R gene, these results imply that ICAM-R is heavily modified post-translationally to yield the mature cell surface form of the protein.

Immunohistologic staining with anti-ICAM-R monoclonal antibodies 26I10E-2, 26E3D-1 and 26H11C-2 and control antibodies was carried out on various human tissues including tonsil, spleen, liver, lung, kidney, heart, digestive tract, skin, synovium, and brain (both normal and multiple sclerosis-affiicted brain tissue). Similar staining patterns were obtained using the different anti-ICAM-R antibodies as well as when using purified anti-ICAM-R monoclona antibody 26E3D or hybridoma supernatant.

Sections (6 .mu.m) of various tissues were layered onto Vectabond (Vector) coated slides and stored at -70.degree. C. (some sections were stored at -20.degree. C.). Prior to use, slides were removed from -70.degree. C. and placed at 55.degree. C. for 5 minutes. Sections were then fixed in cold acetone for 10 minutes and air dried. Sections were blocked in a solution containing 1% BSA, 60% normal human sera, and 6% normal horse sera for 30 minutes at room temperature. Primary antibody directed against ICAM-R, a negative control antibody, anti-ICAM-1 monoclonal antibody or anti-ICAM-2 monoclonal antibody was applied to each section for 1 hour at room temperature. Unbound antibody was washed off by immersing the slides 3 times in 1X PBST for 5 minutes each time. Biotinylated anti-mouse immunoglobulin (Vector) was then applied to each section in the same fashion. ABC-HPO (Avidin-Biotin Complex-HPO) was used to detect the second antibody. A solution of reagent A (9 .mu.l) (Vector) combined with reagent B (9 .mu.l) (Vector) in 1 ml of 1% BSA/PBST was applied to each section for 30 minutes at room temperature. Slides were then washed 3 times in 1X PBST. DAB substrate (3'3 diaminobenzidine-tetrahydrochloride, Sigma) (stock: 600 mg/ml DAB diluted 1:10 in 0.05M Tris Buffer, pH 7.6, with 3% H.sub.2 O.sub.2 added to a final concentration of 1%) was applied to each slide for 8 minutes at room temperature. Slides were washed in water for 5-10 minutes at room temperature and then 1% osmic acid was added (to enhance color development) for one minute at room temperature. Slides were then washed in tap water for 5-10 minutes and counterstained in 1% Nuclear Fast Red (NFR) for 30 seconds at room temperature. Lastly, slides were alcohol dehydrated, treated with Histroclear and mounted with coverslips using histomount.

A selection of results of staining with the monoclonal antibodies is presented in FIG. 8(A through G) as photomicrographs wherein the tissue in 8A, 8B and 8E is human tonsil; in 8C and 8D is human liver; in 8F is brain from a human patient afflicted with multiple sclerosis; and in 8G is normal human brain. Sections shown in 8A, 8C, 8F and 8G were stained with anti-ICAM-R monoclonal antibody 26I10E-2. Sections shown in 8B and 8D were stained with the negative control antibody, while the section shown in 8E was stained with the anti-ICAM-1 antibody. Staining revealed high level expression of ICAM-R in lymphoid tissues such as tonsil (8A). Expression was also detected on tissue leukocytes in other nonlymphoid organs such as the liver wherein Kupfer cells (liver macrophages) were positively stained (8C). Evidence that ICAM-1 and ICAM-R expression are regulated distinctly in vivo is given by the staining pattern observed in tonsil and lymph node: ICAM-1 is strongly expressed on B cells in the germinal centers of secondary follicles and not expressed in primary follicles, whereas ICAM-R is expressed in cells in the primary follicles and not in the germinal centers (8A and 8E). Significantly, ICAM-R expression was also detected on leukocytes infiltrating sites of inflammation. For example, ICAM-R expression was observed on perivascular infiltrating leukocytes in the brain tissue of individuals afflicted with multiple sclerosis (8F). Similar staining was not observed in anatomically equivalent locations of brain tissue from normal individuals (8G). ICAM-R expression was also detected on leukocytes infiltrating synovia of arthfitic joints. Also, whereas expression of ICAM-1 and ICAM-2 was detected on endothelia ligning vessels, ICAM-R was not typically observed on vascular endothelium. Expression of ICAM-R was detected on cells in the aveoli of the lung.

More generally, cells expressing ICAM-R were detected in all normal and pathological tissues. These ICAM-R expressing cells could be identified morphologically as leucocytes and antigen-presenting cells. In non-lymphoid tissues, the morphology of the cells that were labelled with the anti-ICAM-R antibodies was compatible with resident tissue macrophages and antigen-presenting cells.

In contrast to the wide distribution of ICAM-R on different tissues and epithelia, ICAM-2 was expressed almost exclusively in blood vessels on normal and pathological tissues while ICAM-1 was expressed on both blood vessels and leukocytes but mainly in pathological tissues.

