OX2 RECEPTOR HOMOLOGS

Abstract: Nucleic acids encoding mammalian, e.g., primate, receptors of OX2, purified proteins and fragments thereof. Antibodies, both polyclonal and monoclonal, are also provided. Method of using the compositions for both diagnostic and therapeutic utilities are described.

Description: OX2 RECEPTOR HOMOLOGS FIELD OF THE INVENTION The present invention relates to compositions and methods for affecting mammalian physiology, including immune system function. In particular, it provides reagents or methods which may regulate development and/or the immune system. Diagnostic and therapeutic uses of these materials are also described. BACKGROUND OF THE INVENTION The 0X2 antigen (0X2) is a cell surface protein identified on a variety of cells including thymocytes, B lymphocytes, activated T lymphocytes, neurons, endothelial cells, and follicular dendritic cells. Barclay (1981) Immunology 44:727- 736. Sequence analysis indicates that it is a transmembrane protein containing two extracellular immunoglobulin-like (Ig- like) domains and a short cytoplasmic domain. Clark, et al. (1985) EMBO J. 4:113-118. This domain organization is common and found in many different leukocyte surface proteins. Barclay, et al. (1997) Leucocyte Antigens Factsbook (2d. ed.) Academic Press, London. These types of proteins often interact with other proteins on the surfaces of other cells, also having Ig-like domains . The distribution of the 0X2 antigen is consistent with a hypothesis that 0X2 relays a signal through a binding partner, e.g., the 0X2 receptor (0X2R) , to cells within the leukocyte lineage including macrophages, which express the receptor (Preston, et al . (1997) Eur. J. Immunol. 27:1911-1918) and possibly other cells of the monocyte-macrophage lineage. Also, the 0X2 has been implicated in regulation of various functions of macrophages. In this scenario, for instance, expression of 0X2 on neurons could establish a direct means of communication to the resident macrophages of the brain called microglia that might express OX2R, since they originate from the monocyte-macrophage lineage. Perry and Gordon (1988) Trends Neurosci. 11:273-277. Generally, defective or exaggerated activation of macrophages contributes to pathogenesis of a wide range of immunological and other diseases. See, e.g., McGee, et al . (eds. 1992) Oxford Textbook of Pathology Oxford University Press, Oxford; Lewis and McGee (eds. 1992) The Macrophage IRL Press, Oxford; and Bock and Goode (eds. 1997) The Molecular Basis of Cellular Defence Mechanisms Wiley & Sons. Also, identification of the 0X2 interacting proteins, e.g., the OX2R for the 0X2 antigen, is difficult because the affinities of the interactions are often very low. This means that the binding of recombinant forms of cell surface proteins, e.g., 0X2, to their binding partners, the interacting proteins, e.g., OX2R, is insufficiently stable to allow detection by normal methods. Thus, the interaction between CD48 and CD2, of which both partners contain two Ig-like domains in their extracellular regions, has a half-life of a fraction of a second. See Van der Merwe, et al. (1993) Biochem. Soc. Trans. 21:340S; and Van der Merwe and Barclay (1994) Trends Biochem. Sci. 19:354-358. Recombinant forms of cell surface proteins such as 0X2 can be made multivalent by a number of methods and used to detect novel proteins. An 0X2 has been engineered to include a tag of two Ig-like domains from CD4. The recombinant soluble proteins are expressed by conventional expression methods in eukaryotic cells. In an earlier study, an interaction was observed between the multivalent recombinant 0X2 protein on fluorescent beads and mouse macrophages. Preston, et al. (1997) Eur. J. Immunol. 27:1911-1918. Despite the above, attempts to identify 0X2R on mouse macrophages through use of a blocking antibody 0X89 were not successful. Preston, et al . (1997) Eur. J. Immunol. 27:1911- 1918. From the foregoing, it is evident that the discovery, identification, and understanding of novel receptors for 0X2-like molecules would be highly advantageous. The present invention provides new receptor homologs for 0X2 ligands and related compounds, and methods for their use. SUMMARY OF THE INVENTION The present invention is directed to novel receptor homologs, for the ligand designated 0X2, e.g., rodent and primate embodiments. These have been designated generically OX2 receptor homologs (OX2RH) , with embodiments from various rodent and primate species. Two have been established as actually binding to the respective species 0X2. In particular, it provides description of homologs designated 0X2RH1, OX2RH2, OX2RH3, and OX2RH4. It includes nucleic acids encoding the polypeptides themselves and methods for their production and use. The nucleic acids of the invention are characterized, in part, by their homology to cloned complementary DNA (cDNA) sequences enclosed herein. The present inventors have produced a new monoclonal antibody (mAb) , designated OX102, for 0X2R on rat macrophages which blocks the interaction between 0X2 and 0X2R. They have also isolated and characterised the rat OX2R gene and polypeptide. Sequences for the rat 0X2R nucleic acid molecule and polypeptide (predicted amino acid sequence) are provided herein. By analogy with similar proteins, the inventors teach that the nucleotide and amino acid sequences of human 0X2R will be at least 50% homologous with the corresponding rat OX2R sequences. The availability of the rat 0X2R cDNA and a predicted 0X2R polypeptide sequence enable identification of the equivalent human 0X2R sequences, either through screening of known human sequences or the isolation of human nucleic acids by hybridisation or PCR technology. The presence of a large cytoplasmic sequence in the 0X2R polypeptide indicates that 0X2R has a role in macrophage function, either in signalling or through interactions with components of the cytoplasm. Thus, the present invention provides for reagents based on 0X2R that either mimic or recognise OX2R polypeptide or nucleic acid sequences, e.g., small molecular entities designed to react with OX2R binding sites, mAbs raised against 0X2R or antisense sequences, which reagents constitute therapeutically useful compounds for modifying the function of cells carrying 0X2 and/or OX2R cell surface proteins (e.g., the function of cells such as macrophages, activated lymphocytes, neurons, endothelial cells, dendritic cells, thymocytes and B lymphocytes), either by enhancing or inhibiting cell activity. Thus, reagents based on OX2R that either mimic or recognise OX2R polypeptide or nucleic acid sequences have potential applications for controlling the wide range of functions of macrophages, including responses to bacterial infections, autoimmune diseases, etc. Since the extracellular domain of OX2R is believed to be responsible for interacting with 0X2, the present inventors provide a means of screening candidate compounds for an ability to affect (positively or negatively) binding between 0X2 and 0X2R. Thus 0X2R as provided by the present invention can, e.g., be used to detect compounds which inhibit the interaction between 0X2 and OX2R, and hence which are likely to affect the interaction between macrophages and other cells of the immune system, such as lymphocytes or follicular dendritic cells. The nucleic acid and amino acid sequences for rat 0X2R are shown in Table 1. Various aspects of the invention are stated below. Other aspects are clear from the detailed description. Hence, in a first aspect, the present invention provides a substance comprising a polypeptide having the amino acid sequence set out in Table 1. In a further aspect, the present invention provides a substance comprising a polypeptide having at least 50% amino acid sequence identity with the amino acid sequence set out in Table 1. In a further aspect, the present invention provides a polypeptide which is a mutant, variant, derivative or allele of an above polypeptide and which has a characteristic property of full-length 0X2R, e.g., an ability to bind with an 0X2 or with an antibody for full-length OX2R. In a further aspect, the present invention provides a substance which is a fragment of an above polypeptide (e.g., a fragment of a polypeptide having the amino acid sequence set out in Table 1), which fragment exhibits a characteristic property of full-length OX2R protein. For example, the fragment may bind with an 0X2 protein or with an antibody for full-length OX2R protein. In one embodiment, the fragment includes part or all of the cytoplasmic domain of OX2R or an active portion of that domain. In another embodiment, the fragment includes part or all of the extracellular domain of OX2R or an active portion of that domain. Since the extracellular domain is believed to be responsible for interacting with 0X2, such fragments according to the present invention including part or all of the extracellular domain, can be used to screen candidate compounds for an ability to interfere with the binding between 0X2 and 0X2R. Accordingly, the present invention provides methods and materials for screening candidate compounds likely to have the ability to interfere with the 0X2/0X2R interaction between macrophages and other cells, including thymocytes, B lymphocytes, activated T lymphocytes, neurons, endothelial cells and follicular dendritic cells. Polypeptides and fragments as above may be recombinant and/or isolated polypeptides. In a further aspect, the present invention provides a substance comprising a nucleic acid having the nucleotide sequence of Table 1. The present invention also provides a substance which comprises a nucleic acid molecule encoding an above polypeptide or fragment. Thus, Table 1 shows the cDNA sequence of an exemplary nucleic acid molecule coding for an 0X2R polypeptide. The nucleic acid molecule may have at least 50% sequence homology with the nucleic acid sequence of Table 1. The invention also provides a substance comprising a nucleic acid molecule having part of a coding nucleotide sequence of Table 1. Where the substance comprises a part of a coding nucleotide sequence of Table 1, it will be a part which is characteristic of an OX2R gene. Thus, the part may encode a polypeptide fragment as stated above, which binds with 0X2 or an antibody for full-length 0X2R. Alternatively, the part may comprise at least 4 to 7 contiguous codons, often at least 7 to 9 contiguous codons, typically at least 9 to 13 contiguous codons and, most preferably, at least 20 to 30 contiguous codons of a nucleotide sequence of Table 1. Alternatively, the part may encode at least 4 to 7 contiguous amino acids, often at least 7 to 9 contiguous amino acids, typically at least about 9 to 13 contiguous amino acids and, most preferably, at least about 20 to 30 contiguous amino acids of a polypeptide sequence of Table 1. Nucleic acid molecules as above may be recombinant and/or isolated. In further aspects, the present invention provides vectors comprising an OX2R nucleic acid as herein provided, e.g., expression vectors in which an OX2R nucleic acid sequence is operably linked to control sequences to direct its expression. Also provided are host cells transformed with such vectors. The present invention further includes a method of producing OX2R polypeptides, comprising culturing such host cells and isolating OX2R polypeptide produced. In a further aspect, the present invention provides a method of expressing OX2R in host cells, the method including the steps of inserting a nucleic acid molecule as above into a host cell and providing conditions for expression of said nucleic acid molecule in the host cell. The method may employ an expression vector. In a further aspect, the present invention provides a composition comprising a soluble form of an 0X2R polypeptide or fragment as above, the composition also optionally including an adjuvant, pharmaceutical carrier, or excipient. The composition can be used, e.g., to generate an antibody response to an OX2R polypeptide. In further aspects, the present invention provides above OX2R polypeptides and nucleic acid molecules for use in screening candidate compounds likely to be useful as therapeutics. The present invention provides the use of an 0X2R polypeptide or fragment as above in the screening for substances likely to be useful for the treatment of bacterial infections, autoimmune diseases, and the like. The present invention also provides the use of OX2R polypeptides, polypeptide fragments, and nucleic acids for the identification of ligands for OX2R other than 0X2. The present invention also provides the use of OX2R polypeptides, polypeptide fragments, and nucleic acids for the design of mimetics of 0X2. In a further aspect, the present invention provides antibodies capable of specifically binding to 0X2R polypeptides, polypeptide fragments, and nucleic acids as above, and compositions comprising such antibodies. These antibodies can be used in assays to detect and quantify the presence of OX2R, as well as in methods of purifying 0X2R. The antibodies may be polyclonal. Preferably, the antibodies are IgG antibodies, more preferably monoclonal IgG antibodies. In a further aspect, the present invention provides the use of 0X2R polypeptides, polypeptide fragments, and nucleic acid molecules as provided herein to produce binding molecules, such as substances with one or more antibody domains, which can block the interaction between 0X2 and 0X2R. These may be included in a composition likely to be useful in the preparation of medicaments for the treatment of bacterial infections, autoimmune diseases, and the like. Where the binding molecules are antibodies, they may be IgG antibodies, preferably monoclonal IgG antibodies. In a further aspect, the present invention provides the use of 0X2R nucleic acids as defined above in the design of antisense oligonucleotides to restrict 0X2R expression in a population of macrophage cells, e.g., phosphorothiolated or cholesterol-linked oligonucleotides which can facilitate internalization and stabilization of the oligonucleotides. In a further aspect, the present invention provides a method of amplifying a nucleic acid test sample, which comprises priming a nucleic acid polymerase reaction with primer oligonucleotides obtainable from the sequence information provided herein. The nucleic acid test sample may be of a human, such that nucleic acid coding for a human 0X2R is amplified using such a method. In a further aspect, the present invention provides a method of obtaining a nucleic acid molecule coding for part or all of an 0X2R from a species other than rat, e.g., human 0X2R, which comprises probing a nucleic acid test sample from the species of interest with a nucleic acid probe obtainable from the sequence information provided herein. In a further aspect, the present invention provides a method of obtaining an 0X2R polypeptide sequence from a species other than rat, e.g., a human 0X2R, which comprises searching databases for polypeptide sequences at least 50% homologous with an OX2R amino acid sequence as provided herein (Table 1) . Similarly, OX2R nucleic acid sequences from species other than rat, e.g., human 0X2R, can be obtained by searching databases for nucleotide sequences at least 50% homologous with an 0X2R nucleotide sequence as provided herein. The present invention also provides the use of the nucleic acid sequence information provided herein in the search for mutations in OX2R genes, e.g., using techniques such as single stranded conformation polymorphism (SSCP) . The present invention provides a composition of matter selected from: a substantially pure or recombinant polypeptide comprising at least three distinct nonoverlapping segments of at least four amino acids identical to segments of SEQ ID NO: 2; a substantially pure or recombinant polypeptide comprising at least two distinct nonoverlapping segments of at least five amino acids identical to segments of SEQ ID NO: 2; a natural sequence rodent OX2RH1 polypeptide comprising mature SEQ ID NO: 2; a fusion polypeptide comprising rat OX2RH1 sequence; a substantially pure or recombinant polypeptide comprising at least three distinct nonoverlapping segments of at least four amino acids identical to segments of SEQ ID NO: 4; a substantially pure or recombinant polypeptide comprising at least two distinct nonoverlapping segments of at least five amino acids identical to segments of SEQ ID NO: 4; a natural sequence rodent OX2RH1 polypeptide comprising mature SEQ ID NO: 4; a fusion polypeptide comprising human OX2RH1 sequence; a substantially pure or recombinant polypeptide comprising at least three distinct nonoverlapping segments of at least four amino acids identical to segments of SEQ ID NO: 6; a substantially pure or recombinant polypeptide comprising at least two distinct nonoverlapping segments of at least five amino acids identical to segments of SEQ ID NO: 6; a natural sequence rodent OX2RH1 polypeptide comprising mature SEQ ID NO: 6; a fusion polypeptide comprising mouse OX2RH1 sequence; a substantially pure or recombinant polypeptide comprising at least three distinct nonoverlapping segments of at least four amino acids identical to segments of SEQ ID NO: 8; a substantially pure or recombinant polypeptide comprising at least two distinct nonoverlapping segments of at least five amino acids identical to segments of SEQ ID NO: 8; a natural sequence rodent OX2RH1 polypeptide comprising mature SEQ ID NO: 8; a fusion polypeptide comprising human OX2RH2 sequence; a substantially pure or recombinant polypeptide comprising at least three distinct nonoverlapping segments of at least four amino acids identical to segments of SEQ ID NO: 10; a substantially pure or recombinant polypeptide comprising at least two distinct nonoverlapping segments of at least five amino acids identical to segments of SEQ ID NO: 10; a natural sequence rodent OX2RH2 polypeptide comprising mature SEQ ID NO: 10; a fusion polypeptide comprising mouse OX2RH2 sequence; a substantially pure or recombinant polypeptide comprising at least three distinct nonoverlapping segments of at least four amino acids identical to segments of SEQ ID NO: 12; a substantially pure or recombinant polypeptide comprising at least two distinct nonoverlapping segments of at least five amino acids identical to segments of SEQ ID NO: 12; a natural sequence rodent OX2RH3 comprising mature SEQ ID NO: 12; a fusion polypeptide comprising mouse OX2RH3 sequence; a substantially pure or recombinant polypeptide comprising at least three distinct nonoverlapping segments of at least four amino acids identical to segments of SEQ ID NO: 20; a substantially pure or recombinant polypeptide comprising at least two distinct nonoverlapping segments of at least five amino acids identical to segments of SEQ ID NO: 20; a natural sequence primate OX2RH1.2 polypeptide comprising mature SEQ ID NO: 20; a fusion polypeptide comprising primate OX2RH1.2 sequence; a substantially pure or recombinant polypeptide comprising at least three distinct nonoverlapping segments of at least four ammo acids identical to segments of SEQ ID NO: 23; a substantially pure or recombinant polypeptide comprising at least two distinct nonoverlapping segments of at least five ammo acids identical to segments of SEQ ID NO: 23; a natural sequence rodent OX2RH4 polypeptide comprising mature SEQ ID NO: 23; or a fusion polypeptide comprising mouse OX2RH4 sequence. Some preferred embodiments include wherein the distinct nonoverlapping segments of identity: include one of at least eight ammo acids; include one of at least four ammo acids and a second of at least five amino acids; include at least three segments of at least four, five, and six ammo acids, or include one of at least twelve ammo acids. Other preferred embodiment include those wherein the: a) OX2RH1 polypeptide: comprises a mature sequence of Tables 1 or 2; is an unglycosylated form of OX2RH polypeptide; is from a primate, such as a human; is from a rodent, such as a rat or mouse; comprises at least seventeen ammo acids of SEQ ID NO: 2, 4, 6, or 20; exhibits at least four nonoverlapping segments of at least seven ammo acids of SEQ ID NO: 2, 4, 6, or 20; is a natural allelic variant of OX2RH1; has a length at least about 30 ammo acids; exhibits at least two non-overlapping epitopes which are specific for a primate or rodent OX2RH1; is glycosylated; has a molecular weight of at least 30 kD with natural glycosylation; is a synthetic polypeptide; is attached to a solid substrate; is con3ugated to another chemical moiety; is 5-fold or less substituted from natural sequence; or is a deletion or insertion variant from a natural sequence; b) OX2RH2 polypeptide: comprises a mature sequence of Table 2; is an unglycosylated form of OX2RH2 polypeptide; is from a primate, such as a human; is from a rodent, such as a mouse; comprises at least seventeen ammo acids of SEQ ID NO: 8 or 10; exhibits at least four nonoverlapping segments of at least seven ammo acids of SEQ ID NO: 8 or 10; is a natural allelic variant of OX2RH2; has a length at least about 30 ammo acids; exhibits at least two non-overlapping epitopes which are specific for a primate or rodent OX2RH2; is glycosylated; has a molecular weight of at least 30 kD with natural glycosylation; is a synthetic polypeptide; is attached to a solid substrate; is conjugated to another chemical moiety; is a 5-fold or less substitution from natural sequence; or is a deletion or insertion variant from a natural sequence; c) OX2RH3 polypeptide: comprises a mature sequence of Table 3; is an unglycosylated form of OX2RH3; is from a rodent, such as a mouse; comprises at least seventeen amino acids of SEQ ID NO: 12; exhibits at least four nonoverlapping segments of at least seven amino acids of SEQ ID NO: 12; is a natural allelic variant of OX2RH3; has a length at least about 30 amino acids; exhibits at least two non-overlapping epitopes which are specific for a rodent OX2RH3; is glycosylated; has a molecular weight of at least 30 kD with natural glycosylation; is a synthetic polypeptide; is attached to a solid substrate; is conjugated to another chemical moiety; is 5-fold or less substituted from natural sequence; or is a deletion or insertion variant from a natural sequence; or d) OX2RH4 polypeptide: comprises a mature sequence of Table 2; is an unglycosylated form of OX2RH4; is from a rodent, such as a mouse; comprises at least seventeen amino acids of SEQ ID NO: 23; exhibits at least four nonoverlapping segments of at least seven amino acids of SEQ ID NO: 23; is a natural allelic variant of OX2RH4; has a length at least about 30 amino acids; exhibits at least two non-overlapping epitopes which are specific for a rodent OX2RH4; is glycosylated; has a molecular weight of at least 30 kD with natural glycosylation; is a synthetic polypeptide; is attached to a solid substrate; is conjugated to another chemical moiety; is 5-fold or less substituted from natural sequence; or is a deletion or insertion variant from a natural sequence. In yet other embodiments, the invention provides a composition comprising: al) a substantially pure 0X2RH1 and another Ig superfamily member; a2) a substantially pure OX2RH2 and: another Ig superfamily member, DAP12, or DAP10; a3) a substantially pure OX2RH3 and: another Ig superfamily member, DAP12, or DAP10; a4) a substantially pure OX2RH4 and: another Ig superfamily member, DAP12, or DAP10; or a sterile OX2RH1 polypeptide; a sterile OX2RH2 polypeptide; a sterile OX2RH3 polypeptide; a sterile OX2RH4 polypeptide; the OX2RH1, OX2RH2, OX2RH3, or OX2RH4 polypeptide and a carrier, wherein the carrier is an aqueous compound, including water, saline, and/or buffer; and/or formulated for oral, rectal, nasal, topical, or parenteral administration. Fusion polypeptides are also provided, e.g., comprising: mature protein sequence of Tables 1-3; a detection or purification tag, including a FLAG, Hisβ, or Ig sequence; or sequence of another Ig superfamily protein. Kits are also provided, e.g., comprising an OX2RH polypeptide and: a compartment comprising the protein or polypeptide; or instructions for use or disposal of reagents in the kit. The invention also embraces various antibody like reagents, including antibodies derived from different species. It provides, e.g., a binding compound comprising an antigen binding site from an antibody, which specifically binds to a natural 0X2RH polypeptide, e.g., OX2RH1, OX2RH2, OX2RH3, and/or OX2RH4, wherein: the binding compound is in a container; the OX2RH polypeptide is from a rodent or primate; the binding compound is an Fv, Fab, or Fab2 fragment; the binding compound is conjugated to another chemical moiety; or the antibody: is raised against a peptide sequence of a mature polypeptide of Tables 1-3; is raised against a mature OX2RH; is raised to a purified mammalian OX2RH; is immunoselected; is a polyclonal antibody; binds to a denatured OX2RH; exhibits a Kd to antigen of at least 30 μM; is attached to a solid substrate, including a bead or plastic membrane; is in a sterile composition; or is detectably labeled, including a radioactive or fluorescent label. Kits are thereby provided, e.g., comprising such binding compounds and: a compartment comprising the binding compound; or instructions for use or disposal of reagents in the kit. Methods are also provided, e.g., producing an antigen:binding compound or antigen: antibody complex, comprising contacting under appropriate conditions a mammalian 0X2RH polypeptide with an antibody, thereby allowing the complex to form. Preferably, in this method: the complex is purified from other cytokine or Ig superfamily receptors; the complex is purified from other antibody; the contacting is with a sample comprising a mammalian 0X2; the contacting allows quantitative detection of the antigen; the contacting is with a sample comprising the antibody; or the contacting allows quantitative detection of the antibody. Related compositions are made available, e.g., comprising: a sterile binding compound, or the binding compound and a carrier, wherein the carrier is: an aqueous compound, including water, saline, and/or buffer; and/or formulated for oral, rectal, nasal, topical, or parenteral administration. The present invention further provides nucleic acids, e.g., an isolated or recombinant nucleic acid encoding a OX2RH polypeptide wherein the: OX2RH is from a mammal; or the nucleic acid: encodes an antigenic peptide sequence of Tables 1-3; encodes a plurality of antigenic peptide sequences of Tables 1-3; exhibits identity over at least thirteen nucleotides to a natural cDNA encoding the segment; is an expression vector; further comprises an origin of replication; is from a natural source; comprises a detectable label; comprises synthetic nucleotide sequence; is less than 6 kb, preferably less than 3 kb; is from a primate or rodent; comprises a natural full length coding sequence; is a hybridization probe for a gene encoding the OX2RH; further encodes DAP12 or DAP10; or is a PCR primer, PCR product, or mutagenesis primer. Cells comprising the recombinant nucleic acid are also provided, e.g., wherein the cell is: a prokaryotic cell; a eukaryotic cell; a bacterial cell; a yeast cell; an insect cell; a mammalian cell; a mouse cell; a primate cell; or a human cell. Kits comprising the nucleic acid are provided, e.g., with a compartment comprising the nucleic acid; with a compartment further comprising a mammalian OX2RH polypeptide; or with instructions for use or disposal of reagents in the kit. Alternatively, the invention provides a nucleic acid which: hybridizes under wash conditions of 30 minutes at 40° C and less than 2M salt to the coding portion of SEQ ID NO: 1, 3, 5, 7, 9, 11, 19, or 22; or exhibits identity over a stretch of at least about 30 nucleotides to a primate or rodent OX2RH cDNA. Preferably, the wash conditions are at: 50° C and/or 500 mM salt; or 60° C and/or 150 mM salt; the stretch is at least 55 nucleotides or 75 nucleotides; or the nucleic acid further encodes a DAP12 or DAP10 peptide. Other methods are further embraced, e.g., a method of modulating physiology or development of a cell or tissue culture cells comprising contacting the cell with an agonist or antagonist of a mammalian OX2RH. Often, the cell is transformed with a nucleic acid encoding an OX2RH. