POLYNUCLEOTIDES ENCODING MEMBERS OF THE HUMAN B LYMPHOCYTE ACTIVATION ANTIGEN B7 FAMILY AND POLYPEPTIDES ENCODED THEREBY

Abstract: The present invention provides novel isolated BLAA polynucleotides and the membrane-associated or secreted polypeptides encoded by the BLAA polynucleotides. Also provided are the antibodies that immunospecifically bind to a BLAA polypeptide or any derivative, variant, mutant or fragment of the BLAA polypeptide, polynucleotide or antibody. The invention additionally provides methods in which the BLAA polypeptide, polynucleotide and antibody are utilized in the detection and treatment of a broad range of pathological states, as well as to other uses.

Description: POLYNUCLEOTIDES ENCODING MEMBERS OF THE HUMAN B LYMPHOCYTE ACTIVATION ANTIGEN B7 FAMILY AND POLYPEPTIDES ENCODED THEREBY FIELD OF THE INVENTION The invention relates generally to polynucleotides and polypeptides encoded thereby, as well as vectors, antibodies and recombinant methods for producing the polypeptides and polynucleotides BACKGROUND OF THE INVENTION The immune system of vertebrates is characteπzed by its ability to discriminate "self from "non-self and to mount an appropπate, selective response to pathogens and other potentially harmful agents Cell types involved in immune responses include lymphocytes known as B cells and T cells Interactions between B cells and T cells are important for the propagation of full immune responses T cells must be activated in order to effect an immune response T cell activation is thought to require two signals an antigen-specific signal and a signal that is not antigen- specific T cells can become activated by binding to B cells, particularly B cells which are themselv es activated B cell-mediated activation of T cells is thought to be mediated, at least in part, b\ B7 proteins, which are expressed on the surface of B cells B7 proteins are members of the immunoglobuhn superfamily They bmd to activated T lymphocytes and provide regulatory signals for T lymphocyte cell growth and activation (See, e g , "Immunobiology - The Immune System in Health and Disease", 1997, Third edition, chapter 7, Janeway, C A et al , eds , Garland Publishing Inc , New York ) Cell surface molecules on T cells which bind to B7 molecules include CTLA4 and CD28 SUMMARY OF THE INVENTION The present invention is based, in part, upon the discovery of BLAA polynucleotide sequences encoding novel members of the human B Lymphocyte Activation Antigen B7 family (henceforth "BLAA"). In one aspect, the present invention involves an isolated nucleic acid molecule encoding a BLAA. This nucleic acid molecule may be a nucleotide that encodes a polypeptide having a sequence that is at least 95% identical to SEQ ID NO:2 or SEQ ID NO:6. Alternatively, it may be the complement of such a nucleic acid molecule. In another aspect, this invention involves an oligonucleotide that is less than 100 nucleotides in length and contains at least 6 contiguous nucleotides of SEQ ID NO: l, 3, 5, 7, 8, 9, 10, 11, or 12. This oligonucleotide contains at least 6 contiguous nucleotides of a complement of SEQ ID NO: 1, 3, 5, 7, 8, 9, 10, 11, or 12. Another aspect of this invention relates to a vector containing an isolated nucleic acid molecule encoding a BLAA, as described above. In one embodiment, this vector is an expression vector. In another embodiment, this vector contains a regulatory element that is operably linked to the isolated nucleic acid molecule. A further aspect of this invention involves an isolated polypeptide that is at least 80% identical to a polypeptide having an amino acid sequence of SEQ ID NO:2, SEQ ID NO:4, or SEQ ID NO:6. In another embodiment of this aspect of the invention, the isolated polypeptide is at least 80% homologous to a fragment of a polypeptide having an amino acid sequence of SEQ ID NO:2, SEQ ID NO:4, or SEQ ID NO:6. In this embodiment, the fragment contains at least 6 contiguous amino acids of SEQ ID NO:2, SEQ IDNO:4, or SEQ ID NO:6. Other embodiments of this aspect of the invention require that the isolated polypeptides of the invention be at least 80% homologous to a derivative, analog, or homolog of a polypeptide having an amino acid sequence of SEQ ID NO:2, SEQ ID NO:4, or SEQ ID NO:6. Yet another embodiment involves an isolated polypeptide that is at least 80% identical to a naturally occurring allelic variant of a polypeptide having an amino acid sequence of SEQ ID NO:2, SEQ ID NO:4, or SEQ ID NO:6. This embodiment requires that the polypeptide be encoded by a nucleic acid molecule capable of hybridizing to a nucleic acid molecule of SEQ ID NO: 1 , SEQ ID NO:3, or SEQ ID NO:5, under stπngent conditions. Another embodiment of this invention involves an antibody that selectively binds to the polypeptιde(s) descπbed above Further embodiments of this invention provide methods for (a) producing such polypeptιde(s) by cultuπng a host cell under conditions in which the nucleic acid molecule is expressed, (b) detecting the presence of the polypeptιde(s) in a sample by contacting the sample with a compound that selectively binds to the polypeptιde(s) of the invention, and (c) modulating the activity of such polypeptιde(s) by contacting a cell sample containing the polypeptιde(s) of the instant invention with a compound that binds to the polypeptιde(s) to modulate its activity Additionally, a method of detecting the presence of one of the nucleic acid molecules of this invention is also provided This method involves contacting a sample with a compound that selectively binds to the polypeptιde(s) of this invention and determining whether the compound bound to the polypeptιde(s) is present in the sample Other embodiments of this invention include methods of treating or preventing immune response-associated disorders and therapeutic or prophylactic pharmaceutical compositions Additionally, another aspect of this invention involves a kit containing therapeutically or prophylactically effective amounts of the pharmaceutical compositions provided for in the instant invention Another aspect of this invention involves the use of a therapeutic m the manufacture of a medicament for treating diseases associated with immune-response disorders Another embodiment of this invention olves a method for screening for a modulator of activity, latency or predisposition to an immune response-associated disorder In this embodiment, a test compound is administered to an animal at an increased πsk for an immune response- associated disorder, measuπng the expression of the polypeptide of the invention m the test animal, measuring polypeptide expression in a control animal, and compaπng the expression m both animals Other embodiments of this invention include methods for determining the presence of or predisposition to a disease associate with altered levels of a BLAA polypeptide or a BLAA nucleic acid by measuπng the amount of BLAA polypeptide or nucleic acid m a sample and compaπng it to the amount present in a control sample Yet other embodiments of this invention involve methods of treating a pathological state in a mammal by admimsteπng a BLAA polypeptide or a BLAA nucleic acid in amounts sufficient to alleviate the pathological state Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains Although methods and mateπals similar or equivalent to those descnbed herein can be used in the practice or testing of the present invention, suitable methods and mateπals are descπbed below All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety In case of conflict, the present specification, including definitions, will control In addition, the matenals, methods, and examples are illustrative only and are not intended to be limiting Other features and advantages of the invention will be apparent from the following detailed descπption and claims BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a representation of a 2691 nucleotide human cDNA sequence (SEQ ID NO 1), and an amino acid sequence of the encoded polypeptide (SEQ ID NO 2) Figure 2 is a representation of a 2885 nucleotide human cDNA sequence (SEQ ID NO 3), and an ammo acid sequence of the encoded polypeptide (SEQ ID NO 4) Figure 3 is a representation of a 2229 nucleotide human cDNA sequence (SEQ ID NO 5), and an amino acid sequence of the encoded polypeptide (SEQ ID NO 6) Figure 4 shows the ClustalW Alignment of the BLAA polypeptide of SEQ ID NO 6 as compared to several homologous B7 proteins and indicates the conserved regions by dark highlighting and conservative ammo acid substitutions by lighter highlighting Figure 5 depicts the hydrophobicity plot for the polypeptide of SEQ ID NO 6 DETAILED DESCRIPTION OF THE INVENTION The invention provides novel polynucleotides encoding polypeptides beaπng sequence similaπty to the B7 family of B lymphocyte antigens (BLAA) These cDNA sequences according to the invention, along with their encoded BLAA polypeptides are shown in Figures 1, 2 and 3 The BLAA polypeptides are 20-25% identical and 40-45% similar to previously descπbed members of the B7 family (i e , B7-1 and B7-2) As discussed in detail below, several motifs of the BLAA polypeptides are highly conserved with B7 polypeptides Additionally, comparable similaπty to human, mouse, and bovme butyrophilm as well as human myehn o godendrocyte glycoprotein (MOG) has been observed The polypeptides of this invention have two (SEQ ID NO 2), three (SEQ ID NO 4), or four (SEQ ID NO 6) Ig- ke domains, followed by a transmembrane domain and a 44 ammo acid cytoplasmic domain This is consistent with previously descπbed members of the B7 protein family, which are known to be localized on the cell surface (see, e g , Selvakumar et al , Immunogenetics 36 175-181 (1992) and Lmsley et al , Protein Sci 3 1341-1343 (1994)) As used herein, the term "human B lymphocyte activation antigen B7-hke activity" encompasses binding to activated T lymphocytes and providing regulatory signals for T lymphocyte cell growth and activation Accordingly, the polypeptides of the instant invention are novel members of the B7 protein family The nucleic acid molecules and polypeptides of the present invention can be used to modulate immune responses As such, they are useful in potential therapeutic applications implicated in the treatment of infectious diseases, cancers, autoimmune disorders and complications associated with graft vs host disease in organ transplantation, and/or in similar immune system pathologies and disorders For example, a cDNA encoding a polypeptide of the instant invention may be useful in gene therapy Alternatively, a BLAA polypeptide can be administered directly to treat immune disorders The nucleic acids, polypeptides and antibodies of the instant invention may be further useful in diagnostic and therapeutic applications The BLAA polypeptides contain numerous regions and/or single ammo acids that are conser ed at corresponding position in other homologous B7 proteins For example, Figure 4 depicts the ClustalW alignment of the polypeptide of SEQ ID NO 6 Conserved regions include, e g . amino acids 16, 42, 46, 48, 50, 52, 59, 60, 63, 67-68, 75, 82, 89, 92-93, 107-109, 1 16, 118, 122, 134, 136, 138, 140, 143, 145, 152, 164-167, 170, 172-173, 187, 191 , 194, 198, 210, 217, 223, 242 and 310 In addition, there are also regions with conservative ammo acid substitutions as defined in the section "Conservative Mutations" By "conservative amino acid substitutions" is meant amino acids having similar side chains Such substitutions are found, e g , at amino acids 14, 25, 38, 65, 71, 79, 84, 106, 112, 114, 119, 123-124, 127-128, 142, 148- 149 161 , 163, 171 , 202, 212, 217, 221-223, 264, 266, 278, 283-284, 291, 305 and 335 The BLAA polypeptides include hydrophihc and hydrophobic regions As shown in Figure 5, the polypeptide of SEQ ID NO 6 contains both hydrophihc and hydrophobic portions Hydrophobic regions include from about ammo acid 1 to about amino acid 75, from about ammo acid 1 10 to about amino acid 150, from about ammo acid 200 to about amino acid 225, from about ammo acid 250 to about ammo acid 290, from about amino acid 310 to about ammo acid 380, from about ammo acid 420 to about amino acid 440, and from about amino acid 460 to about amino acid 500 Conversely, the hydrophihc regions include from about amino acid 75 to about amino acid 110, from about ammo acid 150 to about amino acid 200, from about amino acid 225 to about ammo acid 250, from about amino acid 290 to about ammo acid 310, from about ammo acid 380 to about ammo acid 420, from about amino acid 440 to about ammo acid 534 Accordingly, these regions are useful for designing epitopes or selecting antigens For ease of reference, the novel polynucleotide and polypeptide sequences of the present invention shall be referred to collectively as BLAA (for B Lymphocyte Activation Antigen) A summary of the BLAA nucleic acid and polypeptide sequences of the present invention is provided in Table 1 Table 1 : Sequences and Corresponding SEQ ID Numbers As used herein, "identical" residues correspond to those residues in a compaπson between two sequences where the equivalent nucleotide base or amino acid residue in an alignment of two sequences is the same residue Residues are "similar" when the compaπsons between two sequences in an alignment show that residues in an equivalent position in a comparison are either the same amino acid or a conservatively substituted amino acid as defined below in the section "Conservative Mutations" Nucleic Acids One aspect of the invention pertains to isolated BLAA nucleic acid molecules that encode BLAA polypeptides or biologically active portions thereof BLAA nucleic acid molecules also include nucleic acid fragments sufficient for use as hybπdization probes to identify BLAA-encodmg nucleic acids (e g , BLAA mRNA) and fragments for use as PCR pπmers for the amplification or mutation of BLAA nucleic acid molecules As used herein, the term "nucleic acid molecule" is intended to include DNA molecules (e g , cDNA or genomic DNA), RNA molecules (e g , mRNA), analogs of the DNA or RNA generated using nucleotide analogs, and deπvatives, fragments and homologs thereof The nucleic acid molecule can be single-stranded or double-stranded, but preferably is double-stranded DNA "Probes" refer to nucleic acid sequences of vaπable length, preferably between at least about 10 nucleotides (nt). 