In order to determine whether ICAM-R is involved in homotypic cell adhesion, aggregation assays were performed with a panel of cell lines which express ICAM-R including T lymphoblastoid cell lines (SupT1, CEM, Molt 4, Hut 78, Jurkat, SKW3), B lymphoblastoid cells lines (Jijoye, Raji), monocytic cell lines (U937, HL60), a myelogenous cell line (KG-1) and the erythroleukemia cell line K562. To determine the function of the ICAM-R molecule, the cells were incubated with various antibodies before aggregation was assayed. Anti-ICAM-R supernatants produced by hybridomas 26H 11 C-2, 26E3D-1,26I10E-2, and 26I8F-2 were used as well as antibody preparations known to block aggregation through a .beta.2 integrin pathway: TS1/18 (ATCC HB203) specific for the CD18 molecule, the .beta.-subunit of LFA-1; TS 1/22 (ATCC HB202) specific for the CD 11 a molecule, the .alpha.-chain of LFA-1; and LM2/1 (ATCC HB204) specific for the CD11b molecule, the .alpha.-subunit of MAC-1. Purified anti-ICAM-1 antibody and hybridoma supernatant directed against the .alpha.-chain of the VLA-4 molecule (hybridoma clone 163H, Michael Longenecker, Alberta, Canada) were used as controls.

Aggregation assays were done in duplicate, with and without addition of phorbol 12-myristate 13-acetate (PMA) (50 ng/ml). 3.times.10.sup.5 cells in RPMI 1640 medium with 10% fetal calf ierum were added in a flat-bottomed 96-well microtest plate. When one antibody was tested in an experiment, 50 .mu.l of purified antibody or hybridoma supernatant were added to the wells (PMA was added at the same time to selected wells). When two antibodies were tested in the same experiment, the antibodies were added sequentially to the cells at room temperature and incubated for 30 minutes each (incubation for 15 minutes at 37.degree. C. produced the same results), and then the cells were incubated at 37.degree. C. Incubating the antibodies with the cells before addition of PMA or at the same time as the PMA did not cause any significant change in the aggregation results. After incubation with the antibody or antibodies, cells were uniformly resuspended and then incubated at 37.degree. C. for 4 to 24 hours. Aggregation scoring was done with an inverted microscope. In each experiment, the efficacy of the PMA stimulation was checked in parallel by stimulating Raji cells with an equal amount of PMA and determining the amount of aggregation blockable by monoclonal antibodies to CD18, CD11a, and ICAM-1 molecules.

Table 2 below, sets out the results of one representative aggregation experiment wherein PMA was added. Aggregation scores are reported on a range from 0 to 5, wherein 0 indicates that no cells were in clusters; 1 indicates that less than 10% of the cells were in clusters; 2 indicates that 10 to 50% cells were aggregated; 3 indicates that 50 to 100% cells were in loose clusters; and 4 indicates that almost 100% of the cells were in compact aggregates.

Interestingly, treatment with three of the antibodies specific for ICAM-R (26H11C-2, 26E3D-1 and 26I8F-2) stimulated homotypic cell-cell aggregation (dam for 26E3D-1 and 26I8F-2 not shown). Stimulation occurred in both the presence and absence of co-stimulatory agents such as a phorbol ester (PMA). The fourth anti-ICAM-R monoclonal antibody (26I10E-2) did not stimulate cell aggregation but blocked the aggregation stimulated by the other anti-ICAM-R antibodies. At least a portion of the aggregation stimulated by anti-ICAM-R antibodies in PMA treated cells was blocked by pretreatment with monoclonal antibodies against CD18 or CD11a indicating that one or more leukointegrins may participate in this type of adhesion.

To confirm that aggregation was induced by the anti-ICAM-R antibodies 26HllC-2, 26E3D-1 and 26I8F-2, the aggregation assays were performed using both the whole immunoglobulin (26E3D-Ig) and Fab' fragments (26E3D-Fab') purified from the same anti-ICAMR monoclonal antibody (26E3D). See Johnstone et al., p. 52 in Blackwell, Immunochemistry in Practice, Oxford Press (1982) for Fab' fragment production. The assays were performed with SKW3 T cells as described above using 26E3D-Ig and 26E3D-Fab' at a concentration of 1 .mu.g/ml. Supernatants of anti-CD 18 and anti-ICAM-R (26E3D-sup and 26I10E-sup) hybridomas were used as controls. After four hours, the same increase in cell aggregation was found for whole immunoglobulin as for the Fab' fragments or the 26E3D supernatant (See Table 3 below).

No increase in aggregation was found with anti-CD 18 supernatant or anti-ICAM-R 26I10E supernalant. These results rule out the trivial explanation that enhanced aggregation was due to antibody mediated cross-linking of the cells. The engagement of ICAM-R protein, in this case by selected antibodies, may transduce a signal which alters the bound cells' adhesive potential.

The process of activation and proliferation of cells of the immune system is marked by a continuum of cellular events. The upregulation of certain cell surface molecules (e.g., CD69 and the transferrin receptor) is an early marker of cell activation. Similarly, cell agglutination occurs early in the process of activation. The upregulation of the IL-2 receptor occurs at an intermediate to late stage and cell proliferation is a late event. Two types of experiments were performed to determine the extent to which ICAM-R is involved in immune cell activation/proliferation. In the first type, the capacity of ICAM-R presented on the surface of a transfected cell to stimulate proliferation of lymphocytes was examined. In the second type, antibodies of the invention recognizing distinct epitopes on ICAM-R were used as probes to engage the external domain of ICAM-R to determine the effects of antibody binding either alone or in combination with other stimuli on lymphocyte activation and proliferation.