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OUTLINE I . General II. Activities III. Nucleic acids A. encoding fragments, sequence, probes B. mutations, chimeras, fusions C. making nucleic acids D. vectors, cells comprising IV. Proteins, Peptides A. fragments, sequence, immunogens, antigens B. muteins C. agonists/antagonists, functional equivalents D. making proteins V. Making nucleic acids, proteins A. synthetic B. recombinant C. natural sources VI. Antibodies A. polyclonals B. monoclonal C. fragments; Kd D. anti-idiotypic antibodies E. hybridoma cell lines VII. Kits and Methods to quantify OX2RHs A. ELISA B. assay mRNA encoding C. qualitative/quantitative D. kits VIII. Therapeutic compositions, methods A. combination compositions B. unit dose C. administration IX. Screening X. Ligands I . General The present invention provides amino acid sequences and DNA sequences of mammalian, herein primate and rodent, receptor-like subunit molecules, these designated 0X2 receptor homologs (OX2RH) . These genes have particular defined properties, either or both structural and biological. Various cDNAs encoding these molecules were obtained from mammal, e.g., human and rodent, cDNA sequence libraries. Other mammalian, e.g., primate, rodent, or other, counterparts would also be desired. The 0X2 antigen was first characterized in rat, using a monoclonal antibody (mAb) MRC OX2. See, e.g., McMaster and Williams (1979) Eur. J. Immunol. 9:426-433; Barclay (1981) Immunology 44:727-736; Barclay (1981) Immunology 42:593-600; Bukovsky, et al . (1984) Immunology 52:631-640; and Webb and Barclay (1984) J. Neurochem. 43:1061-1067. Using this antibody in immunohistochemical (IHC) staining of tissue sections or cell suspensions for flow cytometry revealed that the OX2 antigen was expressed by a wide variety of cells, e.g. neurons, vascular endothelium, B cells, activated T cells, follicular dendritic cells, smooth muscle cells and trophoblasts . Furthermore, human 0X2 is known to be expressed in normal brain and by B cells. McCaughan, et al . (1987) Immunogenetics 25:329-335. Characterization of the rat protein recognized by MRC 0X2 (Clark, et al. (1985) EMBO J. 4:113-118) revealed that 0X2 consists of about 248 amino acids comprising two extracellular immunoglobulin (Ig) domains, a transme brane domain and a short C-terminal cytoplasmic tail. The molecule is glycosylated through 6 N- linked glycosylation sites, three of which are present in the N- terminal V-like Ig domain and the others reside in the membrane proximal C2-like Ig domain. This places 0X2 in the Ig superfamily (IgSF) , forming a sub-group of small IgSF molecules with molecules like CD2, CD48, CD58, CD80, CD86, CD90, and CD147, which are characterized structurally, e.g., by the existence of the immunoglobulin-like domains corresponding to Ig variable and constant domains, a transmembrane segment, an intracellular domain, and characteristic cysteine and tryptophan residue spacings. See, e.g., Campbell, et al . (1979) Nature 282:341-342. Interestingly, CD90 is also highly expressed by neurons. Williams, et al . (1977) Cold Soring Harb. Svmp. Quant. Biol. 41 Pt 1:51-61. Furthermore, it was shown that 0X2 was a structural homologue of CD80 and CD86 (Borriello, et al . (1997) J. Immunol. 158:4548-4554) and that the 0X2 gene was closely linked to those coding for CD80 and CD86 on chromosome 16 in the mouse. Borriello, et al . (1998) Mamm. Genome 9:114-118. Both CD80 and CD86 serve as ligands in a process known as co-stimulation, and therefore it is likely that 0X2 would act as a ligand as well. The 0X2 antigen will be referred hereafter as the 0X2 protein or ligand 0X2. The binding partner will be referred to as the 0X2 receptor. To identify the receptor for 0X2 (0X2R) , a multivalent reagent was prepared using rat 0X2-rat CD4 fusion protein bound to fluorescent beads. This reagent was shown to bind to mouse and rat peritoneal macrophages, and this binding could be blocked by the mAb MRC 0X88. Preston, et al . (1997) Eur. J. Immunol. 27:1911-1918. This mAb was shown to bind to macrophages isolated from both peritoneum and spleen and in IHC on spleen sections staining was found in areas known to contain high proportions of macrophages. A second monoclonal antibody raised by the Barclay group, designated 0X102, was shown to bind macrophages in the rat species and also to prevent specifically the binding of the 0X2 molecule to rat peritoneal macrophages. Isolation of material binding to the 0X102 molecule and N-terminal sequencing showed the putative 0X2 receptor (0X2R) to be a novel molecule. This was cloned as described herein. That the protein recognized by the OX102 antibody was indeed the receptor was supported by the demonstration of a longer cytoplasmic tail on this molecule relative to the 0X2 molecule itself (the ligand) . Clark, et al. (1985) EMBO J. 4:113-118. Preliminary analysis of the 0X2R did not reveal obvious motifs consistent with known signaling molecules although this does not exclude the potential role of this molecule in mediating 0X2-delivered signals. Then, a mouse homolog was identified, designated 0X2RH1. Because the terminology 0X2R should be reserved for those proteins which have been verified to actually bind to the 0X2, the initial designation applied is a receptor homolog of the group 1. The nucleotide and amino acid sequences of this molecule are described herein. Further analysis of available sequence databases revealed the presence of another distinct form of OX2RH, a molecule that showed significant homology in the putative extracellular Ig- domain structures with OX2RH1 but with a different transmembrane and cytoplasmic sequence. These forms have herein been designated OX2RH2, and both human and mouse embodiments have been identified. Of particular note is the presence of a lysine (K) moiety at positions 224 (human) and 170 (mouse) that lies within the transmembrane portion of the molecule. Such a residue suggests that this molecule will associate with molecular partners such as DAP12 known to express motifs capable of signaling for cellular activation. See, e.g., Lanier, et al. (1998) Nature 391:703-707; Colonna (1998) Nature 391:642-3; Campbell, et al . (1999) Int. J. Biochem. Cell. Biol. 31:631-636; and Lopez-Botet, et al . (1999) Curr. Ooin. Immunol. 11:301-307. Moreover, such suggests various signaling pathways and associated biochemistry. See, e.g., Lanier, et al . (1998) Immunity 8:693- 701; Smith, et al . (1998) J. Immunol. 161:7-10; Gosselin, et al. (1999) J. Leukoc. Biol. 66:165-171; Tomasello, et al.(1998) i_ Biol. Chem. 273:34115-34119; and McVicar, et al . (1998) J. Biol. Chem. 273:32934-32942. But, a full length mouse or human OX2RH2 form is yet to be isolated. There is high homology between the mouse and rat extracellular regions of the OX2RH1 molecule, both of which have been confirmed to bind to their respective species 0X2. Thus, the rat and mouse 0X2RH1 embodiments are properly also referred to functionally as 0X2R. Both contain typical extracellular, transmembrane, and intracellular domain structures. Human OX2RH1 embodiments were discovered. Additionally, soluble forms of the rat and mouse OX2RH1 may exist. Related homologs, designated OX2RH2 and OX2RH4, have also been described, various embodiments originating in mouse and human. OX2RH2, H3, and H4 embodiments exhibit a charged lysine residue in the transmembrane segment. The human OX2RH2 embodiment lacks a signal sequence and shows some genomic sequence earmarks, suggesting that the functional form of the natural human OX2RH2 should be closely related but slightly different from the sequence provided. The functional relationship of the mouse and human homologs 2 and 4 remain to be confirmed. A further 0X2R homolog was also found in the mouse. Although its homology is much more divergent, it exhibits some similarities in sequence. In particular, it has a lysine residue in the transmembrane region. Thus, like the other OX2RH2, H3, and H4 molecules exhibiting this feature, it would be expected to signal via an associating molecule such as DAP12. This embodiment is herein designated OX2RH3 from rodent, e.g., mouse. Ongoing analysis of the expression patterns of the OX2RH1 indicates that in rat, mouse, and human leukocytes, OX2RH1 (as determined by flow cytometric staining with the OX102 antibody and/or analysis of mRNA expression by PCR techniques) is expressed most strongly by monocytes, granulocytes, and mast cells, marginally by B cells, and weakly by T cells. This is consistent with the preferential binding of the ligand 0X2 to macrophages in earlier studies. In the normal rat central nervous system, a proportion of resident macrophage (or microglial cells) also express the 0X2R, but at a low level. Some applicable standard methods are described or referenced, e.g., in Maniatis, et al. (1982) Molecular Cloning, A Laboratory Manual. Cold Spring Harbor Laboratory, Cold Spring Harbor Press; Sambrook, et al . (1989) Molecular Cloning: A Laboratory Manual. (2d ed.), vols. 1-3, CSH Press, NY; Ausubel, et al., Biology, Greene Publishing Associates, Brooklyn, NY; or Ausubel, et al . (1987 and periodic supplements) Current Protocols in Molecular Biology, Greene/Wiley, New York; each of which is incorporated herein by reference. Nucleotide (SEQ ID NO: 1) and corresponding amino acid sequence (SEQ ID NO: 2) of a rodent, e.g., rat, 0X2 receptor homolog 1 (0X2RH1) coding segment is shown in Table 1. Similarly, further embodiments, primate, e.g., human, and rodent, e.g., mouse, are described, designated 0X2RH1, 1.2, 2, and 4. The nucleic acid sequences are SEQ ID NO: 3, 19, 5, 7, 9, and 22; the corresponding amino acid sequences are SEQ ID NO: 4, 20, 6, 8, 10, and 23 which are presented in Table 2. Table 3 provides the sequence of other rodent, e.g., mouse, OX2RH3 (SEQ ID NO: 11 and 12) . Reverse translation nucleic acid sequences are provided in Table 4 (SEQ ID NO: 13-14, 21, 15-17, 24, and 18) . Table 5 provides alignment and numeric comparison of polypeptide sequences. Table 1: Nucleotide and polypeptide sequences of rodent 0X2R (homolog 1) • rat OX2RH1 (SEQ ID NO: 1 and 2) : agcggaggga tcctggtcat ggtcaccgct gctcccctac ctgtgaagag aaagagcacc 60 gagtgagccg ctgaaaacca gaaaaccgaa atg etc tgc ttt tgg aga act tct 114 Met Leu Cys Phe Trp Arg Thr Ser -20 cac gta gca gta etc ttg ate tgg ggg gtc ttc gcg get gag tea agt 162 His Val Ala Val Leu Leu lie Trp Gly Val Phe Ala Ala Glu Ser Ser -15 -10 -5 -1 tgt ect gat aag aat caa aca atg cag aac aat tea tea act atg aca 210 Cys Pro Asp Lys Asn Gin Thr Met Gin Asn Asn Ser Ser Thr Met Thr 1 5 10 15 gaa gtt aac act aca gtg ttt gta cag atg ggt aaa aag get ctg etc 258 Glu Val Asn Thr Thr Val Phe Val Gin Met Gly Lys Lys Ala Leu Leu 20 25 30 tgc tgc ect tct att tea ctg aca aaa gta ata tta ata aca tgg aca 306 Cys Cys Pro Ser lie Ser Leu Thr Lys Val lie Leu lie Thr Trp Thr 35 40 45 ata ace etc aga gga cag ect tec tgc ata ata tec tac aaa gca gac 354 lie Thr Leu Arg Gly Gin Pro Ser Cys lie lie Ser Tyr Lys Ala Asp 50 55 60 aca agg gag ace cat gaa age aac tgc teg gac aga age ate ace tgg 402 Thr Arg Glu Thr His Glu Ser Asn Cys Ser Asp Arg Ser lie Thr Trp 65 70 75 80 gee tec aca ect gac etc get ect gac ctt cag ate agt gca gtg gee 450 Ala Ser Thr Pro Asp Leu Ala Pro Asp Leu Gin lie Ser Ala Val Ala 85 90 95 etc cag cat gaa ggg cgt tac tea tgt gat ata gca gta ect gac ggg 498 Leu Gin His Glu Gly Arg Tyr Ser Cys Asp lie Ala Val Pro Asp Gly 100 105 110 aat ttc caa aac ate tat gac etc caa gtg ctg gtg ccc ect gaa gta 546 Asn Phe Gin Asn lie Tyr Asp Leu Gin Val Leu Val Pro Pro Glu Val 115 120 125 ace cac ttt cca ggg gaa aat aga act gca gtt tgt gag gcg att gca 594 Thr His Phe Pro Gly Glu Asn Arg Thr Ala Val Cys Glu Ala lie Ala 130 135 140 ggc aaa ect get gcg cag ate tct tgg acg cca gat ggg gat tgt gtc 642 Gly Lys Pro Ala Ala Gin lie Ser Trp Thr Pro Asp Gly Asp Cys Val 145 150 155 160 get aag aat gaa tea cac age aat ggc ace gtg act gtc egg age aca 690 Ala Lys Asn Glu Ser His Ser Asn Gly Thr Val Thr Val Arg Ser Thr 165 170 175 tgc cac tgg gag cag age cac gtg tct gtc gtg ttc tgt gtt gtc tct 738 Cys His Trp Glu Gin Ser His Val Ser Val Val Phe Cys Val Val Ser 180 185 190 cac ttg aca act ggt aac cag tct ctg tct ata gaa ctg ggt aga ggg 786 His Leu Thr Thr Gly Asn Gin Ser Leu Ser lie Glu Leu Gly Arg Gly 195 200 205 ggt gac caa tta tta gga tea tac att caa tac ate ate cca tct att 834 Gly Asp Gin Leu Leu Gly Ser Tyr lie Gin Tyr lie lie Pro Ser lie 210 215 220 att att ttg ate ate ata gga tgc att tgt ctt ttg aaa ate agt ggc 882 lie lie Leu He He He Gly Cys He Cys Leu Leu Lys He Ser Gly 225 230 235 240 tgc aga aaa tgt aaa ttg cca aaa teg gga get act cca gat att gag 930 Cys Arg Lys Cys Lys Leu Pro Lys Ser Gly Ala Thr Pro Asp He Glu 245 250 255 gag gat gaa atg cag ccg tat get age tac aca gag aag age aat cca 978 Glu Asp Glu Met Gin Pro Tyr Ala Ser Tyr Thr Glu Lys Ser Asn Pro 260 265 270 etc tat gat act gtg ace acg acg gag gca cac cca gcg tea caa ggc 1026 Leu Tyr Asp Thr Val Thr Thr Thr Glu Ala His Pro Ala Ser Gin Gly 275 280 285 aaa gtc aat ggc aca gac tgt ctt act ttg tea gcc atg gga ate 1071 Lys Val Asn Gly Thr Asp Cys Leu Thr Leu Ser Ala Met Gly He 290 295 300 tagaaccaag gaaaagaagt caagagacat cataattact gcttttcttt ctttaaactt 1131 ctccaatgga gggaaattag ctcttctgaa gttcttagaa agcacaaatg ttctaatgga 1191 tttgccttta agttcttcta tcattggaag tttggaatct ttgctgctac ctgttaattc 1251 taggaagaac tgatttaatt attacaaaga aagcacattg ttatggtaaa atatcaaatt 1311 gtgcaataca atgatgaaaa ctgagtttcc tcaagaaata actgcagaag gaacaatcat 1371 tactaaagca tttcatgtga gttcttccaa aaaagaaaat ccctgtgtat acgacatgat 1431 tatggtatgt gtgtgccttt atatgtttgt ttacaaatgt gtatatatgc acacatctga 1491 ttatcaagac atctctgtca aaaactcact ggcgttccag atttatgaaa gctaataaag 1551 tgagtattgg agatgttttt ata 1574 MLCFWRTSHVAVLLI GVFAAESSCPDKNQTMQNNSSTMTEVNTTVFVQMGKPCALLCCPSISLTKVILIT TITLR GQPSCIISYKADTRETHESNCSDRSIT ASTPDLAPDLQISAVALQHEGRYSCDIAVPDGNFQNIYDLQVLVPPEV THFPGENRTAVCEAIAGKPAAQIS TPDGDCVAKNESHSNGTVTVRSTCH EQSHVSWFCWSHLTTGNQSLSIE LGRGGDQLLGSYIQYIIPSIIILIIIGCICLLKISGCRKCKLPKSGATPDIEEDEMQPYASYTEKSNPLYDTVTTT EAHPASQGKVNGTDCLTLSAMGI Table 2: Nucleotide and polypeptide sequences of additional OX2R homologs . primate, e.g., human, OX2RH1 (SEQ ID NO: 3 and 4): cagagaaaag ettetgttcg tecaagttae taaccaggct aaaccacata gacgtgaagg 60 aaggggctag aaggaaggga gtgccccaet gttgatgggg taagaggatc etgtaetgag 120 aagttgacea gagagggtet caceatgege acagttcctt etgtaecagt gtggaggaaa 180 agtactgagt gaagggcaga aaaagagaaa acagaa atg etc tgc ect tgg aga 234 Met Leu Cys Pro Trp Arg -25 act get aac eta ggg eta ctg ttg att ttg act ate ttc tta gtg gee 282 Thr Ala Asn Leu Gly Leu Leu Leu He Leu Thr He Phe Leu Val Ala -20 -15 -10 -5 gaa gcg gag ggt get get caa cca aac aac tea tta atg ctg caa act 330 Glu Ala Glu Gly Ala Ala Gin Pro Asn Asn Ser Leu Met Leu Gin Thr -1 1 5 10 age aag gag aat cat get tta get tea age agt tta tgt atg gat gaa 378 Ser Lys Glu Asn His Ala Leu Ala Ser Ser Ser Leu Cys Met Asp Glu 15 20 25 aaa cag att aca cag aac tac teg aaa gta etc gca gaa gtt aac act 426 Lys Gin He Thr Gin Asn Tyr Ser Lys Val Leu Ala Glu Val Asn Thr 30 35 40 tea tgg ect gta aag atg get aca aat get gtg ctt tgt tgc ect ect 474 Ser Trp Pro Val Lys Met Ala Thr Asn Ala Val Leu Cys Cys Pro Pro 45 50 55 60 ate gca tta aga aat ttg ate ata ata aca tgg gaa ata ate ctg aga 522 He Ala Leu Arg Asn Leu He He He Thr Trp Glu He He Leu Arg 65 70 75 ggc cag ect tec tgc aca aaa gee tac aag aaa gaa aca aat gag ace 570 Gly Gin Pro Ser Cys Thr Lys Ala Tyr Lys Lys Glu Thr Asn Glu Thr 80 85 90 aag gaa ace aac tgt act gat gag aga ata ace tgg gtc tec aga ect 618 Lys Glu Thr Asn Cys Thr Asp Glu Arg He Thr Trp Val Ser Arg Pro 95 100 105 gat cag aat teg gac ctt cag att cgt ace gtg gee ate act cat gac 666 Asp Gin Asn Ser Asp Leu Gin He Arg Thr Val Ala He Thr His Asp 110 115 120 ggg tat tac aga tgc ata atg gta aca ect gat ggg aat ttc cat cgt 714 Gly Tyr Tyr Arg Cys He Met Val Thr Pro Asp Gly Asn Phe His Arg 125 130 135 140 gga tat cac etc caa gtg tta gtt aca ect gaa gtg ace ctg ttt caa 762 Gly Tyr His Leu Gin Val Leu Val Thr Pro Glu Val Thr Leu Phe Gin 145 150 155 aac agg aat aga act gca gta tgc aag gca gtt gca ggg aag cca get 810 Asn Arg Asn Arg Thr Ala Val Cys Lys Ala Val Ala Gly Lys Pro Ala 160 165 170 gcg cat ate tec tgg ate cca gag ggc gat tgt gee act aag caa gaa 858 Ala His He Ser Trp He Pro Glu Gly Asp Cys Ala Thr Lys Gin Glu 175 180 185 tac tgg age aat ggc aca gtg act gtt aag agt aca tgc cac tgg gag 906 Tyr Trp Ser Asn Gly Thr Val Thr Val Lys Ser Thr Cys His Trp Glu 190 195 200 gtc cac aat gtg tct ace gtg ace tgc cac gtc tec cat ttg act ggc 954 Val His Asn Val Ser Thr Val Thr Cys His Val Ser His Leu Thr Gly 205 210 215 220 aac aag agt ctg tac ata gag eta ctt ect gtt cca ggt gee aaa aaa 1002 Asn Lys Ser Leu Tyr He Glu Leu Leu Pro Val Pro Gly Ala Lys Lys 225 230 235 ate age aaa att ata tat tec ata tat cat ect tac tat tat tat tta 1050 He Ser Lys He He Tyr Ser He Tyr His Pro Tyr Tyr Tyr Tyr Leu 240 245 250 gac cat cgt ggg att cat ttg gtt gtt gaa agt caa tgg ctg cag aaa 1098 Asp His Arg Gly He His Leu Val Val Glu Ser Gin Trp Leu Gin Lys 255 260 265 ata taaattgaat aaaacagaat ctactccagt tgttgaggag gatgaaatgc 1151 He agccctatgc cagctacaca gagaagaaca atcctctcta tgatactaca aacaaggtga 1211 aggcatctga ggcattacaa agtgaagttg acacagacct ccatacttta taagttgttg 1271 gactctagta ccaagaaaca acaacaaacg agatacatta taattactgt ctgattttct 1331 tacagttcta gaatgaagac ttatattgaa attaggtttt ccaaggttct tagaagacat 1391 tttaatggat tctcattcat acccttgtat aattggaatt tttgattctt agctgctacc 1451 agctagttct ctgaagaact gatgttatta caaagaaaat acatgcccat gaccaaatat 1511 tcaaattgtg caggacagta aataatgaaa accaaatttc ctcaagaaat aactgaagaa 1571 ggagcaagtg tgaacagttt cttgtgtatc ctt 1604 MLCP RTANLGLLLILTIFLVAEAEGAAQPNNSLMLQTSKENHALASSSLCMDEKQITQNYSKVLAEVNTS PVKM ATNAVLCCPPIALRNLIIIT EHLRGQPSCTKAYKKETNETKETNCTDERIT VSRPDQNSDLQIRTVAITHDGY YRCIMVTPDGNFHRGYHLQVLVTPEVTLFQNRNRTAVCKAVAGKPAAHISWIPEGDCATKQEYWSNGTVTVKSTCH WEVHNVSTVTCHVSHLTGNKSLYIELLPVPGAKKI SKI IYS IYHPYYYYLDHRGIHLWESQWLQKI primate, e.g., human, OX2RH1.2 (SEQ ID NO: 19 and 20): atg etc tgc ect tgg aga act get aac eta ggg eta ctg ttg att ttg 48 Met Leu Cys Pro Trp Arg Thr Ala Asn Leu Gly Leu Leu Leu He Leu -25 -20 -15 act ate ttc tta gtg gee gaa gcg gag ggt get get caa cca aac aac 96 Thr He Phe Leu Val Ala Glu Ala Glu Gly Ala Ala Gin Pro Asn Asn -10 -5 -1 1 5 tea tta atg ctg caa act age aag gag aat cat get tta get tea age 144 Ser Leu Met Leu Gin Thr Ser Lys Glu Asn His Ala Leu Ala Ser Ser 10 15 20 agt tta tgt atg gat gaa aaa cag att aca cag aac tac teg aaa gta 192 Ser Leu Cys Met Asp Glu Lys Gin He Thr Gin Asn Tyr Ser Lys Val 25 30 35 etc gca gaa gtt aac act tea tgg ect gta aag atg get aca aat get 240 Leu Ala Glu Val Asn Thr Ser Trp Pro Val Lys Met Ala Thr Asn Ala 40 45 50 gtg ctt tgt tgc ect ect ate gca tta aga aat ttg ate ata ata aca 288 Val Leu Cys Cys Pro Pro He Ala Leu Arg Asn Leu He He He Thr 55 60 65 70 tgg gaa ata ate ctg aga ggc cag ect tec tgc aca aaa gee tac agg 336 Trp Glu He He Leu Arg Gly Gin Pro Ser Cys Thr Lys Ala Tyr Arg 75 80 85 aaa gaa aca aat gag ace aag gaa ace aac tgt act gat gag aga ata 384 Lys Glu Thr Asn Glu Thr Lys Glu Thr Asn Cys Thr Asp Glu Arg He 90 95 100 ace tgg gtc tec aga ect gat cag aat teg gac ctt cag att cgt cca 432 Thr Trp Val Ser Arg Pro Asp Gin Asn Ser Asp Leu Gin He Arg Pro 105 110 115 gtg gee ate act cat gac ggg tat tac aga tgc ata atg gta aca ect 480 Val Ala He Thr His Asp Gly Tyr Tyr Arg Cys He Met Val Thr Pro 120 125 130 gat ggg aat ttc cat cgt gga tat cac etc caa gtg tta gtt aca ect 528 Asp Gly Asn Phe His Arg Gly Tyr His Leu Gin Val Leu Val Thr Pro 135 140 145 150 gaa gtg ace ctg ttt caa aac agg aat aga act gca gta tgc aag gca 576 Glu Val Thr Leu Phe Gin Asn Arg Asn Arg Thr Ala Val Cys Lys Ala 155 160 165 gtt gca ggg aag cca get gcg cag ate tec tgg ate cca gag ggc gat 624 Val Ala Gly Lys Pro Ala Ala Gin He Ser Trp He Pro Glu Gly Asp 170 175 180 tgt gee act aag caa gaa tac tgg age aat ggc aca gtg act gtt aag 672 Cys Ala Thr Lys Gin Glu Tyr Trp Ser Asn Gly Thr Val Thr Val Lys 185 190 195 agt aca tgc cac tgg gag gtc cac aat gtg tct ace gtg ace tgc cac 720 Ser Thr Cys His Trp Glu Val His Asn Val Ser Thr Val Thr Cys His 200 205 210 gtc tec cat ttg act ggc aac aag agt ctg tac ata gag eta ctt ect 768 Val Ser His Leu Thr Gly Asn Lys Ser Leu Tyr He Glu Leu Leu Pro 215 220 225 230 gtt cca ggt gee aaa aaa tea gca aaa tta tat att cca tat ate ate 816 Val Pro Gly Ala Lys Lys Ser Ala Lys Leu Tyr He Pro Tyr He He 235 240 245 ctt act att att att ttg ace ate gtg gga ttc att tgg ttg ttg aaa 864 Leu Thr He He He Leu Thr He Val Gly Phe He Trp Leu Leu Lys 250 255 260 gtc aat ggc tgc aga aaa tat aaa ttg aat aaa aca gaa tct act cca 912 Val Asn Gly Cys Arg Lys Tyr Lys Leu Asn Lys Thr Glu Ser Thr Pro 265 270 275 gtt gtt gag gag gat gaa atg cag ccc tat gee age tac aca gag aag 960 Val Val Glu Glu Asp Glu Met Gin Pro Tyr Ala Ser Tyr Thr Glu Lys 280 285 290 aac aat ect etc tat gat act aca aac aag gtg aag gca tct cag gca 1008 Asn Asn Pro Leu Tyr Asp Thr Thr Asn Lys Val Lys Ala Ser Gin Ala 295 300 305 310 tta caa agt gaa gtt gac aca gac etc cat act tta taa 1047 Leu Gin Ser Glu Val Asp Thr Asp Leu His Thr Leu 315 320 MLCP RTANLGLLLILTI FLVAEAEGAAQPNNSLMLQTSKENHALAS SSLCMDEKQITQNYSKVLAEVNTS PVKM ATNAVLCCPPIALRNLIIIT EHLRGQPSCTKAYRKETNETKETNCTDERIT VSRPDQNSDLQIRPVAITHDGY YRCIMVTPDGNFHRGYHLQVLVTPEVTLFQNRNRTAVCKAVAGKPAAQI SWI PEGDCATKQEY SNGTVTVKSTCH EVHNVSTVTCHVSHLTGNKSLYIELLPVPGAKKSAKLYI PYI ILTI I ILTIVGFI LLKVNGCRKYKLNKTESTP WEEDEMQPYASYTEKNNPLYDTTNKVKASQALQSEVDTDLHTLZ rodent, e.g., mouse, OX2RH1 (SEQ ID NO: 5 and 6): aaaaccgaa atg ttt tgc ttt tgg aga act tct gee eta gca gtg etc tta 51 Met Phe Cys Phe Trp Arg Thr Ser Ala Leu Ala Val Leu Leu 1 5 10 ata tgg ggg gtc ttt gtg get ggg tea agt tgt act gat aag aat caa 99 He Trp Gly Val Phe Val Ala Gly Ser Ser Cys Thr Asp Lys Asn Gin 15 20 25 30 aca aca cag aac aac agt tea tct ect ctg aca caa gtg aac act aca 147 Thr Thr Gin Asn Asn Ser Ser Ser Pro Leu Thr Gin Val Asn Thr Thr 35 40 45 gtg tct gta cag ata ggt aca aag get ctg etc tgc tgc ttt tct att 195 Val Ser Val Gin He Gly Thr Lys Ala Leu Leu Cys Cys Phe Ser He 50 55 60 cca ctg aca aaa gca gta tta ate aca tgg ata ata aag etc aga ggc 243 Pro Leu Thr Lys Ala Val Leu He Thr Trp He He Lys Leu Arg Gly 65 70 75 ctg cca tec tgc aca ata gca tac aaa gta gat aca aag ace aat gaa 291 Leu Pro Ser Cys Thr He Ala Tyr Lys Val Asp Thr Lys Thr Asn Glu 80 85 90 ace age tgc ttg ggc agg aac ate ace tgg gee tec aca ect gac cac 339 Thr Ser Cys Leu Gly Arg Asn He Thr Trp Ala Ser Thr Pro Asp His 95 100 105 110 agt ect gaa ctt cag ate agt gca gtg ace etc cag cat gag ggg act 387 Ser Pro Glu Leu Gin He Ser Ala Val Thr Leu Gin His Glu Gly Thr 115 120 125 tac aca tgt gag aca gta aca ect gaa ggg aat ttt gaa aaa aac tat 435 Tyr Thr Cys Glu Thr Val Thr Pro Glu Gly Asn Phe Glu Lys Asn Tyr 130 135 140 gac etc caa gtg ctg gtg ccc ect gaa gta ace tac ttt cca gag aaa 483 Asp Leu Gin Val Leu Val Pro Pro Glu Val Thr Tyr Phe Pro Glu Lys 145 150 155 aac aga tct gca gtc tgt gag gca atg gca ggc aag ect get gca cag 531 Asn Arg Ser Ala Val Cys Glu Ala Met Ala Gly Lys Pro Ala Ala Gin 160 165 170 ate tct tgg tct cca gat ggg gac tgt gtc act acg agt gaa tea cac 579 He Ser Trp Ser Pro Asp Gly Asp Cys Val Thr Thr Ser Glu Ser His 175 180 185 190 age aat ggc act gtg act gtc agg age aca tgc cac tgg gag cag aac 627 Ser Asn Gly Thr Val Thr Val Arg Ser Thr Cys His Trp Glu Gin Asn 195 200 205 aat gtg tct gat gtg tec tgc att gtc tct cat ttg act ggt aac caa 675 Asn Val Ser Asp Val Ser Cys He Val Ser His Leu Thr Gly Asn Gin 210 215 220 tct ctg tec ata gaa ctg agt aga ggt ggt aac caa tea tta cga cca 723 Ser Leu Ser He Glu Leu Ser Arg Gly Gly Asn Gin Ser Leu Arg Pro 225 230 235 tat att cca tac ate ata cca tea att ate att ttg ate ate ata gga 771 Tyr He Pro Tyr He He Pro Ser He He He Leu He He He Gly 240 245 250 tgc att tgt ctt ttg aaa ate agt ggc ttc aga aaa tgc aaa ttg cca 819 Cys He Cys Leu Leu Lys He Ser Gly Phe Arg Lys Cys Lys Leu Pro 255 260 265 270 aaa tta gaa get act tea get att gag gag gat gaa atg cag ect tat 867 Lys Leu Glu Ala Thr Ser Ala He Glu Glu Asp Glu Met Gin Pro Tyr 275 280 285 get age tat aca gag aag age aat cca etc tat gat act gtg act aag 915 Ala Ser Tyr Thr Glu Lys Ser Asn Pro Leu Tyr Asp Thr Val Thr Lys 290 295 300 gtg gag gca ttt cca gta tea caa ggc gaa gtc aat ggc aca gac tgc 963 Val Glu Ala Phe Pro Val Ser Gin Gly Glu Val Asn Gly Thr Asp Cys 305 310 315 ctt act ttg teg gee att gga ate tagaaccaag aaaaaagaag tcaagagaca 1017 Leu Thr Leu Ser Ala He Gly He 320 325 tcataattac tgctttgctt tctttaaaat tcgacaatgg aaggactact tggaaattag 1077 ctcttccaaa gctattaaaa agcacaaatg ttctaatgaa attgcattta aattctatca 1137 ttggaagttt ggaatctctg ctgctacctg ttaattttag gaagaactga tttaattatt 1197 acaaagaaag cacatggtta tggtgaaata tcaagttgtg caataaagta tgatgaaaac 1257 tgagtttcct caagaaataa ctgcaggagg aacaatcatc actaaagaat ttcatgtgag 1317 ttcttacaaa aaaattccta tgtatacatg actatggtat gtgtgtccaa ttacatgttt 1377 atttacaaat gtgtatatat gcacacattt gcttttcagg acatctcctt gtaaaaaaca 1437 cactggagtt ttggatttat aaaagcttat aaagtgagca ttggagatat ttt 1490 MFCFWRTSALAVLLIWGVFVAGSSCTDKNQTTQNNSSΞPLTQVNTTVSVQIGTKALLCCFSIPLTKAVLIT IIKL RGLPSCTIAYKVDTKTNETSCLGRNIT