100 nt, or as many as about, e g , 6,000 nt, depending on use Probes are used in the detection of identical, similar, or complementary nucleic acid sequences Longer length probes are usually obtained from a natural or recombinant source and are highly specific and much slower to hybridize than o gomers Probes may be single- or double-stranded and designed to have specificity in PCR, membrane-based hybπdization technologies, or ELISA-hke technologies An "isolated" nucleic acid molecule is one that is separated from other nucleic acid molecules which are present in the natural source of the nucleic acid Preferably, an "isolated" nucleic acid is free of sequences which naturally flank the nucleic acid (i e , sequences located at the 5' and 3' ends of the nucleic acid) in the genomic DNA of the organism from which the nucleic acid is deπved For example, in vanous embodiments, the isolated BLAA nucleic acid molecule can contain less than about 5 kb, 4 kb, 3 kb, 2 kb, 1 kb, 0 5 kb or 0 1 kb of nucleotide sequences which naturally flank the nucleic acid molecule in genomic DNA of the cell from which the nucleic acid is deπved Moreover, an "isolated" nucleic acid molecule, such as a cDNA molecule, can be substantially free of other cellular mateπal or culture medium when produced by recombinant techniques, or of chemical precursors or other chemicals when chemically synthesized A nucleic acid molecule of the present invention, e g , a nucleic acid molecule having a nucleotide sequence selected from the group consisting of SEQ ID NO 1, SEQ ID NO 3, SEQ ID NO 5, SEQ ID NO 7, SEQ ID NO 8, SEQ ID NO 9, SEQ ID NO 10, SEQ ID NO 11, and SEQ ID NO 12, or a complement of any of these nucleotide sequences, can be isolated using standard molecular biology techniques and the sequence information provided herein Using all or a portion of the nucleic acid sequences of SEQ ID NO 1, 3, 5, 7, 8, 9, 10, 1 1, or 12 as a hybndization probe, BLAA molecules can be isolated using standard hybπdization and cloning techniques (e g , as descπbed in Sambrook et al , (eds ), MOLECULAR CLONING A LABORATORY MANUAL 2 nd Ed , Cold Spπng Harbor Laboratory Press, Cold Spnng Harbor, NY, 1989, and Ausubel, et al , (eds ), CURRENT PROTOCOLS IN MOLECULAR BIOLOGY, John Wiley & Sons, New York, NY, 1993 ) A nucleic acid of the invention can be amplified using cDNA, mRNA or, alternatively, genomic DNA, as a template and appropπate oligonucleotide pπmers according to standard PCR amplification techniques The nucleic acid so amplified can be cloned into an appropriate v ector and characteπzed by DNA sequence analysis Furthermore, oligonucleotides corresponding to BLAA nucleotide sequences can be prepared by standard synthetic techniques, e g , using an automated DNA synthesizer As used herein, the term "oligonucleotide" refers to a seπes of linked nucleotide residues, which oligonucleotide has a sufficient number of nucleotide bases to be used in a PCR reaction A short oligonucleotide sequence may be based on, or designed from, a genomic or cDNA. sequence and is used to amplify, confirm, or reveal the presence of an identical, similar or complementary DNA or RNA in a particular cell or tissue Oligonucleotides compπse portions of a nucleic acid sequence having about 10 nt, 50 nt, or 100 nt in length, preferably about 15 nt to 30 nt in length In one embodiment, an oligonucleotide composing a nucleic acid molecule less than 100 nt m length would further compπse at lease 6 contiguous nucleotides of SEQ ID NO 1, 3, 5, 7, 8, 9, 10, 11, or 12 or a complement thereof Oligonucleotides may be chemically synthesized and may be used as probes In another embodiment, an isolated nucleic acid molecule of the invention comprises a nucleic acid molecule that is a complement of the nucleotide sequence shown in SEQ ID NO 1, 3, 5, 7, 8, 9, 10, 11, or 12 A nucleic acid molecule that is complementary to the nucleotide sequence shown in SEQ ID NO 1, 3, 5, 7, 8, 9, 10, 11, or 12 is one that is sufficiently complementary to the nucleotide sequence shown in SEQ ID NO 1, 3, 5, 7, 8, 9, 10, 1 1, or 12, that it can hydrogen bond with little or no mismatches to the nucleotide sequence shown in SEQ ID NO 1. 3, 5, 7, 8, 9, 10, 11, or 12, thereby forming a stable duplex As used herein, the term "complementary" refers to Watson-Cπck or Hoogsteen base paiπng between nucleotides units of a nucleic acid molecule, and the term "binding" means the physical or chemical interaction between two polypeptides or compounds or associated polypeptides or compounds or combinations thereof Binding includes ionic, non-ionic, Van der Waals, hydrophobic interactions, etc A physical interaction can be either direct or indirect Indirect interactions may be through or due to the effects of another polypeptide or compound Direct binding refers to interactions that do not take place through, or due to, the effect of another polypeptide or compound, but instead are without other substantial chemical intermediates Moreov er, the nucleic acid molecule of the invention can compπse only a portion of the nucleic acid sequence of SEQ ID NO 1 , 3, 5, 7, 8, 9, 10, 1 1, or 12, e g , a fragment that can be used as a probe or pπmer or a fragment encoding a biologically active portion of BLAA Fragments provided herein are defined as sequences of at least 6 (contiguous) nucleic acids or at least 4 (contiguous) ammo acids, a length sufficient to allow for specific hybridization in the case of nucleic acids or for specific recognition of an epitope in the case of amino acids respectively, and are at most some portion less than a full length sequence Fragments may be deπved from any contiguous portion of a nucleic acid or amino acid sequence of choice Deπvatives are nucleic acid sequences or ammo acid sequences formed from the native compounds either directly or by modification or partial substitution Analogs are nucleic acid sequences or amino acid sequences that have a structure similar to, but not identical to, the native compound but differs from it in respect to certain components or side chains Analogs may be synthetic or from a different evolutionary origin and may have a similar or opposite metabolic activity compared to wild type Homologs are nucleic acid sequences or ammo acid sequences of a particular gene that are deπved from different species Deπvatives and analogs may be full length or other than full length, if the deπvative or analog contains a modified nucleic acid or amino acid, as descπbed below Derivatives or analogs of the nucleic acids or proteins of the invention include, but are not limited to, molecules compπsing regions that are substantially homologous to the nucleic acids or proteins of the invention, in vaπous embodiments, by at least about 30%, 50%, 70%, 80%, or 95% identity (with a preferred identity of 80-95%) over a nucleic acid or amino acid sequence of identical size or when compared to an aligned sequence in which the alignment is done by a computer homology program known in the art, or whose encoding nucleic acid is capable of hybπdizing to the complement of a sequence encoding the aforementioned proteins under stπngent, moderately stπngent, or low stπngent conditions See e g Ausubel, et al , CURRENT PROTOCOLS IN MOLECULAR BIOLOGY, John Wiley & Sons, New York, NY, 1993, and below A "homologous nucleic acid sequence" or "homologous ammo acid sequence," or vaπations thereof, refer to sequences characteπzed by a homology at the nucleotide level or ammo acid lev el as discussed above Homologous nucleotide sequences encode those sequences coding lor isoforms ot a BLAA polypeptide Isoforms can be expressed in different tissues of the same organism as a result of, for example, alternative splicing of RNA Alternatively, isoforms can be encoded by different genes In the present invention, homologous nucleotide sequences include nucleotide sequences encoding for a BLAA polypeptide of species other than humans, including, but not limited to, mammals, and thus can include, e g , mouse, rat, rabbit, dog, cat cow, horse, and other organisms Homologous nucleotide sequences also include, but are not limited to, naturally occurπng allelic vaπations and mutations of the nucleotide sequences set forth herein A homologous nucleotide sequence does not, however, include a nucleotide sequence encoding a human BLAA polypeptide Homologous nucleic acid sequences include those nucleic acid sequences that encode conservative amino acid substitutions (see below) in SEQ ID NO 2, SEQ ID NO 4, or SEQ ID NO 6, as well as a polypeptide having BLAA activity Biological activities of the BLAA proteins are descπbed below A homologous amino acid sequence does not encode the amino acid sequence of a human BLAA polypeptide A BLAA polypeptide can be encoded by an open reading frame ("ORF") of a BLAA nucleic acid, as descπbed herein For example, the invention includes a nucleic acid sequence compπsing the stretch of nucleic acid sequences of SEQ ID NO 7, SEQ ID NO 9, and SEQ ID NO 1 1 that compπse the ORFs of the instant invention and encode a polypeptide of SEQ ID NO 2, SEQ ID NO 4, and SEQ ID NO 6, respectively An "open reading frame" ("ORF") corresponds to a nucleotide sequence that can potentially be translated into a polypeptide A stretch of nucleic acids comprising an ORF is uninterrupted by a stop codon An ORF that represents the coding sequence for a full protein begins with an ATG "start" codon and terminates with one of the three "stop" codons, namely, TAA. TAG, or TGA For the purposes of this invention, an ORF may be any part of a coding sequence, ith or without a start codon, a stop codon, or both For an ORF to be considered as a good candidate for coding for a bona fide cellular protein, a minimum size requirement is often set, for example, a stretch of DNA that would encode a protein of 50 amino acids or more In one embodiment, a 1020 base pair (bp) ORF (SEQ ID NO 7) includes nucleotide 111 to nucleotide 1 130 of SEQ ID NO 1 This ORF can be translated into a 340 ammo acid polypeptide according to SEQ ID NO 2 In another embodiment, a 1323 bp ORF (SEQ ID NO 9) includes nucleotide 2 to nucleotide 1324 of SEQ ID NO 3 This ORF can be translated into a 441 amino acid polypeptide according to SEQ ID NO 4 In another embodiment, a 1601 bp ORF (SEQ ID NO 1 1 ) includes nucleotide 60 to nucleotide 1661 of SEQ ID NO 5 This ORF could be translated into a 534 amino acid polypeptide according to SEQ ID NO 6 The nucleotide sequence determined from the cloning of the human BLAA gene allows for the generation of probes and pπmers designed for use in identifying and/or cloning BLAA homologues in other cell types, e g from other tissues, as well as BLAA homologues from other mammals The probe/pπmer typically compπses substantially puπfied oligonucleotide The oligonucleotide typically compπses a region of nucleotide sequence that hybπdizes under stπngent conditions to at least about 12, 25, 50, 100, 150, 200, 250, 300, 350 or 400 consecutive sense strand nucleotide sequence of SEQ ID NO 1 , 3, 5, 7, 8, 9, 10. 1 1 , or 12, or an anti-sense strand nucleotide sequence of SEQ ID NO 1, 3, 5, 7, 8, 9, 10, 11, or 12. or of a naturallv occurπng mutant of SEQ ID NO 1, 3, 5, 7, 8, 9, 10, 11, or 12 Probes based on a human BLAA nucleotide sequence can be used to detect transcripts or genomic sequences encoding the same or homologous proteins In vaπous embodiments, the probe further compπses a label group attached thereto, e g the label group can be a radioisotope, a fluorescent compound, an enzyme, or an enzyme co-factor Such probes can be used as a part of a diagnostic test kit for identifying cells or tissue which misexpress a BLAA protein, such as by measuπng a level of a BLAA-encodmg nucleic acid in a sample of cells from a subject e g , detecting BLAA mRNA levels or determining whether a genomic BLAA gene has been mutated or deleted "A polypeptide having a biologically active portion of BLAA" refers to polypeptides exhibiting activity similar, but not necessaπly identical to, an activity of a polypeptide of the present invention, including mature forms, as measured in a particular biological assay, with or without dose dependency A nucleic acid fragment encoding a "biologically active portion of BLAA" can be prepared by isolating a portion of SEQ ID NO 1, 3, 5, 7, 9, or 11, that encodes a polypeptide having a BLAA biological activity (the biological activities of the BLAA proteins are descπbed below), expressing the encoded portion of BLAA polypeptide (e g , bv recombinant expression in vitro) and assessing the activity of the encoded portion of BLAA BLAA variants The invention further encompasses nucleic acid molecules that differ from the nucleotide sequence shown in SEQ ID NO 1, 3, 5, 7, 9, or 1 1, due to degeneracy of the genetic code and thus encode the same BLAA protein as that encoded by the nucleotide sequence shown in SEQ ID NO 1, 3, 5, 7, 9, or 11 In another embodiment, an isolated nucleic acid molecule of the invention has a nucleotide sequence encoding a protein having an ammo acid sequence shown in SEQ ID NO 2, SEQ ID NO 4 or SEQ ID NO 6 In addition to the human BLAA nucleotide sequence shown in SEQ ID NO 1, 3, 5, 7, 9, or 1 1, it will be appreciated by those skilled in the art that DNA sequence polymorphisms that lead to changes in the amino acid sequences of BLAA may exist within a population (e g , the human population) Such genetic polymorphism in the BLAA gene may exist among individuals within a population due to natural allelic vaπation As used herein, the terms ' gene" and "recombinant gene" refer to nucleic acid molecules compπsing an open reading frame encoding a BLAA polypeptide, preferably a mammalian BLAA polypeptide Such natural allelic vaπations can typically result in 1-5% vaπance m the nucleotide sequence of the BLAA gene Any and all such nucleotide vaπations and resulting amino acid polymorphisms in BLAA that are the result of natural allelic vaπation and that do not alter the functional activitv of BLAA are intended to be within the scope of the invention Moreover, nucleic acid molecules encoding BLAA polypeptides from other species, and thus that hav e a nucleotide sequence that differs from the human sequence of SEQ ID NO 1, 3, 5, 7, 9, or 1 1 , are intended to be within the scope of the invention Nucleic acid molecules corresponding to natural allelic vaπants and homologues of the BLAA cDNAs of the invention can be isolated based on their homology to the human BLAA nucleic acids disclosed herein using the human cDNAs, or a portion thereof, as a hybπdization probe according to standard hybπdization techniques under stπngent hybπdization conditions For example, a soluble human BLAA cDNA can be isolated based on its homology to human membrane-bound BLAA Likewise, a membrane-bound human BLAA cDNA can be isolated based on its homology to soluble human BLAA accordingly, in another embodiment, an isolated nucleic acid molecule of the invention is at least 6 nucleotides m length and hybπdizes under stπngent conditions to the nucleic acid molecule comprising the nucleotide sequence of SEQ ID NO 1 , 3, 5, 7, 8, 9, 10, 1 1 , or 12 In another embodiment, the nucleic acid is at least 10, 25, 50, 100, 250, 500, 1000, 1500, 2000. or more nucleotides in length In another embodiment, an isolated nucleic acid molecule of the invention hybπdizes to the coding region, for example SEQ ID NO 1, 3, 5, 7, 9, or 11 As used herein, the term "hybπdizes under stnngent conditions" is intended to descπbe conditions for hybπdization and washing under which nucleotide sequences at least 60% homologous to each other typically remain hybπdized to each other Homologs (i e nucleic acids encoding BLAA polypeptides deπved from species other than human) or other related sequences (e g , paralogs) can be obtained by low, moderate or high stπngency hybπdization with all or a portion of the particular human sequence as a probe using methods well known in the art for nucleic acid hybπdization and cloning As used herein, the phrase "stπngent hybridization conditions" refers to conditions under hich a probe, primer or oligonucleotide will hybπdize to its target sequence, but to no other sequences Stπngent conditions are sequence-dependent and will be different in different circumstances Longer sequences hybπdize specifically at higher temperatures than shorter sequences Generally, stπngent conditions are selected to be about 5°C lower than the thermal melting point (Tm) for the specific sequence at a defined ionic strength and pH The Tm is the temperature (under defined ionic strength, pH and nucleic acid concentration) at which 50% of the probes complementary to the target sequence hybπdize to the target sequence at equihbπum Since the target sequences are generally present at excess, at Tm, 50% of the probes are occupied at equihbπum Typically, stπngent conditions will be those in which the salt concentration is less than about 1 0 M sodium ion, typically about 0 01 to 1 0 M sodium ion (or other salts) at pH 7 0 to 8 3 and the temperature is at least about 30°C for short probes, primers or oligonucleotides (e g , 10 nt to 50 nt) and at least about 60°C for longer probes, pπmers and oligonucleotides Stnngent conditions may also be achieved with the addition of destabilizing agents, such as formamide Stπngent conditions are known to those skilled in the art and can be found in Ausubel et al . (eds ), CURRENT PROTOCOLS IN MOLECULAR BIOLOGY, John Wiley & Sons, N Y (1989), 6 3 1-6 3 6 Preferably, the conditions are such that sequences at least about 65%, 70%, 75%. 