Mouse L cells transfected with either ICAM-R cDNA or ICAM-1 cDNA (Example 7) were assayed for their ability to stimulate human peripheral blood mononuclear cell (PBMC) proliferation as measured by .sup.3 H-thymidine incorporation assays which indicate changes in the rate of DNA replication. Nontransfected mouse L cells or transfected L cells were obtained by trypsinization from tissue culture flasks and washed in RPMI-1640 containing 10% fetal bovine serum. Five.times.10.sup.4 L cells in 120 .mu.l tissue culture media (RPMI-1640 with 10% fetal bovine serum) were added to individual wells of a sterile 96-well flat bottom tissue culture plate and the plates were incubated for 24-36 hours at 37.degree. C. in a 5% CO.sub.2 incubator. The media was then removed in a sterile manner and 2.times.10.sup.5 freshly isolated PBMC in a total volume of 200 .mu.l tissue culture media were added to individual wells containing either transfected or non-transfected mouse L cells. PBMC were also added to control wells containing no L cells. The PBMC were previously isolated from healthy donors by centrifugation on Histopaque gradients (Sigma). Fresh peripheral blood was mixed with an equal volume of PBS, layered onto Histopaque and centrifuged at 450 g for 20 minutes with no brake applied. PBMC-containing fractions were collected, washed in PBS and adjusted to 1.times.10.sup.6 viable cells/ml prior to addition into wells. The tissue culture plates were then incubated for a total of 4 days either in the presence or absence of PMA at a final concentration of 5 ng/ml. Lymphocyte proliferation was then assessed after the addition of 1 uCi .sup.3 H-thymidine (NEN, Boston, Mass.) to individual wells for the last 18-24 hours of culture. All cultures were then terminated by harvesting the contents of each well onto glass fiber filter strips using a PHD model plate harvester (Costar, Cambridge, Mass.). Individual filter mats were then placed in 3 ml Ecolume scintillation cocktail (ICN Biomedicals, Costa Mesa, Calif.) and counted using a beta-scintillation counter. LTK cells expressing ICAM-R stimulated proliferation of PBMC (as indicated by increased DNA replication) in comparison to nontransfected control LTK cells or in the absence of any stimulus. LTK cells expressing ICAM- 1 induced the proliferation of PBMC to approximately an equal extent. By binding to its receptor(s) on PBMC, ICAM-R transmits an intercellular signal to the PBMC which in this cellular context results in cell proliferation.

Anti-ICAM-R antibodies of the invention were also tested to determine their effect on immune cell activation and proliferation.

First, anti-ICAM-R monoclonal antibodies were preliminarily tested for the ability to affect early events in cell activation including upregulation of the cell surface molecules CD69, the transferrin receptor and the IL-2 receptor on the target cells as measured by flow cytometry analysis. Unstimulated lymphocytes express low levels of the transfertin and IL-2 receptors. Expression of the receptors increases dramatically when lymphocytes are activated.

Anti-ICAM-R monoclonal antibodies 26E3D-1 and 26I10E-2 were each tested for the ability to induce PMBC activation in the absence of other inducing stimuli. Monoclonal antibodies 26E3D-1 or 26I10E-2 (or control monoclonal antibodies) were added (10 .mu.g/well in PBS) to individual wells of a 96-well flat bottom tissue culture plate and incubated for 3 hours at 37.degree. C. in a 5 % CO.sub.2 incubator. The plates were washed 3 times with sterile PBS to remove unbound antibody and freshly isolated PBMC were immediately added to a final concentration of 2.times.10.sup.5 cells/well in a volume of 200 .mu.l media. The plates were then incubated for either 1 or 3 days at which time the cells cultured in the presence of different antibodies were removed, washed as described above in PBS containing 0.01% sodium azide and 1% BSA (FACS buffer) and stained with either FITC (Becton Dickinson)--conjugated negative control antibodies or a panel of FITC-conjugated anti-CD69, anti-transferrin receptor and anti-IL-2 receptor antibodies. Results were obtained by FACScan analysis. Expression of CD69 and the transferrin receptor but not the IL-2 receptor increased after 1 day when PBMC were cultured on immobilized (i.e., cross-linked) antibody 26E3D-1 but not when cultured on immobilized antibody 26I10-2. PBMC incubated for 3 days on immobilized 26E3D-1 or 26I10E-2 had increased levels of cell surface expression of both the transferrin receptor and IL-2 receptor but not CD69. However, while increased expression of these lymphocyte activation markers was observed after 1 and 3 days this increased expression was unaccompanied by increased cell size. These results suggest that the anti-ICAM-R monoclonals 26E3D-1 and 26I10E-2 are able to directly induce early events in PMBC activation in the absence of additional exogenous stimuli but this activation does not result in blast transformation and associated increases in cell size.