ASTPDHSPELQISAVTLQHEGTYTCETVTPEGNFEKNYDLQVLVPPEV TYFPEKNRSAVCEAMAGKPAAQIS SPDGDCVTTΞESHSNGTVTVRSTCH EQNNVSDVSCIVSHLTGNQSLSIEL SRGGNQSLRPYIPYIIPSIIILIIIGCICLLKISGFRKCKLPKLEATSAIEEDEMQPYASYTEKSNPLYDTVTKVE AFPVSQGEVNGTDCLTLSAIGI primate, e.g., human, 0X2RH2 (SEQ ID NO: 7 and 8) atg ggt gga aag cag atg aca cag aac tat tea aca att ttt gca gaa 48 Met Gly Gly Lys Gin Met Thr Gin Asn Tyr Ser Thr He Phe Ala Glu 1 5 10 15 ggt aac att tea cag ect gta ctg atg gat ata aat get gtg ctt tgt 96 Gly Asn He Ser Gin Pro Val Leu Met Asp He Asn Ala Val Leu Cys 20 25 30 tgc ect ect att gca tta aga aat ttg ate ata ata aca tgg gaa ata 144 Cys Pro Pro He Ala Leu Arg Asn Leu He He He Thr Trp Glu He 35 40 45 ate ctg aga ggc cag ect tec tgc aca aaa gcc tac aag aaa gaa aca 192 He Leu Arg Gly Gin Pro Ser Cys Thr Lys Ala Tyr Lys Lys Glu Thr 50 55 60 aat gag ace aag gaa ace aac tgt act gtt gag aga ata ace tgg gtc 240 Asn Glu Thr Lys Glu Thr Asn Cys Thr Val Glu Arg He Thr Trp Val 65 70 75 80 tct aga ect gat cag aat teg gac ctt cag att cgt ccg gtg gac ace 288 Ser Arg Pro Asp Gin Asn Ser Asp Leu Gin He Arg Pro Val Asp Thr 85 90 95 act cat gac ggg tat tac aga ggc ata gtg gta aca ect gat ggg aat 336 Thr His Asp Gly Tyr Tyr Arg Gly He Val Val Thr Pro Asp Gly Asn 100 105 110 ttc cat cgt gga tat cac etc caa gtg tta gtt aca ccc gaa gtg aac 384 Phe His Arg Gly Tyr His Leu Gin Val Leu Val Thr Pro Glu Val Asn 115 120 125 eta ttt caa age agg aat ata act gca gta tgc aag gca gtt aca ggg 432 Leu Phe Gin Ser Arg Asn He Thr Ala Val Cys Lys Ala Val Thr Gly 130 135 140 aag cca get gcc cag ate tec tgg ate cca gag gga tct att ctt gcc 480 Lys Pro Ala Ala Gin He Ser Trp He Pro Glu Gly Ser He Leu Ala 145 150 155 160 act aag caa gaa tac tgg ggc aat ggc aca gtg acg gtt aag agt aca 528 Thr Lys Gin Glu Tyr Trp Gly Asn Gly Thr Val Thr Val Lys Ser Thr 165 170 175 tgc ccc tgg gag ggc cac aag tct act gtg ace tgc cat gtc tec cat 576 Cys Pro Trp Glu Gly His Lys Ser Thr Val Thr Cys His Val Ser His 180 185 190 ttg act ggc aac aag agt ctg tec gta aag ttg aat tea ggt etc aga 624 Leu Thr Gly Asn Lys Ser Leu Ser Val Lys Leu Asn Ser Gly Leu Arg 195 200 205 ace tea gga tct cca gcg ttg tec tta ctg ate att ctt tat gtg aaa 672 Thr Ser Gly Ser Pro Ala Leu Ser Leu Leu He He Leu Tyr Val Lys 210 215 220 etc tct ctt ttt gtg gtc att ctg gtc ace aca gga ttt gtt ttc ttc 720 Leu Ser Leu Phe Val Val He Leu Val Thr Thr Gly Phe Val Phe Phe 225 230 235 240 cag agg ata aat cat gtc aga aaa gtt ctt taaagaagaa ggaagggtct 770 Gin Arg He Asn His Val Arg Lys Val Leu 245 250 tcttttgctt ctcctccttg tctctggact gcaacattgg tgagatgagt gatggtccag 830 cagtgaactt gggccatgga tgatgttaag gatagaagcc actcagtagg atagaagaaa 890 agaaagatgg aagaaggatc ctgggcttga tgaccatgaa gtttccctat aaaccctcaa 950 ccacctattc attgacttct tttgtgttag agtgaataaa attttgttca tgccagtgtt 1010 MGGKQMTQNYSTIFAEGNISQPVLMDINAVLCCPPIALRNLIIITWEIILRGQPSCTKAYKKETNETKETNCTVER IT VSRPDQNSDLQIRPVDTTHDGYYRGIWTPDGNFHRGYHLQVLVTPEVNLFQSRNITAVCKAVTGKPAAQIS IPEGSILATKQEY GNGTVTVKSTCP EGHKSTVTCHVSHLTGNKSLSVKLNSGLRTSGSPALSLLIILYVKLSLF WILVTTGFVFFQRINHVRKVL rodent, e.g., mouse, OX2RH2 (SEQ ID NO: 9 and 10): aga ggc cag ect tec tgc ata atg gcc tac aaa gta gaa aca aag gag 48 Arg Gly Gin Pro Ser Cys He Met Ala Tyr Lys Val Glu Thr Lys Glu 1 5 10 15 ace aat gaa ace tgc ttg ggc agg aac ate ace tgg gcc tec aca ect 96 Thr Asn Glu Thr Cys Leu Gly Arg Asn He Thr Trp Ala Ser Thr Pro 20 25 30 gac cac att ect gac ctt cag ate agt gcg gtg gcc etc cag cat gag 144 Asp His He Pro Asp Leu Gin He Ser Ala Val Ala Leu Gin His Glu 35 40 45 ggg aat tac tta tgt gag ata aca aca ect gaa ggg aat ttc cat aaa 192 Gly Asn Tyr Leu Cys Glu He Thr Thr Pro Glu Gly Asn Phe His Lys 50 55 60 gtc tat gac etc caa gtg ctg gtg ccc ect gaa gta ace tac ttt etc 240 Val Tyr Asp Leu Gin Val Leu Val Pro Pro Glu Val Thr Tyr Phe Leu 65 70 75 80 ggg gaa aat aga act gca gtt tgt gag gca atg gca ggc aag ect get 288 Gly Glu Asn Arg Thr Ala Val Cys Glu Ala Met Ala Gly Lys Pro Ala 85 90 95 gca cag ate tct tgg act cca gat ggg gac tgt gtc act aag agt gag 336 Ala Gin He Ser Trp Thr Pro Asp Gly Asp Cys Val Thr Lys Ser Glu 100 105 110 tea cac age aat ggc act gtg act gtc agg age act tgc cac tgg gag 384 Ser His Ser Asn Gly Thr Val Thr Val Arg Ser Thr Cys His Trp Glu 115 120 125 cag aac aat gtg tct get gtg tec tgc att gtc tct cat teg act ggt 432 Gin Asn Asn Val Ser Ala Val Ser Cys He Val Ser His Ser Thr Gly 130 135 140 aat cag tct ctg tec ata gaa ctg agt aga ggt ace ace age ace ace 480 Asn Gin Ser Leu Ser He Glu Leu Ser Arg Gly Thr Thr Ser Thr Thr 145 150 155 160 ect tec ttg ctg ace att etc tac gtg aaa atg gtc ctt ttg ggg att 528 Pro Ser Leu Leu Thr He Leu Tyr Val Lys Met Val Leu Leu Gly He 165 170 175 att ctt ctt aaa gtg gga ttt get ttc ttc cag aag aga aat gtt ace 576 He Leu Leu Lys Val Gly Phe Ala Phe Phe Gin Lys Arg Asn Val Thr 180 185 190 aga aca tgaatatcca gatttctgga agctcattag tctgatgaca cataccagaa 632 Arg Thr aacagcattt gtaatcaact ttctcattgg aatccagctt acccgtccct gctgtcttca 692 tgtttgttag acactcacct ccaaattctt aactgagaag ggctcctgtc taaaggaaat 752 atggggacaa attgtggagc atagaccaaa agaaaggcca tccagagact gccccaccta 812 aggacccatc ccatatacag acaccaaacc cagacactac tgaagatgct gcgaagcgtt 872 tgctgacagg agcctgttat agctgtctcc tgagaggctc agccagagcc tgacaaatac 932 ataggtagat gcttgcagcc aacaactgga ctgagcaaaa aatctccatt ggaggagtta 992 gagaaaggac tgaagagggt gaaagggttt geagecceat aggaagaaca aeaatateaa 1052 ccaaccagat ctcccagagc tcccagggac taa 1085 RGQPSCIMAYKVETKETNETCLGRNIT ASTPDHIPDLQISAVALQHEGNYLCEITTPEGNFHKVYDLQVLVPPEV TYFLGENRTAVCEAMAGKPAAQIS TPDGDCVTKSESHSNGTVTVRSTCH EQNNVSAVSCIVSHSTGNQSLSIEL SRGTTSTTPSLLTILYVKMVLLGIILLKVGFAFFQKRNVTRT Rodent, e.g., mouse, 0X2RH4 (SEQ ID NO: 22 and 23): atg cat get ctg ggg agg att ccg act ttg act ttg ctg ate ttc ate 48 Met His Ala Leu Gly Arg He Pro Thr Leu Thr Leu Leu He Phe He -25 -20 -15 -10 aat att ttt gtg tct ggg tea agt tgt act gat gag aat caa aca ata 96 Asn He Phe Val Ser Gly Ser Ser Cys Thr Asp Glu Asn Gin Thr He -5 -1 1 5 cag aat gac agt tea tct tct ctg aca caa gtt aac act aca atg tct 144 Gin Asn Asp Ser Ser Ser Ser Leu Thr Gin Val Asn Thr Thr Met Ser 10 15 20 gta cag atg gat aaa aag get ctg etc tgc tgc ttt tct agt cca ctg 192 Val Gin Met Asp Lys Lys Ala Leu Leu Cys Cys Phe Ser Ser Pro Leu 25 30 35 ata aat gca gta tta ate aca tgg ata ata aaa cac aga cac ctg ect 240 He Asn Ala Val Leu He Thr Trp He He Lys His Arg His Leu Pro 40 45 50 55 tec tgc aca ata gca tac aac eta gat aaa aag ace aat gaa ace age 288 Ser Cys Thr He Ala Tyr Asn Leu Asp Lys Lys Thr Asn Glu Thr Ser 60 65 70 tgc ttg ggc agg aac ate ace tgg gcc tec aca ect gac cac agt ect 336 Cys Leu Gly Arg Asn He Thr Trp Ala Ser Thr Pro Asp His Ser Pro 75 80 85 gaa ctt cag ate agt gca gtg gcc etc cag cat gag ggg act tac aca 384 Glu Leu Gin He Ser Ala Val Ala Leu Gin His Glu Gly Thr Tyr Thr 90 95 100 tgt gag ata gta aca ect gaa ggg aat tta gaa aaa gtc tat gac etc 432 Cys Glu He Val Thr Pro Glu Gly Asn Leu Glu Lys Val Tyr Asp Leu 105 110 115 caa gtg ctg gtg ccc ect gag gta ace tac ttt cca ggg aaa aac aga 480 Gin Val Leu Val Pro Pro Glu Val Thr Tyr Phe Pro Gly Lys Asn Arg 120 125 130 135 act gca gtc tgt gag gca atg gca ggc aag ect get gca cag ate tct 528 Thr Ala Val Cys Glu Ala Met Ala Gly Lys Pro Ala Ala Gin He Ser 140 145 150 tgg act cca gat ggg gac tgt gtc act aag agt gag tea cac age aat 576 Trp Thr Pro Asp Gly Asp Cys Val Thr Lys Ser Glu Ser His Ser Asn 155 160 165 ggc act gtg act gtc agg age acg tgc cac tgg gag cag aac aat gtg 624 Gly Thr Val Thr Val Arg Ser Thr Cys His Trp Glu Gin Asn Asn Val 170 175 180 tct gtt gtg tec tgc tta gtc tct cat teg act ggt aat cag tct ctg 672 Ser Val Val Ser Cys Leu Val Ser His Ser Thr Gly Asn Gin Ser Leu 185 190 195 tec ata gaa ctg agt caa ggt aca atg ace ace ccc cgt tec ttg ctg 720 Ser He Glu Leu Ser Gin Gly Thr Met Thr Thr Pro Arg Ser Leu Leu 200 205 210 215 ace att etc tat gtg aaa atg gcc ctt ttg gtg att att ctt ctt aac 768 Thr He Leu Tyr Val Lys Met Ala Leu Leu Val He He Leu Leu Asn 220 225 230 gta gga ttt get ttc ttc cag aag aga aat ttt gcc aga aca tga 813 Val Gly Phe Ala Phe Phe Gin Lys Arg Asn Phe Ala Arg Thr 235 240 245 MHALGRIPTLTLLIFINIFVSGSSCTDENQTIQNDSSSSLTQVNTTMSVQMDKKALLCCFSSPLINAVLIT IIKHRHLPSCTIAYNLDKKTNETSCLGRNIT ASTPDHSPELQISAVALQHEGTYTCEIVTPEGNLEKVY DLQVLVPPEVTYFPGKNRTAVCEAMAGKPAAQIS TPDGDCVTKSESHSNGTVTVRSTCHWEQNNVSWSC LVSHSTGNQSLSIELSQGTMTTPRSLLTILYVKMALLVIILLNVGFAFFQKRNFART Table 3: Rodent, e.g., mouse, OX2RH3 (SEQ ID NO: 11 and 12): ggcacgagtt acgatttgtg ettaaeetga ctceaeteea g atg cat get ttg ggg 56 Met His Ala Leu Gly -25 agg act ctg get ttg atg tta etc ate ttc ate act att ttg gtg ect 104 Arg Thr Leu Ala Leu Met Leu Leu He Phe He Thr He Leu Val Pro -20 -15 -10 -5 gag tea agt tgt tea gtg aaa gga egg gag gag ate cca ccg gat gat 152 Glu Ser Ser Cys Ser Val Lys Gly Arg Glu Glu He Pro Pro Asp Asp -1 1 5 10 tea ttt ect ttt tea gat gat aat ate ttc ect gat gga gtg ggc gtc 200 Ser Phe Pro Phe Ser Asp Asp Asn He Phe Pro Asp Gly Val Gly Val 15 20 25 ace atg gag att gag att ate act cca gtg tct gta cag ata ggt ate 248 Thr Met Glu He Glu He He Thr Pro Val Ser Val Gin He Gly He 30 35 40 aag get cag ctt ttc tgt cat ect agt cca tea aaa gaa gca aca ctt 296 Lys Ala Gin Leu Phe Cys His Pro Ser Pro Ser Lys Glu Ala Thr Leu 45 50 55 60 aga ata tgg gaa ata act ccc aga gac tgg ect tec tgc aga eta ccc 344 Arg He Trp Glu He Thr Pro Arg Asp Trp Pro Ser Cys Arg Leu Pro 65 70 75 tac aga gca gag ttg cag cag ate agt aaa aaa ate tgt act gag aga 392 Tyr Arg Ala Glu Leu Gin Gin He Ser Lys Lys He Cys Thr Glu Arg 80 85 90 gga ace act agg gtc ect gca cat cac cag agt tct gac ctt ccc ate 440 Gly Thr Thr Arg Val Pro Ala His His Gin Ser Ser Asp Leu Pro He 95 100 105 aaa tea atg gcc etc aag cat gat ggg cat tac tea tgt egg ata gaa 488 Lys Ser Met Ala Leu Lys His Asp Gly His Tyr Ser Cys Arg He Glu 110 115 120 aca aca gat ggg att ttc caa gag aga cat age ate caa gtg cca ggg 536 Thr Thr Asp Gly He Phe Gin Glu Arg His Ser He Gin Val Pro Gly 125 130 135 140 gaa aat aga act gta gtt tgt gag gca att gca age aag ect get atg 584 Glu Asn Arg Thr Val Val Cys Glu Ala He Ala Ser Lys Pro Ala Met 145 150 155 cag ate ttg tgg act cca gat gag gac tgt gtc act aag agt aaa tea 632 Gin He Leu Trp Thr Pro Asp Glu Asp Cys Val Thr Lys Ser Lys Ser 160 165 170 cac aat gac ace atg att gtc agg age aag tgc cac agg gag aaa aac 680 His Asn Asp Thr Met He Val Arg Ser Lys Cys His Arg Glu Lys Asn 175 180 185 aat ggc cac agt gtg ttc tgc ttt ate tec cat ttg act gat aac tgg 728 Asn Gly His Ser Val Phe Cys Phe He Ser His Leu Thr Asp Asn Trp 190 195 200 att etc tec atg gaa cag aat cga ggt aca ace age ate ctg ect tec 776 He Leu Ser Met Glu Gin Asn Arg Gly Thr Thr Ser He Leu Pro Ser 205 210 215 220 ttg ctg age att etc tat gtg aaa ctg get gta act gtt etc ate gta 824 Leu Leu Ser He Leu Tyr Val Lys Leu Ala Val Thr Val Leu He Val 225 230 235 gga ttt get ttt ttc cag aag aga aat tat ttc aga gtg cca gaa ggc 872 Gly Phe Ala Phe Phe Gin Lys Arg Asn Tyr Phe Arg Val Pro Glu Gly 240 245 250 tec tgaggagagt ggtctgtggt taagatgaga tttaccacca tctgaaagac 925 Ser atcttgtcta ccgcgcagcg tgctgagatt ccgagaagca gccacagaac ctactaggaa 985 gacaaatctg atgtggttgt caatcctttc aatggacctg agtacttcta taaacccgag 1045 tgaggttgtg ctggacccag gagccaggct aggtcatata tgttgatttt tgctgcaaga 1105 cctcatggtt tatctacaaa tcctaaattc tttcacttcc agttttaaaa cttttggccc 1165 aagcatttta tccacagcat aacaccttta aagaaactct cccacggaaa ctgctggttc 1225 catggaatgg aaaattgcaa catggtttac aagacagtgc aaaccaagca gcattccaag 1285 atatgagctt cagaaagtta caggaactgt cttgggacga gaaagaagga ttaaatagtt 1345 cccagtccc 1354 MHALGRTLALMLLI FITILVPESSCSVKGREEI PPDDSFPFSDDNI FPDGVGVTMEIEI ITPVSVQI GI KAQLFCH PS PΞKEATLRI EITPRDWPSCRLPYRAELQQI SKKI CTERGTTRVPAHHQS ΞDLPIKSMALKHDGHYSCRIETTD GIFQERHSIQVPGENRTWCEAIASKPAMQIL TPDEDCVTKSKSHNDTMIVRSKCHREKNNGHSVFCFI SHLTDN ILSMEQNRGTTSILPSLLS ILYVKLAVTVLIVGFAFFQKRNYFRVPEGS Table 4: Reverse translations of 0X2R homologs: rodent, e.g., rat, 0X2RH1 (SEQ ID NO: 13): atgytntgyt tytggmgnac n sncaygtn gcngtnytny tnathtgggg ngtnttygcn 60 gengarwsnw sntgyccnga yaaraaycar aenatgeara ayaaywsnws naenatgacn 120 gargtnaaya cnacngtntt ygtncaratg ggnaaraarg cnytnytntg ytgyccnwsn 180 athwsnytna cnaargtnat hytnathacn tggacnatha cnytnmgngg ncarccnwsn 240 tgyathathw sntayaargc ngayacnmgn garaeneayg arwsnaaytg ywsngaymgn 300 wsnathacnt gggenwsnae nccngayytn genecngayy tncarathws ngcngtngcn 360 ytncarcayg arggnmgnta ywsntgygay athgcngtnc cngayggnaa yttycaraay 420 athtaygayy tncargtnyt ngtnccnccn gargtnacnc ayttyccngg ngaraaymgn 480 acngcngtnt gygargcnat hgcnggnaar ccngcngcnc arathwsntg gacnccngay 540 ggngaytgyg tngcnaaraa ygarwsncay wsnaayggna cngtnacngt nmgnwsnacn 600 tgycaytggg arcarwsnca ygtnwsngtn gtnttytgyg tngtnwsnca yytnacnacn 660 ggnaaycarw snytnwsnat hgarytnggn mgnggnggng aycarytnyt nggnwsntay 720 athcartaya thathccnws nathathath ytnathatha thggntgyat htgyytnytn 780 aarathwsng gntgymgnaa rtgyaarytn ccnaarwsng gngcnacncc ngayathgar 840 gargaygara tgcarccnta ygcnwsntay acngaraarw snaayccnyt ntaygayacn 900 gtnacnacna cngargcnca yccngcnwsn carggnaarg tnaayggnac ngaytgyytn 960 acnytnwsng cnatgggnat h 981 primate, e.g., human, 0X2RH1 (SEQ ID NO: 14] atgytntgyc cntggmgnac ngcnaayytn ggnytnytny tnathytnac nathttyytn 60 gtngcngarg cngarggngc ngcncarccn aayaaywsny tnatgytnca racnwsnaar 120 garaaycayg cnytngcnws nwsnwsnytn tgyatggayg araarcarat hacncaraay 180 taywsnaarg tnytngcnga rgtnaayacn wsntggccng tnaaratggc nacnaaygcn 240 gtnytntgyt gyccnccnat hgcnytnmgn aayytnatha thathacntg ggarathath 300 ytnmgnggnc arccnwsntg yacnaargcn tayaaraarg aracnaayga racnaargar 360 acnaaytgya cngaygarmg nathacntgg gtnwsnmgnc cngaycaraa ywsngayytn 420 carathmgna cngtngcnat hacncaygay ggntaytaym gntgyathat ggtnacnccn 480 gayggnaayt tycaymgngg ntaycayytn cargtnytng tnacnccnga rgtnacnytn 540 ttycaraay gnaaymgnac ngcngtntgy aargcngtng cnggnaarcc ngcngcncay 600 athwsntgga thccngargg ngaytgygcn acnaarcarg artaytggws naayggnacn 660 gtnacngtna arwsnacntg ycaytgggar gtncayaayg tnwsnacngt nacntgycay 720 gtnwsncayy tnacnggnaa yaarwsnytn tayathgary tnytnccngt nccnggngcn 780 aaraarathw snaarathat htaywsnath taycayccnt aytaytayta yytngaycay 840 mgnggnathc ayytngtngt ngarwsncar tggytncara arath 885 primate, e.g., human, OX2RH1.2 (SEQ ID NO: 21): atgytntgyc cntggmgnac ngcnaayytn ggnytnytny tnathytnac nathttyytn 60 gtngcngarg cngarggngc ngcncarccn aayaaywsny tnatgytnca racnwsnaar 120 garaaycayg cnytngcnws nwsnwsnytn tgyatggayg araarcarat hacncaraay 180 taywsnaarg tnytngcnga rgtnaayacn wsntggccng tnaaratggc nacnaaygcn 240 gtnytntgyt gyccnccnat hgcnytnmgn aayytnatha thathacntg ggarathath 300 ytnmgnggnc arccnwsntg yacnaargcn taymgnaarg aracnaayga racnaargar 360 acnaaytgya cngaygarmg nathacntgg gtnwsnmgnc cngaycaraa ywsngayytn 420 carathmgnc cngtngcnat hacncaygay ggntaytaym gntgyathat ggtnacnccn 480 gayggnaayt tycaymgngg ntaycayytn cargtnytng tnacnccnga rgtnacnytn 540 ttycaraaym gnaaymgnac ngcngtntgy aargcngtng cnggnaarcc ngcngcncar 600 athwsntgga thccngargg ngaytgygcn acnaarcarg artaytggws naayggnacn 660 gtnacngtna arwsnacntg ycaytgggar gtncayaayg tnwsnacngt nacntgycay 720 gtnwsncayy tnacnggnaa yaarwsnytn tayathgary tnytnccngt nccnggngcn 780 aaraarwsng cnaarytnta yathccntay athathytna cnathathat hytnacnath 840 gtnggnttya thtggytnyt naargtnaay ggntgymgna artayaaryt naayaaracn 900 garwsnacnc cngtngtnga rgargaygar atgcarccnt aygcnwsnta yacngaraar 960 aayaayccny tntaygayac nacnaayaar gtnaargenw sncargenyt ncarwsngar 1020 gtngayacng ayytncayac nytn 1044 rodent, e.g., mouse, OX2RH1 (SEQ ID NO: 15): atgttytgyt tytggmgnac nwsngenytn gcngtnytny tnathtgggg ngtnttygtn 60 gcnggnwsnw sntgyacnga yaaraaycar acnacncara ayaaywsnws nwsnccnytn 120 acncargtna ayacnacngt nwsngtncar athggnacna argcnytnyt ntgytgytty 180 wsnathccny tnacnaargc ngtnytnath acntggatha thaarytnmg nggnytnccn 240 wsntgyacna thgcntayaa rgtngayacn aaracnaayg aracnwsntg yytnggnmgn 300 aayathaent gggenwsnae ncengayeay wsnecngary tncarathws ngengtnacn 360 ytncarcayg arggnacnta yacntgygar acngtnacnc cngarggnaa yttygaraar 420 aaytaygayy tncargtnyt ngtnccnccn gargtnacnt ayttyccnga raaraaymgn 480 wsngcngtnt gygargcnat ggcnggnaar ccngcngcnc arathwsntg gwsnccngay 540 ggngaytgyg tnacnacnws ngarwsncay wsnaayggna cngtnacngt nmgnwsnacn 600 tgycaytggg arcaraayaa ygtnwsngay gtnwsntgya thgtnwsnca yytnacnggn 660 aaycarwsny tnwsnathga rytnwsnmgn ggnggnaayc arwsnytnmg nccntayath 720 ccntayatha thccnwsnat hathathytn athathathg gntgyathtg yytnytnaar 780 athwsnggnt tymgnaartg yaarytnccn aarytngarg cnacnwsngc nathgargar 840 gaygaratgc arccntaygc nwsntayacn garaarwsna ayccnytnta ygayacngtn 900 acnaargtng argcnttycc ngtnwsncar ggngargtna ayggnacnga ytgyytnacn 960 ytnwsngcna thggnath 978 primate, e.g., human, OX2RH2 (SEQ ID NO: 16): atgggnggna arcaratgac ncaraaytay wsnacnatht tygcngargg naayathwsn 60 carccngtny tnatggayat haaygcngtn ytntgytgyc cnccnathgc nytnmgnaay 120 ytnathatha thacntggga rathathytn mgnggncarc cnwsntgyac naargcntay 180 aaraargara cnaaygarac naargaracn aaytgyacng tngarmgnat hacntgggtn 240 wsnmgnccng aycaraayws ngayytncar athmgnccng tngayacnac ncaygayggn 300 taytaymgng gnathgtngt nacnccngay ggnaayttyc aymgnggnta ycayytncar 360 gtnytngtna cnccngargt naayytntty carwsnmgna ayathacngc ngtntgyaar 420 gcngtnacng gnaarccngc ngcncarath wsntggathc cngarggnws nathytngcn 480 acnaarcarg artaytgggg naayggnacn gtnacngtna arwsnacntg yccntgggar 540 ggncayaarw snacngtnac ntgycaygtn wsncayytna cnggnaayaa rwsnytnwsn 600 gtnaarytna aywsnggnyt nmgnacnwsn ggnwsnccng cnytnwsnyt nytnathath 660 ytntaygtna arytnwsnyt nttygtngtn athytngtna cnacnggntt ygtnttytty 720 carmgnatha aycaygtnmg naargtnytn 750 rodent, e.g., mouse, OX2RH2 (SEQ ID NO: 17): mgnggncarc cnwsntgyat hatggcntay aargtngara cnaargarac naaygaracn 60 tgyytnggnm gnaayathac ntgggcnwsn acnccngayc ayathccnga yytncarath 120 wsngengtng cnytncarca ygarggnaay tayytntgyg arathaenac necngarggn 180 aayttycaya argtntayga yytncargtn ytngtnccnc cngargtnac ntayttyytn 240 ggngaraaym gnacngcngt ntgygargcn atggcnggna arccngcngc ncarathwsn 300 tggacnceng ayggngaytg ygtnacnaar wsngarwsne aywsnaaygg naengtnacn 360 gtnmgnwsna cntgycaytg ggarcaraay aaygtnwsng cngtnwsntg yathgtnwsn 420 caywsnacng gnaaycarws nytnwsnath garytnwsnm gnggnacnac nwsnacnacn 480 ccnwsnytny tnacnathyt ntaygtnaar atggtnytny tnggnathat hytnytnaar 540 gtnggnttyg cnttyttyca raarmgnaay gtnacnmgna en 582 rodent, e.g., mouse OX2RH4 (SEQ ID NO: 24) atgcaygcny tnggnmgnat hccnacnytn acnytnytna thttyathaa yathttygtn 60 wsnggnwsnw sntgyacnga ygaraaycar aenathcara aygaywsnws nwsnwsnytn 120 acncargtna ayacnacnat gwsngtncar atggayaara argcnytnyt ntgytgytty 180 wsnwsnccny tnathaaygc ngtnytnath acntggatha thaarcaymg ncayytnccn 240 wsntgyacna thgcntayaa yytngayaar aaracnaayg aracnwsntg yytnggnmgn 300 aayathaent gggenwsnae ncengayeay wsnecngary tncarathws ngcngtngcn 360 ytncarcayg arggnacnta yacntgygar athgtnacnc cngarggnaa yytngaraar 420 gtntaygayy tncargtnyt ngtnccnccn gargtnacnt ayttyccngg naaraaymgn 480 acngcngtnt gygargcnat ggcnggnaar ccngcngcnc arathwsntg gacnccngay 540 ggngaytgyg tnacnaarws ngarwsncay wsnaayggna cngtnacngt nmgnwsnacn 600 tgycaytggg arcaraayaa ygtnwsngtn gtnwsntgyy tngtnwsnca ywsnacnggn 660 aaycarwsny tnwsnathga rytnwsncar ggnacnatga cnacnccnmg nwsnytnytn 720 acnathytnt aygtnaarat ggcnytnytn gtnathathy tnytnaaygt nggnttygcn 780 ttyttycara armgnaaytt ygcnmgnacn 810 rodent, e.g., mouse, OX2RH3 (SEQ ID NO: 18) atgcaygcny tnggnmgnac nytngcnytn atgytnytna thttyathac nathytngtn 60 ccngarwsnw sntgywsngt naarggnmgn gargarathc cnccngayga ywsnttyccn 120 ttywsngayg ayaayathtt yccngayggn gtnggngtna cnatggarat hgarathath 180 acnccngtnw sngtncarat hggnathaar gcncarytnt tytgycaycc nwsnccnwsn 240 aargargcna cnytnmgnat htgggarath acnccnmgng aytggccnws ntgymgnytn 300 ccntaymgng cngarytnca rcarathwsn aaraaratht gyacngarmg nggnacnacn 360 mgngtnccng cncaycayca rwsnwsngay ytnccnatha arwsnatggc nytnaarcay 420 gayggncayt aywsntgymg nathgaracn acngayggna thttycarga rmgncaywsn 480 athcargtnc cnggngaraa y gnacngtn gtntgygarg cnathgcnws naarccngcn 540 atgcarathy tntggacncc ngaygargay tgygtnacna arwsnaarws ncayaaygay 600 acnatgathg tnmgnwsnaa rtgycaymgn garaaraaya ayggncayws ngtnttytgy 660 ttyathwsnc ayytnacnga yaaytggath ytnwsnatgg arcaraaymg nggnacnacn 720 wsnathytnc cnwsnytnyt nwsnathytn taygtnaary tngcngtnac ngtnytnath 780 gtnggnttyg cnttyttyca raarmgnaay tayttymgng tnccngargg nwsn 834 Table 5: Alignment of various species 0X2R homologs 1 and 2: 0X2RH1 MU MFCFWRTSALAVLLIWGVFVAGSS CTDKNQTTQN 0X2RH1_RT MLCFWRTSHVAVLLI GVFAAESS CPDKNQTMQN 0X2RH2_MU 0X2RH1 HU MLCP RTANLGLLLILTIFLVAEAEGAAQPNNSLMLQTSKENHALASSSLCMDEKQITQN OX2RH2 HU MGGKQMTQN OX2RHl_MU NSSSPLTQVNTTVSVQIGTKALLCCFSIPLTKAVLIT IIKLRGLPSCTIAYKVDT-KTN OX2RHl_RT NSST-MTEVNTTVFVQMGKKALLCCPSISLTKVILIT TITLRGQPSCIISYKADTRETH OX2RH2_MU RGQPSCIMAYKVETKETN OX2RHl_HU YSKV-LAEVNTS PVKMATNAVLCCPPIALRNLIIIT EIILRGQPSCTKAYKKETNETK OX2RH2_HU YSTI-FAEGNISQPVLMDINAVLCCPPIALRNLHIT EIILRGQPSCTKAYKKETNETK *+ * ■ *• * . + + . * . + . OX2RHl_MU ETSCLGRNITWASTPDHΞPELQISAVTLQHEGTYTCETVTPEGNFEKNYDLQVLVPPEVT OX2RHl_RT ESNCSDRSITWASTPDLAPDLQISAVALQHEGRYSCDIAVPDGNFQNIYDLQVLVPPEVT OX2RH2_MU ET-CLGRNIT ASTPDHIPDLQISAVALQHEGNYLCEITTPEGNFHKVYDLQVLVPPEVT 0X2RH1_HU ETNCTDERIT VSRPDQNSDLQIRTVAITHDGYYRCIMVTPDGNFHRGYHLQVLVTPEVT OX2 RH2 HU ETNCTVERIT VSRPDQNΞDLQIRPVDTTHDGYYRGIWTPDGNFHRGYHLQVLVTPEVN OX2RHl_MU YFPEKNRSAVCEAMAGKPAAQIS SPDG-DCVTTSESHSNGTVTVRSTCH EQNNVSDVS OX2RHl_RT HFPGENRTAVCEAIAGKPAAQISWTPDG-DCVAKNESHSNGTVTVRSTCH EQSHVSWF OX2RH2_MU YFLGENRTAVCEAMAGKPAAQIS TPDG-DCVTKSESHSNGTVTVRSTCHWEQNNVSAVS OX2RHl_HU LFQNRNRTAVCKAVAGKPAAHIS IPEG-DCATKQEYWSNGTVTVKSTCH EVHNVSTVT OX2 RH2 HU LFQSRNITAVCKAVTGKPAAQIS IPEGSILATKQEY GNGTVTVKΞTCP EGH-KSTVT *★**++.+*+ ++ OX2RHl_MU CIVSHLT-GNQSLSIELSRGGNQSLRPYI PYII PSIIILIIIGCICLLKISGFRKCKLPK OX2RHl_RT CWSHLTTGNQSLSIELGRGGDQLLGSYIQYIIPSIIILIIIGCICLLKISGCRKCKLPK OX2RH2_MU CIVSHST-GNQSLSIELSRGTTSTTPSLLTILYVKMVLLGII LLKV-G — FAFFQK OX2RHl_HU CHVSHLT-GNKSLYIEL LPVPG— AKKISKI I SIYHPY— YYYLDHRG--IHLWE OX2RH2 HU CHVSHLT-GNKSLSVKLNSGLRTSGSPALSLLI ILYVKLSLF — WILVTTG — FVFFQR + + . + * OX2RHl_MU LEATSAIEEDEMQPYASYTEKSNPLYDTVTKVEAFPVSQGEVNGTDCLTLSAIGI OX2RHl_RT SGATPDIEEDEMQPYASYTEKSNPLYDTVTTTEAHPASQGKVNGTDCLTLSAMGI OX2RH2_MU RNVTRT OX2RHl_HU SQ LQKI OX2RH2 HU INHVRKVL OX2R homolog polypeptide relationships (ϊ) human HI human H2 mouse HI mouse H2 mouse H3 rat HI Ig domain 54 52 72 73 32 TM/cyt 0 84 0 0 mouse H3 Ig domain 33 29 39 46 TM/cyt 46 0 54 mouse H2 Ig domain 60 51 82 TM/cyt 7 49 0 mouse HI Ig domain 53 47 TM/cyt 7 0 human H2 Ig domain 79 TM/cyt 7 sequence unavailable; "0" = no significant matching Comparison of primate and rodent H2 with rodent H4 polypeptides; note similarity between the rodent H2 and H4 : pOX2RH2 1 MGGK QMTQN-YSTIFAEGNISQPVL 24 rOX2RH2 1 0 rOX2RH4 1 MHALGRIPTLTLLIFINIFVSGSSCTDENQTIQNDSSSSLTQVNTTMSVQ 50 pOX2RH2 25 MDINAVLCCPPIALRNLIIITWEIILRGQPSCTKAYKKETNETKETNCTV 74 rOX2RH2 1 RGQPSCIMAYKVETKETNET-CLG 23 rOX2RH4 51 MDKKALLCCFSSPLINAVLITWIIKHRHLPSCTIAYN-LDKKTNETSCLG 99 * *** ** * ** * pOX2RH2 75 ERITWVSRPDQNSDLQIRPVDTTHDGYYRGIWTPDGNFHRGYHLQVLVT 124 rOX2RH2 24 RNITWASTPDHIPDLQISAVALQHEGNYLCEITTPEGNFHKVYDLQVLVP 73 rOX2RH4 100 RNITWASTPDHSPELQIΞAVALQHEGTYTCEIVTPEGNLEKVYDLQVLVP 149 *** * **_ *** * * * * t ** ^ ** * ***** pOX2RH2 125 PEVNLFQSRNITAVCKAVTGKPAAQIS IPEGSILATKQEY GNGTVTVK 174 rOX2RH2 74 PEVTYFLGENRTAVCEAMAGKPAAQIS TPDG-DCVTKSESHSNGTVTVR 122 rOX2RH4 150 PEVTYFPGKNRTAVCEAMAGKPAAQISWTPDG-DCVTKSEΞHSNGTVTVR 198 *** * * **** * ****** * ** * * ** * * * **** ^ pOX2RH2 175 STCP EG-HKSTVTCHVSHLTGNKSLSVKLNSGLRTSGSPALSLLIILYV 223 rOX2RH2 123 STCHWEQNNVSAVSCIVSHSTGNQSLSIELSRGTTST-TP- -SLLTILYV 169 rOX2RH4 199 STCHWEQNNVSWSCLVSHSTGNQSLSIELSQGTMTT- -PR-SLLTILYV 245 *** ** _ * * . * *** * * * ^ * * * * * ^ * *** **★* pOX2RH2 224 KLSLFWILVTTGFVFFQRINHVRKVL 250 rOX2RH2 170 KMVLLGIILLKVGFAFFQKRNVTRT 194 rOX2RH4 246 KMALLVIILLNVGFAFFQKRNFART 270 * _ * .**. * * ***. * * The OX2RH1 and 2 embodiments show particular similarity to one another, see, e.g., Table 5. Particular regions or positions of interest are, for the rat HI: boundaries adjacent to (before, at, or after) cys2, leu33, cys35, ile46, trp48, arg53, pro56, cys58, tyr62, cys74, thr80, trpδl, leu91, ile93, hislOO, glyl02, tyrl04, glyll3, phell5, leul22, vall23, prol27, asnl36, alal39, vall40, cysl41, alal43, lysl47, prol48, alal49, ilel52, trpl54, prol56, asnl69, thrl71, vall74, serl76, cysl78, glulδl, serl86, vall88, cysl90, serl93, hisl94, thrl96, asnl98, leu202, gly215, tyr217, leu237, lys238, and ile304. Many of the residues are conserved across the HI and H2 classes. Likewise with H2 and H4. See Table 5. Particular domains of interest in rat OX2RH1 are the C2 domain from about cys2 to prol27, the C2 domain from about glul28-gly215, the TM segment from about tyr217-leu237, and the intracellular domain from about lys238- ile304. Corresponding segments in mouse HI are about ser24- prol50, glul51-gly231, tyr239-leu259, and Iys260-ile326. In the mouse H2, the segments correspond, in available sequence, from about argl-pro74, glu75-glyl55, prol61-glyl82, and phel83- thrl94. For human H2, the transmembrane segment is about ala214-val233, and thr234-leu250, and in mouse H3, about proll9- gly237, with the intramembrane lys228, and phe238-gly252. Table 5 also indicates alignment of the H2 snd H4 embodiments. Additional positions of interest, e.g., as boundaries for fragments, will be those conserved across homolog groups with the rat 0X2RH1 or various subsets of the family members. Functionally, the rat and mouse HI have been shown to bind to the 0X2. This has not yet been confirmed for the human HI, but can be easily tested. Ligand matching for the H2, H4, and H3 groups is described below. The rodent H3 has been shown to associate with DAP12, as predicted. Recombinantly expressed epitope tagged DAP12 is not membrane associated in the absence of coexpression of a chaparone partner. see, e.g., Bakker, et al. (1999) Proc. Nat ' 1 Acad. Sci. USA 96:9792-9796. Mouse H3 can serve as the chaparone partner. However, the signal pathway through DAP12 requires binding to the H3 ligand, which has not yet been identified, but can be found using appropriate screening strategies, e.g., biochemical or physical methods. Sequence similarity of H2 and rodent H4 suggest a similar association with either the DAP12, or possibly the DAP10. The mouse H2 and H4 and human H2 are likely also to possess such properties, e.g., association with DAP12 (activating) or DAP10. The signaling pathways have been determined with some of the related receptors on NK cells. See, e.g., Lanier, et al. (1998) Immunity 8:693-701; Smith, et al . (1998) J. Immunol. 161:7-10; Gosselin, et al. (1999) J. Leukoc. Biol. 66:165-171; Tomasello, et al.