85%, 90%, 95%. 98%, or 99% homologous to each other typically remain hybπdized to each other A non-hmitmg example of stnngent hybπdization conditions are hybridization m a high salt buffer compπsing 6X SSC, 50 mM Tns-HCl (pH 7 5), 1 mM EDTA, 0 02% PVP, 0 02% Ficoll, 0 02% BSA, and 500 mg/ml denatured salmon sperm DNA at 65°C, followed by one or more washes in 0 2X SSC, 0 01% BSA at 50°C An isolated nucleic acid molecule of the invention that hybndizes under stπngent conditions to the sequence of SEQ ID NO 1, 3, 5, 7, 8, 9, 10, 11, or 12, corresponds to a naturally-occurπng nucleic acid molecule As used herein, a "naturally-occurπng" nucleic acid molecule refers to an RNA or DNA. molecule having a nucleotide sequence that occurs in nature (e g , encodes a natural protein) In a second embodiment, a nucleic acid sequence that is hybπdizable to the nucleic acid molecule compπsing the nucleotide sequence of SEQ ID NO 1, 3, 5, 7, 8, 9, 10, 11, or 12, or fragments, analogs or deπvatives thereof, under conditions of moderate stπngency is provided A non-limiting example of moderate stπngency hybridization conditions are hybridization in 6X SSC, 5X Denhardt's solution, 0 5% SDS and 100 mg/ml denatured salmon sperm DNA at 55°C, followed by one or more washes in IX SSC, 0 1% SDS at 37°C Other conditions of moderate stπngency that may be used are well-known in the art See, e g , Ausubel et al (eds ), 1993, CURRENT PROTOCOLS IN MOLECULAR BIOLOGY, John Wiley & Sons, NY, and Kπegler, 1990, GENE TRANSFER AND EXPRESSION, A LABORATORY MANUAL, Stockton Press, NY In a third embodiment, a nucleic acid that is hybπdizable to the nucleic acid molecule compπsing the nucleotide sequence of SEQ ID NO 1, 3, 5, 7, 8, 9, 10, 11, or 12, or fragments, analogs or deπvatives thereof, under conditions of low stπngency, is provided A non-hmitmg example of low stπngency hybπdization conditions are hybridization m 35% formamide, 5X SSC, 50 mM Tπs-HCl (pH 7 5), 5 mM EDTA, 0 02% PVP, 0 02% Ficoll, 0 2% BSA, 100 mg/ml denatured salmon sperm DNA, 10% (wt/vol) dextran sulfate at 40°C, followed by one or more washes in 2X SSC, 25 mM Tπs-HCl (pH 7 4), 5 mM EDTA, and 0 1% SDS at 50°C Other conditions of low stπngency that may be used are well known in the art (e g , as employed for cross-species hybπdizations) See, e g , Ausubel et al (eds ), 1993, CURRENT PROTOCOLS IN MOLECULAR BIOLOGY, John Wiley & Sons, NY, and Kπegler, 1990, GENE TRANSFER AND EXPRESSION, A LABORATORY MANUAL, Stockton Press NY, Shilo and Wembeτg, l9S\ , Proc Natl Acad Scι USA 78 6789-6792 Conservative mutations In addition to naturally-occurπng allelic vaπants of the BLAA sequence that may exist in the population, the skilled artisan will further appreciate that changes can be introduced by mutation into the nucleotide sequence of SEQ ID NO 1, 3, 5, 7, 9, or 1 1, thereby leading to changes in the amino acid sequence of the encoded BLAA polypeptide, without alteπng the functional ability of the BLAA polypeptide For example, nucleotide substitutions leading to amino acid substitutions at "non-essential" ammo acid residues can be made in the sequence of SEQ ID NO 1 , 3, 5, 7, 9, or 1 1 A "non-essential" ammo acid residue is a residue that can be altered from the wild-type sequence of BLAA without alteπng the biological activity, whereas an "essential" amino acid residue is required for biological activity For example, amino acid residues that are conserved among the BLAA polypeptides of the present invention, are predicted to be particularly unamenable to alteration (See Figure 4 and discussion above) In addition, ammo acid residues that are conserved among family members of the BLAA polypeptides of the present invention, as indicated by the alignment presented in Figure 4, and as descπbed above, are also predicted to be particularly unamenable to alteration Other ammo acid residues, however, (e g , those that are not conserved or only semi-conserved among members of the BLAA polypeptides) may not be essential for activity and thus are likely to be amenable to alteration Another aspect of the invention pertains to nucleic acid molecules encoding BLAA polypeptides that contain changes in ammo acid residues that are not essential for activity Such BLAA polypeptides differ in ammo acid sequence from SEQ ID NO 2, SEQ ID NO 4 or SEQ ID NO 6, yet retain biological activity In one embodiment, the isolated nucleic acid molecule compπses a nucleotide sequence encoding a polypeptide, wherein the polypeptide compπses an amino acid sequence at least about 45% homologous to the amino acid sequence of SEQ ID NO 2, SEQ ID NO 4, or SEQ ID NO 6 Preferably, the polypeptide encoded by the nucleic acid molecule is at least about 60% homologous to SEQ ID NO 2, SEQ ID NO 4, or SEQ ID NO 6, more preferably at least about 70% homologous to SEQ ID NO 2, SEQ ID NO 4, or SEQ ID NO 6, still more preferably at least about 80% homologous to SEQ ID NO 2, SEQ ID NO 4, or SEQ ID NO 6, or SEQ ID NO 6, even more preferably at least about 90% homologous to SEQ ID NO 2, SEQ ID NO 4, or SEQ ID NO 6, and most preferably at least about 95% homologous to SEQ ID NO 2, SEQ ID NO 4, or SEQ ID NO 6 An isolated nucleic acid molecule encoding a BLAA polypeptide homologous to the polypeptide of SEQ ID NO 2, SEQ ID NO 4, or SEQ ID NO 6 can be created by introducing one or more nucleotide substitutions, additions or deletions into the nucleotide sequence of SEQ ID NO 1 3, 5, 7, 9, or 1 1 such that one or more ammo acid substitutions, additions or deletions are introduced into the encoded polypeptide Mutations can be introduced into SEQ ID NO 1, 3, 5, 7, 9, or 11 by standard techniques, such as site-directed mutagenesis and PCR-mediated mutagenesis Preferably, conservative amino acid substitutions are made at one or more predicted non-essential amino acid residues A "conservative ammo acid substitution" is one in which the amino acid residue is replaced with an ammo acid residue having a similar side chain Families of amino acid residues having similar side chains have been defined in the art These families include amino acids with basic side chains (e g , lysine, arginme, histidme), acidic side chains (e g , aspartic acid, glutamic acid), uncharged polar side chains (e g , glycine, asparagine, glutamine, seπne, threonine, tyrosine, cysteme), nonpolar side chains (e g , alanine, valme, leucine, isoleucine, prohne, phenylalanine, methionme, tryptophan), beta-branched side chains (e g , threonine, valme, isoleucine) and aromatic side chains (e g , tyrosine, phenylalanine, tryptophan, histidme) Thus, a predicted nonessential amino acid residue in BLAA is replaced with another amino acid residue from the same side chain family Alternatively, in another embodiment, mutations can be introduced randomly along all or part of a BLAA coding sequence, such as by saturation mutagenesis, and the resultant mutants can be screened for BLAA biological activity to identify mutants that retain activity Following mutagenesis of SEQ ID NO 1, 3, 5, 7, 9, or 11, the encoded polypeptide can be expressed by any recombinant technology known in the art and the activity of the polypeptide can be determined In one embodiment, a mutant BLAA polypeptide can be assayed for (1) the ability to form protein protein interactions with other BLAA polypeptides, other cell-surface proteins, or biologically active portions thereof, (2) complex formation between a mutant BLAA polypeptide and a BLAA gand, e g , CTLA4, (3) the ability of a mutant BLAA polypeptide to bind to an intracellular target protein or biologically active portion thereof (e g avidin proteins) In yet another embodiment, a mutant BLAA can be assayed for the ability to perform immunoglobuhn superfamily member activities, such as, (I) complex formation between a BLAA polypeptide and activated T lymphocytes, (n) interaction of a BLAA polypeptide with a protein having substantial homology to the human B lymphocyte activation antigen B7 family of proteins, (in) interaction of a BLAA polypeptide with a human B lymphocyte activation antigen B7 family member protein, and (IV) interaction of a BLAA polypeptide with other proteins In yet another embodiment, a BLAA activity is at least one or more of the following activities (l) modulation of immunoglobuhn superfamily-related protein activity, (n) regulation of T lymphocyte growth, and (in) regulation of T lymphocyte activation Antisense Another aspect of the invention pertains to isolated antisense nucleic acid molecules that are hybπdizable to or complementary to the nucleic acid molecule compπsing the nucleotide sequence of SEQ ID NO 1 , 3, 5, 7, 8, 9, 10, 1 1 , or 12, or fragments, analogs or deπvati es thereof An "antisense" nucleic acid compπses a nucleotide sequence that is complementary to a "sense" nucleic acid encoding a protein, e g , complementary to the coding strand of a double-stranded cDNA molecule or complementary to an mRNA sequence In specific aspects, antisense nucleic acid molecules are provided that compπse a sequence complementary to at least about 10, 25, 50, 100, 250 or 500 nucleotides or an entire BLAA coding strand, or to only a portion thereof Nucleic acid molecules encoding fragments, homologs. deπvatives and analogs of a BLAA polypeptide of SEQ ID NO 2, SEQ ID NO 4, or SEQ ID NO 6 or antisense nucleic acids complementary to a BLAA nucleic acid sequence of SEQ ID NO 1 3, 5, 7, 8, 9, 10, 1 1 , or 12, are additionally provided In one embodiment, an antisense nucleic acid molecule is antisense to a "coding region" of the coding strand of a nucleotide sequence encoding BLAA The term "coding region" refers to the region of the nucleotide sequence compπsing codons which are translated into amino acid residues (e g , the coding region of human BLAA corresponds to nucleotides 1 1 1-1 130 of SEQ ID NO 1 (SEQ ID NO 7), nucleotides 2-1324 of SEQ ID NO 3 (SEQ ID NO 9). or nucleotides 60-1601 of SEQ ID NO 5 (SEQ ID NO 1 1)) In another embodiment, the antisense nucleic acid molecule is antisense to a "noncodmg region" of the coding strand of a nucleotide sequence encoding BLAA The term "noncodmg region" lefers to 5' and 3' sequences which flank the coding region that are not translated into amino acids (i e , also referred to as 5' and 3' untranslated regions) Examples or "noncodmg regions" include the non-translated regions ("NTRs") of SEQ ID NO 8, SEQ ID NO 10, and SEQ ID NO 12 Given the coding strand sequences encoding BLAA disclosed herein (e g , SEQ ID NO 5, SEQ ID NO 7, and SEQ ID NO 9), antisense nucleic acids of the invention can be designed according to the rules of Watson and Cπck or Hoogsteen base paiπng The antisense nucleic acid molecule can be complementary to the entire coding region of BLAA mRNA, but more preferably is an oligonucleotide that is antisense to only a portion of the coding or noncodmg region of BLAA mRNA For example, the antisense oligonucleotide can be complementary to the region surrounding the translation start site of BLAA mRNA An antisense oligonucleotide can be, for example, about 5, 10, 15, 20, 25, 30, 35, 40, 45 or 50 nucleotides in length An antisense nucleic acid of the invention can be constructed using chemical synthesis or enzymatic hgation reactions using procedures known in the art For example, an antisense nucleic acid (e g , an antisense oligonucleotide) can be chemically synthesized using naturally occurπng nucleotides or vaπously modified nucleotides designed to increase the biological stability of the molecules or to increase the physical stability of the duplex formed between the antisense and sense nucleic acids, e g , phosphorothioate deπvatives and acπdine substituted nucleotides can be used Examples of modified nucleotides that can be used to generate the antisense nucleic acid include 5-fluorouracιl, 5-bromouracιl. 5-chlorouracιl. 5-ιodouracιl, hypoxanthine. xanthme, 4-acetylcytosme, 5-(carboxyhydroxylmethyl) uracil, 5-carboxymethylamιnomethyl- 2-thιouπdme, 5-carboxymethylamιnomethyluracιl, dihydrouracil, beta-D-galactosylqueosine, inosine, N6-ιsopentenyladenme, 1 -methylguanme, 1 -methylinosine, 2,2-dιmethylguamne, 2-methyladenιne, 2-methylguanme, 3-methylcytosme, 5-methylcytosme, N6-adenιne, 7-methylguanme, 5-methylammomethyluracιl, 5-methoxyammomethyl-2-thιouracιl, beta-D-mannosylqueosme, 5'-methoxycarboxymethyluracιl, 5-methoxyuracιl, 2-methylthιo-N6-ιsopentenyladenme, uracιl-5-oxyacetιc acid (v), wybutoxosine, pseudouracil, queosme, 2-thιocytosιne. 5-methyl-2-thιouracιl, 2-thιouracιl, 4-thιouracιl, 5-methyluracιl, uracιl-5-oxyacetιc acid meth lester. uracιl-5-oxyacetιc acid (v), 5-methyl-2-thιouracιl. 