Anti-ICAM-R monoclonal antibodies were also tested for their ability to alter early events in PMBC activation stimulated by immobilized anti-CD3 monoclonal antibody G19 [Ledbetter et at., J. Immunol., 135(4): 2331-2336 (1985)]. Monoclonal antibody G19 binds to the CD3 complex on T cells (the T cell receptor) and activates T cells. When PBMC were cultured in wells precoated with anti-CD3 antibody (0.05 .mu.g/well) alone, only CD69 expression was elevated after one day. After three days, cell surface expression of CD69, the transferrin receptor and the IL-2 receptor was dramatically elevated. Upregulation of these activation markers was correlated with increases in cell size.

Ten .mu.g of anti-ICAM-R monoclonal antibodies 26E3D or 26I10E (or control monoclonal antibodies to HLA Class I; Serotec, Oxford, England) were added per well of 96-well flat bottom tissue culture plates either in the presence or absence of anti-CD3 antibody initially added at 0.025 .mu.g/well and washed to remove unbound antibody. Freshly obtained PBMC were immediately added (2.times.10.sup.5 cells/well). The cells were then incubated for a total of either 16 hours or 3 days at which time the cells were removed and washed 2 times in ice cold FACS buffer. Two.times.10.sup.5 cells were then resuspended in 50 .mu.l ice cold FACS buffer, and 5 .mu.l of FITC-conjugated anti-CD69, anti-transferfin receptor, anti-IL-2 receptor antibody or anti-FITC conjugated control Ig was added. The cells were incubated at 4.degree. C. for 30 minutes and then washed 2 times in 0.5 ml ice cold FACS buffer. After the final wash the cells were resuspended in 0.5 ml FACS buffer and fluorescence determined by FACScan analysis. When PBMC were cultured for 3 days on 0.025 .mu.g/well immobilized anti-CD3 either alone or in the presence of immobilized antibody to HLA Class I, expression of the transferfin and IL-2 receptors is not upregulated at this low does of immobilized anti-CD3. In contrast, culturing of PBMC in the presence of 0.025 .mu.g/well immunobilized anti-CD3 and either immobilized anti-ICAM-R antibodies 26E3D-1 or 26I10E-2 antibodies resulted in significant upregulation of both the transferfin and IL-2 receptors. The effect was more pronounced with antibody 26E3D-1. Similar results were also obtained after 16 hours in culture. Low dose anti-CD3 in the presence of immobilized 26E3D-1 or 26I10E-2 antibody induced expression of CD69, but not the transferrin receptor, while low dose anti-CD3 (0.025 .mu.g/well) in the presence of immobilized anti-HLA-I did not induce increased expression of either CD69 or the transferrin receptor. These results indicate that these anti-ICAM-R antibodies may serve as costimulatory molecules in early immune cell activation events.

Second, preliminary experiments were performed to determine if anti-ICAM-R monoclonal antibodies could affect the late event of cell proliferation again as measured by .sup.3 H-thymidine incorporation assays.

Monoclonal antibodies to ICAM-R were tested for their ability to directly stimulate PMBC proliferation in either the presence or absence of human recombinant IL-2 which potentiates but does not induce cell proliferation. Ten .mu.g of ICAM-R monoclonal antibodies 26E3D-1 or 26I10E-2 (or control IgG.sub.1 and IgG.sub.2) antibodies) in PBS were added per well of 96-well flat bottom tissue culture plates and the plates were incubated for 3-4 hours at 37.degree. C. in a 5% CO.sub.2 incubator. After incubation, each well was rinsed 3 times with PBS and freshly obtained PBL were added to a final concentration of 2.times.10.sup.5 cells/well in a volume of 200 .mu.l. Ten units/ml human recombinant IL-2 (Genzyme, Boston, Mass.) was then added to selected wells. The plates were incubated for a total of 3 days at 37.degree. C. in a 5 % CO.sub.2 incubator. .sup.3 H-thymidine incorporation by the PMBC was determined as described earlier in this example. The anti-ICAM-R antibodies 26E3D and 26I10E did not induce PMBC proliferation even in the presence of rIL2. Positive controls for lymphocyte proliferation included immobilized anti-CD3 and anti-LFA-1 (60.3) [Beatty et al., J. lmmunol., 131:2913-2918 (1983)] monclonal antibodies. These results indicate that while the immobilized anti-ICAM-R antibodies stimulate expression of activation markers such as CD69, etc., by themselves they do not directly stimulate the entry of large numbers of PBMC into S phase of the cell cycle.