(1998) J. Biol. Chem. 273:34115-34119; and McVicar, et al . (1998) J. Biol. Chem. 273:32934-32942. Because of the similarity of the extracellular domains with the HI members, OX2-like genes, particularly 0X2, are likely ligands. As used herein, the term OX2RH1, 0X2RH2, or OX2RH4 shall be used to describe a protein comprising amino acid sequences shown, e.g., in Tables 1-2. In many cases, a substantial fragment thereof will be functionally or structurally equivalent, including, e.g., an extracellular or intracellular domain. The invention also includes protein variants of the respective OX2RH alleles whose sequences are provided, e.g., uteins or soluble extracellular constructs. Typically, such agonists or antagonists will exhibit less than about 10% sequence differences, and thus will often have between 1 and 11 residue substitutions, e.g., 2, 3, 5, 7, and others. It also encompasses allelic and other variants, e.g., natural polymorphic, of the proteins described. Typically, the receptor will bind to a corresponding biological ligand with high affinity, e.g., at least about 100 nM, usually better than about 30 nM, preferably better than about 10 nM, and more preferably at better than about 3 nM. The term shall also be used herein to refer to related naturally occurring forms, e.g., alleles, polymorphic variants, and metabolic variants of the mammalian proteins. Preferred forms of the receptor complexes will bind the appropriate ligand with an affinity and selectivity appropriate for a ligand- receptor interaction. This invention also encompasses combinations of proteins or peptides having substantial amino acid sequence identity with the amino acid sequences in Tables 1-3. It will include sequence variants with relatively few substitutions, e.g., preferably less than about 3-5. A substantial polypeptide "fragment", or "segment", is a stretch of amino acid residues of at least about 8 amino acids, generally at least 10 amino acids, more generally at least 12 amino acids, often at least 14 amino acids, more often at least 16 amino acids, typically at least 18 amino acids, more typically at least 20 amino acids, usually at least 22 amino acids, more usually at least 24 amino acids, preferably at least 26 amino acids, more preferably at least 28 amino acids, and, in particularly preferred embodiments, at least about 30 or more amino acids. Sequences of segments of different proteins can be compared to one another over appropriate length stretches. In many situations, fragments may exhibit functional properties of the intact subunits, e.g., the extracellular domain of the transmembrane receptor may retain the ligand binding features, and may be used to prepare a soluble receptor-like complex. Amino acid sequence homology, or sequence identity, is determined by optimizing residue matches. In some comparisons, gaps may be introduced, as required. See, e.g., Needleham, et al. (1970) J. Mol. Biol. 48:443-453; Sankoff, et al . (1983) chapter one in Time Warps, String Edits, and Macromolecules : The Theory and Practice of Sequence Comparison, Addison-Wesley, Reading, MA; and software packages from IntelliGenetics, Mountain View, CA; and the University of Wisconsin Genetics Computer Group (GCG), Madison, WI; each of which is incorporated herein by reference. This changes when considering conservative substitutions as matches. Conservative substitutions typically include substitutions within the following groups: glycine, alanine; valine, isoleucine, leucine; aspartic acid, glutamic acid; asparagine, glutamine; serine, threonine; lysine, arginine; and phenylalanine, tyrosine. Homologous amino acid sequences are intended to include natural allelic and interspecies variations in the receptor homolog sequence. Typical homologous proteins or peptides will have from 50-100% homology (if gaps can be introduced), to 60-100% homology (if conservative substitutions are included) with an amino acid sequence segment of Tables 1-3. Homology measures will be at least about 70%, generally at least 76%, more generally at least 81%, often at least 85%, more often at least 88%, typically at least 90%, more typically at least 92%, usually at least 94%, more usually at least 95%, preferably at least 96%, and more preferably at least 97%, and in particularly preferred embodiments, at least 98% or more. The degree of homology will vary with the length of the compared segments. Homologous proteins or peptides, such as the allelic variants, will share most biological activities with the embodiments described in Tables 1-3. As used herein, the term "biological activity" is used to describe, without limitation, effects on inflammatory responses, innate immunity, and/or morphogenic development by receptor-like proteins. For example, these receptors are likely to mediate their effects through phosphatase or phosphorylase activities, which activities are easily measured by standard procedures. See, e.g., Hardie, et al . (eds. 1995) The Protein Kinase FactBook vols. I and II, Academic Press, San Diego, CA; Hanks, et al . (1991) Meth. Enzvmol. 200:38-62; Hunter, et al . (1992) Cell 70:375-388; Lewin (1990) Cell 61:743-752; Pines, et al . (1991) Cold Soring Harbor Svmo. Quant. Biol. 56:449-463; and Parker, et al. (1993) Nature 363:736-738. The receptor homologs, or portions thereof, may be useful as phosphate labeling enzymes to label general or specific substrates. The subunits may also be functional immunogens to elicit recognizing antibodies, or antigens capable of binding antibodies. The terms ligand, agonist, antagonist, and analog of, e.g., an OX2RH, include molecules that modulate the characteristic cellular responses to binding of 0X2 proteins, as well as molecules possessing the more standard structural binding competition features of ligand-receptor interactions, e.g., where the antagonist is a soluble extracellular domain of a receptor homolog or an antibody. The cellular responses likely are typically mediated through receptor tyrosine kinase pathways. Also, a receptor homolog may be a molecule which serves either as a natural receptor to which said ligand, or an analog thereof, binds, or a molecule which is a functional analog of the natural receptor. The functional analog may be a receptor homolog with structural modifications, or may be a wholly unrelated molecule which has a molecular shape which interacts with the appropriate ligand binding determinants. The ligands may serve as agonists or antagonists, see, e.g., Goodman, et al. (eds. 1990) Goodman & Gil an's: The Pharmacological Bases of Therapeutics, Pergamon Press, New York. Rational drug design may also be based upon structural studies of the molecular shapes of a receptor homolog, antibody, or other effectors or receptor homolog associated entities. See, e.g., Herz, et al . (1997) J. Receot. Signal Transduct . Res. 17:671-776; and Chaiken, et al . (1996) Trends Biotechnol. 14:369- 375. Effectors may be other proteins which mediate other functions in response to ligand binding, or other proteins which normally interact with the receptor homolog. One means for determining which sites interact with specific other proteins is a physical structure determination, e.g., x-ray crystallography or 2 dimensional NMR techniques. These will provide guidance as to which amino acid residues form molecular contact regions. For a detailed description of protein structural determination, see, e.g., Blundell and Johnson (1976) Protein Crystallography, Academic Press, New York, which is hereby incorporated herein by reference. II. Activities The receptor-like proteins will have a number of different biological activities, e.g., modulating cell proliferation, or in phosphate metabolism, being added to or removed from specific substrates, typically proteins. Such will generally result in modulation of an inflammatory function, other innate immunity response, or a morphological effect. The receptor homolog will probably have a specific low affinity binding to the ligand, as described. The 0X2RH1 has motifs suggestive of a receptor signaling through a receptor tyrosine kinase pathway. See, e.g., Ihle, et al. (1997) Stem Cells 15 (suppl. 1):105-111; Silvennoinen, et al . (1997) APMIS 105:497-509; Levy (1997) Cvtokine Growth Factor Review 8:81-90; Winston and Hunter (1996) Current Biol. 6:668- 671; Barrett (1996) Baillieres Clin. Gastroenterol . 10:1-15; and Briscoe, et al . (1996) Philos. Trans. R. Soc. Lond. B. Biol. Sci. 351:167-171. The biological activities of the OX2R homologs will likely be related to addition or removal of phosphate moieties to substrates, typically in a specific manner, but occasionally in a non specific manner. Substrates may be identified, or conditions for enzymatic activity may be assayed by standard methods, e.g., as described in Hardie, et al. (eds. 1995) The Protein Kinase FactBook vols. I and II, Academic Press, San Diego, CA; Hanks, et al. (1991) Meth. Enzvmol. 200:38-62; Hunter, et al . (1992) Cell 70:375-388; Lewin (1990) Cell 61:743-752; Pines, et al . (1991) Cold Soring Harbor Svmp. Quant. Biol. 56:449-463; and Parker, et al. (1993) Nature 363:736-738. A receptor homolog may combine with one or more other proteins to form functional complexes, e.g., which may be useful for binding ligand or preparing antibodies. These will have substantial diagnostic uses, including detection or quantitation. III. Nucleic Acids This invention contemplates use of isolated nucleic acid or fragments, e.g., which encode these or closely related proteins, or fragments thereof, e.g., to encode a corresponding polypeptide, preferably one which is biologically active. In addition, this invention covers isolated or recombinant DNAs which encode combinations of such proteins or polypeptides having characteristic sequences, e.g., of the homologs. Typically, the nucleic acid is capable of hybridizing, under appropriate conditions, with a nucleic acid sequence segment shown in Tables 1-3, but preferably not with a corresponding segment of other known Ig superfamily receptors. Said biologically active protein or polypeptide can be a full length protein, or fragment, and will typically have a segment of amino acid sequence highly homologous, e.g., exhibiting significant stretches of identity, to one shown in Tables 1-3. Further, this invention covers the use of isolated or recombinant nucleic acid, or fragments thereof, which encode proteins having fragments which are equivalent to the OX2RH proteins. The isolated nucleic acids can have the respective regulatory sequences in the 5 1 and 3' flanks, e.g., promoters, enhancers, poly-A addition signals, and others from the natural gene . An "isolated" nucleic acid is a nucleic acid, e.g., an RNA, DNA, or a mixed polymer, which is substantially pure, e.g., separated from other components which naturally accompany a native sequence, such as ribosomes, polymerases, and flanking genomic sequences from the originating species. The term embraces a nucleic acid sequence which has been removed from its naturally occurring environment, and includes recombinant or cloned DNA isolates, which are thereby distinguishable from naturally occurring compositions, and chemically synthesized analogs or analogs biologically synthesized by heterologous systems. A substantially pure molecule includes isolated forms of the molecule, either completely or substantially pure. An isolated nucleic acid will generally be a homogeneous composition of molecules, but will, in some embodiments, contain heterogeneity, preferably minor. This heterogeneity is typically found at the polymer ends or portions not critical to a desired biological function or activity. A "recombinant" nucleic acid is typically defined either by its method of production or its structure. In reference to its method of production, e.g., a product made by a process, the process is use of recombinant nucleic acid techniques, e.g., involving human intervention in the nucleotide sequence. Typically this intervention involves in vitro manipulation, although under certain circumstances it may involve more classical animal breeding techniques. Alternatively, it can be a nucleic acid made by generating a sequence comprising fusion of two fragments which are not naturally contiguous to each other, but is meant to exclude products of nature, e.g., naturally occurring mutants as found in their natural state. Thus, for example, products made by transforming cells with an unnaturally occurring vector is encompassed, as are nucleic acids comprising sequence derived using most any synthetic oligonucleotide process. Such a process is often done to replace a codon with a redundant codon encoding the same or a conservative amino acid, while typically introducing or removing a restriction enzyme sequence recognition site. Alternatively, the process is performed to join together nucleic acid segments of desired functions to generate a single genetic entity comprising a desired combination of functions not found in the commonly available natural forms, e.g., encoding a fusion protein. Restriction enzyme recognition sites are often the target of such artificial manipulations, but other site specific targets, e.g., promoters, DNA replication sites, regulation sequences, control sequences, or other useful features may be incorporated by design. A similar concept is intended for a recombinant, e.g., fusion, polypeptide. This will include a dimeric repeat. Specifically included are synthetic nucleic acids which, by genetic code redundancy, encode equivalent polypeptides to fragments of 0X2 receptor homologs and fusions of sequences from various different related molecules, e.g., other Ig superfamily members . A "fragment" in a nucleic acid context is a contiguous segment of at least about 17 nucleotides, generally at least 21 nucleotides, more generally at least 25 nucleotides, ordinarily at least 30 nucleotides, more ordinarily at least 35 nucleotides, often at least 39 nucleotides, more often at least 45 nucleotides, typically at least 50 nucleotides, more typically at least 55 nucleotides, usually at least 60 nucleotides, more usually at least 66 nucleotides, preferably at least 72 nucleotides, more preferably at least 79 nucleotides, and in particularly preferred embodiments will be at least 85 or more nucleotides. Typically, fragments of different genetic sequences can be compared to one another over appropriate length stretches, particularly defined segments such as the domains described below. A nucleic acid which codes for 0X2R homologs will be particularly useful to identify genes, mRNA, and cDNA species which code for itself or closely related proteins, as well as DNAs which code for polymorphic, allelic, or other genetic variants, e.g., from different individuals or related species. Preferred probes for such screens are those regions of the receptor homolog which are conserved between different polymorphic variants or which contain nucleotides which lack specificity, and will preferably be full length or nearly so. In other situations, polymorphic variant specific sequences will be more useful. Quantitation or specific sequence analysis may be useful as markers for disease or medical conditions, or in selecting particular therapeutic treatments. This invention further covers recombinant nucleic acid molecules and fragments having a nucleic acid sequence identical to or highly homologous to the isolated DNA set forth herein. In particular, the sequences will often be operably linked to DNA segments which control transcription, translation, and/or DNA replication. These additional segments typically assist in expression of the desired nucleic acid segment. Homologous, or highly identical, nucleic acid sequences, when compared to one another, e.g., OX2RH sequences, exhibit significant similarity. The standards for homology in nucleic acids are either measures for homology generally used in the art by sequence comparison or based upon hybridization conditions. Comparative hybridization conditions are described in greater detail below. Substantial identity in the nucleic acid sequence comparison context means either that the segments, or their complementary strands, when compared, are identical when optimally aligned, with appropriate nucleotide insertions or deletions, in at least about 60% of the nucleotides, generally at least 66%, ordinarily at least 71%, often at least 76%, more often at least 80%, usually at least 84%, more usually at least 88%, typically at least 91%, more typically at least about 93%, preferably at least about 95%, more preferably at least about 96 to 98% or more, and in particular embodiments, as high at about 99% or more of the nucleotides, including, e.g., segments encoding structural domains such as the segments described below. Alternatively, substantial identity will exist when the segments will hybridize under selective hybridization conditions, to a strand or its complement, typically using a sequence derived from Tables 1-3. Typically, selective hybridization will occur when there is at least about 55% homology over a stretch of at least about 14 nucleotides, more typically at least about 65%, preferably at least about 75%, and more preferably at least about 90%. See, Kanehisa (1984) Nucl. Acids Res. 12:203-213, which is incorporated herein by reference. The length of homology comparison, as described, may be over longer stretches, and in certain embodiments will be over a stretch of at least about 17 nucleotides, generally at least about 20 nucleotides, ordinarily at least about 24 nucleotides, usually at least about 28 nucleotides, typically at least about 32 nucleotides, more typically at least about 40 nucleotides, preferably at least about 50 nucleotides, and more preferably at least about 75 to 100 or more nucleotides. This includes, e.g., 125, 150, 175, 200, 225, 246, 273, 300, 325, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, and other lengths. Stringent conditions, in referring to homology in the hybridization context, will be stringent combined conditions of salt, temperature, organic solvents, and other parameters typically controlled in hybridization reactions. Stringent temperature conditions will usually include temperatures in excess of about 30 ° C, more usually in excess of about 37 " C, typically in excess of about 45' C, more typically in excess of about 50° C, e.g., 55 C or 60 C, preferably m excess of about 65° C, and more preferably m excess of about 70° C. Stringent salt conditions will ordinarily be less than about 1 M, more ordinarily less than about 500 mM, usually less than about 400 mM, more usually less than about 300 mM, typically less than about 200 mM, preferably less than about 100 mM, and more preferably less than about 80 mM, e.g., less than 50 mM, even down to less than about 20 mM. However, the combination of parameters is much more important than the measure of any single parameter. See, e.g., Wetmur and Davidson (1968) J. Mol. Biol. 31:349-370, which is hereby incorporated herein by reference. The isolated DNA can be readily modified by nucleotide substitutions, nucleotide deletions, nucleotide insertions, and inversions of nucleotide stretches. These modifications generally result m novel DNA sequences which encode this protein or its derivatives. These modified sequences can be used to produce mutant proteins (mutems) or to enhance the expression of variant species. Enhanced expression may involve gene amplification, increased transcription, increased translation, and other mechanisms. Such mutant OX2R homolog derivatives include predetermined or site-specifie mutations of the protein or its fragments, including silent mutations using genetic code degeneracy. "Mutant 0X2 receptor homolog" as used herein encompasses a polypeptide otherwise falling withm the definition of the 0X2 receptor homologs as set forth above, but having an ammo acid sequence which differs from that of other Ig superfamily as found in nature, whether by way of deletion, substitution, or insertion. In particular, "site specific mutant 0X2 receptor homolog" encompasses a protein having substantial sequence identity with a protein of Tables 1-3, and typically shares some or most of the biological activities or effects, e.g., immunogenicity, of the forms disclosed herein. Although site specific mutation sites are predetermined, mutants need not be site specific. Mammalian 0X2 receptor homolog mutagenesis can be achieved by making ammo acid insertions or deletions the gene, coupled with expression. Substitutions, deletions, insertions, or many combinations may be generated to arrive at a final construct. Insertions include amino- or carboxy- terminal fusions. Random mutagenesis can be conducted at a target codon and the expressed mammalian OX2RH mutants can then be screened for the desired activity, providing some aspect of a structure-activity relationship. Methods for making substitution mutations at predetermined sites in DNA having a known sequence are well known in the art, e.g., by M13 primer mutagenesis. See also Sambrook, et al. (1989) and Ausubel, et al . (1987 and periodic Supplements). The mutations in the DNA normally should not place coding sequences out of reading frames and preferably will not create complementary regions that could hybridize to produce secondary mRNA structure such as loops or hairpins. The phosphoramidite method described by Beaucage and Carruthers (1981) Tetra. Letts. 22:1859-1862, will produce suitable synthetic DNA fragments. A double stranded fragment will often be obtained either by synthesizing the complementary strand and annealing the strand together under appropriate conditions or by adding the complementary strand using DNA polymerase with an appropriate primer sequence. Polymerase chain reaction (PCR) techniques can often be applied in mutagenesis. Alternatively, mutagenesis primers are commonly used methods for generating defined mutations at predetermined sites. See, e.g., Innis, et al. (eds. 1990) PCR Protocols: A Guide to Methods and Applications Academic Press, San Diego, CA; and Dieffenbach and Dveksler (1995; eds.) PCR Primer: A Laboratory Manual Cold Spring Harbor Press, CSH, NY. Certain embodiments of the invention are directed to combination compositions comprising the receptor homolog or ligand sequences described. In other embodiments, functional portions of the sequences may be joined to encode fusion proteins. In other forms, variants of the described sequences may be substituted. IV. Proteins, Peptides As described above, the present invention encompasses mammalian 0X2RH polypeptides, e.g., whose sequences are disclosed in Tables 1-3, and described above. Allelic and other variant polypeptides are also contemplated, including, e.g., fusion proteins combining portions of such sequences with others, including, e.g., epitope tags, functional domains, and DAP12 or DAP10 sequences. The present invention also provides recombinant proteins, e.g., heterologous fusion proteins using segments from these primate or rodent proteins. A heterologous fusion protein is a fusion of proteins or segments which are naturally not normally fused in the same manner. Thus, the fusion product of two OX2RHs is a continuous protein molecule having sequences fused in a typical peptide linkage, typically made as a single translation product and exhibiting properties, e.g., sequence or antigenicity, derived from each source peptide. A similar concept applies to heterologous nucleic acid sequences. Combinations of various designated proteins into complexes are also provided. In addition, new constructs may be made from combining similar functional or structural domains from other related proteins, e.g., other ITIM, ITAM, or YxxM motif containing receptors, including species variants. For example, ligand- binding or other segments may be "swapped" between different new fusion polypeptides or fragments. See, e.g., Cunningham, et al . (1989) Science 243:1330-1336; and O'Dowd, et al . (1988) J. Biol. Chem. 263:15985-15992, each of which is incorporated herein by reference. Thus, new chimeric polypeptides exhibiting new combinations of specificities will result from the functional linkage of receptor-binding specificities. For example, the ligand binding domains from other related receptor homolog molecules may be added or substituted for other domains of this or related proteins. The resulting protein will often have hybrid function and properties. For example, a fusion protein may include a targeting domain which may serve to provide sequestering of the fusion protein to a particular subcellular organelle. Candidate fusion partners and sequences can be selected from various sequence data bases, e.g., GenBank, c/o IntelliGenetics, Mountain View, CA; and BCG, University of Wisconsin Biotechnology Computing Group, Madison, WI, which are each incorporated herein by reference. In particular, combinations of polypeptide sequences provided in Tables 1-3 are particularly preferred. Variant forms of the proteins may be substituted in the described combinations. The present invention particularly provides muteins which bind 0X2-like ligands, and/or which are affected in signal transduction. Structural alignment of various members of the 0X2 receptor homolog family show conserved features/residues. See, e.g., Table 5. Alignment of the 0X2R homolog sequences indicates various structural and functionally shared features. See also, Bazan, et al. (1996) Nature 379:591; Lodi, et al . (1994) Science 263:1762-1766; Sayle and Milner-White (1995) TIBS 20:374-376; and Gronenberg, et al . (1991) Protein Engineering 4:263-269. Substitutions with either mouse sequences or human sequences are particularly preferred. Conversely, conservative substitutions away from the ligand binding interaction regions will probably preserve most signaling activities; and conservative substitutions away from the intracellular domains will probably preserve most ligand binding properties. "Derivatives" of a mammalian OX2RH include amino acid sequence mutants, glycosylation variants, metabolic derivatives and covalent or aggregative conjugates with other chemical moieties. Covalent derivatives can be prepared by linkage of functionalities to groups which are found in the 0X2RH amino acid side chains or at the N- or C- termini, e.g., by means which are well known in the art. These derivatives can include, without limitation, aliphatic esters or amides of the carboxyl terminus, or of residues containing carboxyl side chains, O-acyl derivatives of hydroxyl group-containing residues, and N-acyl derivatives of the amino terminal amino acid or amino-group containing residues, e.g., lysine or arginine . Acyl groups are selected from the group of alkyl-moieties, including C3 to C18 normal alkyl, thereby forming alkanoyl aroyl species. In particular, glycosylation alterations are included, e.g., made by modifying the glycosylation patterns of a polypeptide during its synthesis and processing, or in further processing steps. Particularly preferred means for accomplishing this are by exposing the polypeptide to glycosylating enzymes derived from cells which normally provide such processing, e.g., mammalian glycosylation enzymes. Deglycosylation enzymes are also contemplated. Also embraced are versions of the same primary amino acid sequence which have other minor modifications, including phosphorylated amino acid residues, e.g., phosphotyrosine, phosphoserine, or phosphothreonine. A major group of derivatives are covalent conjugates of the receptor homologs or fragments thereof with other proteins of polypeptides. These derivatives can be synthesized in recombinant culture such as N- or C-terminal fusions or by the use of agents known in the art for their usefulness in cross-linking proteins through reactive side groups. Preferred derivatization sites with cross-linking agents are at free amino groups, carbohydrate moieties, and cysteine residues. Fusion polypeptides between the receptor homologs and other homologous or heterologous proteins are also provided. Homologous polypeptides may be fusions between different receptors, resulting in, for instance, a hybrid protein exhibiting binding specificity for multiple different 0X2 related ligands, or a receptor which may have broadened or weakened specificity of substrate effect. Likewise, heterologous fusions may be constructed which would exhibit a combination of properties or activities of the derivative proteins. Typical examples are fusions of a reporter polypeptide, e.g., luciferase, with a segment or domain of a receptor, e.g., a ligand-binding segment, so that the presence or location of a desired ligand may be easily determined. See, e.g., Dull, et al., U.S. Patent No. 4,859,609, which is hereby incorporated herein by reference. Other gene fusion partners include glutathione-S-transferase (GST) , bacterial β-galactosidase, trpE, Protein A, β-lactamase, alpha amylase, alcohol dehydrogenase, and yeast alpha mating factor. See, e.g., Godowski, et al. (1988) Science 241:812-816. Labeled proteins will often be substituted in the described combinations of proteins. The phosphoramidite method described by Beaucage and Carruthers (1981) Tetra. Letts. 