3-(3-ammo-3-N-2-carboxypropyl) uracil, (acp3)w, and 2,6-dιammopuπne Alternatively, the antisense nucleic acid can be produced biologically using an expression vector into which a nucleic acid has been subcloned in an antisense oπentation (/ e , RNA transcπbed from the inserted nucleic acid will be of an antisense oπentation to a target nucleic acid of interest, descπbed further in the following subsection) The antisense nucleic acid molecules of the invention are typically administered to a subject or generated in situ such that they hybπdize with or bmd to cellular mRNA and/or genomic DNA encoding a BLAA polypeptide to thereby inhibit expression of the protein, e g , by inhibiting transcπption and/or translation The hybπdization can be by conventional nucleotide complementarity to form a stable duplex, or, for example, in the case of an antisense nucleic acid molecule that binds to DNA duplexes, through specific interactions in the major groove of the double helix An example of a route of administration of antisense nucleic acid molecules of the invention includes direct injection at a tissue site Alternatively, antisense nucleic acid molecules can be modified to target selected cells and then administered systemically For example, for systemic administration, antisense molecules can be modified such that they specifically bmd to receptors or antigens expressed on a selected cell surface, e g , by linking the antisense nucleic acid molecules to peptides or antibodies that bind to cell surface receptors or antigens The antisense nucleic acid molecules can also be delivered to cells using the vectors descπbed herein To achieve sufficient mtracellular concentrations of antisense molecules, vector constructs in which the antisense nucleic acid molecule is placed under the control of a strong pol II or pol III promoter are preferred In yet another embodiment, the antisense nucleic acid molecule of the invention is an α-anomeπc nucleic acid molecule An α-anomeπc nucleic acid molecule forms specific double-stranded hybπds with complementary RNA in which, contrary to the usual β-units, the strands run parallel to each other (Gaultier et / (1987) Nucleic Acids Res 15 6625-6641) The antisense nucleic acid molecule can also compπse a 2'-o-methylπbonucleotιde (Inoue et al (1987) Nucleic Acids Res 15 6131-6148) or a chimeπc RNA-DNA analogue (Inoue et al (1987) FEBS Lett 215 327-330) Ribozymes and PNA moieties Nucleic acid modifications include, by way of nonhmiting example, modified bases, and nucleic acids whose sugar phosphate backbones are modified or deπvatized These modifications are earned out at least in part to enhance the chemical stability of the modified nucleic acid, such that they may be used, for example, as antisense binding nucleic acids in therapeutic applications in a subject In one embodiment, an antisense nucleic acid of the invention is a πbozyme Ribozymes are catalytic RNA molecules with nbonuclease activity that are capable of cleaving a single-stranded nucleic acid, such as an mRNA, to which they have a complementary region Thus, ribozymes (e g , hammerhead ribozymes (descπbed in Haselhoff and Gerlach (1988) Nature 334 585-591)) can be used to catalytically cleave BLAA mRNA transcnpts to thereby inhibit translation of BLAA mRNA A nbozyme having specificity for a BLAA-encoding nucleic acid can be designed based upon the nucleotide sequence of a BLAA cDNA disclosed herein (i e., SEQ ID NO' 1, 3, 5, 7, 9, or 1 1). For example, a deπvative of a Tetrahymena L-19 IVS RNA can be constmcted in which the nucleotide sequence of the active site is complementary to the nucleotide sequence to be cleaved in a BLAA-encoding mRNA. See, e g., Cech et al U.S. Pat No. 4,987,071 ; and Cech et al. U.S. Pat. No. 5,116,742. Alternatively, BLAA mRNA can be used to select a catalytic RNA having a specific πbonuclease activity from a pool of RNA molecules. See, e.g., Bartel et al., (1993) Science 261 : 1411-1418. Alternatively, BLAA gene expression can be inhibited by targeting nucleotide sequences complementary to the regulatory region of the BLAA (e.g., the BLAA promoter and/or enhancers) to form tπple helical structures that prevent transcπption of the BLAA gene in target cells. See generally, Helene. (1991) Anticancer Drug Des. 6: 569-84, Helene. et al. (1992) Ann. N Y Acad Sci 660:27-36; and Maher (1992) Bwassays 14: 807-15. In vaπous embodiments, the nucleic acids of BLAA can be modified at the base moiety, sugar moiety or phosphate backbone to improve, e.g., the stability, hybπdization, or solubility of the molecule. For example, the deoxyribose phosphate backbone of the nucleic acids can be modified to generate peptide nucleic acids (see Hyrup et al. (1996) Bioorg Med Chem 4 5-23) As used herein, the terms "peptide nucleic acids" or "PNAs" refer to nucleic acid mimics, e g.. DNA mimics, m which the deoxyπbose phosphate backbone is replaced by a pseudopeptide backbone and only the four natural nucleobases are retained. The neutral backbone of PNAs has been shown to allow for specific hybridization to DNA and RNA under conditions of low ionic strength. The synthesis of PNA ohgomers can be performed using standard solid phase peptide synthesis protocols as described in Hyrup et al. (1996) above; Perry-O'Keefe et al. (1996) PNAS 93: 14670-675 PNAs of BLAA can be used in therapeutic and diagnostic applications. For example, PNAs can be used as antisense or antigene agents for sequence-specific modulation of gene expression by, e.g., inducing transcnption or translation arrest or inhibiting replication. PNAs of BLAA can also be used, e.g., in the analysis of single base pair mutations in a gene by, e.g., PNA directed PCR clamping, as artificial restπction enzymes when used m combination with other enzymes, e g , SI nucleases (Hyrup B (1996) above), or as probes or primers for DNA sequence and hybπdization (Hyrup et al (1996), above, Perry-O'Keefe (1996), above) In another embodiment, PNAs of BLAA can be modified, e g , to enhance their stability or cellular uptake, by attaching hpophihc or other helper groups to PNA, by the formation of PNA-DNA chimeras, or by the use of hposomes or other techniques of drug delivery known m the art For example, PNA-DNA chimeras of BLAA can be generated that may combine the advantageous properties of PNA and DNA Such chimeras allow DNA recognition enzymes, e g , RNase H and DNA polymerases, to interact with the DNA portion while the PNA portion would provide high binding affinity and specificity PNA-DNA chimeras can be linked using linkers of appropnate lengths selected in terms of base stacking, number of bonds between the nucleobases, and oπentation (Hyrup (1996) above) The synthesis of PNA-DNA chimeras can be performed as descπbed in Hyrup (1996) above and Finn et al (1996) Nucl Acids Res 24 3357-63 For example, a DNA chain can be synthesized on a solid support using standard phosphoramidite coupling chemistry, and modified nucleoside analogs, e g , 5'-(4-methoxytπtyl)amιno-5'-deoxy-thymιdme phosphoramidite, can be used between the PNA and the 5' end of DNA (Mag et al (1989) Nucl Acid Res 17 5973-88) PNA monomers are then coupled in a stepwise manner to produce a chimenc molecule with a 5' PNA segment and a 3' DNA segment (Finn et al (1996) above) Alternatively, chimenc molecules can be synthesized with a 5' DNA segment and a 3' PNA segment See. Petersen et al (1975) Bioorg Med Chem Lett 5 1119-11 124 In other embodiments, the oligonucleotide may include other appended groups such as peptides {e g , for targeting host cell receptors in vivo), or agents facilitating transport across the cell membrane (see, e g , Letsinger et al , 1989, Proc Natl Acad Sci USA 86 6553-6556, Lemaitre et α/ , 1987, Proc Natl Acad Sci 84-648-652, PCT Publication No W088/09810) or the blood-brain barπer (see, e g , PCT Publication No W089/10134) In addition, oligonucleotides can be modified with hybndization tπggered cleavage agents (See, e g , Krol et al , 1988, BioTechmques 6 958-976) or intercalating agents (See, e g , Zon, 1988, Pharm Res 5 539-549) To this end, the oligonucleotide may be conjugated to another molecule, e g , a peptide, a hybπdization tπggered cross-linking agent, a transport agent, a hybπdization-tπggered cleavage agent, etc BLAA polypeptides As used herein, the terms "protein" and "polypeptide" are intended to be interchangeable The novel polypeptides of the invention include the BLAA polypeptides whose sequence is provided in SEQ ID NO 2, SEQ ID NO 4, or SEQ ID NO 6 The invention also includes mutant or vanant polypeptides any of whose residues may be changed from the corresponding residue shown in SEQ ID NO 2, SEQ ID NO 4, or SEQ ID NO- 6 while still encoding a polypeptide that maintains its BLAA activities and physiological functions, or a functional fragment thereof In the mutant or vanant protein, up to 20% or more of the residues may be so changed In general, an BLAA vanant that preserves BLAA-hke function includes any vanant in which residues at a particular position in the sequence have been substituted by other ammo acids, and further include the possibility of inserting an additional residue or residues between two residues of the parent protein as well as the possibility of deleting one or more residues from the parent sequence Any amino acid substitution, insertion, or deletion is encompassed by the invention In favorable circumstances, the substitution is a conservative substitution as defined above One aspect of the invention pertains to isolated BLAA polypeptides, and biologically active portions thereof, or denvatives, fragments, analogs or homologs thereof Also provided are polypeptide fragments suitable for use as immunogens to raise anti-BLAA antibodies In one embodiment, native BLAA polypeptides can be isolated from cells or tissue sources by an appropnate punfication scheme using standard protein puπfication techniques In another embodiment, BLAA polypeptides are produced by recombinant DNA techniques Alternative to recombinant expression, a BLAA protein or polypeptide can be synthesized chemically using standard peptide synthesis techniques An "isolated" or "punfied" polypeptide or biologically active portion thereof is substantially free of cellular matenal or other contaminating proteins or polypeptides from the cell or tissue source from which the BLAA polypeptide is deπved, or substantially free from chemical precursors or other chemicals when chemically synthesized The language "substantially free of cellular matenal" includes preparations of BLAA polypeptide in which the polypeptide is separated from cellular components of the cells from which it is isolated or recombmantly produced In one embodiment, the language "substantially free of cellular matenal" includes preparations of BLAA polypeptide having less than about 30% (by dry weight) of non-BLAA protein (also referred to herein as a "contaminating protein"), more preferably less than about 20% of non-BLAA protein, still more preferably less than about 10% of non-BLAA protein, and most preferably less than about 5% non-BLAA protein When the BLAA polypeptide or biologically active portion thereof is recombmantly produced, it is also preferably substantially free of culture medium, i e , culture medium represents less than about 20%, more preferably less than about 10%, and most preferably less than about 5% of the volume of the protein preparation The language "substantially free of chemical precursors or other chemicals" includes preparations of BLAA polypeptide in which the polypeptide is separated from chemical precursors or other chemicals that are involved in the synthesis of the polypeptide In one embodiment, the language "substantially free of chemical precursors or other chemicals" includes preparations of BLAA polypeptide having less than about 30% (by dry weight) of chemical precursors or non-BLAA chemical, more preferably less than about 20% chemical precursors or non-BLAA chemicals, still more preferably less than about 10% chemical precursors or non-BLAA chemicals, and most preferably less than about 5% chemical precursors or non-BLAA chemicals Biologically active portions of a BLAA polypeptide include peptides compπsing amino acid sequences sufficiently homologous to or deπved from the amino acid sequence of the BLAA polypeptides, e g , the amino acid sequence shown in SEQ ID NO 2, SEQ ID NO 4, or SEQ ID NO 6, that include fewer amino acids than the full length BLAA polypeptides, and exhibit at least one activity of a BLAA polypeptide Typically, biologically active portions compπse a domain or motif with at least one activity of the BLAA polypeptide A biologically active portion of a BLAA polypeptide can be a polypeptide which is, for example, 10, 25, 50, 100 or more ammo acids in length The polypeptide disclosed in SEQ ID NO 2 has two Ig-hke domains, followed by a transmembrane domain and a 44 ammo acid cytoplasmic domain The polypeptide disclosed in SEQ ID NO 4 has three Ig-hke domains, followed by a transmembrane domain and a 44 amino acid cytoplasmic domain The polypeptide disclosed in SEQ ID NO 6 has four Ig-hke domains, followed by a transmembrane domain and a 44 amino acid cytoplasmic domain Its hydrophobicity plot analysis is shown in Figure 5 In an embodiment, the BLAA polypeptide has an ammo acid sequence shown in SEQ ID NO 2, SEQ ID NO 4, or SEQ ID NO 6 In other embodiments, the BLAA polypeptide is substantially homologous to SEQ ID NO 2, SEQ ID NO 4, or SEQ ID NO 6 and retains the functional activity of the polypeptide of SEQ ID NO 2, SEQ ID NO 4, or SEQ ID NO 6, yet differs in amino acid sequence due to natural allelic vanation or mutagenesis, as descπbed m detail below Accordingly, in another embodiment, the BLAA polypeptide is a polypeptide that compπses an amino acid sequence at least about 45% homologous to the amino acid sequence of SEQ ID NO 2, SEQ ID NO 4, or SEQ ID NO 6 and retains the functional activity of the BLAA polypeptides of SEQ ID NO 2, SEQ ID NO 4, or SEQ ID NO 6 Determining homology between two or more sequences To determine the percent homology of two ammo acid sequences or of two nucleic acids, the sequences are aligned for optimal compaπson purposes (e g , gaps can be introduced in the sequence of a first amino acid or nucleic acid sequence for optimal alignment with a second amino or nucleic acid sequence) The amino acid residues or nucleotides at corresponding ammo acid positions or nucleotide positions are then compared When a position in the first sequence is occupied by the same ammo acid residue or nucleotide as the corresponding position in the second sequence, then the molecules are homologous at that position (/ e , as used herein ammo acid or nucleic acid "homology" is equivalent to amino acid or nucleic acid "identity") The nucleic acid sequence homology may be determined as the degree of identity between two sequences The homology may be determined using computer programs known in the art, such as GAP software provided in the GCG program package See, Needleman and Wunsch 1970 J Mol Bwl 48 443-453 Using GCG GAP software with the following settings for nucleic acid sequence compaπson GAP creation penalty of 5 0 and GAP extension penalty of 0 3, the coding region of the analogous nucleic acid sequences referred to above exhibits a degree of identity preferably of at least 70%, 75%, 80%, 85%, 90%, 95%, 98%, or 99%, with the CDS (encoding) part of the DNA sequence shown in SEQ ID NO 1, 3, 5, 7, 9, or 11 The term "sequence identity" refers to the degree to which two polynucleotide or polypeptide sequences are identical on a residue-by-residue basis over a particular region of comparison The term "percentage of sequence identity" is calculated by comparing two optimally aligned sequences over that region of compaπson, determining the number of positions at which the identical nucleic acid base (e g , A, T, C, G, U, or I, in the case of nucleic acids) occurs in both sequences to yield the number of matched positions, dividing the number of matched positions by the total number of positions in the region of companson (/ e , the window size), and multiplying the result by 100 to yield the percentage of sequence identity The term "substantial identity" as used herein denotes a characteπstic of a polynucleotide sequence, wherein the polynucleotide compnses a sequence that has at least 80 percent sequence identity, preferably at least 85 percent identity and often 90 to 95 percent sequence identity, more usually at least 99 percent sequence identity as compared to a reference sequence over a companson region Chimeric and fusion proteins The invention also provides for BLAA chimenc or fusion proteins. As used herein, a BLAA "chimenc protein" or "fusion protein" compnses a BLAA polypeptide operatively linked to a non-BLAA polypeptide A "BLAA polypeptide" refers to a polypeptide having an ammo acid sequence corresponding to BLAA, whereas a "non-BLAA polypeptide" refers to a polypeptide having an ammo acid sequence conesponding to a protein that is not substantially homologous to the BLAA polypeptide, e g , a protein that is different from the BLAA polypeptide and that is derived from the same or a different organism Within a BLAA fusion protein the BLAA polypeptide can correspond to all or a portion of a BLAA polypeptide. In one embodiment, a BLAA fusion protein compπses at least one biologically active portion of a BLAA protein In another embodiment, a BLAA fusion protein compπses at least two biologically active portions of a BLAA polypeptide In yet another embodiment, a BLAA fusion protein comprises at least three biologically active portions of a BLAA polypeptide Within the fusion protein, the term "operatively linked" is intended to indicate that the BLAA polypeptide and the non-BLAA polypeptide are fused in-frame to each other The non-BLAA polypeptide can be fused to the N-terminus or C-termmus of the BLAA polypeptide Such fusion proteins can be further utilized in screening assays for compounds which modulate BLAA activity (such assays are descπbed m detail below) In one embodiment, the fusion protein is a GST-BLAA fusion protein in which the BLAA sequences are fused to the C-terminus of the GST (1 e , glutathione S-transferase) sequences Such fusion proteins can facilitate the purification of recombinant BLAA In another embodiment, the fusion protein is a BLAA polypeptide containing a heterologous signal sequence at it's N-terminus For example, the nature BLAA signal sequence (e g , about amino acids 1 to 26 of SEQ ID NO 2, SEQ ID NO 4, or SEQ ID NO 6) can be removed and replaced with a signal sequence from another protein In certain host cells (e g , mammalian host cells), expression and/or secretion of BLAA can be increased through use of a heterologous signal sequence In yet another embodiment, the fusion protein is a BLAA-immunoglobulm fusion protein in which the BLAA sequences are fused to sequences deπved from a member of the immunoglobuhn protein family The BLAA-immunoglobuhn fusion proteins of the invention can be incorporated into pharmaceutical compositions and administered to a subject to inhibit an interaction between a BLAA hgand and a BLAA protein on the surface of a cell, to thereby suppress BLAA-mediated signal transduction in vivo The BLAA-immunoglobuhn fusion proteins can be used to affect the bioavailabihty of a BLAA cognate hgand Inhibition of the BLAA hgand'BLAA interaction may be useful therapeutically for both the treatment of immune response-associated disorders Moreover, the BLAA-immunoglobulm fusion proteins of the invention can be used as immunogens to produce anti-BLAA antibodies m a subject, to puπfy BLAA hgands, and in screening assays to identify molecules that inhibit the interaction of BLAA with a BLAA hgand A BL A A chimenc or fusion protein of the invention can be produced by standard recombinant DNA techniques For example, DNA fragments coding for the different polypeptide sequences are hgated together in-frame in accordance with conventional techniques, e g , by employing blunt-ended or stagger-ended termini for hgation, restπction enzyme digestion to provide for appropriate termini, filling- in of cohesive ends as appropnate, alkaline phosphatase treatment to avoid undesirable joining, and enzymatic hgation In another embodiment, the fusion gene can be synthesized by conventional techniques including automated DNA synthesizers Alternatively, PCR amplification of gene fragments can be carried out using anchor pnmers that give πse to complementary overhangs between two consecutive gene fragments that can subsequently be annealed and reamplified to generate a chimenc gene sequence (see, for example, Ausubel et al (eds ) CURRENT PROTOCOLS IN MOLECULAR BIOLOGV , John Wiley & Sons, 1992) Moreover, many expression vectors are commercially available that already encode a fusion moiety (e g , a GST polypeptide) A BLAA-encodmg nucleic acid can be cloned into such an expression vector such that the fusion moiety is linked m-frame to the BLAA polypeptide BLAA agonists and antagonists The present invention also pertains to vaπants of the BLAA polypeptides that function as either BLAA agonists (mimetics) or as BLAA antagonists Vaπants of the BLAA polypeptide can be generated by mutagenesis, e g , discrete point mutation or truncation of the BLAA polypeptide An agonist of the BLAA polypeptide can retain substantially the same, or a subset of, the biological activities of the naturally occurπng form of the BLAA polypeptide An antagonist of the BLAA polypeptide can inhibit one or more of the activities of the naturally occurπng form of the BLAA polypeptide by, for example, competitively binding to a downstream or upstream member of a cellular signaling cascade which includes the BLAA polypeptide Thus, specific biological effects can be elicited by treatment with a vanant of limited function In one embodiment, treatment of a subject with a vanant having a subset of the biological activities of the naturally occurnng form of the polypeptide has fewer side effects in a subject relative to treatment with the naturally occurnng form of the BLAA polypeptides Vanants of the BLAA polypeptide that function as either BLAA agonists (mimetics) or as BLAA antagonists can be identified by screening combmatoπal hbranes of mutants, e g , truncation mutants, of the BLAA polypeptide for BLAA polypeptide agonist or antagonist activity In one embodiment, a vanegated library of BLAA vaπants is generated by combmatoπal mutagenesis at the nucleic acid level and is encoded by a vanegated gene library A vanegated library of BLAA vaπants can be produced by, for example, enzymatically hgating a mixture of synthetic oligonucleotides into gene sequences such that a degenerate set of potential BLAA sequences is expressible as individual polypeptides, or alternatively, as a set of larger fusion proteins (e g , for phage display) containing the set of BLAA sequences therein There are a vanety of methods which can be used to produce hbraπes of potential BLAA vanants from a degenerate oligonucleotide sequence Chemical synthesis of a degenerate gene sequence can be performed in an automatic DNA synthesizer, and the synthetic gene then ligated into an appropnate expression vector Use of a degenerate set of genes allows for the provision, in one mixture, of all of the sequences encoding the desired set of potential BLAA sequences Methods for synthesizing degenerate oligonucleotides are known in the art (see, e g , Narang (1983) Tetrahedron 39 3, Itakura et al (1984) Annu Re\ Biochem 53 323, Itakura et al (1984) Science 198 1056, Ike et al (1983) Polypeptide libraries In addition, hbraπes of fragments of the BLAA protein coding sequence can be used to generate a vanegated population of BLAA fragments for screening and subsequent selection of vanants of a BLAA polypeptide In one embodiment, a library of coding sequence fragments can be generated by treating a double stranded PCR fragment of a BLAA coding sequence with a nuclease under conditions wherein nicking occurs only about once per molecule, denatuπng the double stranded DNA, renatunng the DNA to form double stranded DNA that can include sense/antisense pairs from different nicked products, removing single stranded portions from reformed duplexes by treatment with S I nuclease, and hgating the resulting fragment library into an expression vector By this method, an expression library can be denved which encodes N-termmal and internal fragments of vanous sizes of a BLAA polypeptide Several techniques are known in the art for screening gene products of combinatonal hbranes made by point mutations or truncation, and for screening cDNA hbraπes for gene products having a selected property Such techniques are adaptable for rapid screening of the gene hbranes generated by the combinatonal mutagenesis of a BLAA polypeptide The most widely used techniques, which are amenable to high throughput analysis, for screening large gene hbranes typically include cloning the gene library into rephcable expression vectors, transforming appropnate cells with the resulting library of vectors, and expressing the combinatonal genes under conditions in which detection of a desired activity facilitates isolation of the vector encoding the gene whose product was detected Recrusive ensemble mutagenesis (REM), a new technique that enhances the frequency of functional mutants in the hbranes, can be used in combination with the screening assays to identify BLAA vaπants (Ar in and Yourvan (1992) PNAS 89 781 1-7815, Delgrave et al (1993) Protein Engineering 6 327-331) Anti-BLAA antibodies The invention encompasses antibodies and antibody fragments, such as F ab or (F ab ) 2 that bmd lmmunospecifically to any of the polypeptides of the invention An isolated BLAA polypeptide, or a portion or fragment thereof, can be used as an immunogen to generate antibodies that bmd BLAA using standard techniques for polyclonal and monoclonal antibody preparation The full-length BLAA polypeptide can be used or, alternatively, the invention provides antigemc peptide fragments of BLAA for use as immunogens The antigemc peptide of BLAA compπses at least 4 ammo acid residues of the amino acid sequence shown in SEQ ID NO 2, SEQ ID NO 4, or SEQ ID NO 6 and encompasses an epitope of BLAA such that an antibody raised against the peptide forms a specific immune complex with BLAA Preferably, the antigemc peptide compnses at least 6, 8, 10, 15, 20, or 30 amino acid residues Longer antigemc peptides are sometimes preferable over shorter antigemc peptides, depending on use and according to methods well known to someone skilled in the art In certain embodiments of the invention, at least one epitope encompassed by the antigemc peptide is a region of BLAA that is located on the surface of the polypeptide, e g , a hydrophihc region A hydrophobicity analysis of the human BLAA polypeptide sequence of SEQ ID NO 6, shown in FIG 5, indicates that the hydrophihc regions include from about ammo acid 75 to about ammo acid 110, from about amino acid 150 to about amino acid 200, from about amino acid 225 to about amino acid 250, from about ammo acid 290 to about amino acid 310 from about amino acid 380 to about amino acid 420, and from about amino acid 440 to about amino acid 534 These regions are likely to encode surface residues useful for targeting antibody production As a means for targeting antibody production, hydropathy plots showing regions of hydrophihcity and hydrophobicity may be generated by any method well known m the art, including, for example, the Kyte Doolittle or the Hopp Woods methods, either with or without Founer transformation See, e g , Hopp and Woods, 1981, Proc Nat Acad Sci USA IS 3824-3828, Kyte and Doolittle 1982, J Mol Biol 157 105-142, each reference is incorporated herein by reference in their entirety As disclosed herein, BLAA polypeptide sequence of SEQ ID NO 2, SEQ ID NO 4, or SEQ ID NO 6 or denvatives, fragments, analogs or homologs thereof, may be utilized as immunogens in the generation of antibodies that immunospecifically-bind these protein components The term "antibody" as used herein refers to immunoglobuhn molecules and immunologically active portions of immunoglobuhn molecules, i e , molecules that contain an antigen binding site that specifically binds (immunoreacts with) an antigen, such as BLAA Such antibodies include, but are not limited to, polyclonal, monoclonal, chimenc, single chain, F ab and F (ab fragments, and an F ab expression library In a specific embodiment, antibodies to human BLAA polypeptides are disclosed Vaπous procedures known within the art may be used for the production of polyclonal or monoclonal antibodies to a BLAA polypeptide sequence of SEQ ID NO 2, SEQ ID NO 4, or SEQ ID NO 6, or denvative, fragment, analog or homolog thereof Some of these proteins are discussed below For the production of polyclonal antibodies, vaπous suitable host animals (e g , rabbit, goat, mouse or other mammal) may be immunized by injection with the native polypeptide, or a synthetic vanant thereof, or a denvative of the foregoing An appropnate lmmunogenic preparation can contain, for example, recombmantly expressed BLAA polypeptide or a chemically synthesized BLAA polypeptide The preparation can further include an adjuvant Vanous adjuvants used to increase the immunological response include, but are not limited to, Freund's (complete and incomplete), mineral gels (e g aluminum hydroxide), surface active substances (e g lysolecithin, pluromc polyols, polyamons, peptides, oil emulsions, dimtrophenol, etc ), human adjuvants such as Bacille Calmette-Guenn and Corvnebacterium parvum, or similar immunostimulatory agents If desired, the antibody molecules directed against BLAA can be isolated from the mammal (e g , from the blood) and further puπfied by well known techniques, such as protein A chromatography to obtain the IgG fraction The term "monoclonal antibody" or "monoclonal antibody composition", as used herein, refers to a population of antibody molecules that contain only one species of an antigen binding site capable of lmmunoreacting with a particular epitope of BLAA A monoclonal antibody composition thus typically displays a single binding affinity for a particular BLAA polypeptide with which it immunoreacts For preparation of monoclonal antibodies directed towards a particular BLAA polypeptide, or