Because anti-ICAM-R antibodies with anti-CD3 antibodies costimulated early PBMC activation events, anti-ICAM-R antibodies were tested for the ability to costimulate lymphocyte proliferation induced by immobilized anti-CD3 antibody. PBMC from normal donors were obtained and adjusted to a concentration of 1.times.10.sup.6 viable cells/ml in tissue culture medium. Individual wells of a 96-well flat bottom tissue culture plate were precoated with 0.001 .mu.g anti-CD3 monoclonal antibody G19/well. The plates were incubated for 3 hours at 37.degree. C. in a 5% CO.sub.2 incubator and unbound antibody was removed by rinsing the wells 3 times in PBS. After the final PBS wash, monoclonal antibodies to ICAM-R (26I10E-2 or 26E3D-1) or control antibodies were immediately added to a final concentration of 10 .mu.g/well. The plates were then reincubated for an additional 3 hours at 37.degree. C. The wells were again washed three times with PBS to remove unbound antibody and freshly isolated PBMC were immediately added to the wells (2.times.10.sup.5 cells in a volume of 200 .mu.l/well). The plates were then incubated for 3 days. Lymphocyte proliferation was measured by .sup.3 H-thymidine incorporation by the PMBC. Immobilized anti-ICAM-R monoclonal antibody 26E3D-1 increased the PBMC cell response to anti-CD3. Effects of the immobilized anti-ICAM-R antibodies on PBMC aggregation (an earlier event than PBMC proliferation) induced by anti-CD3 monoclonal antibody were also examined in this experiment. Anti-CD3 stimulated aggregation was inhibited almost 100% by antibody 26E3D-1, but was unaffected by immobilized 26I10E-2 and minimally inhibited by antibodies 26H11C-2 and 26I8F-2.

The results of the assays for the ability of anti-ICAM-R antibodies to affect the proliferation of cells on which ICAM-R is expressed indicate that binding of the antibodies of the invention to ICAM-R transmits an intracellular signal to the PBMC which modulates cell proliferation.

Finally, preliminary experiments were also performed to determine if lCAM-R is involved in early events of cell-cell contact dependent T-lymphocyte activation.

Superantigen-induced proliferation and aggregation of human peripheral blood lymphocytes (PBL) were assessed in the presence of the ICAM-R specific antibodies of the invention. The effect of soluble and plate-bound 26E3D-1, 26I10E-2 and anti-HLA class I control B-H9 (Serotee) antibodies on proliferation and cell aggregation was measured three days after stimulation of human PBL with Staphylococcus Enterotoxin A (SEA) (Toxin Technology, Sarasota, Fla.). Plate-bound antibodies were prepared on the day of culture as follows. Purified antibody (10 .mu.g in 0.1 ml PBS) was added to individual wells of 96-well flat bottom plates. Plates were then incubated for 4 hours at 37.degree. C. Following incubation, unbound antibody was removed by aspirating each well and rinsing 4 times with fresh PBS. Human PBL were isolated from healthy donors on Histopaque (Sigma) gradients. Fresh peripheral blood was mixed with an equal volume of phosphate buffered saline (PBS), layered onto Histopaque and centrifuged at 450 x g for 20 minutes with no brake applied. Lymphocyte fractions were collected and washed twice by adding a fresh volume of RPMI supplemented with 10% fetal bovine serum and centrifuging at 200 x g for 8 minutes. PBL were suspended in a final volume of 10 ml of RPMI-FBS. Viable PBL were counted using the method of vital dye exclusion. Twenty .mu.l of a dilution of cell suspension in 0.4% trypan blue stain (Gibco) was added to a hemacytometer chamber and dye-excluding cells were then counted using an inverted microscope. Two-hundred thousand viable PBL were then added to 96-well flat-bottom tissue culture plates containing 10 .mu.g soluble or plate-bound 26E3D-1, 26I10E-2 or B-H9 antibody. Finally, each culture was stimulated with SEA (1000 or 10 pg/ml in triplicate) and cultured at 37.degree. C. in 5 % CO.sub.2. After 3 days, proliferation was measured as .sup.3 H-thymidine incorporation and aggregation was measured using an inverted microscope.

Treatment with soluble 26E3D-1 or 26I10E-2 anti-ICAM-R antibody failed to alter proliferation of PBL in comparison to soluble B-H9 antibody. Plate-bound (i.e., cross-linked) antibody 26E3D-1, however, significantly inhibited proliferation at both doses of SEA (p<0.05) while antibody 26I10E-2 only inhibited proliferation at the lower dose of SEA. Plate-bound 26E3D-1 also significantly inhibited cell aggregation at both SEA concentrations in comparison to plate-bound B-H9 and 26I10E-2 antibodies. Inhibition of aggregation by plate-bound 26E3D-1 was almost complete. In contrast, plate-bound 26I10E-2 antibody only slightly inhibited aggregation in comparison to plate-bound B-H9. Aggregation of PBL induced by SEA was not affected by soluble anti-ICAM-R antibodies 26E3D-1 or 26I10E-2 in comparison to soluble B-H9 antibody. The minimum time required for plate-bound anti-ICAM-R to inhibit SEA-induced proliferation was also determined. PBL were pre-incubated on plate-bound 26I10E-2, 26E3D-1 or isotype-matched anti-HLA-I control antibodies B-H9 (IgG.sub.1) and IOT2 (IgG.sub.2) (AMAC, Inc., Westbrook, Me.) with or without SEA (10 pg/ml) for 3, 5, and 7 hours. PBL were then transferred to clean wells and cultured in the presence of SEA (10 pg/ml) for 3 days. The results of .sup.3 H-thymidine incorporation (proliferation) assays are summarized in FIG. 9. Immobilized 26E3D-1 antibody and, to a lesser extent 26I10E-2 antibody, significantly reduced proliferation in comparison to isotype-matched controls after only 3 hours of incubation. This result indicates that binding of plate-bound 26E3D-1 or 26I10E-2 to ICAM-R transmits an intracellular signal capable of inhibiting proliferation after cells have been removed from the immobilized antibodies.