22:1859-1862, will produce suitable synthetic DNA fragments. A double stranded fragment will often be obtained either by synthesizing the complementary strand and annealing the strand together under appropriate conditions or by adding the complementary strand using DNA polymerase with an appropriate primer sequence. Such polypeptides may also have amino acid residues which have been chemically modified by phosphorylation, sulfonation, biotinylation, or the addition or removal of other moieties, particularly those which have molecular shapes similar to phosphate groups. In some embodiments, the modifications will be useful labeling reagents, or serve as purification targets, e.g., affinity ligands. Fusion proteins will typically be made by either recombinant nucleic acid methods or by synthetic polypeptide methods. Techniques for nucleic acid manipulation and expression are described generally, for example, in Sambrook, et al . (1989) Molecular Cloning: A Laboratory Manual (2d ed.), Vols. 1-3, Cold Spring Harbor Laboratory, and Ausubel, et al. (eds. 1987 and periodic supplements) Current Protocols in Molecular Biology, Greene/Wiley, New York, which are each incorporated herein by reference. Techniques for synthesis of polypeptides are described, for example, in Merrifield (1963) J. Amer. Chem. Soc. 85:2149-2156; Merrifield (1986) Science 232:341-347; and Atherton, et al . (1989) Solid Phase Peptide Svnthesis: A Practical Approach, IRL Press, Oxford; each of which is incorporated herein by reference. See also Dawson, et al. (1994) Science 266:776-779 for methods to make larger polypeptides. This invention also contemplates the use of derivatives of an OX2RH other than variations in amino acid sequence or glycosylation. Such derivatives may involve covalent or aggregative association with chemical moieties. These derivatives generally fall into three classes: (1) salts, (2) side chain and terminal residue covalent modifications, and (3) adsorption complexes, e.g., with cell membranes. Such covalent or aggregative derivatives are useful as i munogens, as reagents in immunoassays, or in purification methods such as for affinity purification of a receptor or other binding molecule, e.g., an antibody. For example, an 0X2 ligand can be immobilized by covalent bonding to a solid support such as cyanogen bromide-activated Sepharose, by methods which are well known in the art, or adsorbed onto polyolefin surfaces, with or without glutaraldehyde cross-linking, for use in the assay or purification of an OX2RH, antibodies, or other similar molecules. The ligand can also be labeled with a detectable group, for example radioiodinated by the chloramine T procedure, covalently bound to rare earth chelates, or conjugated to another fluorescent moiety for use in diagnostic assays. A combination, e.g., including an OX2RH, of this invention can be used as an immunogen for the production of antisera or antibodies specific, e.g., capable of distinguishing between other 0X2 receptor homologs, or for desired combination specificity. The 0X2RHs can be used to screen monoclonal antibodies or antigen-binding fragments prepared by immunization with various forms of impure preparations containing the protein. In particular, the term "antibodies" also encompasses antigen binding fragments of natural antibodies, e.g., Fab, Fab2, Fv, etc. The purified 0X2RH can also be used as a reagent to detect antibodies generated in response to the presence of elevated levels of expression, or immunological disorders which lead to antibody production to the endogenous receptor homolog. Additionally, 0X2RH fragments may also serve as immunogens to produce the antibodies of the present invention, as described immediately below. For example, this invention contemplates antibodies having binding affinity to or being raised against the amino acid sequences shown in Tables 1-3, fragments thereof, or various homologous peptides or subsets. In particular, this invention contemplates antibodies having binding affinity to, or having been raised against, specific fragments which are predicted to be, or actually are, exposed at the exterior protein surface of the native 0X2RH. Complexes of combinations of proteins will also be useful, and antibody preparations thereto can be made . The blocking of physiological response to the receptor ligands may result from the inhibition of binding of the ligand to the receptor, likely through competitive inhibition, or perhaps down-regulation of receptor expression due to antibody binding. Thus, in vitro assays of the present invention will often use antibodies or antigen binding segments of these antibodies, or fragments attached to solid phase substrates. These assays will also allow for the diagnostic determination of the effects of either ligand binding region mutations and modifications, or other mutations and modifications, e.g., which affect signaling or enzymatic function. This invention also contemplates the use of competitive drug screening assays, e.g., where neutralizing antibodies to the receptor complexes or fragments compete with a test compound for binding to a ligand or other antibody. In this manner, the neutralizing antibodies or fragments can be used to detect the presence of a polypeptide which shares one or more binding sites to a receptor and can also be used to occupy binding sites on a receptor that might otherwise bind a ligand. V. Making Nucleic Acids and Protein DNA which encodes the protein or fragments thereof can be obtained by chemical synthesis, screening cDNA libraries, or by screening genomic libraries prepared from a wide variety of cell lines or tissue samples. Natural sequences can be isolated using standard methods and the sequences provided herein, e.g., in Tables 1-3. Reverse translation sequences are provided in Table 4. Other species counterparts can be identified by hybridization techniques, or by various PCR techniques, combined with or by searching in sequence databases, e.g., GenBank. Antibodies may be used in expression cloning efforts on species counterparts. This DNA can be expressed in a wide variety of host cells for the synthesis of a full-length receptor or fragments which can, e.g., be used to generate polyclonal or monoclonal antibodies; for binding studies; for construction and expression of modified ligand binding or kinase/phosphatase domains; and for structure/function studies. Variants or fragments can be expressed in host cells that are transformed or transfected with appropriate expression vectors. These molecules can be substantially free of protein or cellular contaminants, other than those derived from the recombinant host, and therefore are particularly useful in pharmaceutical compositions when combined with a pharmaceutically acceptable carrier and/or diluent. The protein, or portions thereof, may be expressed as fusions with other proteins. Combinations of the described proteins, or nucleic acids encoding them, are particularly interesting. Expression vectors are typically self-replicating DNA or RNA constructs containing the desired receptor homolog gene or its fragments, usually operably linked to suitable genetic control elements that are recognized in a suitable host cell. These control elements are capable of effecting expression within a suitable host. The multiple genes may be coordinately expressed, and may be on a polycistronic message. The specific type of control elements necessary to effect expression will depend upon the eventual host cell used. Generally, the genetic control elements can include a prokaryotic promoter system or a eukaryotic promoter expression control system, and typically include a transcriptional promoter, an optional operator to control the onset of transcription, transcription enhancers to elevate the level of mRNA expression, a sequence that encodes a suitable ribosome binding site, and sequences that terminate transcription and translation. Expression vectors also usually contain an origin of replication that allows the vector to replicate independently of the host cell. The vectors of this invention include those which contain DNA which encodes a combination of proteins, as described, or a biologically active equivalent polypeptide. The DNA can be under the control of a viral promoter and can encode a selection marker. This invention further contemplates use of such expression vectors which are capable of expressing eukaryotic cDNAs coding for such protems in a prokaryotic or eukaryotic host, where the vector is compatible with the host and where the eukaryotic cDNAs are inserted mto the vector such that growth of the host containing the vector expresses the cDNAs m question. Usually, expression vectors are designed for stable replication m their host cells or for amplification to greatly mcrease the total number of copies of the desirable gene per cell. It is not always necessary to require that an expression vector replicate in a host cell, e.g., it is possible to effect transient expression of the protem or its fragments various hosts using vectors that do not contain a replication origin that is recognized by the host cell. It is also possible to use vectors that cause integration of the prote encoding portions mto the host DNA by recombination. Vectors, as used herein, comprise plasmids, viruses, bacteriophage, integratable DNA fragments, and other vehicles which enable the integration of DNA fragments mto the genome of the host. Expression vectors are specialized vectors which contain genetic control elements that effect expression of operably linked genes. Plasmids are the most commonly used form of vector but all other forms of vectors which serve an equivalent function and which are, or become, known the art are suitable for use herem. See, e.g., Pouwels, et al. (1985 and Supplements) Clonmg Vectors: A Laboratory Manual, Elsevier, N.Y., and Rodriguez, et al . (eds. 1988) Vectors: A Survey of Molecular Clon g Vectors and Their Uses, Buttersworth, Boston, which are incorporated herein by reference. Transformed cells are cells, preferably mammalian, that have been transformed or transfected with vectors constructed using recombinant DNA techniques. Transformed host cells usually express the desired proteins, but for purposes of cloning, amplifying, and manipulating its DNA, do not need to express the subject proteins. This invention further contemplates culturing transformed cells in a nutrient medium, thus permitting the proteins to accumulate. The proteins can be recovered, either from the culture or, in certain instances, from the culture medium. For purposes of this invention, nucleic acid sequences are operably linked when they are functionally related to each other. For example, DNA for a presequence or secretory leader is operably linked to a polypeptide if it is expressed as a preprotein or participates in directing the polypeptide to the cell membrane or in secretion of the polypeptide. A promoter is operably linked to a coding sequence if it controls the transcription of the polypeptide; a ribosome binding site is operably linked to a coding sequence if it is positioned to permit translation. Usually, operably linked means contiguous and in reading frame, however, certain genetic elements such as repressor genes are not contiguously linked but still bind to operator sequences that in turn control expression. Suitable host cells include prokaryotes, lower eukaryotes, and higher eukaryotes. Prokaryotes include both gram negative and gram positive organisms, e.g., E. coli and B. subtilis. Lower eukaryotes include yeasts, e.g., S. cerevisiae and Pichia, and species of the genus Dictyostelium. Higher eukaryotes include established tissue culture cell lines from animal cells, both of non-mammalian origin, e.g., insect cells, and birds, and of mammalian origin, e.g., human, primates, and rodents. Prokaryotic host-vector systems include a wide variety of vectors for many different species. E. coli and its vectors will be described, but equivalent vectors and hosts can generally be substituted. A representative vector for amplifying DNA is pBR322 or many of its derivatives. Vectors that can be used to express the receptor homolog or its fragments include, but are not limited to, such vectors as those containing the lac promoter (pUC-series) ; trp promoter (pBR322-trp) ; Ipp promoter (the pIN-series) ; lambda-pP or pR promoters (pOTS) ; or hybrid promoters such as ptac (pDR540) . See Brosius, et al. (1988) "Expression Vectors Employing Lambda-, trp-, lac-, and Ipp-derived Promoters", in Vectors: A Survey of Molecular Cloning Vectors and Their Uses, (eds. Rodriguez and Denhardt) , Buttersworth, Boston, Chapter 10, pp. 205-236, which is incorporated herein by reference. Lower eukaryotes, e.g., yeasts and Dictyostelium, may be transformed with OX2RH sequence containing vectors. The most popular lower eukaryotic host is the baker's yeast, Saccharomyces cerevisiae. It will be used to exemplify lower eukaryotes, though many other strains and species are also available. Yeast vectors typically consist of a replication origin (unless of the integrating type) , a selection gene, a promoter, DNA encoding the receptor homolog or its fragments, and sequences for translation termination, polyadenylation, and transcription termination. Suitable expression vectors for yeast include such constitutive promoters as 3-phosphoglycerate kinase and various other glycolytic enzyme gene promoters or such inducible promoters as the alcohol dehydrogenase 2 promoter or metallothionme promoter. Suitable vectors include derivatives of the following types: self-replicating low copy number (such as the YRp-series) , self-replicating high copy number (such as the YEp-series) ; integrating types (such as the Yip-series), or mini-chromosomes (such as the YCp-series) . Higher eukaryotic tissue culture cells are normally the preferred host cells for expression of functionally active OX2RH proteins. In principle, many higher eukaryotic tissue culture cell lines are workable, e.g., insect baculovirus expression systems, whether from an invertebrate or vertebrate source. However, mammalian cells are preferred. Transformation or transfection and propagation of such cells has become a routine procedure. Examples of useful cell lines include HeLa cells, Chinese hamster ovary (CHO) cell lines, baby rat kidney (BRK) cell lines, insect cell lines, bird cell lines, and monkey (COS) cell lines. Expression vectors for such cell lines usually include an origin of replication, a promoter, a translation initiation site, RNA splice sites (if genomic DNA is used) , a polyadenylation site, and a transcription termination site. These vectors also usually contain a selection gene or amplification gene. Suitable expression vectors may be plasmids, viruses, or retroviruses carrying promoters derived, e.g., from such sources as from adenovirus, SV40, parvoviruses, vaccinia virus, or cytomegalovirus . Representative examples of suitable expression vectors include pCDNAl; pCD, see Okayama, et al . (1985) Mol. Cell Biol. 5:1136-1142; pMClneo PolyA, see Thomas, et al. (1987) Cell 51:503-512; and a baculovirus vector such as pAC 373 or pAC 610. For secreted proteins and some membrane proteins, an open reading frame usually encodes a polypeptide that consists of a mature or secreted product covalently linked at its N-terminus to a signal peptide. The signal peptide is cleaved prior to secretion of the mature, or active, polypeptide. The cleavage site can be predicted with a high degree of accuracy from empirical rules, e.g., von-Heijne (1986) Nucleic Acids Research 14:4683-4690, and Nielsen, et al . (1997) Protein Enα. 10:1-12. And the precise amino acid composition of the signal peptide often does not appear to be critical to its function, e.g., Randall, et al . (1989) Science 243:1156-1159; Kaiser, et al . (1987) Science 235:312-317. The mature proteins of the invention can be readily determined using standard methods. It will often be desired to express these polypeptides in a system which provides a specific or defined glycosylation pattern. In this case, the usual pattern will be that provided naturally by the expression system. However, the pattern will be modifiable by exposing the polypeptide, e.g., an unglycosylated form, to appropriate glycosylating proteins introduced into a heterologous expression system. For example, the OX2RH gene may be co-transformed with one or more genes encoding mammalian or other glycosylating enzymes. Using this approach, certain mammalian glycosylation patterns will be achievable in prokaryote or other cells. Expression in prokaryote cells will typically lead to unglycosylated forms of protein. The source of 0X2RH can be a eukaryotic or prokaryotic host expressing recombinant polypeptide, such as is described above. The source can also be a cell line, but other mammalian cell lines are also contemplated by this invention, with the preferred cell line being from the human species. Now that the sequences are known, the primate OX2RH, fragments, or derivatives thereof can be prepared by conventional processes for synthesizing peptides. These include processes such as are described in Stewart and Young (1984) Solid Phase Peptide Synthesis, Pierce Chemical Co., Rockford, IL; Bodanszky and Bodanszky (1984) The Practice of Peptide Svnthesis, Springer-Verlag, New York; and Bodanszky (1984) The Principles of Peptide Svnthesis, Springer-Verlag, New York; all of each which are incorporated herein by reference. For example, an azide process, an acid chloride process, an acid anhydride process, a mixed anhydride process, an active ester process (for example, p-nitrophenyl ester, N-hydroxysuccinimide ester, or cyanomethyl ester) , a carbodiimidazole process, an oxidative-reductive process, or a dicyclohexylcarbodiimide (DCCD) /additive process can be used. Solid phase and solution phase syntheses are both applicable to the foregoing processes. Similar techniques can be used with partial OX2RH sequences. The OX2RH proteins, fragments, or derivatives are suitably prepared in accordance with the above processes as typically employed in peptide synthesis, generally either by a so-called stepwise process which comprises condensing an amino acid to the terminal amino acid, one by one in sequence, or by coupling peptide fragments to the terminal amino acid. Amino groups that are not being used in the coupling reaction typically must be protected to prevent coupling at an incorrect location. If a solid phase synthesis is adopted, the C-terminal amino acid is bound to an insoluble carrier or support through its carboxyl group. The insoluble carrier should have a binding capability to a reactive carboxyl group, e.g., halo ethyl resins, such as chloromethyl resin or bromomethyl resin, hydroxymethyl resins, phenol resins, tert-alkyloxycarbonylhydrazidated resins, and the like. An amino group-protected amino acid is bound in sequence through condensation of its activated carboxyl group and the reactive amino group of the previously formed peptide or chain, to synthesize the peptide step by step. After synthesizing the complete sequence, the peptide is split off from the insoluble carrier to produce the peptide. This solid-phase approach is generally described by Merrifield, et al. (1963) in J. Am. Chem. Soc. 85:2149-2156, which is incorporated herein by reference. The prepared protein and fragments thereof can be isolated and purified from the reaction mixture by means of peptide separation, e.g., by extraction, precipitation, electrophoresis, various forms of chromatography, and the like. The receptor homologs of this invention can be obtained in varying degrees of purity depending upon desired uses. Purification can be accomplished using standard protein purification techniques or the antibodies herein described in immunoabsorbant affinity chromatography methods. Typically, affinity chromatography is carried out by first linking the antibodies to a solid support and then contacting the linked antibodies with solubilized lysates of appropriate cells, lysates of other cells expressing the 0X2RH, or lysates or supematants of cells producing the protein as a result of DNA techniques, see below. Generally, the purified protein will be at least about 40% pure, ordinarily at least about 50% pure, usually at least about 60% pure, typically at least about 70% pure, more typically at least about 80% pure, preferable at least about 90% pure and more preferably at least about 95% pure, and in particular embodiments, 97%-99% or more. Purity will usually be on a weight basis, but can also be on a molar basis. Different assays will be applied as appropriate. Individual proteins may be purified and thereafter combined. VI. Antibodies Antibodies can be raised to the various mammalian, e.g., primate, OX2RH proteins and fragments thereof, both in naturally occurring native forms and in their denatured forms. Antibodies raised to native OX2RH are more likely to recognize epitopes which are only present in the native conformations. Denatured antigen detection can also be useful in, e.g., Western analysis. Anti-idiotypic antibodies are also contemplated, which would be useful, e.g., diagnostic reagents. Antibodies, including binding fragments and single chain versions, against predetermined fragments of the protein can be raised by immunization of animals with conjugates of the fragments with immunogenic proteins . Monoclonal antibodies are prepared from cells secreting the desired antibody. These antibodies can be screened for binding to normal or defective protein, or screened for agonistic or antagonistic activity. These monoclonal antibodies will usually bind with at least a KQ of about 1 mM, more usually at least about 300 μM, typically at least about lOOμM, more typically at least about 30 μM, preferably at least about 10 μM, and more preferably at least about 3 μM or better. The antibodies, including antigen binding fragments, of this invention can have significant diagnostic or therapeutic value. They can be potent antagonists that bind to a receptor homolog and inhibit binding to ligand or inhibit the ability of the receptor homolog to elicit a biological response, e.g., act on its substrate. They also can be useful as non-neutralizing antibodies and can be coupled to toxins or radionuclides to bind OX2RH producing cells. Further, these antibodies can be conjugated to drugs or other therapeutic agents, either directly or indirectly, e.g., by means of a linker. The antibodies of this invention can also be useful in diagnostic applications. As capture or non-neutralizing antibodies, they might bind to the OX2RH without inhibiting ligand or substrate binding. As neutralizing antibodies, they can be useful in competitive binding assays. They will also be useful in detecting or quantifying ligand. They may be used as reagents for Western blot analysis, or for immunoprecipitation or immunopurification of the respective protein. Likewise, nucleic acids and proteins may be immobilized to solid substrates for affinity purification or detection methods. The substrates may be, e.g., solid resin beads, sheets of plastic, or derivatized glass. Protein fragments may be joined to other materials, particularly polypeptides, as fused or covalently joined polypeptides, to be used as immunogens. Mammalian 0X2RH polypeptides and fragments may be fused or covalently linked to a variety of immunogens, such as keyhole limpet hemocyanin, bovine serum albumin, tetanus toxoid, etc. See Microbiology, Hoeber Medical Division, Harper and Row, 1969; Landsteiner (1962) Specificity of Serological Reactions, Dover Publications, New York; and Williams, et al. (1967) Methods in Immunology and Immunochemistrv, Vol. 1, Academic Press, New York; each of which are incorporated herein by reference. A typical method involves hyperimmunization of an animal with an antigen. The blood of the animal is then collected shortly after the repeated immunizations and serum or gamma globulin is isolated. In some instances, it is desirable to prepare monoclonal antibodies from various mammalian hosts, such as mice, rodents, primates, humans, etc. See, e.g., Stites, et al . (eds.) Basic and Clinical Immunology (4th ed.), Lange Medical Publications, Los Altos, CA, and references cited therein; Harlow and Lane (1988) Antibodies: A Laboratory Manual, CSH Press; Goding (1986) Monoclonal Antibodies: Principles and Practice (2d ed.) Academic Press, New York; and particularly Kohler and Milstein (1975) Nature 256:495-497, each of these references is incorporated herein by reference. Briefly, an immunogen is injected into an animal to induce an immune response. The animal is then