denvatives, fragments, analogs or homologs thereof, any technique that provides for the production of antibody molecules by continuous cell line culture may be utilized Such techniques include, but are not limited to, the hybπdoma technique (see Kohler & Milstem, 1975 Nature 256 495-497), the tnoma technique, the human B-cell hybndoma technique (see Kozbor, et al 1983 Immunol Today 4 72) and the EBV hybndoma technique to produce human monoclonal antibodies (see Cole, et al , 1985 In MONOCLONAL ANTIBODIES AND CANCER THERAPY, Alan R Liss, Inc , pp 77-96) Human monoclonal antibodies may be utilized in the practice of the present invention and may be produced by using human hybndomas (see Cote, et al 1983 Proc Natl Acad Sci USA 80 2026-2030) or by transforming human B-cells with Epstein Barr Virus in vitro (see Cole, et al 1985 In MONOCLONAL ANTIBODIES AND CANCER THERAPY, Alan R Liss, Inc , pp 77-96) Each of the above citations are incorporated herein by reference in their entirety According to the invention, techniques can be adapted for the production of single-chain antibodies specific to a BLAA polypeptide (see e g , U S Patent No 4,946,778) In addition, methodologies can be adapted for the construction of F ab expression hbranes (see e g Huse, et al 1989 Science 246 1275-1281) to allow rapid and effective identification of monoclonal F ab fragments with the desired specificity for a BLAA polypeptide or denvatives, fragments, analogs or homologs thereof Non-human antibodies can be "humanized" by techniques well known in the art See e g U S Patent No 5,225,539 Antibody fragments that contain the ldiotypes to a BLAA polypeptide may be produced by techniques known in the art including, but not limited to (i) an F (ab ) , fragment produced by pepsin digestion of an antibody molecule, (it) an F ab fragment generated by reducing the disulfide bndges of an F (ab )2 fragment, (in) an F ab fragment generated by the treatment of the antibody molecule with papam and a reducing agent and (zv) F, fragments Additionally, recombinant anti-BLAA antibodies, such as chimenc and humanized monoclonal antibodies, compπsing both human and non-human portions, which can be made using standard recombinant DNA techniques, are within the scope of the invention Such chimenc and humanized monoclonal antibodies can be produced by recombinant DNA techniques known in the art, for example using methods descπbed in International Application No PCT/US86/02269, European Patent Application No 184,187, European Patent Application No 171 ,496, European Patent Application No 173,494, PCT International Publication No WO 86/01533, U S Pat No 4,816,567, U S Pat No 5,225,539, European Patent Application No 125,023, Better et al (1988) Science 240 1041 -1043, Liu et al ( 1987) PNAS 84 3439-3443, Liu et al (1987) J Immunol 139 3521-3526, Sun et al (1981) PNAS 84 214-218, Nishimura et al (1987) Cancer Res 47 999-1005, Wood et al (1985) Nature 314 446-449, Shaw et al (1988) J Natl Cancer Inst 80 1553-1559), Morπson(1985) Science 229 1202-1207, Oi et al (1986) BioTechmques 4 214, Jones et al (1986) Nature 321 552-525, Verhoeyan et al (1988) Science 239 1534, and Beidler et al (1988) J Immunol 141 4053-4060 Each of the above citations are incorporated herein by reference in their entirety In one embodiment, methodologies for the screening of antibodies that possess the desired specificity include, but are not limited to, enzyme-linked immunosorbent assay (ELISA) and other immunologically-mediated techniques known within the art In a specific embodiment, selection of antibodies that are specific to a particular domain of a BLAA polypeptide is facilitated by generation of hybndomas that bmd to the fragment of a BLAA polypeptide possessing such a domain Antibodies that are specific for an Ig-hke domain within a BLAA polypeptide, or deπvatives, fragments, analogs or homologs thereof, are also prov ided herein Anti-BLAA antibodies may be used in methods known withm the art relating to the localization and or quantitation of a BLAA polypeptide (e g , for use in measuπng levels of the BLAA polypeptide within appropriate physiological samples, for use m diagnostic methods, for use in imaging the polypeptide, and the like) In a given embodiment, antibodies for BLAA polypeptides, or denvatives, fragments, analogs or homologs thereof, that contain the antibody deπved binding domain, are utilized as pharmacologically-active compounds [hereinafter "therapeutics"] An anti-BLAA antibody (e g , monoclonal antibody) can be used to isolate BLAA by standard techniques, such as affinity chromatography or immunoprecipitation An anti-BLAA antibody can facilitate the punfication of natural BLAA from cells and of recombmantly produced BLAA expressed in host cells Moreover, an anti-BLAA antibody can be used to detect BLAA polypeptide (e g , in a cellular lysate or cell supernatant) in order to evaluate the abundance and pattern of expression of the BLAA polypeptide Anti-BLAA antibodies can be used diagnostically to monitor protein levels in tissue as part of a clinical testing procedure, e g , to, for example, determine the efficacy of a given treatment regimen Detection can be facilitated by coupling (i e , physically linking) the antibody to a detectable substance Examples of detectable substances include vaπous enzymes, prosthetic groups, fluorescent mateπals, luminescent matenals, bioluminescent matenals, and radioactive matenals Examples of suitable enzymes include horseradish peroxidase, alkaline phosphatase, β-galactosidase, or acetylchohnesterase, examples of suitable prosthetic group complexes include streptav ldin/biotin and avidin/biotm, examples of suitable fluorescent mateπals include umbelhferone, fluorescein, fluorescein isothiocyanate, rhodamme, dichlorotπazinylamine fluorescein, dansyl chloπde or phycoerythnn, an example of a luminescent matenal includes luminol, examples of bioluminescent matenals include luciferase, lucifenn, and aequoπn, and examples of suitable radioactive matenal include ,25 I, 131 I, 3s S or Η BLAA Recombinant Expression Vectors and Host Cells Another aspect of the invention pertains to vectors, preferably expression vectors, containing a nucleic acid encoding BLAA polypeptide, or deπvatives, fragments, analogs or homologs thereof As used herein, the term "vector" refers to a nucleic acid molecule capable of transporting another nucleic acid to which it has been linked One type of vector is a "plasmid", which refers to a circular double stranded DNA loop into which additional DNA segments can be ligated Another type of vector is a viral vector, wherein additional DNA segments can be ligated into the viral genome Certain vectors are capable of autonomous replication in a host cell into which they are introduced (e g , bacteπal vectors having a bactenal oπgin of replication and episomal mammalian vectors) Other vectors (e g , non-episomal mammalian vectors) are integrated into the genome of a host cell upon introduction into the host cell, and thereby are replicated along with the host genome Moreover, certain vectors are capable of directing the expression of genes to which they are operatively linked Such vectors are refeπed to herein as "expression vectors" In general, expression vectors of utility in recombinant DNA techniques are often in the form of plasmids In the present specification, "plasmid" and "vector" can be used interchangeably as the plasmid is the most commonly used form of vector However, the invention is intended to include such other forms of expression vectors, such as viral vectors (e g , replication defective retroviruses, adenoviruses and adeno-associated viruses), which serve equivalent functions The recombinant expression vectors of the invention compnse a nucleic acid of the invention in a form suitable for expression of the nucleic acid in a host cell, which means that the recombinant expression vectors include one or more regulatory sequences, selected on the basis of the host cells to be used for expression, that is operatively linked to the nucleic acid sequence to be expressed Withm a recombinant expression vector, "operably linked" is intended to mean that the nucleotide sequence of interest is linked to the regulatory sequence(s) in a manner that allows for expression of the nucleotide sequence (e g , m an in vitro transcnption/translation system or in a host cell when the vector is introduced into the host cell) The term "regulatory sequence" is intended to includes promoters, enhancers and other expression control elements (e g , polyadenylation signals) Such regulatory sequences are descπbed, for example, in Goeddel, GENE EXPRESSION TECHNOLOGY METHODS IN ENZYMOLOGY 185, Academic Press, San Diego, Calif (1990) Regulatory sequences include those that direct constitutive expression of a nucleotide sequence in many types of host cell and those that direct expression of the nucleotide sequence only in certain host cells (e g , tissue-specific regulatory sequences) It will be appreciated by those skilled in the art that the design of the expression vector can depend on such factors as the choice of the host cell to be transformed, the level of expression of protein desired, etc The expression vectors of the invention can be introduced into host cells to thereby produce proteins or peptides, including fusion proteins or peptides, encoded by nucleic acids as descπbed herein (e g , BLAA polypeptides, mutant forms of BLAA, fusion proteins, etc ) The recombinant expression vectors of the invention can be designed for expression of BLAA m prokaryotic or eukaryotic cells For example, BLAA can be expressed m bacteπal cells such as E coli, insect cells (using baculovirus expression vectors) yeast cells or mammalian cells Suitable host cells are discussed further in Goeddel, GENE EXPRESSION TECHNOLOGY METHODS IN ENZYMOLOGY 185, Academic Press, San Diego, Calif (1990) Alternatively, the recombinant expression vector can be transcribed and translated in vitro, for example using T7 promoter regulatory sequences and T7 polymerase. Expression of proteins in prokaryotes is most often carried out in E. coli with vectors containing constitutive or inducible promoters directing the expression of either fusion or non- fusion proteins. Fusion vectors add a number of amino acids to a protein encoded therein, usually to the amino terminus of the recombinant protein. Such fusion vectors typically serve three purposes: (1) to increase expression of recombinant protein; (2) to increase the solubility of the recombinant protein; and (3) to aid in the purification of the recombinant protein by acting as a ligand in affinity purification. Often, in fusion expression vectors, a proteolytic cleavage site is introduced at the junction of the fusion moiety and the recombinant protein to enable separation of the recombinant protein from the fusion moiety subsequent to purification of the fusion protein. Such enzymes, and their cognate recognition sequences, include Factor Xa, thrombin and enterokinase. Typical fusion expression vectors include pGEX (Pharmacia Biotech Inc; Smith and Johnson (1988) Gene 67:31-40), pMAL (New England Biolabs, Beverly, Mass.) and pRIT5 (Pharmacia, Piscataway, N.J.) that fuse glutathione S-transferase (GST), maltose E binding protein, or protein A, respectively, to the target recombinant protein. Examples of suitable inducible non-fusion E. coli expression vectors include pTrc (Amrann et al, (1988) Gene 69:301-315) and pET l id (Studier et al., GENE EXPRESSION TECHNOLOGY: METHODS IN ENZYMOLOGY 185, Academic Press, San Diego, Calif. (1990) 60-89). One strategy to maximize recombinant protein expression in E. coli is to express the protein in a host bacteria with an impaired capacity to proteolytically cleave the recombinant protein. See, Gottesman, GENE EXPRESSION TECHNOLOGY: METHODS IN ENZYMOLOGY 185, Academic Press, San Diego, Calif. (1990) 119-128. Another strategy is to alter the nucleic acid sequence of the nucleic acid to be inserted into an expression vector so that the individual codons for each amino acid are those preferentially utilized in E. coli (Wada et al., (1992) Nucleic Acids Res. 20:211 1-2118). Such alteration of nucleic acid sequences of the invention can be carried out by standard DNA synthesis techniques. In another embodiment, the BLAA expression vector is a yeast expression vector. Examples of vectors for expression in yeast S. cerivisae include pYepSecl (Baldari, et al., (1987) EMBO J 6 229-234), pMFa (Kurjan and Herskowitz, ( 1982) Cell 30 933-943), pJRY88 (Schultz et al , (1987) Gene 54 113-123), pYES2 (Invitrogen Co oration, San Diego, Calif), and picZ (InVitrogen Corp, San Diego, Calif ) Alternatively, BLAA can be expressed m insect cells using baculovirus expression v ectors Baculovirus vectors available for expression of proteins in cultured insect cells (e g , SF9 cells) include the pAc seπes (Smith et al (1983) Mol Cell Biol 3 2156-2165) and the pVL senes (Lucklow and Summers (1989) Vιrolog\ 170 31-39) In yet another embodiment, a nucleic acid of the invention is expressed in mammalian cells using a mammalian expression vector Examples of mammalian expression vectors include pCDM8 (Seed (1987) Nature 329 840) and pMT2PC (Kaufman et al (1987) EMBO J 6 187-195) When used in mammalian cells, the expression v ector's control functions are often provided by viral regulatory elements For example, commonly used promoters are deπved from polyoma, Adenovirus 2, cytomegalovirus and Simian Virus 40 For other suitable expression systems for both prokaryotic and eukaryotic cells See, e g , Chapters 16 and 17 of Sambrook et al , MOLECULAR CLONING A LABORATORY MANUAL 2nd ed , Cold Spπng Harbor Laboratory, Cold Spnng Harbor Laboratory Press, Cold Spπng Harbor, N Y , 1989 In another embodiment, the recombinant mammalian expression vector is capable of directing expression of the nucleic acid preferentially in a particular cell type (e g , tissue-specific regulatory elements are used to express the nucleic acid) Tissue-specific regulatory elements are known in the art Non-hmitmg examples of suitable tissue-specific promoters include the albumin promoter (liver-specific, Pinkert et al (1987) Genes Dev 1 268-277), lymphoid-specific promoters (Calame and Eaton (1988) Adv Immunol 43 235-275), in particular promoters of T cell receptors (Wmoto and Baltimore (1989) EMBO J 8 729-733) and lmmunoglobuhns (Banerji et al (1983) Cell 33 729-740, Queen and Baltimore (1983) Cell 33 741 -748), neuron-specific promoters (e g , the neurofilament promoter, Byrne and Ruddle (1989) PNAS 86 5473-5477), pancreas-specific promoters (Edlund et al (1985) Science 230 912-916), and mammary gland-specific promoters (e g , milk whey promoter, U S Pat No 4,873,316 and European Application Publication No 264,166) Developmentally-regulated promoters are also encompassed, e g , the munne hox promoters (Kessel and Gruss (1990) Science 249 374-379) and the -fetoprotein promoter (Campes and Tilghman (1989) Genes Dev 3 537-546) The invention further provides a recombinant expression vector compπsing a DNA molecule of the invention cloned into the expression vector in an antisense onentation That is, the DNA molecule is operatively linked to a regulatory sequence in a manner that allows for expression (by transcnption of the DNA molecule) of an RNA molecule that is antisense to BLAA mRNA Regulatory sequences operatively linked to a nucleic acid cloned in the antisense oπentation can be chosen that direct the continuous expression of the antisense RNA molecule in a vaπety of cell types, for instance viral promoters and/or enhancers, or regulatory sequences can be chosen that direct constitutive, tissue specific or cell type specific expression of antisense RNA The antisense expression vector can be in the form of a recombinant plasmid, phagemid or attenuated virus in which antisense nucleic acids are produced under the control of a high efficiency regulatory region, the activity of which can be determined by the cell type into which the vector is introduced For a discussion of the regulation of gene expression using antisense genes see Wemtraub et al , "Antisense RNA as a molecular tool for genetic analysis," Reviews—Trends in Genetics, Vol 1(1) 1986 Another aspect of the invention pertains to host cells into which a recombinant expression vector of the invention has been introduced The terms "host cell" and "recombinant host cell" are used interchangeably herein It is understood that such terms refer not only to the particular subject cell but to the progeny or potential progeny of such a cell Because certain modifications may occur in succeeding generations due to either mutation or environmental influences, such progeny may not, in fact, be identical to the parent cell, but are still included within the scope of the term as used herein A host cell can be any prokaryotic or eukaryotic cell For example, BLAA polypeptide can be expressed in bactenal cells such as E coli, insect cells, yeast or mammalian cells (such as Chinese hamster ovary cells (CHO) or COS cells) Other suitable host cells are known to those skilled in the art Vector DNA can be introduced into prokaryotic or eukaryotic cells via conventional transformation or transfection techniques As used herein, the terms "transformation" and "transfection" are intended to refer to a vanety of art-recognized techniques for introducing foreign nucleic acid (e g , DNA) into a host cell, including calcium phosphate or calcium chloπde co-precipitation, DEAE-dextran-mediated transfection, hpofection, or electroporation Suitable methods for transforming or transfecting host cells can be found in Sambrook, et al (MOLECULAR CLONING A LABORATORY MANUAL 2nd ed , Cold Spnng Harbor Laboratory, Cold Spnng Harbor Laboratory Press, Cold Spnng Harbor, N Y , 1989), and other laboratory manuals For stable transfection of mammalian cells, it is known that, depending upon the expression vector and transfection technique used, only a small fraction of cells may integrate the foreign DNA into their genome In order to identify and select these integrants, a gene that encodes a selectable marker (e g , resistance to antibiotics) is generally introduced into the host cells along with the gene of interest Vanous selectable markers include those that confer resistance to drugs, such as G418, hygromycin and methotrexate Nucleic acid encoding a selectable marker can be introduced into a host cell on the same vector as that encoding BLAA or can be introduced on a separate vector Cells stably transfected with the introduced nucleic acid can be identified by drug selection (e g , cells that have incorporated the selectable marker gene will survive, while the other cells die) A host cell of the invention, such as a prokaryotic or eukaryotic host cell in culture, can be used to produce (i e , express) BLAA polypeptide Accordingly, the invention further provides methods for producing BLAA polypeptide using the host cells of the invention In one embodiment, the method compπses cultuπng the host cell of invention (into which a recombinant expression vector encoding BLAA has been introduced) in a suitable medium such that BLAA polypeptide is produced In another embodiment, the method further compnses isolating BLAA from the medium or the host cell Transgenic animals The host cells of the invention can also be used to produce nonhuman transgenic animals For example, in one embodiment, a host cell of the invention is a fertilized oocyte or an embryonic stem cell into which BLAA-codmg sequences have been introduced Such host cells can then be used to create non-human transgenic animals in which exogenous BLAA sequences have been introduced into their genome or homologous recombinant animals in which endogenous BLAA sequences have been altered Such animals are useful for studying the function and or activity of BLAA and for identifying and/or evaluating modulators of BLAA activity As used herein, a "transgenic animal" is a non-human animal, preferably a mammal, more preferably a rodent such as a rat or mouse, in which one or more of the cells of the animal includes a transgene Other examples of transgenic animals include non-human pnmates, sheep, dogs, cows, goats, chickens, amphibians, etc A transgene is exogenous DNA that is integrated into the genome of a cell from which a transgenic animal develops and that remains in the genome of the mature animal, thereby directing the expression of an encoded gene product in one or more cell types or tissues of the transgenic animal As used herein, a "homologous recombinant animal" is a non-human animal, preferably a mammal, more preferably a mouse, in which an endogenous BLAA gene has been altered by homologous recombination between the endogenous gene and an exogenous DNA molecule introduced into a cell of the animal, e g , an embryonic cell of the animal, pnor to development of the animal A transgenic animal of the invention can be created by introducing BLAA-encoding nucleic acid into the male pronuclei of a fertilized oocyte, e g , by microinjection, retroviral infection, and allowing the oocyte to develop in a pseudopregnant female foster animal The human BLAA cDNA sequence of SEQ ID NO 1, 3, 5, 7, 9, or 11, can be introduced as a transgene into the genome of a non-human animal Alternatively, a nonhuman homologue of the human BLAA gene, such as a mouse BLAA gene, can be isolated based on hybπdization to the human BLAA cDNA (descπbed further above) and used as a transgene Intromc sequences and polyadenylation signals can also be included in the transgene to increase the efficiency of expression of the transgene A tissue-specific regulatory sequence(s) can be operably linked to the BLAA transgene to direct expression of BLAA polypeptide to particular cells Methods for generating transgenic animals via embryo manipulation and microinjection, particularly animals such as mice, have become conventional in the art and are descπbed, for example, in U S Pat Nos 4,736,866, 4,870,009, and 4,873,191, and Hogan 1986, In MANIPULATING THE MOUSE EMBRYO, Cold Spπng Harbor Laboratory Press, Cold Spnng Harbor, N Y Similar methods are used for production of other transgenic animals A transgenic founder animal can be identified based upon the presence of the BLAA transgene in its genome and or expression of BLAA mRNA in tissues or cells of the animals A transgenic founder animal can then be used to breed additional animals carrying the transgene Moreover, transgenic animals carrying a transgene encoding BLAA can further be bred to other transgenic animals carrying other transgenes. To create a homologous recombinant animal, a vector is prepared which contains at least a portion of a BLAA gene into which a deletion, addition or substitution has been introduced to thereby alter, e.g., functionally disrupt, the BLAA gene. The BLAA gene can be a human gene (e.g., the cDNA of SEQ ID NO: 1, 3, 5, 7, 9, or 11), but more preferably, is a non-human homologue of a human BLAA gene. For example, a mouse homologue of human BLAA gene of SEQ ID NO: 1, 3, 5, 7, 9, or 11 can be used to construct a homologous recombination vector suitable for altering an endogenous BLAA gene in the mouse genome. In one embodiment, the vector is designed such that, upon homologous recombination, the endogenous BLAA gene is functionally disrupted (i.e., no longer encodes a functional protein; also referred to as a "knock out" vector). Alternatively, the vector can be designed such that, upon homologous recombination, the endogenous BLAA gene is mutated or otherwise altered but still encodes functional protein (e.g., the upstream regulatory region can be altered to thereby alter the expression of the endogenous BLAA polypeptide). In the homologous recombination vector, the altered portion of the BLAA gene is flanked at its 5' and 3' ends by additional nucleic acid of the BLAA gene to allow for homologous recombination to occur between the exogenous BLAA gene carried by the vector and an endogenous BLAA gene in an embryonic stem cell. The additional flanking BLAA nucleic acid is of sufficient length for successful homologous recombination with the endogenous gene. Typically, several kilobases of flanking DNA (both at the 5' and 3' ends) are included in the vector. See e.g., Thomas et al. (1987) Cell 51 :503 for a description of homologous recombination vectors. The vector is introduced into an embryonic stem cell line (e.g., by electroporation) and cells in which the introduced BLAA gene has homologously recombined with the endogenous BLAA gene are selected (see e.g., Li et al. (1992) Cell 69:915). The selected cells are then injected into a blastocyst of an animal (e.g., a mouse) to form aggregation chimeras. See e.g., Bradley 1987, In: TERATOCARCINOMAS AND EMBRYONIC STEM CELLS: A PRACTICAL APPROACH, Robertson, ed. IRL, Oxford, pp. 1 13-152. A chimeric embryo can then be implanted into a suitable pseudopregnant female foster animal and the embryo brought to term Progeny harboπng the homologously recombined DNA in their germ cells can be used to breed animals in which all cells of the animal contain the homologously recombined DNA by germhne transmission of the transgene Methods for constructing homologous recombination vectors and homologous recombinant animals are descnbed further in Bradley (1991) Curr Opin Bwtechnol 2 823-829, PCT International Publication Nos WO 90/11354, WO 91/01 140, WO 92/0968, and WO 93/04169 In another embodiment, transgenic non-humans animals can be produced that contain selected systems that allow for regulated expression of the transgene One example of such a system is the cre/loxP recombinase system of bacteπophage PI For a descnption of the cre/loxP recombinase system, see, e g , Lakso et al (1992) PNAS 89 6232-6236 Another example of a recombinase system is the FLP recombinase system of Saccharom\ces cerevisiae (O'Gorman et al (1991) Science 251 1351-1355 If a cre/loxP recombinase system is used to regulate expression of the transgene, animals containing transgenes encoding both the Cre recombinase and a selected protein are required Such animals can be provided through the construction of "double" transgenic animals, e g , by mating two transgenic animals, one containing a transgene encoding a selected protein and the other containing a transgene encoding a recombinase Clones of the non-human transgenic animals descnbed herein can also be produced according to the methods descnbed in Wilmut et al (1997) Nature 385 810-813 In brief, a cell, e g , a somatic cell, from the transgenic animal can be isolated and induced to exit the growth cycle and enter G 0 phase The quiescent cell can then be fused, e g , through the use of electπcal pulses, to an enucleated oocyte from an animal of the same species from which the quiescent cell is isolated The reconstructed oocyte is then cultured such that it develops to morula or blastocyte and then transferred to pseudopregnant female foster animal The offspπng borne of this female foster animal will be a clone of the animal from which the cell, e g , the somatic cell, is isolated Pharmaceutical Compositions The BLAA nucleic acid molecules, BLAA polypeptides, and anti-BLAA antibodies (also referred to herein as "active compounds") of the invention, and denvatives, fragments, analogs and homologs thereof, can be incorporated into pharmaceutical compositions suitable for administration Such compositions typically compnse the nucleic acid molecule, protein, or antibody and a pharmaceutically acceptable earner As used herein, "pharmaceutically acceptable earner" is intended to include any and all solvents, dispersion media, coatings, antibactenal and antifungal agents, lsotomc and absorption delaying agents, and the like, compatible with pharmaceutical administration Suitable earners are descnbed in the most recent edition of Remington's Pharmaceutical Sciences, a standard reference text in the field, which is incorporated herein by reference Preferred examples of such earners or diluents include, but are not limited to, water, saline, finger's solutions, dextrose solution, and 5% human serum albumin Liposomes and non-aqueous vehicles such as fixed oils may also be used The use of such media and agents for pharmaceutically active substances is well known in the art Except insofar as any conventional media or agent is incompatible with the active compound, use thereof in the compositions is contemplated Supplementary active compounds can also be incorporated into the compositions A pharmaceutical composition of the invention is formulated to be compatible with its intended route of administration. Examples of routes of administration include parenteral, e g , intravenous, mtradermal, subcutaneous, oral (e g , inhalation), transdermal (topical), transmucosal, and rectal administration Solutions or suspensions used for parenteral, mtradermal, or subcutaneous application can include the following components a stenle diluent such as water for injection, saline solution, fixed oils, polyethylene glycols, glyceπne. propylene glycol or other synthetic solvents, antibactenal agents such as benzyl alcohol or methyl parabens, antioxidants such as ascorbic acid or sodium bisulfite, chelatmg agents such as ethylenediaminetetraacetic acid, buffers such as acetates, citrates or phosphates, and agents for the adjustment of tonicity such as sodium chloπde or dextrose The pH can be adjusted with acids or bases, such as hydrochloπc acid or sodium hydroxide The parenteral preparation can be enclosed m ampoules, disposable synnges or multiple dose vials made of glass or plastic Pharmaceutical compositions suitable for injectable use include stenle aqueous solutions (where water soluble) or dispersions and stenle powders for the extemporaneous preparation of stenle injectable solutions or dispersion For intravenous administration, suitable earners include physiological saline, bactenostatic water, Cremophor EL™ (BASF, Parsippany, N