Monoclonal antibodies to ICAM-R were also tested for the ability to alter lymphocyte proliferation (as measured by .sup.3 H-thymidine) in response to alloantigenic irradiated stimulator cells. Ten .mu.g of monoclonal antibodies to either ICAM-R (26E3D-1 or 26I10E-2) ICAM-1 (LB2), ICAM-2 (IC2/2, Bender) or control anti-CD2 (TS2/9) antibodies in 100 .mu.l PBS were added to individual wells of 96-well flat bottom tissue culture plates and the plates were incubated for 3-4 hours at 37.degree. C. The wells were then rinsed 3 times with 200 .mu.l PBS to remove unbound antibody immediately before addition of responder T cells. Isotype control mouse IgG.sub.2 a and IgG.sub.1 antibodies (Sigma) were added to control wells. PBL were obtained by Histopaque centrifugation as described above and T lymphocytes were isolated from the PBL after depletion of adherent cells by incubation on plastic tissue culture flasks for 2 hours at 37.degree. C. and negative immunomagnetic selection using magnetic beads coated with anti-human IgM. The resulting cells were enriched >90% for CD2 positive cells as determined by FACScan analysis and were adjusted to 1.times.10.sup.6 cells/ml in tissue culture media. Cells (2.times.10.sup.5) in a volume of 200 .mu.l were added to individual wells of the 96-well tissue culture plates coated with antibodies. PBL were concurrently isolated from a second unrelated normal human donor by Histopaque centrifugation and irradiated at 1500R by exposure to a gamma emitting cesium source. The irradiated stimulator PBL were then added at a concentration of 2.times.10.sup.5 in 50 .mu.l to individual wells which contained nonirradiated T cells and the plates were incubated for a total of 6 days at 37.degree. C. in 5% CO.sub.2 incubator. Lymphocyte activation was then assessed after the addition of 1 .mu.Ci .sup.3 H-thymidine to individual wells for the last 18-24 hours of culture.

The results are shown in FIG. 10 and are expressed either as the percent enhancement or percent inhibition of the response observed in the presence of plate-bound antibody relative to the response observed in the presence of plate-bound isotype identical control antibody. As shown in FIG. 10, antibodies to either ICAM-1 or ICAM-2 significantly inhibited T cell responses to irradiated alloantigenic stimulator cells by 60-80% when compared to control antibodies. In contrast, anti-CD2 antibody did not alter T cell responses. The two anti-ICAM-R monoclonal antibodies differed in their ability to inhibit T cell proliferation in this assay. For example, antibody 26E3D-1 blocked alloantigen-induced T cell responses to the same degree as antibodies to either ICAM-1 or ICAM-2, while 26I10E-2 enhanced the T cell response to alloantigen. Anti-ICAM-R antibodies 26I8F-2 and 26H11C-2 blocked T cell responses to a much lower degree than antibody 26E3D- 1. The ability of monoclonal antibody 26E3D-1 to block alloantigen induced lymphocyte activation was dependent upon immobilization of the antibody). Published observations [Dustin et al., Nature, 341:619 (1989)] indicate that enhanced signalling is optimally achieved by stimulatory monoclonal antibodies which are not in soluble form and are either conjugated to Sepharose or immobilized to plastic.

One inference from the aforementioned examples that antibodies specific for ICAM-R modulate the response of lymphocytes to a variety of stimuli (e.g., SEA and allogeneic cells) is that engagement of ICAM-R by either its natural counter-receptors or by antibodies of the invention transduces a signal to the ICAM-R expressing cell. ICAM-R specific signalling events are likely to involve the interaction of the cytoplasmic domain of ICAM-R with cellular enzymatic components (e.g., kinases, phosphatases) of one or more second messenger pathways and/or with cytoskeletal components in a pattern unique to ICAM-R.

Preliminary experiments are consistent with this concept and with the idea that ICAM-R is distinct from ICAM-1 in its linkages with second messenger systems. Extracts from unstimulated Raji cells were prepared, fractionated and assayed for kinase activity as follows. Seven.times.10.sup.7 cells were washed once in PBS and lysed in buffer containing 20 mM Tris pH 7.5, 0.5 mM EDTA, 1% Triton X-100 (Pierce), 10 .mu.g/ml pepstalin and leupeptin (Boehringer), 2 mM PMSF for 1 hour on ice. Lysates were pelleted in a refrigerated microfuge at 14,000 rpm for 15 minutes and the resulting supernatant was applied to a DEAE sephacel column (Pharmacia) equilibrated in 20mM Tris pH 7.5, 0.5 mM EDTA (Buffer A). The column was run at a rate of 0.25 ml/minute and developed with a gradient of 0 to 0.35M NaCl in buffer A over 60 minutes. In these initial experiments, only those fractions enriched in protein kinase C (PKC) activity (as determined using an Amersham assay kit and following manufacturers instructions) were examined. Fractions enriched in PKC activity were pooled and used as a source of kinase(s) to test for differential phosphorylation of synthetic peptides of the complete cytoplasmic domains of ICAM-1, ICAM-2 and ICAM-R (amino acids 481 to 518 of SEQ ID NO: 1). Assays were performed according to manufacture's instructions with peptides at 75 uM final concentration. Ten ul of the reaction mixture was boiled in 30 ul Laemmli sample buffer and resolved on a 12.5 % SDS-PAGE gel. Following a 1.5 hour exposure of the gel on X-ray film phosphorylation of ICAM-R and ICAM-2 but not ICAM-1 was detected. Whether the phosphorylation was due to PKC or another co-fractionated kinase was not determined.