sacrificed and cells taken from its spleen, which are fused with myeloma cells to produce a hybridoma. The population of hybridomas is then screened to isolate an individual clone which secretes an antibody which binds to the immunogen. Other suitable techniques involve in vitro exposure of lymphocytes to the antigenic polypeptides or alternatively to selection of libraries of antibodies in phage or similar vectors. See, Huse, et al . (1989) "Generation of a Large Combinatorial Library of the Immunoglobulin Repertoire in Phage Lambda, " Science 246:1275-1281; and Ward, et al . (1989) Nature 341:544- 546, each of which is hereby incorporated herein by reference. Chimeric or humanized antibodies may be produced, see Cabilly, U.S. Patent No. 4,816,567; or made in transgenic mice, see Mendez, et al. (1997) Nature Genetics 15:146-156. These references are incorporated herein by reference. Polypeptides and antibodies will often be labeled. A wide variety of labels and conjugation techniques are known and are reported extensively in both the scientific and patent literature. Suitable labels include radionuclides, enzymes, substrates, cofactors, inhibitors, fluorescent moieties, chemiluminescent moieties, magnetic particles, and the like. Patents teaching the use of such labels include, e.g., U.S. Patent Nos. 3,817,837; 3,850,752; 3,939,350; 3,996,345; 4,277,437; 4,275,149; and 4, 366, 241. The antibodies of this invention can also be used for affinity chromatography in isolating the 0X2RH proteins or peptides. Columns can be prepared where the antibodies are linked to a solid support, e.g., particles, such as agarose, Sephadex, or the like, where a cell lysate may be passed through the column, the column washed, followed by increasing concentrations of a mild denaturant, whereby the purified protein will be released. Alternatively, the protein may be used to purify antibody. Appropriate cross absorptions or depletions may be applied. The antibodies may also be used to screen expression libraries for particular expression products. Usually the antibodies used in such a procedure will be labeled with a moiety allowing easy detection of presence of antigen by antibody binding. Antibodies raised against an OX2RH will also be used to raise anti-idiotypic antibodies. These will be useful in detecting or diagnosing various immunological conditions related to expression of the protein or cells which express the protein. They also will be useful as agonists or antagonists of the ligand, which may be competitive inhibitors or substitutes for naturally occurring ligands. A receptor homolog protein that specifically binds to or that is specifically immunoreactive with an antibody generated against a defined immunogen, such as an immunogen consisting of the amino acid sequence of SEQ ID NO: 2, is typically determined in an immunoassay. The immunoassay typically uses a polyclonal antiserum which was raised, e.g., to a protein of SEQ ID NO: 2. This antiserum is selected to have low crossreactivity against other Ig superfamily receptor members, e.g., NKG2D, preferably from the same species, and any such crossreactivity is removed by immunoabsorption prior to use in the immunoassay. In order to produce antisera for use in an immunoassay, the protein, e.g., of SEQ ID NO: 2, is isolated as described herein. For example, recombinant protein may be produced in a mammalian cell line. An appropriate host, e.g., an inbred strain of mice such as Balb/c, is immunized with the selected protein, typically using a standard adjuvant, such as Freund's adjuvant, and a standard mouse immunization protocol (see Harlow and Lane, supra) . Alternatively, a synthetic peptide derived from the sequences disclosed herein and conjugated to a carrier protein can be used an immunogen. Polyclonal sera are collected and titered against the immunogen protein in an immunoassay, e.g., a solid phase immunoassay with the immunogen immobilized on a solid support. Polyclonal antisera with a titer of 10^ or greater are selected and tested for their cross reactivity against other Ig superfamily receptor members using a competitive binding immunoassay such as the one described in Harlow and Lane, supra, at pages 570-573. Preferably at least two receptor family members are used in this determination. These receptor family members can be produced as recombinant proteins and isolated using standard molecular biology and protein chemistry techniques as described herein. Immunoassays in the competitive binding format can be used for the crossreactivity determinations. For example, the protein of SEQ ID NO: 2 can be immobilized to a solid support. Proteins added to the assay compete with the binding of the antisera to the immobilized antigen. The ability of the above proteins to compete with the binding of the antisera to the immobilized protein is compared to the proteins. The percent crossreactivity for the above proteins is calculated, using standard calculations. Those antisera with less than 10% crossreactivity with each of the proteins listed above are selected and pooled. The cross-reacting antibodies are then removed from the pooled antisera by immunoabsorption with the above-listed proteins. The immunoabsorbed and pooled antisera are then used in a competitive binding immunoassay as described above to compare a second protein to the immunogen protein (e.g., the OX2RH1 like protein of SEQ ID NO: 2) . In order to make this comparison, the two proteins are each assayed at a wide range of concentrations and the amount of each protein required to inhibit 50% of the binding of the antisera to the immobilized protein is determined. If the amount of the second protein required is less than twice the amount of the protein of the selected protein or proteins that is required, then the second protein is said to specifically bind to an antibody generated to the immunogen. It is understood that these 0X2 receptor homolog proteins are members of a family of homologous proteins that comprise at least 6 so far identified genes. For a particular gene product, such as the 0X2RH1, the term refers not only to the amino acid sequences disclosed herein, but also to other proteins that are allelic, non-allelic, or species variants. It is also understood that the terms include nonnatural mutations introduced by deliberate mutation using conventional recombinant technology such as single site mutation, or by excising short sections of DNA encoding the respective proteins, or by substituting new amino acids, or adding new amino acids. Such minor alterations typically will substantially maintain the immunoidentity of the original molecule and/or its biological activity. Thus, these alterations include proteins that are specifically immunoreactive with a designated naturally occurring OX2RH protein. The biological properties of the altered proteins can be determined by expressing the protein in an appropriate cell line and measuring the appropriate effect, e.g., upon transfected lymphocytes. Particular protein modifications considered minor would include conservative substitution of amino acids with similar chemical properties, as described above for the receptor homolog family as a whole. By aligning a protein optimally with the protein of the receptor homologs and by using the conventional immunoassays described herein to determine immunoidentity, one can determine the protein compositions of the invention. VII. Kits and quantitation Both naturally occurring and recombinant forms of the receptor like molecules of this invention are particularly useful in kits and assay methods. For example, these methods would also be applied to screening for binding activity, e.g., ligands for these proteins. Several methods of automating assays have been developed in recent years so as to permit screening of tens of thousands of compounds per year. See, e.g., a BIOMEK automated workstation, Beckman Instruments, Palo Alto, California, and Fodor, et al . (1991) Science 251:767-773, which is incorporated herein by reference. The latter describes means for testing binding by a plurality of defined polymers synthesized on a solid substrate. The development of suitable assays to screen for a ligand or agonist/antagonist homologous proteins can be greatly facilitated by the availability of large amounts of purified, soluble receptors in an active state such as is provided by this invention. Purified OX2RH can be coated directly onto plates for use in the aforementioned ligand screening techniques. However, non-neutralizing antibodies to these proteins can be used as capture antibodies to immobilize the respective receptor homolog on the solid phase, useful, e.g., in diagnostic uses. This invention also contemplates use of OX2RH, fragments thereof, peptides, and their fusion products in a variety of diagnostic kits and methods for detecting the presence of the protein or its ligand. Alternatively, or additionally, antibodies against the molecules may be incorporated into the kits and methods and may be used in quantitating the 0X2RH or cells expressing them. Typically the kit will have a compartment containing either an 0X2RH peptide or gene segment or a reagent which recognizes one or the other. Typically, recognition reagents, in the case of peptide, would be a receptor homolog or antibody, or in the case of a gene segment, would usually be a hybridization probe. A preferred kit for determining the concentration of OX2RH in a sample would typically comprise a labeled compound, e.g., ligand or antibody, having known binding affinity for OX2RH, a source of OX2RH (naturally occurring or recombinant) as a positive control, and a means for separating the bound from free labeled compound, for example a solid phase for immobilizing the OX2RH in the test sample. Compartments containing reagents, and instructions, will normally be provided. Appropriate nucleic acid or protein containing kits are also provided. Antibodies, including antigen binding fragments, specific for mammalian OX2RH or a peptide fragment, or receptor homolog fragments are useful in diagnostic applications to detect the presence of elevated levels of homolog and/or its fragments. Diagnostic assays may be homogeneous (without a separation step between free reagent and antibody-antigen complex) or heterogeneous (with a separation step) . Various commercial assays exist, such as radioimmunoassay (RIA) , enzyme-linked im unosorbent assay (ELISA) , enzyme immunoassay (EIA) , enzyme-multiplied immunoassay technique (EMIT) , substrate-labeled fluorescent immunoassay (SLFIA) and the like. For example, unlabeled antibodies can be employed by using a second antibody which is labeled and which recognizes the antibody to a receptor homolog or to a particular fragment thereof. These assays have also been extensively discussed in the literature. See, e.g., Harlow and Lane (1988) Antibodies: A Laboratory Manual, CSH., and Coligan (ed. 1991 and periodic supplements) Current Protocols In Immunology Greene/Wiley, New York. Anti-idiotypic antibodies may have similar use to serve as agonists or antagonists of the receptor homologs. These should be useful as therapeutic reagents under appropriate circumstances . Frequently, the reagents for diagnostic assays are supplied in kits, so as to optimize the sensitivity of the assay. For the subject invention, depending upon the nature of the assay, the protocol, and the label, either labeled or unlabeled antibody, or labeled ligand is provided. This is usually in conjunction with other additives, such as buffers, stabilizers, materials necessary for signal production such as substrates for enzymes, and the like. Preferably, the kit will also contain instructions for proper use and disposal of the contents after use. Typically the kit has compartments for each useful reagent, and will contain instructions for proper use and disposal of reagents. Desirably, the reagents are provided as a dry lyophilized powder, where the reagents may be reconstituted in an aqueous medium having appropriate concentrations for performing the assay. The aforementioned constituents of the diagnostic assays may be used without modification or may be modified in a variety of ways. For example, labeling may be achieved by covalently or non-covalently joining a moiety which directly or indirectly provides a detectable signal. In many of these assays, a test compound, receptor homolog, or antibodies thereto can be labeled either directly or indirectly. Possibilities for direct labeling include label groups: radiolabels such as ^^1 , enzymes (U.S. Pat. No. 3,645,090) such as peroxidase and alkaline phosphatase, and fluorescent labels (U.S. Pat. No. 3,940,475) capable of monitoring the change in fluorescence intensity, wavelength shift, or fluorescence polarization. Both of the patents are incorporated herein by reference. Possibilities for indirect labeling include biotinylation of one constituent followed by binding to avidin coupled to one of the above label groups. There are also numerous methods of separating the bound from the free ligand, or alternatively the bound from the free test compound. The receptor homolog can be immobilized on various matrixes followed by washing. Suitable matrices include plastic such as an ELISA plate, filters, and beads. Methods of immobilizing the receptor homolog to a matrix include, without limitation, direct adhesion to plastic, use of a capture antibody, chemical coupling, and biotin-avidin. The last step in this approach involves the precipitation of antibody/antigen complex by any of several methods including those utilizing, e.g., an organic solvent such as polyethylene glycol or a salt such as ammonium sulfate. Other suitable separation techniques include, without limitation, the fluorescein antibody magnetizable particle method described in Rattle, et al. (1984) Clin. Chem. 30 (9) : 1457-1461, and the double antibody magnetic particle separation as described in U.S. Pat. No. 4,659,678, each of which is incorporated herein by reference. The methods for linking protein or fragments to various labels have been extensively reported in the literature and do not require detailed discussion here. Many of the techniques involve the use of activated carboxyl groups either through the use of carbodiimide or active esters to form peptide bonds, the formation of thioethers by reaction of a mercapto group with an activated halogen such as chloroacetyl, or an activated olefin such as maleimide, for linkage, or the like. Fusion proteins will also find use in these applications. Another diagnostic aspect of this invention involves use of oligonucleotide or polynucleotide sequences taken from the sequence of a receptor homolog. These sequences can be used as probes for detecting levels of the respective receptor homolog in patients suspected of having an immunological disorder. The preparation of both RNA and DNA nucleotide sequences, the labeling of the sequences, and the preferred size of the sequences has received ample description and discussion in the literature. Normally an oligonucleotide probe should have at least about 14 nucleotides, usually at least about 18 nucleotides, and the polynucleotide probes may be up to several kilobases. Various labels may be employed, most commonly radionuclides, particularly 3 2p, However, other techniques may also be employed, such as using biotin modified nucleotides for introduction into a polynucleotide. The biotin then serves as the site for binding to avidin or antibodies, which may be labeled with a wide variety of labels, such as radionuclides, fluorescers, enzymes, or the like. Alternatively, antibodies may be employed which can recognize specific duplexes, including DNA duplexes, RNA duplexes, DNA-RNA hybrid duplexes, or DNA-protein duplexes. The antibodies in turn may be labeled and the assay carried out where the duplex is bound to a surface, so that upon the formation of duplex on the surface, the presence of antibody bound to the duplex can be detected. The use of probes to the novel anti-sense RNA may be carried out in conventional techniques such as nucleic acid hybridization, plus and minus screening, recombinational probing, hybrid released translation (HRT) , and hybrid arrested translation (HART) . This also includes amplification techniques such as polymerase chain reaction (PCR) . Diagnostic kits which also test for the qualitative or quantitative presence of other markers are also contemplated. Diagnosis or prognosis may depend on the combination of multiple indications used as markers. Thus, kits may test for combinations of markers. See, e.g., Viallet, et al . (1989) Progress in Growth Factor Res. 1:89-97. VIII. Therapeutic Utility This invention provides reagents with significant therapeutic value. See, e.g., Levitzki (1996) Curr. Qpin. Cell Biol. 8:239-244. The receptor homologs (naturally occurring or recombinant), fragments thereof, mutein receptors, and antibodies, along with compounds identified as having binding affinity to the receptor homologs or antibodies, should be useful in the treatment of conditions wherein modulation of function of myeloid lineage cells particularly is desirable. Such abnormality will typically be manifested by immunological disorders, but also by conditions in which myeloid cell activities impact physiological processes, e.g., CNS maturation or development, etc. Additionally, this invention should provide therapeutic value in various diseases or disorders associated with abnormal expression or abnormal triggering of response to the ligand. In cases where leukocytes, including macrophage/myeloid lineage cells, expressing the OX2R are involved in pathologies and contribute to the disease process, it may be desirable to inhibit the function of these cells. This may be achieved by appropriate stimulation of an OX2R, such that the cell-inhibitory activities of receptor signalling are mobilized. This may be achieved using, e.g., a ligand 0X2 agonist or an antibody to the OX2R that has agonistic activities for the receptor. Suitable conditions would be where the animal exhibits signs or symptoms of an inflammatory, leukoproliferative, neurodegenerative, or post-traumatic condition. Preferred embodiments include where the sign or symptom is in neural tissue; lymphoid tissue; myeloid tissue; pancreas; gastrointestinal tissue; thyroid tissue; muscle tissue; or skin or collagenous tissue. Certain embodiments include where the animal is experiencing signs or symptoms of autoimmunity; an inflammatory condition; tissue specific autoimmunity; degenerative autoimmunity; rheumatoid arthritis; atherosclerosis; multiple sclerosis; vasculitides; delayed hypersensitivities; skin grafting; a transplant; spinal injury; stroke; neurodegeneration; or ischemia. The administering agent may be in combination with: an anti-inflammatory cytokine agonist or antagonist; an analgesic; an anti-inflammatory agent; or a steroid. By contrast, in cases where leukocytes, including macrophage/myeloid lineage cells, expressing the OX2R are involved in processes of immunization and vaccination, repair mechanisms, limiting pathologies, or controlling infection, particularly of bacterial infections, it may be desirable to enhance the function of these cells. This may be achieved therapeutically by appropriate stimulation of an OX2R, such that the cell-activation activities of receptor signalling are mobilized, or by blocking OX2-OX2R interactions completely should this enable cell-activation to proceed. The latter occurs in ligand 0X2 gene knockout mice where the lack of ligand 0X2 leads to myeloid cell activation. This may be achieved using, e.g., a ligand 0X2 antagonist (such as an antibody against ligand 0X2), an antibody to the 0X2R that prevents OX2-OX2R interactions, antisense nucleic acids which may prevent 0X2R expression, an Ig- 0X2R fusion protein that, e.g., by competitive binding, blocks the capacity of cell-bound 0X2 to interact with cell-bound 0X2R, or a small molecule antagonist. That this modality has applications in vivo in promotion of myeloid cell functions has been demonstrated by experiment, e.g., where i.v. injection to mice of an adenovirus construct producing a human IgG-mouse 0X2RH1 fusion protein known to bind mouse 0X2 resulted in accelerated onset of the autoimmune disease experimental autoimmune encephalomyelitis (EAE) in these mice, as compared to mice receiving an adenovirus construct producing only the backbone human IgG-fusion protein. The degree of disease acceleration was comparable to that seen in mice in which a ligand for 0X2R, namely 0X2, had been inactivated by gene targeting. Alternatively, if the various 0X2R molecules described herein have activating vs. inhibitory function, specific activation of the 0X2R that induces cellular activation may be appropriate. This may be achieved, e.g., by the use of specific antibody with agonistic activities of a given 0X2R. In various embodiments, the method is applied where the animal experiences signs or symptoms of wound healing or clot formation in which enhanced macrophage activation may be desirable, or where an animal experiences a bacterial infection where enhanced phagocytic activity by granulocytes and/or macrophages is desirable. The administering will often be in combination with: an angiogenic factor; a growth factor, including FGF or PDGF; an antibiotic; or a clotting factor. Recombinant receptors, muteins, agonist or antagonist antibodies thereto, or antibodies can be purified and then administered to a patient. These reagents can be combined for therapeutic use with additional active ingredients, e.g., in conventional pharmaceutically acceptable carriers or diluents, along with physiologically innocuous stabilizers and excipients. These combinations can be sterile, e.g., filtered, and placed into dosage forms as by lyophilization in dosage vials or storage in stabilized aqueous preparations. This invention also contemplates use of antibodies or binding fragments thereof which are not complement binding. Ligand screening using receptor or fragments thereof can be performed to identify molecules having binding affinity to the receptors. Subsequent biological assays can then be utilized to determine if a putative ligand can provide competitive binding, which can block intrinsic stimulating activity. Receptor fragments can be used as a blocker or antagonist in that it blocks the activity of ligand. Likewise, a compound having intrinsic stimulating activity can activate the receptor and is thus an agonist in that it simulates the activity of ligand, e.g., inducing signaling. This invention further contemplates the therapeutic use of antibodies to receptors as antagonists. The quantities of reagents necessary for effective therapy will depend upon many different factors, including means of administration, target site, reagent physiological life, pharmacological life, physiological state of the patient, and other medicants administered. Thus, treatment dosages should be titrated to optimize safety and efficacy. Typically, dosages used in vitro may provide useful guidance in the amounts useful for in situ administration of these reagents. Animal testing of effective doses for treatment of particular disorders will provide further predictive indication of human dosage. Various considerations are described, e.g., in Gilman, et al . (eds. 1990) Goodman and Gilman's: The Pharmacological Bases of Therapeutics, 8th Ed., Pergamon Press; and Remington's Pharmaceutical Sciences, 17th ed. (1990), Mack Publishing Co., Easton, Penn.; each of which is hereby incorporated herein by reference. Methods for administration are discussed therein and below, e.g., for oral, intravenous, intraperitoneal, or intramuscular administration, transdermal diffusion, and others. Pharmaceutically acceptable carriers will include water, saline, buffers, and other compounds described, e.g., in the Merck Index, Merck & Co., Rahway, New Jersey. Dosage ranges would ordinarily be expected to be in amounts lower than 100 mM concentrations, typically less than about 1 mM concentrations, usually less than about 100 μM, preferably less than about 1 μM, and most preferably less than about 10 nM, with an appropriate carrier. Slow release formulations, or slow release apparatus will often be utilized for continuous administration. Receptor homologs, fragments thereof, and antibodies or its fragments, antagonists, and agonists, may be administered directly to the host to be treated or, depending on the size of the compounds, it may be desirable to conjugate them to carrier proteins such as ovalbumin or serum albumin prior to their administration. Therapeutic formulations may be administered in many conventional dosage formulations. While it is possible for the active ingredient to be administered alone, it is preferable to present it as a pharmaceutical formulation. Formulations comprise at least one active ingredient, as defined above, together with one or more acceptable carriers thereof. Each carrier must be both pharmaceutically and physiologically acceptable in the sense of being compatible with the other ingredients and not injurious to the patient. Formulations include those suitable for oral, rectal, nasal, or parenteral (including subcutaneous, intramuscular, intravenous and intradermal) administration. The formulations may conveniently be presented in unit dosage form and may be prepared by methods well known in the art of pharmacy. See, e.g., Gilman, et al. (eds. 1990) Goodman and Gilman's: The Pharmacological Bases of Therapeutics, 8th Ed., Pergamon Press; and Remington' s Pharmaceutical Sciences, 17th ed. (1990), Mack Publishing Co., Easton, Penn.; Avis, et al. (eds. 1993) Pharmaceutical Dosage Forms: Parenteral Medications Dekker, NY; Lieberman, et al . (eds. 1990) Pharmaceutical Dosage Forms: Tablets Dekker, NY; and Lieberman, et al . (eds. 1990) Pharmaceutical Dosage Forms: Disperse Systems Dekker, NY. The therapy of this invention may be combined with or used in association with other therapeutic agents, particularly agonists or antagonists of other receptor family members. IX. Screening Drug screening using OX2RH or fragments thereof can be performed to identify compounds having binding affinity to the receptor homolog, including isolation of associated components. Subsequent biological assays can then be utilized to determine if the compound has intrinsic stimulating activity and is therefore a blocker or antagonist in that it blocks the activity of the ligand. Likewise, a compound having intrinsic stimulating activity can activate the receptor and is thus an agonist in that it simulates the activity of a ligand, e.g., 0X2. This invention further contemplates the therapeutic use of antibodies to the receptor as agonists or antagonists. Similarly, complexes comprising multiple proteins may be used to screen for ligands or reagents capable of recognizing the complex. Some receptors comprise at least two subunits, which may be the same, or distinct. Alternatively, the transmembrane receptor may bind to a complex comprising a ligand associated with another soluble protein serving, e.g., as a second receptor subunit. One method of drug screening utilizes eukaryotic or prokaryotic host cells which are stably transformed with recombinant DNA molecules expressing the 0X2RH in combination with another receptor subunit. Cells may be isolated which express a receptor in isolation from other functional receptors. Such cells, either in viable or fixed form, can be used for standard antibody/antigen or ligand/receptor binding assays. See also, Parce, et al . (1989) Science 246:243-247; and Owicki, et al. (1990) Proc. Nat ' 1 Acad. Sci. USA 87:4007-4011, which describe sensitive methods to detect cellular responses. Competitive assays are particularly useful, where the cells (source of putative ligand) are contacted and incubated with a labeled receptor or antibody having known binding affinity to the ligand, such as and a test sample whose binding affinity to the binding composition is being measured. The bound and free labeled binding compositions are then separated to assess the degree of ligand binding. The amount of test compound bound is inversely proportional to the amount of labeled receptor binding to the known source. Many techniques can be used to separate bound from free ligand to assess the degree of ligand binding. This separation step could typically involve a procedure such as adhesion to filters followed by washing, adhesion to plastic followed by washing, or centrifugation of the cell membranes. Viable cells could also be used to screen for the effects of drugs on 0X2 mediated functions, e.g., second messenger levels, i.e., Ca ++ ; cell proliferation; inositol phosphate pool changes; and others. Some detection methods allow for elimination of a separation step, e.g., a proximity sensitive detection system. Calcium sensitive dyes will be useful for detecting Ca ++ levels, with a fluorimeter or a fluorescence cell sorting apparatus. X. Ligands The descriptions of the 0X2RHs herein provides means to identify ligands, as described above. Such ligand should bind specifically to the respective receptor with reasonably high affinity. Various constructs are made available which allow either labeling of the receptor to detect its ligand. For example, directly labeling receptor, fusing onto it markers for secondary labeling, e.g., FLAG or other epitope tags, etc., will allow detection of receptor. This can be histological, as an affinity method for biochemical purification, or labeling or selection in an expression cloning approach. A two-hybrid selection system may also be applied making appropriate constructs with the available receptor sequences. See, e.g., Fields and Song (1989) Nature 340:245-246. The broad scope of this invention is best understood with reference to the following examples, which are not intended to limit the inventions to the specific embodiments. EXAMPLES I. General Methods Some of the standard methods are described or referenced, e.g., in Maniatis, et al . (1982) Molecular Cloning, A Laboratory Manual, Cold Spring Harbor Laboratory, Cold Spring Harbor Press; Sambrook, et al . (1989) Molecular Cloning: A Laboratory Manual, (2d ed.), vols. 1-3, CSH Press, NY; or Ausubel, et al. (1987 and Supplements) Current Protocols in Molecular Biology, Greene/Wiley, New York. Methods for protein purification include such methods as ammonium sulfate precipitation, column chromatography, electrophoresis, centrifugation, crystallization, and others. See, e.g., Ausubel, et al . (1987 and periodic supplements); Coligan, et al. (ed. 1996) and periodic supplements, Current Protocols In Protein Science Greene/Wiley, New York; Deutscher (1990) "Guide to Protein Purification" in Methods in Enzvmologv, vol. 182, and other volumes in this series; and manufacturer's literature on use of protein purification products, e.g., Pharmacia, Piscataway, N.J., or BioRad, Richmond, CA. Combination with recombinant techniques allow fusion to appropriate segments, e.g., to a FLAG sequence or an equivalent which can be fused via a protease-removable sequence. See, e.g., Hochuli (1990) "Purification of Recombinant Proteins with Metal Chelate Absorbent" in Setlow (ed.) Genetic Engineering, Principle and Methods 12:87-98, Plenum Press, N.Y.; and Crowe, et al . (1992) OIAexpress: The High Level Expression & Protein Purification System QUIAGEN, Inc., Chatsworth, CA. Computer sequence analysis is performed, e.g., using available software programs, including those from the GCG (U. Wisconsin) and GenBank sources. Public sequence databases were also used, e.g., from GenBank and others. Many techniques applicable to IL-10 receptors may be applied to the 0X2RHs, as described, e.g., in USSN 08/110,683 (IL-10 receptor), which is incorporated herein by reference. 83 II. Monoclonal Antibody which blocks rat OX2/OX2RH interaction on macrophages A bead assay was set up using recombinant OX2-CD4 protein and rat peritoneal macrophages. See Preston, et al . (1997) Eur. J. Immunol. 27:1911-1918. Macrophages bound to fluorescent beads coated with recombinant OX2-CD4 proteins. Six wk old BALB/c mice were immunized 6 times with either 0.1-0.25 mg crude membrane fraction (Williams and Barclay (1986) in Handbook of Experimental Immunology vol. 1, 22.1-22.24, Blackwell Scientific Publications) or resident rat peritoneal exudate cells (5 million) . Mice were screened for high titers of antibodies recognizing macrophages by testing various dilutions of the sera for labeling of macrophages by indirect immunofluorescence and flow cytometry. Mice producing good immune responses to the rat macrophages were finally boosted by injection of peritoneal exudate cells. Four days later, spleens were removed and fused to NS-1 myeloma cells to produce hybridomas. The final injection before screening was intrasplenic. Hybridoma supematants were screened for the ability to label rat macrophages and for the ability to block the rat 0X2 interaction with macrophages. One antibody, designated OX102, was obtained and cloned. This antibody gave clear blocking. This hybridoma was grown in bulk and the antibody was purified by standard procedures. III. Purification of the antigen for the OX102 mAb Purified 0X102 mAb was covalently coupled to CNBr activated sepharose-4B (Pharmacia) as recommended by the manufacturer. Membrane proteins were solubilised using Tween 40 and sodium deoxycholate and incubated with the Sepharose beads coupled to OX102 mAb, for 70 hours. Williams and Barclay (1986) in Handbook of Experimental Immunology vol. 1, 22.1-22.24, Blackwell Scientific Publications. The OX102 mAb-coupled Sepharose beads were pelleted by centrifugation and washed in 0.1% sodium dodecyl sulphate (SDS) and finally eluted in 0.5% SDS at 55° C for 15 min The eluted fraction was analysed by SDS polyacrylamide gel electrophoresis (SDS-PAGE) . IV. N-terminal sequence of the antigen for the OX102 mAb Amino terminal sequencing was performed using automated Edman degradation in an Applied Biosystems Procise 494A protein sequencer (Perkin-Elmer Ltd., UK). The N-terminal sequence was confirmed, as shown in Table 1. Blank cycles are assumed to be asparagine due to the presence of asparagine modified by N-linked glycosylation. The purified polypeptide was identified as novel by screening known protein databases with the N-terminal 20 amino acids of the antigen for the OX102 mAb. This protein is the rat OX2RH1. V. Isolation of cDNA clones coding for the antigen of the OX102 mAb Total RNA was extracted from rat peritoneal exudate cells using RNAzol B (Biogenesis) and then the poly-A fraction purified using oligo dT beads (Oligotex, QIAGEN) as recommended by the manufacturer. Approximately 50 ng of polyA+ purified mRNA was treated with 200 U of Superscript II reverse transcriptase (GIBCO BRL) in the presence of 1 μM of selected sense and antisense oligonucleotides, 1 mM dNTPs, and 2 mM DTT, 50 mM Tris-HCl pH 8.3, 75 mM KC1, 3 mM MgCl2, and incubated at 42° C for 1 h. This cDNA was then used as a template in a PCR reaction, e.g., 40 μl of provided lOx Advantage Taq thermophilic PCR buffer (provided by Clontech) ; 8 μl of 10 mM dNTPs; 8 μl of Advantage Taq (Clontech) ; 2 μl of cDNA prepared as described above; 318 μl of distilled water; 16 μl of an antisense, degenerate oligonucleotide corresponding to the N-terminal peptide at 10 μM; and 8 μl 10 μM sense oligonucleotide. Both oligonucleotide primers were synthesized (Genosys) with a 5' terminal phosphate to facilitate cloning. The PCR mix was aliquoted into 8 x 50 μl samples and subjected to PCR conditions in a Robocycler PCR machine (Stratagene) which allows the operator to vary the annealing temperature in separate samples simultaneously. Example parameters are: 93° C 30 sec; followed by 35 cycles of: 93° C 30 sec; 42-56° C 1 min; 72° C 30 sec; and a final cycle of 72° C for 8 min. Ten μl of the PCR products were analyzed by agarose gel electrophoresis by standard procedures. PCR products of lengths ranging between 100 and 300 base pairs in the 3 samples which had an annealing temperature of about 42°, 44°, and 46° C were excised from the gel and the nucleic acid purified using QIAquick (QIAGEN) . These purified products were ligated at about 16° C for 48 h using standard procedures into PCRScript vector (Stratagene) which had been S al digested and phosphatase treated. Transformants were screened initially by colony PCR and 20 colonies containing appropriately-sized inserts were grown up in LB broth in the presence of 50 μg/ml ampicillin and plasmids purified by a QIAGEN robot. Inserts were sequenced using the BIGDYE fluorescent dideoxy-terminator technology and ABI-PRISM Model 377 (Perkin-Elmer Ltd., UK). Inserts containing nucleotide sequence that coded for the N-terminal sequence of antigen for the OX102 mAb were used to design oligonucleotides for 3' RACE reactions. The full cDNA sequence of the antigen for 0X102 was obtained by 3'RACE PCR (using the same protocol as above) but modified by using appropriate oligonucleotides at a final concentration of 0.2 μM each. PCR conditions, e.g., were: 93° C 30 sec; followed by 30 cycles of: 93° C 30 sec; 51°-65° C 1 min; 72° C 3.5 min; and a final cycle of 72° C for 12 min. A band of approximately 2.3 Kb was excised from the 65° C PCR reaction, gel purified, digested with Notl and Xhol, and ligated into Notl/Xhol digested vector (PCRScript, Stratagene) using standard procedures. Inserts were sequenced as above. The cDNA sequence of the OX102 protein, also referred to herein as rat OX2RH1, is shown in Table 1. Full length isolates of the other homolog embodiments are similarly cloned and sequences confirmed. Standard methods are readily applicable. VI. Obtaining other OX2RH cDNAs The knowledge of the rat OX2RH1 nucleotide and predicted amino acid sequences allows one to obtain homologous functional equivalents from other species, including mouse or human OX2RH1, on the basis of sequence similarity and because the rat OX2RH1 provides a tool for the isolation of such equivalents. Thus, to identify human OX2RH1, one can search existing databases of nucleotide and amino acid sequences for polypeptides of unknown identity (e.g., databases storing sequences obtained from the Human Genome Project) for sequences with homology to the rat OX2RH1 nucleic acid and amino acid sequences provided herein. The databases, which are stored and updated at many sites, including the European Bioinformatics Centre (http: //www. ebi .ac.uk/) and National Center for Biotechnology Information (http://www.ncbi.nlm.nih.gov/), can be accessed by widely-used programs such as FASTA or BLAST. These databases include sequences for expressed sequence tags (ESTs) which are short regions of nucleotide sequence sequenced from random cDNA clones. This allows partial cDNA clones for mouse or human OX2RH to be isolated by comparison with the rat 0X2RH sequence information provided herein. Full length clones can then be isolated by screening macrophage cDNA or genomic libraries or by primer extension techniques such as those described herein for obtaining the full-length rat 0X2RH1 clones. Mouse and human sequences related to the rat 0X2RH1 were identified from genomic sequence database using, e.g., the BLAST server (Altschul, et al. (1994) Nature Genet. 6:119-129). Standard analysis programs may be used to evaluate structure, e.g., PHD (Rost and Sander (1994) Proteins 19:55-72) and DSC (King and Sternberg (1996) Protein Sci. 5:2298-2310) . Standard comparison software includes, e.g., Altschul, et al . (1990) J. Mol. Biol. 215:403-10; Waterman (1995) Introduction to Computational Biology: Maps, Seouences, and Genomes Chapman & Hall; Lander and Waterman (eds. 1995) Calculating the Secrets of Life: Applications of the Mathematical Sciences in Molecular Biology National Academy Press; and Speed and Waterman (eds. 1996) Genetic Mapping and DNA Seguencing (IMA Volumes in Mathematics and Its Applications, Vol 81) Springer Verlag. Nucleic acid sequence for rat and human OX2RH1 will have between 50 and 98% homology, e.g., as can be observed in Table 5. For the other homologs, the similarity may be less, especially with the homolog 3. As an alternative to database screening, the rat OX2RH1 nucleic acid sequence as provided herein can be used to screen macrophage cDNA or genomic libraries to identify human sequences sufficiently homologous to hybridize under conditions of appropriate stringency. This approach was utilized to isolate the human 0X2 gene using rat 0X2 nucleic acid as a probe. McCaughan, et al . (1987) Immunogenetics 25:329-335). PCR based methods using templates of cDNA, genomic DNA, cDNA clones, or genomic clones as templates are also widely used, the general approach being exemplified by the isolation of mouse 0X2 from cDNA. See Preston, et al . (1997) Eur. J. Immunol. 27:1911-1918. PCR primers derived from the provided OX2RH sequences are used to probe a human, or other species or tissue, cDNA library. Sequences may be derived, e.g., from Tables 1-4, preferably those adjacent the ends of sequences. Full length cDNAs for primate, rodent, or other species 0X2RHs are cloned, e.g., by DNA hybridization screening of λgtlO phage. PCR reactions are conducted using T. aquaticus Taqplus DNA polymerase (Stratagene) under appropriate conditions. Further, the rat 0X2RH1 sequence can be used to isolate the corresponding mouse 0X2RH1 sequence, and to identify regions conserved between them. Particularly with the discovery of a group of homologs, regions of similarity may be identified. Conserved-region sequences provide useful reagents for identifying a given gene in a range of species. For instance domain 1 of mouse and rat 0X2 are 90% identical at the amino acid level, compared to 77% identity between the same human and rat domains. Preston, et al . (1997) Eur. J. Immunol. 27:1911-1918. Yet another method is to use antibody reagents to expression clone or identify crossreacting proteins expressed in cDNA libraries from appropriate cell types, e.g., macrophages, or from other species. VII. Chromosomal localization The genes will be mapped. For example, chromosome spreads are prepared. In situ hybridization is performed on chromosome preparations obtained from phytohemagglutinin-stimulated lymphocytes, e.g., from human, cultured for 72 h. 5- bromodeoxyuridine is added for the final seven hours of culture (60 μg/ml of medium) , to ensure a posthybridization chromosomal banding of good quality. A PCR fragment, amplified with the help of primers, is cloned into an appropriate vector. The vector is labeled by nick-translation with . The radiolabeled probe is hybridized to metaphase spreads at final concentration of 200 ng/ml of hybridization solution as described in Mattei, et al. (1985) Hum. Genet. 69:327-331. After coating with nuclear track emulsion (KODAK NTB2), slides are exposed. To avoid any slipping of silver grains during the banding procedure, chromosome spreads are first stained with buffered Giemsa solution and metaphase photographed. R-banding is then performed by the fluorochrome-photolysis-Giemsa (FPG) method and metaphases rephotographed before analysis. Similar appropriate methods are used for other species. VIII. Localization of various OX2RH mRNA While the expected expression patterns of the OX2RH1 are primarily on macrophages, granulocytes, and mast cells, the homologs H2, H3, and/or H4 may not be so closely related functionally. Thus, the distribution of those will be of particular interest. Distribution may be evaluated at the nucleic acid level, e.g., by hybridization or PCR methods, or at the protein level, e.g., by histology or immunochemical methods. Human multiple tissue (Cat #1, 2) and cancer cell line blots (Cat #7757-1), containing approximately 2 μg of poly (A) + RNA per lane, are purchased from Clontech (Palo Alto, CA) . Probes are radiolabeled w th [α-32p] dATP, e.g., using the Amersham Rediprime random primer labeling kit (RPN1633) . Prehybridization and hybridizations are performed, e.g., at 65° C m 0.5 M Na2HP04, 7% SDS, 0.5 M EDTA (pH 8.0) . High stringency washes are conducted, e.g., at 65° C with two initial washes m 2 x SSC, 0.1% SDS for 40 mm followed by a subsequent wash m 0.1 x SSC, 0.1% SDS for 20 mm. Membranes are then exposed at -70° C to X- Ray film (Kodak) m the presence of intensifying screens. More detailed studies by cDNA library Southerns are performed with selected appropriate mammalian OX2RH clones to examine their expression in hemopoietic or other cell subsets. Alternatively, two appropriate primers are selected, e.g., from Tables 1- . RT-PCR is used on an appropriate mRNA sample selected for the presence of message to produce a cDNA, e.g., a sample which expresses the gene. Full length clones may be isolated by hybridization of cDNA libraries from appropriate tissues pre-selected by PCR signal. Northern blots can be performed. Message for genes encoding 0X2RHs will be assayed by appropriate technology, e.g., PCR, immunoassay, hybridization, or otherwise. Tissue and organ cDNA preparations are available, e.g., from Clontech, Mountain View, CA. Identification of sources of natural expression are useful, as described. For mouse distribution, e.g., Southern Analysis can be performed: DNA (5 μg) from a primary amplified cDNA library was digested with appropriate restriction enzymes to release the inserts, run on a It agarose gel and transferred to a nylon membrane (Schleicher and Schuell, Keene, NH) . Samples for mouse mRNA isolation may include: resting mouse fibroblastic L cell lme (C200) ; Braf:ER (Braf fusion to estrogen receptor) transfected cells, control (C201); T cells, THl polarized (Mell4 bright, CD4+ cells from spleen, polarized for 7 days with IFN-γ and anti IL-4; T200) ; T cells, TH2 polarized (Mell4 bright, CD4+ cells from spleen, polarized for 7 days with IL-4 and anti-IFN-γ; T201) ; T cells, highly THl polarized (see Openshaw, et al. (1995) J. EXP. Med. 182:1357-1367; activated with anti-CD3 for 2, 6, 16 h pooled; T202); T cells, highly TH2 polarized (see Openshaw, et al . (1995) J. EXP. Med. 182:1357- 1367; activated with anti-CD3 for 2, 6, 16 h pooled; T203) ; CD44- CD25+ pre T cells, sorted from thymus (T204); THl T cell clone Dl.l, resting for 3 weeks after last stimulation with antigen (T205) ; THl T cell clone Dl.l, 10 μg/ml ConA stimulated 15 h (T206) ; TH2 T cell clone CDC35, resting for 3 weeks after last stimulation with antigen (T207); TH2 T cell clone CDC35, 10 μg/ml ConA stimulated 15 h (T208) ; Mell4+ naive T cells from spleen, resting (T209) ; Mell4+ T cells, polarized to Thl with IFN-γ/IL- 12/anti-IL-4 for 6, 12, 24 h pooled (T210) ; Mell4+ T cells, polarized to Th2 with IL-4/anti-IFN-γ for 6, 13, 24 h pooled (T211) ; unstimulated mature B cell leukemia cell line A20 (B200) ; unstimulated B cell line CH12 (B201); unstimulated large B cells from spleen (B202) ; B cells from total spleen, LPS activated (B203) ; metrizamide enriched dendritic cells from spleen, resting (D200) ; dendritic cells from bone marrow, resting (D201); monocyte cell line RAW 264.7 activated with LPS 4 h (M200) ; bone- marrow macrophages derived with GM and M-CΞF (M201); macrophage cell line J774, resting (M202) ; macrophage cell line J774 + LPS + anti-IL-10 at 0.5, 1, 3, 6, 12 h pooled (M203) ; macrophage cell line J774 + LPS + IL-10 at 0.5, 1, 3, 5, 12 h pooled (M204) ; aerosol challenged mouse lung tissue, Th2 primers, aerosol OVA challenge 7, 14, 23 h pooled (see Garlisi, et al . (1995) Clinical Immunology and Immunopathology 75:75-83; X206) ; Nippostrongulus- infected lung tissue (see Coffman, et al . (1989) Science 245:308- 310; X200) ; total adult lung, normal (O200) ; total lung, rag-1 (see Schwarz, et al. (1993) Immunodeficiency 4:249-252; O205) ; IL-10 K.O. spleen (see Kuhn, et al. (1991) Cell 75:263-274; X201) ; total adult spleen, normal (O201); total spleen, rag-1 (O207); IL-10 K.O. Peyer's patches (O202) ; total Peyer's patches, normal (O210) ; IL-10 K.O. mesenteric lymph nodes (X203); total mesenteric lymph nodes, normal (0211) ; IL-10 K.O. colon (X203) ; total colon, normal (0212) ; NOD mouse pancreas (see Makino, et al. (1980) Jikken Dobutsu 29:1-13; X205) ; total thymus, rag-1 (O208); total kidney, rag-1 (0209); total heart, rag-1 (0202); total brain, rag-1 (O203) ; total testes, rag-1 (0204); total liver, rag-1 (O206) ; rat normal ]omt tissue (O300) ; and rat arthritic joint tissue (X300) . Samples for human mRNA isolation may include: peripheral blood mononuclear cells (monocytes, T cells, ΝK cells, granulocytes, B cells) , resting (T100) ; peripheral blood mononuclear cells, activated with antι-CD3 for 2, 6, 12 h pooled (T101); T cell, THO clone Mot 72, resting (T102); T cell, THO clone Mot 72, activated with antι-CD28 and antι-CD3 for 3, 6, 12 h pooled (T103) ; T cell, THO clone Mot 72, anergic treated with specific peptide for 2, 7, 12 h pooled (T104); T cell, THl clone HY06, resting (T107); T cell, THl clone HY06, activated with ant -CD28 and antι-CD3 for 3, 6, 12 h pooled (T108); T cell, THl clone HY06, anergic treated with specific peptide for 2, 6, 12 h pooled (T109) ; T cell, TH2 clone HY935, resting (TllO) ; T cell, TH2 clone HY935, activated with antι-CD28 and antι-CD3 for 2, 7, 12 h pooled (Till); T cells CD4+CD45RO- T cells polarized 27 days in antι-CD28, IL-4, and anti IFΝ-γ, TH2 polarized, activated with antι-CD3 and antι-CD28 4 h (T116) ; T cell tumor lines Jurkat and Hut78, resting (T117); T cell clones, pooled AD130.2, Tc783.12, Tc783.13, Tc783.58, Tc782.69, resting (T118); T cell random γδ T cell clones, resting (T119) ; Splenocytes, resting (B100) ; Splenocytes, activated w th antι-CD40 and IL-4 (B101) ; B cell EBV lines pooled WT49, RSB, JY, CVIR, 721.221, RM3, HSY, resting (B102); B cell lme JY, activated with PMA and lonomycm for 1, 6 h pooled (B103) ; ΝK 20 clones pooled, resting (K100) ; ΝK 20 clones pooled, activated w th PMA and lonomycm for 6 h (K101) ; ΝKL clone, derived from peripheral blood of LGL leukemia patient, IL-2 treated (K106) ; ΝK cytotoxic clone 640-A30-1, resting (K107) ; hematopoietic precursor lme TF1, activated with PMA and lonomycm for 1, 6 h pooled (C100) ; U937 premonocytic lme, resting (M100) ; U937 premonocytic lme, activated with PMA and lonomycm for 1, 6 h pooled (M101) ; elutriated monocytes, activated with LPS, IFΝγ, antι-IL-10 for 1, 2, 6, 12, 24 h pooled (M102) ; elutriated monocytes, activated with LPS, IFΝγ, IL-10 for 1, 2, 6, 12, 24 h pooled (M103) ; elutriated monocytes, activated 92 with LPS, IFNγ, anti-IL-10 for 4, 16 h pooled (M106); elutriated monocytes, activated with LPS, IFNγ, IL-10 for 4, 16 h pooled (M107); elutriated monocytes, activated LPS for 1 h (M108) ; elutriated monocytes, activated LPS for 6 h (M109) ; DC 70% CDla+, from CD34+ GM-CSF, TNFα 12 days, resting (D101); DC 70% CDla+, from CD34+ GM-CSF, TNFα 12 days, activated with PMA and ionomycin for 1 hr (D102) ; DC 70% CDla÷, from CD34+ GM-CSF, TNFα 12 days, activated with PMA and ionomycin for 6 hr (D103) ; DC 95% CDla+, from CD34+ GM-CSF, TNFα 12 days FACS sorted, activated with PMA and ionomycin for 1, 6 h pooled (D104) ; DC 95% CD14+, ex CD34+ GM-CSF, TNFα 12 days FACS sorted, activated with PMA and ionomycin 1, 6 hr pooled (D105) ; DC CDla+ CD86+, from CD34+ GM- CSF, TNFα 12 days FACS sorted, activated with PMA and ionomycin for 1, 6 h pooled (D106) ; DC from monocytes GM-CSF, IL-4 5 days, resting (D107) ; DC from monocytes GM-CSF, IL-4 5 days, resting (D108) ; DC from monocytes GM-CSF, IL-4 5 days, activated LPS 4, 16 h pooled (D109) ; DC from monocytes GM-CSF, IL-4 5 days, activated TNFα, monocyte supe for 4, 16 h pooled (DUO) ; leiomyoma Lll benign tumor (X101) ; normal myometrium M5 (0115) ; malignant leiomyosarcoma GSl (X103) ; lung fibroblast sarcoma line MRC5, activated with PMA and ionomycin for 1, 6 h pooled (C101); kidney epithelial carcinoma cell line CHA, activated with PMA and ionomycin for 1, 6 h pooled (C102) ; kidney fetal 28 wk male (O100) ; lung fetal 28 wk male (O101); liver fetal 28 wk male (O102); heart fetal 28 wk male (O103) ; brain fetal 28 wk male (0104); gallbladder fetal 28 wk male (O106) ; small intestine fetal 28 wk male (0107); adipose tissue fetal 28 wk male (0108); ovary fetal 25 wk female (0109) ; uterus fetal 25 wk female (OHO) ; testes fetal 28 wk male (0111); spleen fetal 28 wk male (0112); adult placenta 28 wk (0113); and tonsil inflamed, from 12 year old (X100) . Similar samples may isolated in other species for evaluation. Histology may also be performed. IX. Production of mammalian 0X2RH proteins An appropriate, e.g., GST, fusion construct is engineered for expression, e.g., in E. coli. For example, a mouse 0X2RH pGex plasmid is constructed and transformed into E. coli. Freshly transformed cells are grown, e.g., in LB medium containing 50 μg/ml ampicillin and induced with IPTG (Sigma, St. Louis, MO) . After overnight induction, the bacteria are harvested and the pellets containing the OX2RH protein are isolated. The pellets are homogenized, e.g., in TE buffer (50 mM Tris-base pH 8.0, 10 mM EDTA and 2 mM pefabloc) in 2 liters. This material is passed through a microfluidizer (Microfluidics, Newton, MA) three times. The fluidized supernatant is spun down on a Sorvall GS-3 rotor for 1 h at 13,000 rpm. The resulting supernatant containing the 0X2RH protein is filtered and passed over a glutathione-SEPHAROSE column equilibrated in 50 mM Tris- base pH 8.0. The fractions containing the OX2RH-GST fusion