Preliminary experiments also indicate that the cytoplasmic domain of ICAM-R differentially associates with cytoskeletal components. Binding of the non-competing monoclonal antibodies 26E3D and 26I10E to ICAM-R was examined to assess the potential influence of each antibody on the association of lymphocyte ICAM-R with the cytoskeleton. The antibodies may mimic distinct natural ICAM-R ligands which employ ICAM-R as a cell surface receptor through which regulated cellular responses may be elicited.

Other investigators have previously observed that numerous human T lymphocyte surface antigens which occur as cell surface transmembrane glycoproteins can be induced to associate with the cytoskeleton if cell surface-bound antibody specific for these antigens is crosslinked with secondary antibodies [Geppert et al., J. Immunol., 146:3298 (1990)]. Many of these cell surface molecules are defined components of lymphocyte adhesion and/or activation pathways. The phenomenon of inducible association with the cytoskeleton is operationally defined as the resistance of cell-surface immune complexes to detergent extraction under defined conditions. Inducible detergent resistance does not require metabolic energy and can be observed in cells maintained at 0.degree.-4.degree. C. throughout the experiment.

Experiments were conducted using freshly prepared human PBL or the human T lymphoblastoid cell line CEM-CCRF (ATCC CCL119). Briefly, freshly drawn human blood from healthy volunteer donors was diluted 1:1 with PBS and layered onto Sigma HistoPaque density separation medium. The gradients were centrifuged for 30 minutes at 1500 rpm (600 x g) and the mononuclear cell fraction at the interphase was collected and washed three times with PBS. The cell pellet was resuspended in complete RPMI-1640 medium (Gibco, supplemented with L-glutamine, penicillin/streptomycin, sodium pyruvate, 2-mercaptoethanol, and 10% FBS) and plated onto tissue culture-treated petri dishes for adherent cell depletion. Plates were incubated 1-2 hours at 37.degree. C., 5% CO.sub.2 after which nonadherent PBL were harvested and washed twice with ice-cold PBS. Conjugation of monoclonal antibodies to fluorescein using fluorescein isothiocyanate (FITC) was performed according to published procedures [see, e.g., Goding, J. Immunol. Meth., 13:215 (1976)] and, in brief, involves incubation of purified antibody with an excess of FITC (Sigma) in 0.1M bicarbonate buffer pH 8.1 for 90 minutes at 37.degree. C. followed by exhaustive dialysis against PBS to remove unreacted FITC.

PBL or washed CEM cell suspensions (1.times.10.sup.6 cells) were dispensed into Falcon 12.times.75 mm tubes in ice-cold PBS-5% FBS, pelleted, and resuspended in 50 .mu.l of FITC-conjugated anti-ICAM-R monoclonal antibody 26E3D-1 or 26I10E-2 adjusted to saturating concentration in the same buffer. Antibody binding was permitted to proceed for 30 minutes on ice, afterwhich unbound antibody was removed by pelleting cells which had first been resuspended in 1 ml of PBS-5% FBS through an underlaid cushion (0.7 ml) of neat (undiluted) FBS.

For groups stained with FITC-conjugated monoclonal antibody only, the 1 ml suspension was divided into two equal parts, each of which was separately underlaid with FBS, centrifuged, and the supernatant removed by aspiration. Cell pellets were then resuspended in 200 ul of control buffer (13 mM Tris pH 8.0, 150 mM NaCl, 2 mM MgCl.sub.2, 2 mM EGTA, 2% FBS, 2.5 ug/ml aprotinin, 1 mM PMSF, 10 mM iodoacetamide) or detergent buffer [0.5% NP-40 (v/v) CLIS Biochemical, Cleveland, Ohio) in control buffer] and held for 20 minutes at room temperature, or overnight at 4.degree. C., prior to FACS analysis. For groups in which cell surface-bound monoclonal antibody was crosslinked with secondary antibodies, following the first antibody staining step, washed cell pellets were resuspended in 50 ul of FITC-goat anti-mouse IgG (Sigma, St. Louis, Mo.) diluted 1:100 in PBS-5 % FCS and incubated for 30 minutes on ice. The cells were then resuspended, divided into two tubes as described above, pelleted, and buffer-treated in the presence or absence of detergent. FACS analysis was then performed on the cells.