protein are pooled and cleaved, e.g., with thrombin (Enzyme Research Laboratories, Inc., South Bend, IN). The cleaved pool is then passed over a Q-SEPHAROSE column equilibrated in 50 mM Tris-base. Fractions containing 0X2RH are pooled and diluted in cold distilled H2O, to lower the conductivity, and passed back over a fresh Q-Sepharose column, alone or in succession with an immunoaffinity antibody column. Fractions containing the OX2RH protein are pooled, aliquoted, and stored in the -70° C freezer. Various fusion constructs are made with OX2RH. Thus, e.g., fusion of the extracellular portions of the OX2RH2, H3, or H4 may be fused to intracellular portions of the DAP12 or to IgG domains or other labeling or functional domains. A portion of the appropriate gene is fused to an epitope tag, e.g., a FLAG tag, or to a two hybrid system construct. See, e.g., Fields and Song (1989) Nature 340:245-246. The epitope tag may be used in an expression cloning procedure with detection with anti-FLAG antibodies to detect a binding partner, e.g., ligand for the respective receptor homolog. The two hybrid system may also be used to isolate proteins which specifically bind to an 0X2RH. Comparison of the CD spectrum with similar Ig superfamily receptor protem may suggest that the protem s correctly folded. See Hazuda, et al . (1969) J. Biol. Chem. 264:1689-1693; and Campbell, et al. (1979) Nature 282:341-342. The reactivity of the 0X2/0X2R in terms of bmdmg properties, e.g., kinetics and functional effects, can be investigated. The interactions of the OX2R cytoplasmic domain can be determined using well established immunoprecipitation methods or genetic methods such as the yeast two-hybrid system. Transfection of the OX2RH mto cells normally not expressing the protems may be useful m physiological and signaling studies. X. Preparation of antibodies specific for OX2RHs Appropriate species or strains, e.g., inbred Balb/c mice, are immunized mtraperitoneally with recombmant forms of the protem, e.g., purified OX2RH or stable transfected NIH-3T3 cells. Animals are boosted at appropriate time points with protem, with or without additional adjuvant, to further stimulate antibody production. Serum is collected, or hybridomas produced with harvested spleens. Alternatively, the animals, e.g., Balb/c mice, are immunized with cells transformed with the gene or fragments thereof, either endogenous or exogenous cells, or with isolated membranes enriched for expression of the antigen. Serum is collected at the appropriate time, typically after numerous further administrations. Various gene therapy techniques may be useful, e.g., in producing protem in situ, for generating an immune response. Serum or antibody preparations may be cross-absorbed or immunoselected to prepare substantially purified antibodies of defined specificity and high affinity. Thus, antibodies could be prepared which recognize various species counterparts, or antibodies which recognize specific species or groups of subsets, e.g., rodent, embodiments. Monoclonal antibodies may be made. For example, splenocytes are fused with an appropriate fusion partner and hybridomas are selected m growth medium by standard procedures. Hybridoma supematants are screened for the presence of antibodies which bind to the rat OX2RH1, e.g., by ELISA or other assay. Antibodies which specifically recognize specific OX2RH embodiments may also be selected or prepared. In another method, synthetic peptides or purified protein are presented to an immune system to generate monoclonal or polyclonal antibodies. See, e.g., Coligan (ed. 1991) Current Protocols in Immunology Wiley/Greene; and Harlow and Lane (1989) Antibodies: A Laboratory Manual Cold Spring Harbor Press. In appropriate situations, the binding reagent is either labeled as described above, e.g., fluorescence or otherwise, or immobilized to a substrate for panning methods. Nucleic acids may also be introduced into cells in an animal to produce the antigen, which serves to elicit an immune response. See, e.g., Wang, et al . (1993) Proc. Nat ' 1. Acad. Sci. 90:4156-4160; Barry, et al . (1994) BioTechniσues 16:616-619; and Xiang, et al. (1995) Immunity 2: 129-135. XI. Ligand binding and partner specificity Means for testing of the binding selectivity and affinity are readily available. Surface plasmon resonance (see manufacturer's protocol; BIAcore manual, Pharmacia Biosensor) or other methods may be used to determine the ligand for the OX2RHs . The rat and mouse HI bind to their species counterpart ligand 0X2; the human HI will be similarly tested. The H2 will be similarly tested against similar potential ligands, though the similarity of the extracellular domains of the H2 to the known receptor (rat and mouse HI) suggest the same or closely related ligand. A receptor can be used as a specific binding reagent to identify its binding partner, by taking advantage of its specificity of binding, much like an antibody would be used. The binding receptor may be an 0X2RH, or may involve, e.g., a complex of the OX2RH with another subunit. A binding reagent is either labeled as described above, e.g., fluorescence or otherwise, or immobilized to a substrate for panning methods. The bmdmg composition is used to screen an expression library made from a cell line which expresses a bmdmg partner, i.e., ligand, preferably membrane associated. Standard staining techniques are used to detect or sort surface expressed ligand, or surface expressing transformed cells are screened by panning. Screening of intracellular expression is performed by various staining or lmmunofluorescence procedures. See also McMahan, et al. (1991) EMBO J. 10:2821-2832. Alternatively, receptor reagents are used to affinity purify or sort out cells expressing a putative ligand. See, e.g., Sambrook, et al. or Ausubel, et al. Another strategy is to screen for a membrane bound ligand by panning. The receptor cDNA is constructed as described above. Immobilization may be achieved by use of appropriate antibodies which recognize, e.g., a FLAG sequence on an OX2RH fusion construct, or by use of antibodies raised against the first antibodies. Recursive cycles of selection and amplification lead to enrichment of appropriate clones and eventual isolation of receptor expressing clones. Phage expression libraries can be screened by mammalian OX2RH, e.g., labeled forms. Appropriate label techniques, e.g., anti-FLAG antibodies, will allow specific labeling of appropriate phage clones. Upon confirmation of OX2-OX2RH binding, or identification of alternative ligands for the other homologs, signaling pathways will be tested. See, e.g., Preston, et al . (1997) Eur. J. Immunol . 27:1911-1918. Implications of the DAP12 involvement are also clear. See, e.g., Bakker, et al . (2000) Human Immunology 61:18-27; Lanier, et al . (1998) Immunity 8:693-701; Smith, et al . (1998) J. Immunol. 161:7-10; Gossel , et al . (1999) J. Leukoc. Biol. 66:165-171; Tomasello, et al.(1998) J. Biol. Chem. 273:34115-34119; and McVicar, et al. (1998) J. Biol. Chem. 273:32934-32942. Similarly, or alternatively, DAP10 may be involved. See, e.g., Wu J, et al. (1999) Science 285:730-732; and Bauer, et al. (1999) Science 285:727-729. In particular, the DAP12 coreceptor partner is in the same family as the T cell receptor subunit ζ and the FcεRγ, which possess ITIM motifs, and signal through the pathway involving the syk/zap70 protein tyrosine kinases. The DAP10 has the YxxM motif, which signals through or analogously to the PI3 kinase pathway. Certain isoforms of the MHC class I receptors on NK cells lack ITIM sequences in their cytoplasmic domains and it has been proposed that these isoforms activate, rather than inhibit, NK cells. These activating receptors have very short intracellular regions lacking any signaling motifs and they all share a positively charged residue within their transmembrane domain, which suggested the association with an adapter molecule that is capable of signaling. DAP12, a type I disulfide-linked homodimer containing an ITAM non-covalently assembles with the human KIR2DS receptors. DAP12 has a negatively charged aspartic acid residue in its transmembrane region and corresponds to a reported 12-13 kD phosphoprotein that was found to co-immunoprecipitate with KIR2DS . Upon receptor engagement, DAP12 becomes phosphorylated and recruits the Syk kinase, thus inducing a signaling cascade similar to T cell receptor. Besides being associated with KIR2DS, a receptor for HLA-C, DAP12 is also expressed at the cell surface of NK cells associated with the activating mouse Ly49D and Ly49H receptors recognizing H-2 and with the human CD94/NKG2C heterodimer receptor complex recognizing HLA-E. Recent efforts to identify potential membrane signaling proteins by searching the EST databases have led to the identification of DAP10, a novel 10-kD surface adapter primarily expressed in hematopoietic cells. Although DAP10 has only limited homology with DAP12, its transmembrane domain contains a negatively charged residue that is conserved in the transmembrane regions of DAP12 and all of the CD3 subunits of the TCR. In addition, the conserved cysteine residues within the extracellular domain of DAP12 and the CD3 chains are also present in DAP10. Interestingly, the human DAP10 and DAP12 genes lie 98 adjacent on chromosome 19ql3.1, in opposite transcriptional orientation and separated by only approximately 130 base pairs, presumably as a result of gene duplication. One unique feature of DAP10 is its short, but conserved, cytoplasmic tail which, contains a YxxM signaling motif, a potential src-homology 2 (SH2; domain-binding site for the p85 regulatory subunit of the phosphatidylinositol 3-kinase (PI 3-kinase) . The physical and functional association of various OX2RH with DAP12 or DAP10 can be determined. XII. Genetic analysis, animal studies The sequences make available information and reagents useful for determination of the chromosomal mapping, disease marker correlation, and isolation and determination of the genetic structure of the respective genes. Intron/exon structure will be determined, and transgenic and deletion animals will be prepared. See, e.g., Goodnow (1992) "Transgenic Animals" in Roitt (ed.) Encyclopedia of Immunology, Academic Press, San Diego, pp. 1502- 1504; Travis (1992) Science 256:1392-1394; Kuhn, et al . (1991) Science 254:707-710; Capecchi (1989) Science 244:1288; Robertson (ed. 1987) Teratocarcinomas and Embryonic Stem Cells: A Practical Approach, IRL Press, Oxford; Rosenberg (1992) J. Clinical Oncology 10:180-199; and Cournoyer and Caskey (1993) Ann. Rev. Immunol. 11:297-329. To determine function of OX2-OX2R interaction in vitro and in vivo, an adenovirus construct was prepared that produced in soluble form, the extracellular region of OX2RH1 fused to human IgG. A control construct was prepared that produced in soluble form, only the human IgG backbone. In the first instance, supematants containing these fusion proteins were produced by cellular infection in vitro to test whether the OX2R fusion protein had biological function on the basis of binding to normally expressed mouse 0X2. In the first series of studies, tissue sections of mouse spleen from normal as well as OX2-gene knockout (KO) mice, were prepared and 0X2R, or control fusion proteins were added, and these reagents detected by addition of an antibody binding to the human Fc portion of the fusion protein, and subsequent immunoperoxidase staining procedures to reveal binding. Weak binding only of the 0X2R fusion protein, and only in normal but not 0X2 KO mice, was detected on follicular dendritic cells and endothelial cells. Both cell types are know to express very high levels of the ligand 0X2. Thus, the reagent bound to a physiological form of 0X2 and no binding was observed in spleen where the ligand 0X2 was absent due to gene targeting. B cells are known to express the ligand 0X2, but at lower level than on follicular dendritic cells and endothelial cells. Immunohistochemistry is not a particularly sensitive technique. Thus in a second study, the same fusion proteins were applied to isolated splenic leukocytes from normal and 0X2 KO mouse and binding to B cells determined by flow cytometric analysis using mAb specific to the B220 molecule on B cells, and the more sensitive detection of the fusion proteins by secondary antibodies to human IgG coupled to phycoerythrin. In this case, all B cells in normal mice were labeled by the 0X2R fusion protein but not by the control fusion protein. The interaction of the OX2R fusion protein with B cells was blocked by addition of a mAb called 0X90 that is known to bind to the part of the mouse 0X2 molecule that interacts with the 0X2R. In addition, no binding above the background level seen with the control fusion protein was observed when 0X2R fusion protein was added to B cells from 0X2 KO mice. The conclusions of these studies were: (1) that the 0X2R fusion protein was biologically active and bound to 0X2 on hematopoietic and non-hematopoietic cells; and (2) that the major ligand bound by 0X2R is indeed the identified ligand 0X2, on the basis of anti-0X2 (OX90) binding inhibition and lack of detectable binding to B cells from 0X2 KO mice. These data cannot exclude the possibility that there are other ligands bound by the 0X2R in addition to the known ligand 0X2, as even flow cytometry had not detected cell-surface molecules expressed at very low level. Transgenic mice can be generated by standard methods. Such animals are useful to determine the effects of deletion of the gene, in specific tissues, or completely throughout the organism. Such may provide interesting insight into development of the animal or particular tissues in various stages. Moreover, the effect on various responses to biological stress can be evaluated. See, e.g., Hogan, et al. (1995) Manipulating the Mouse Embrvo: A Laboratory Manual (2d ed.) Cold Spring Harbor Laboratory Press. Likewise, deletion mice, e.g., knock out mice may be generated. These animals will be subject to animal models to study the function of the genes in vivo. See, e.g., Gorczynski, et al. (1999) J. Immunol. 163:1654-1660; Mankoo, et al . (1999) Nature 400:69-73; Gorczynski, et al . (1999) Transplant. Proc. 31:577- 578; and Gorczynski L, et al . (1999) J. Immunol. 162:774-781. Of particular interest will be the roles of macrophages or other myeloid cell populations, e.g., in the blood, lymphoid tissues, or solid organs, including the microglia in the nervous system. Tests of susceptibility to infection, autoimmune inflammation, and neural degeneration are indicated. Both antagonist and agonists will be useful reagents in the in vitro or in vivo models described or made available. XIII. Screening for Substances Likely to Have Therapeutic Value The biological effect of the OX2R/OX2 interaction can be investigated by using antibody reactive with OX2R (an experimental substitute for 0X2) to crosslink 0X2R molecules in the macrophage cell surface membrane, and looking for changes in, e.g., nitric oxide production or phosphorylation of signaling proteins. The effects of perturbing the OX2R/OX2 interaction can be tested using macrophages carrying OX2R, by exposing them to a cross-linking binding partner such as a mAb for OX2R (e.g., OX102) or a recombinant multivalent version of 0X2 in the presence and absence of the candidate substance. Comparing activity of the macrophages (e.g., nitric oxide production or phosphorylation of signalling proteins) in the presence or absence of the candidate compound will indicate whether the candidate substance has a modulatory effect (e.g., inhibition or enhancement) . Candidate substances can also be tested in well established models of diseases in which macrophages are involved in the pathology of the disease, such as autoimmunity. For instance, established models such as experimental allergic encephalomyelitis can be used, as described and exemplified above, e.g., with the models exhibiting accelerated onset of the autoimmune disease experimental autoimmune encephalomyelitis (EAE) in mice. OX2R mimetics may be advantageous in chronic conditions such as chronic granulomatosis . Combinations of agonists or antagonists of the OX2/OX2R signaling may be combined with existing therapeutics for such conditions. See Physicians ' Desk Reference Medical Economics Co, Montvale, NJ. Analyses such as the above will indicate ways in which perturbation of the OX2R/OX2 interaction may be therapeutically beneficial. For example, the invention provides the means to make recombinant versions of OX2RH which can be used in conjunction with the available 0X2 proteins to screen for possible pharmacological reagents which block the interaction. The availability of interacting proteins provides the means for high throughput small molecule screening programs, as are used in the pharmacology industry. See, e.g., meetings on High Throughput Screening, International Business Communications, Southborough, MA 01772-1749. Interactions through the cytoplasmic region of OX2RH are likely therapeutic targets and knowledge of the sequence and its interactions provide a means to develop pharmacological reagents through similar screening methods . XIV. Structure activity relationship Information on the criticality of particular residues is determined using standard procedures and analysis. Standard mutagenesis analysis is performed, e.g., by generating many different variants at determined positions, e.g., at the positions identified above, and evaluating biological activities of the variants. This may be performed to the extent of determining positions which modify activity, or to focus on specific positions to determine the residues which can be substituted to either retain, block, or modulate biological activity. Alternatively, analysis of natural variants can indicate what positions tolerate natural mutations. This may result from populational analysis of variation among individuals, or across strains or species. Samples from selected individuals are analyzed, e.g., by PCR analysis and sequencing. This allows evaluation of population polymorphisms. All citations herein are incorporated herein by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference. Many modifications and variations of this invention can be made without departing from its spirit and scope, as will be apparent to those skilled in the art. The specific embodiments described herein are offered by way of example only, and the invention is to be limited by the terms of the appended claims, along with the full scope of equivalents to which such claims are entitled; and the invention is not to be limited by the specific embodiments that have been presented herein by way of example.

Claims: WHAT IS CLAIMED IS: 1. A composition of matter selected from: al) a substantially pure or recombinant polypeptide comprising at least three distinct nonoverlapping segments of at least four amino acids identical to segments of SEQ ID NO: 2; a2) a substantially pure or recombinant polypeptide comprising at least two distinct nonoverlapping segments of at least five amino acids identical to segments of SEQ ID NO: 2; a3) a natural sequence rodent OX2RH1 polypeptide comprising mature SEQ ID NO: 2; a4) a fusion polypeptide comprising rat OX2RH1 sequence; bl) a substantially pure or recombinant polypeptide comprising at least three distinct nonoverlapping segments of at least four amino acids identical to segments of SEQ ID NO: 4; b2) a substantially pure or recombinant polypeptide comprising at least two distinct nonoverlapping segments of at least five amino acids identical to segments of SEQ ID NO: 4; b3) a natural sequence rodent 0X2RH1 polypeptide comprising mature SEQ ID NO: 4; b4) a fusion polypeptide comprising human OX2RH1 sequence; cl) a substantially pure or recombinant polypeptide comprising at least three distinct nonoverlapping segments of at least four amino acids identical to segments of SEQ ID NO: 6; c2) a substantially pure or recombinant polypeptide comprising at least two distinct nonoverlapping segments of at least five amino acids identical to segments of SEQ ID NO: 6; c3) a natural sequence rodent 0X2RH1 polypeptide comprising mature SEQ ID NO: 6; c4) a fusion polypeptide comprising mouse OX2RH1 sequence; dl) a substantially pure or recombinant polypeptide comprising at least three distinct nonoverlapping segments of at least four amino acids identical to segments of SEQ ID NO: 8; d2) a substantially pure or recombinant polypeptide comprising at least two distinct nonoverlapping segments of at least five amino acids identical to segments of SEQ ID NO: 8; d3) a natural sequence rodent OX2RH1 polypeptide comprising mature SEQ ID NO: 8; d4) a fusion polypeptide comprising human OX2RH2 sequence; el) a substantially pure or recombinant polypeptide comprising at least three distinct nonoverlapping segments of at least four amino acids identical to segments of SEQ ID NO: 10; e2) a substantially pure or recombinant polypeptide comprising at least two distinct nonoverlapping segments of at least five amino acids identical to segments of SEQ ID NO: 10; e3) a natural sequence rodent OX2RH2 polypeptide comprising mature SEQ ID NO: 10; e4) a fusion polypeptide comprising mouse OX2RH2 sequence; fl) a substantially pure or recombinant polypeptide comprising at least three distinct nonoverlapping segments of at least four amino acids identical to segments of SEQ ID NO: 12; f2) a substantially pure or recombinant polypeptide comprising at least two distinct nonoverlapping segments of at least five amino acids identical to segments of SEQ ID NO: 12; f3) a natural sequence rodent OX2RH3 comprising mature SEQ ID NO: 12; f4) a fusion polypeptide comprising mouse OX2RH3 sequence; gl) a substantially pure or recombinant polypeptide comprising at least three distinct nonoverlapping segments of at least four amino acids identical to segments of SEQ ID NO: 20; g2) a substantially pure or recombinant polypeptide comprising at least two distinct nonoverlapping segments of at least five amino acids identical to segments of SEQ ID NO: 20; g3) a natural sequence primate OX2RH1.2 polypeptide comprising mature SEQ ID NO: 20; g4) a fusion polypeptide comprising primate OX2RH1.2 sequence; hi) a substantially pure or recombinant polypeptide comprising at least three distinct nonoverlapping segments of at least four amino acids identical to segments of SEQ ID NO: 23; b.2) a substantially pure or recombinant polypeptide comprising at least two distinct nonoverlapping segments of at least five amino acids identical to segments of SEQ ID NO: 23; h3) a natural sequence rodent OX2RH4 polypeptide comprising mature SEQ ID NO: 23; or h4) a fusion polypeptide comprising mouse OX2RH4 sequence. 2. A binding compound comprising an antigen binding site from an antibody, which specifically binds to a natural OX2RH polypeptide of Claim 1, wherein: a) said binding compound is in a container; b) said OX2RH polypeptide is from a rodent or primate; c) said binding compound is an Fv, Fab, or Fab2 fragment; d) said binding compound is conjugated to another chemical moiety; or e) said antibody: i) is raised against a peptide sequence of a mature polypeptide of Tables 1-3; ii) is raised against a mature OX2RH; iii) is raised to a purified mammalian OX2RH; iv) is immunoselected; v) is a polyclonal antibody; vi) binds to a denatured OX2RH; vii) exhibits a Kd to antigen of at least 30 μM; viii) is attached to a solid substrate, including a bead or plastic membrane; ix) is in a sterile composition; or x) is detectably labeled, including a fluorescent label. 3. An isolated or recombinant nucleic acid encoding said OX2RH polypeptide of Claim 1, wherein said: a) OX2RH is from a mammal; or b) said nucleic acid: i) encodes an antigenic peptide sequence of Tables 1- 3; ii) encodes a plurality of antigenic peptide sequences of Tables 1-3; iii) exhibits identity over at least thirteen nucleotides to a natural cDNA encoding said segment; iv) is an expression vector; v) further comprises an origin of replication; vi) is from a natural source; vii) comprises a detectable label; viii) comprises synthetic nucleotide sequence; ix) is less than 6 kb, preferably less than 3 kb; x) is from a primate or rodent; xi) comprises a natural full length coding sequence; xii) is a hybridization probe for a gene encoding said OX2RH; xiii) further encodes DAP12 or DAP10; or xiv) is a PCR primer, PCR product, or mutagenesis primer. 4. A nucleic acid which: a) hybridizes under wash conditions of 30 minutes at 40° C and less than 2M salt to the coding portion of SEQ ID NO: 1, 3, 5, 7, 9, 11, 19, or 22; or b) exhibits identity over a stretch of at least about 30 nucleotides to a primate or rodent OX2RH cDNA. 5. A method of modulating physiology or development of a cell or tissue culture cells comprising contacting said cell with an agonist or antagonist of a mammalian 0X2RH. 6. The method of Claim 5, wherein said: a) modulating physiology is: i) enhancing meloid function; or ii) enhancing immunity; b) agonist or antagonist attentuates 0X2 mediated signaling to said cell; or c) said antagonist is: i) an antibody to said OX2RH; ii) a soluble OX2RH construct; iii) a soluble 0X2RH-Ig fusion; or iv) an 0X2R antisense nucleic acid. 7. The method of Claim 6, wherein: a) said modulating of physiology is enhancement of meloid cell function in vitro, and said antagonist is an 0X2 mutein; or b) said modulating of physiology is enhancement of immunity in an animal being systemically treated with said antagonist. 8. A method for identification of a non-0X2 ligand for an OX2R, said method comprising screening a library of genes from an 0X2 knock out mouse for binding to an 0X2R-Ig fusion protein, and identifying genes which bind to said fusion protein.

Inventors: BARCLAY A NEIL, BROWN MARION H, CHERWINSKI HOLLY, GORMAN DANIEL M, HOEK ROBERT M, LANIER LEWIS L, PHILLIPS JOSEPH H, SEDGWICK JONATHAN D, WRIGHT GAVIN J, BARCLAY, A., NEIL, BROWN, MARION, H., CHERWINSKI, HOLLY, GORMAN, DANIEL, M., HOEK, ROBERT, M., LANIER, LEWIS, L., PHILLIPS, JOSEPH, H., SEDGWICK, JONATHAN, D., WRIGHT, GAVIN, J.
Applicants: BARCLAY A NEIL, BROWN MARION H, CHERWINSKI HOLLY, GORMAN DANIEL M, HOEK ROBERT M, LANIER LEWIS L, MEDICAL RES COUNCIL, PHILLIPS JOSEPH H, SCHERING CORP, SEDGWICK JONATHAN D, WRIGHT GAVIN J, BARCLAY, A., NEIL, BROWN, MARION, H., CHERWINSKI, HOLLY, GORMAN, DANIEL, M., HOEK, ROBERT, M., LANIER, LEWIS, L., MEDICAL RESEARCH COUNCIL, PHILLIPS, JOSEPH, H., SCHERING CORPORATION, SEDGWICK, JONATHAN, D., WRIGHT, GAVIN, J.
Application year: 2000
Main classification: C12N15
IPC codes: A61K31, A61K38, A61K39, A61K45, A61K48, A61P9, A61P17, A61P19, A61P25, A61P29, A61P37, C07K14, C07K16, C12N15, G01N33