Results (see FIG. 11) obtained for CEM cells were similar to those seen with PBL. ICAM-R association with the cytoskeleton as assessed by the detergent resistance assay was negligible when FITC-conjugated 26I10E-2 or 26E3D-1 antibodies alone were permitted to bind to cell surface ICAM-R. However, when cell surface-bound 26I10E antibody was crosslinked with secondary antibodies, a modest increase in detergent resistance was detected. If secondary antibodies were used to crosslink cell surface-bound 26E3D-1, which recognizes a distinct ICAM-R epitope from that seen by 26I10E-2, a much greater (approximately 2-fold in PBL and 2-3 fold in CEM) increase in detergent resistance was reproducibly observed. Interaction of ICAM-R ligands with different structural regions of ICAM-R thus appears to differentially influence association of ICAM-R with the cytoskeleton.

The foregoing illustrative examples relate to presently preferred embodiments of the invention and numerous modifications and variations thereof will be expected to occur to those skilled in the art.

Clearly, polynucleotides (e.g., DNA and RNA) encoding ICAM-R are useful not only in securing expression of ICAM-R and variant polypeptides; they may readily be employed to identify cells (especially cells involved in immunological processes) which express ICAM-R in a normal or activated state. Typical detection assays involving ICAM-R DNA include Northern blot hybridization, RNAse protection, and in situ hybridization cytological assays wherein the DNA or RNA (in suitably labelled, detectable form) hybridizes to RNA in the sample. ICAM-R encoding DNA (especially DNA encoding the first, fourth and fifth domains which have less hornology to DNAs encoding ICAM-1 and ICAM-2 than the DNAs encoding domains 2 and 3) is expected to be useful in isolating genomic DNA encoding ICAM-R including genomic DNA specifying endogenous expression control DNA sequences for ICAM-R DNA. As previously noted, knowledge of polynucleotide sequences encoding ICAM-R and/or controlling expression of ICAM-R makes available a variety of antisense polynucleotides useful in regulating expression of ICAM-R.

The present invention makes available the production of ICAM-R polypeptides and variants thereof, especially including soluble fragments thereof, such as fragments comprising one or more of the five immunoglobulin-like domains of ICAM-R in glycosylated, non-glycosylated, or de-glycosylated forms. Pharmaceutical compositions including the protein products of the invention have therapeutic potential in the modulation of immune cell activation/proliferation, e.g., as competitive inhibitors or stimulatory agents of intercellular and intracellular ligand/receptor binding reactions involving ICAM-R. Such therapeutic potential is especially projected for "immunoadhesin" type recombinant hybrid fusion proteins containing, at their amino terminal, one or more domains of ICAM-R and, at their carboxy terminal, at least one constant domain of an immunoglobulin. Such hybrid fusion proteins are likely to be available in the form of homodimers wherein the Ig portion provides for longer serum half life and the ICAM-R portion has greater affinity for the ICAM-R binding partner than ICAM-R itself. Other multimeric forms of ICAM-R which may have enhanced avidity are also projected to have therapeutic potential.

Antibody substances and binding proteins, especially monospecific antibodies including monoclonal and polyclonal antibodies, are made readily available by the present invention through the use of immunogens comprising cells naturally expressing ICAM-R, recombinant host cells producing polypeptide products of the invention, the ICAM-R polypeptide products themselves, and polypeptide products of the invention bound to an ICAM-R specific antibody that stimulates cell-cell aggregation (i.e., polypeptide products that may be in a "high affinity" binding conformation). Such antibodies and other ICAM-R specific binding proteins can be employed for immunopurification of ICAM-R and variants and in pharmaceutical compositions for therapies premised on blocking and/or stimulating the ligand/receptor binding of ICAM-R and soluble fragments thereof. For use in pharmaceutical compositions, ICAM-R specific antibody and anti-idiotypic antibody substances may be humanized (e.g., CDR-grafted) by recombinant techniques well-known in the art. Antibodies specific for distinct regions of ICAM-R may be employed in ELISA systems involving immunological "sandwiches" for monitoring inflammatory processes characterized by increases in amounts of soluble ICAM-R polypeptides in body fluids such as serum.

Inflammatory conditions which may be treated or monitored with ICAM-R related products include conditions resulting from a response of the non-specific immune system in a mammal (e.g., adult respiratory distress syndrome, multiple organ injury syndrome secondary to septicemia, multiple organ injury syndrome secondary to trauma, reperfusion injury of tissue, acute glomerulonephritis, reactive arthritis, dermatosis with acute inflammatory components, stroke, thermal injury, hemodialysis, leukapheresis, ulcerative colitis, Crohn's disease, necrotizing enterocolitis, granulocyte transfusion associated syndrome, and cytokine-induced toxicity) and conditions resulting from a response of the specific immune system in a mammal (e.g., psoriasis, organ/tissue transplant rejection and autoimmune diseases including Raynaud's syndrome, autoimmune thyroidiris, EAE, multiple sclerosis, rheumatoid arthritis and lupus erythematosus). ICAM-R products of the invention may also be useful in monitoring and treating asthma, tumor growth and/or metastasis, and viral infection (e.g., HIV infection).

Thus only such limitations as appear in the appended claims should be placed upon the scope of the present invention.