J ) or phosphate buffered salme (PBS) In all cases, the composition must be stenle and should be fluid to the extent that easy synngeabihty exists It must be stable under the conditions of manufacture and storage and must be preserved against the contaminating action of microorganisms such as bacteπa and fungi The earner can be a solvent or dispersion medium containing, for example, water, ethanol, polyol (for example, glycerol, propylene glycol, and liquid polyethylene glycol, and the like), and suitable mixtures thereof The proper fluidity can be maintained, for example, by the use of a coating such as lecithin, by the maintenance of the required particle size in the case of dispersion and by the use of surfactants Prevention of the action of microorganisms can be achieved by vaπous antibactenal and antifungal agents, for example, parabens, chlorobutanol, phenol, ascorbic acid, thimerosal, and the like In many cases, it will be preferable to include lsotomc agents, for example, sugars, polyalcohols such as manitol, sorbitol, sodium chloπde in the composition Prolonged absorption of the injectable compositions can be brought about by including m the composition an agent which delays absorption, for example, aluminum monostearate and gelatin Stenle injectable solutions can be prepared by incorporating the active compound (e g , a BLAA polypeptide or anti-BLAA antibody) in the required amount in an appropnate solvent with one or a combination of ingredients enumerated above, as required, followed by filtered steπhzation Generally, dispersions are prepared by incorporating the active compound into a stenle vehicle that contains a basic dispersion medium and the required other ingredients from those enumerated above In the case of stenle powders for the preparation of stenle injectable solutions, methods of preparation are vacuum drying and freeze-drying that yields a powder of the active ingredient plus any additional desired ingredient from a previously stenle-filtered solution thereof Oral compositions generally include an inert diluent or an edible earner They can be enclosed in gelatin capsules or compressed into tablets For the purpose of oral therapeutic administration, the active compound can be incorporated with excipients and used m the form of tablets, troches, or capsules Oral compositions can also be prepared using a fluid earner for use as a mouthwash, wherein the compound in the fluid earner is applied orally and swished and expectorated or swallowed Pharmaceutically compatible binding agents, and/or adjuvant materials can be included as part of the composition. The tablets, pills, capsules, troches and the like can contain any of the following ingredients, or compounds of a similar nature: a binder such as microcrystalline cellulose, gum tragacanth or gelatin; an excipient such as starch or lactose, a disintegrating agent such as alginic acid, Primogel, or corn starch; a lubricant such as magnesium stearate or Sterotes; a glidant such as colloidal silicon dioxide; a sweetening agent such as sucrose or saccharin; or a flavoring agent such as peppermint, methyl salicylate, or orange flavoring. For administration by inhalation, the compounds are delivered in the form of an aerosol spray from pressured container or dispenser which contains a suitable propellant, e.g., a gas such as carbon dioxide, or a nebulizer. Systemic administration can also be by transmucosal or transdermal means. For transmucosal or transdermal administration, penetrants appropriate to the barrier to be permeated are used in the formulation. Such penetrants are generally known in the art, and include, for example, for transmucosal administration, detergents, bile salts, and fusidic acid derivatives. Transmucosal administration can be accomplished through the use of nasal sprays or suppositories. For transdermal administration, the active compounds are formulated into ointments, salves, gels, or creams as generally known in the art. The compounds can also be prepared in the form of suppositories (e.g., with conventional suppository bases such as cocoa butter and other glycerides) or retention enemas for rectal delivery. In one embodiment, the active compounds are prepared with carriers that will protect the compound against rapid elimination from the body, such as a controlled release formulation, including implants and microencapsulated delivery systems. Biodegradable, biocompatible polymers can be used, such as ethylene vinyl acetate, polyanhydrides, polyglycolic acid, collagen, polyorthoesters, and polylactic acid. Methods for preparation of such formulations will be apparent to those skilled in the art. The materials can also be obtained commercially from Alza Corporation and Nova Pharmaceuticals, Inc. Liposomal suspensions (including liposomes targeted to infected cells with monoclonal antibodies to viral antigens) can also be used as pharmaceutically acceptable carriers. These can be prepared according to methods known to those skilled in the art, for example, as described in U.S. Pat. No. 4,522,811. It is especially advantageous to formulate oral or parenteral compositions in dosage unit form for ease of administration and uniformity of dosage. Dosage unit form as used herein refers to physically discrete units suited as unitary dosages for the subject to be treated; each unit containing a predetermined quantity of active compound calculated to produce the desired therapeutic effect in association with the required pharmaceutical carrier. The specification for the dosage unit forms of the invention are dictated by and directly dependent on the unique characteristics of the active compound and the particular therapeutic effect to be achieved, and the limitations inherent in the art of compounding such an active compound for the treatment of individuals. The nucleic acid molecules of the invention can be inserted into vectors and used as gene therapy vectors. Gene therapy vectors can be delivered to a subject by, for example, intravenous injection, local administration (see U.S. Pat. No. 5,328,470) or by stereotactic injection (see e.g., Chen et al. (1994) PNAS 91 :3054-3057). The pharmaceutical preparation of the gene therapy vector can include the gene therapy vector in an acceptable diluent, or can comprise a slow release matrix in which the gene delivery vehicle is imbedded. Alternatively, where the complete gene delivery vector can be produced intact from recombinant cells, e.g., retroviral vectors, the pharmaceutical preparation can include one or more cells that produce the gene delivery system. The pharmaceutical compositions can be included in a container, pack, or dispenser together with instructions for administration. Uses and Methods of the Invention The immunoglobuhn superfamily members include multifunctional secreted and membrane-bound proteins that modulate a number of functions. B7 molecules known in the prior art are located on the cell surface. (See Selvakumar et al. 1992, Immunogenetics 36:175- 181 and Linsley et al. \994, Protein Sc. 3: 1341-1343). Sequence analysis studies using programs known in the prior art (e.g., PSORT) show that the polypeptides of the instant invention are most likely localized in the membrane of the endoplasmic reticulum. The nucleic acid molecules, proteins, protein homologues, and antibodies descnbed herein can be used in one or more of the following methods (a) screening assays, (b) detection assays (e g , chromosomal mapping, tissue typing, forensic biology), (c) predictive medicine (e g , diagnostic assays, prognostic assays, momtonng clinical tπals, and pharmacogenomics), and (d) methods of treatment (e g , therapeutic and prophylactic) As described herein, in one embodiment, a BLAA polypeptide of the invention has the ability to bind to activated T lymphocytes and provide regulatory signals for T lymphocyte cell growth and activation A BLAA polypeptide interacts with other cellular proteins and can thus be used to modulate immune response-associated protein activity Such modulation may have an effect on the regulation of cellular proliferation, the regulation of cellular differentiation, and/or the regulation of cell survival The isolated nucleic acid molecules of the invention can be used to express BLAA polypeptide (e g , via a recombinant expression vector m a host cell in gene therapy applications), to detect BLAA mRNA (e g , in a biological sample) or a genetic lesion in a BLAA gene, and to modulate BLAA activity, as descnbed further below In addition, the BLAA polypeptides can be used to screen drugs or compounds that modulate the BLAA activity or expression as well as to treat disorders characteπzed by insufficient or excessive production of BLAA polypeptide or production of BLAA polypeptide forms that have decreased or aberrant activity compared to BLAA wild type polypeptide (e g infectious diseases, cancers, autoimmune disorders, and complications associated with transplantation) In addition, the anti-BLAA antibodies of the invention can be used to detect and isolate BLAA polypeptides and modulate BLAA activity This invention further pertains to novel agents identified by the above descnbed screening assays and uses thereof for treatments as descnbed herein Screening Assays The invention provides a method (also referred to herein as a "screening assay") for identifying modulators, i e , candidate or test compounds or agents (e g , peptides, peptidomimetics, small molecules or other drugs) that bmd to BLAA polypeptides or have a stimulatory or inhibitory effect on, for example, BLAA expression or BLAA activity In one embodiment, the invention provides assays for screening candidate or test compounds which bmd to or modulate the activity of a BLAA protein or polypeptide or biologically active portion thereof. The test compounds of the present invention can be obtained using any of the numerous approaches in combinatonal library methods known in the art, including biological hbranes; spatially addressable parallel solid phase or solution phase hbranes, synthetic library methods requmng deconvolution, the "one-bead one-compound" library method, and synthetic library methods using affinity chromatography selection. The biological library approach is limited to peptide hbranes, while the other four approaches are applicable to peptide, non-peptide ohgomer or small molecule hbranes of compounds (Lam (1997) Anticancer Drug Des 12-145) Examples of methods for the synthesis of molecular hbranes can be found in the art, for example in: DeWitt et al. (1993) Proc Natl Acad Sci USA. 90:6909; Erb et al. (1994) Proc Natl Acad Sci USA. 91 :11422; Zuckermann et al. (1994) J Med Chem 37:2678, Cho et al. (1993) Science 261 :1303; Carrell et al. (1994) Angew Chem Int Ed Engl 33:2059; Carell et al. (1994) Angew Chem Int Ed Engl 33.2061; and Gallop et al. (1994) J Med Chem 37.1233. Libraπes of compounds may be presented in solution (e.g., Houghten (1992) Biotechniques 13:412-421), or on beads (Lam (1991) Nature 354:82-84), on chips (Fodor (1993) Nature 364-555-556), bacteπa (Ladner U.S Pat. No. 5,223,409), spores (Ladner USP '409), plasmids (Cull et al (1992) Proc Natl Acad Sci USA 89 1865-1869) or on phage (Scott and Smith (1990) Science 249-386-390; Devlin (1990) Science 249 404-406; Cwiria et al (1990) Proc Natl Acad Sci U SA 87 6378-6382, Fehci (1991) JMol Bwl 222:301-310; Ladner above.). In one embodiment, an assay is a cell-based assay in which a cell which expresses a form of BLAA polypeptide, or a biologically active portion thereof, on the cell surface is contacted with a test compound and the ability of the test compound to bmd to a BLAA protein determined. The cell, for example, can be of mammalian ongm or be a yeast cell. Determining the ability of the test compound to bind to the BLAA polypeptide can be accomplished, for example, by coupling the test compound with a radioisotope or enzymatic label such that binding of the test compound to the BLAA polypeptide or biologically active portion thereof can be determined by detecting the labeled compound in a complex For example, test compounds can be labeled with 12 T, "S, 14 C, or Η, either directly or indirectly, and the radioisotope detected by direct counting of radioemission or by scintillation counting. Alternatively, test compounds can be enzymatically labeled with, for example, horseradish peroxidase, alkaline phosphatase, or luciferase, and the enzymatic label detected by determination of conversion of an appropriate substrate to product. In one embodiment, the assay comprises contacting a cell which expresses a membrane-bound form of BLAA polypeptide, or a biologically active portion thereof, on the cell surface with a known compound which binds BLAA to form an assay mixture, contacting the assay mixture with a test compound, and determining the ability of the test compound to interact with a BLAA polypeptide, wherein determining the ability of the test compound to interact with a BLAA polypeptide comprises determining the ability of the test compound to preferentially bind to BLAA or a biologically active portion thereof as compared to the known compound. In another embodiment, an assay is a cell-based assay comprising contacting a cell expressing a membrane-bound form of BLAA polypeptide, or a biologically active portion thereof, on the cell surface with a test compound and determining the ability of the test compound to modulate (e.g., stimulate or inhibit) the activity of the BLAA polypeptide or biologically active portion thereof. Determining the ability of the test compound to modulate the activity of BLAA or a biologically active portion thereof can be accomplished, for example, by determining the ability of the BLAA polypeptide to bind to or interact with a BLAA target molecule. As used herein, a "target molecule" is a molecule with which a BLAA polypeptide binds or interacts in nature, for example, a molecule on the surface of a cell which expresses a BLAA-interacting protein, a molecule on the surface of a second cell, a molecule in the extracellular milieu, a molecule associated with the internal surface of a cell membrane or a cytoplasmic molecule. A BLAA target molecule can be a non-BLAA molecule or a BLAA protein or polypeptide of the present invention. In one embodiment, a BLAA target molecule is a component of a signal transduction pathway that facilitates transduction of an extracellular signal (e.g. a signal generated by binding of a compound to a membrane-bound BLAA molecule) through the cell membrane and into the cell. The target, for example, can be a second intercellular protein that has catalytic activity or a protein that facilitates the association of downstream signaling molecules with BLAA. Determining the ability of the BLAA polypeptide to bind to or interact with a BLAA target molecule can be accomplished by one of the methods descnbed above for determining direct binding In one embodiment, determining the ability of the BLAA polypeptide to bind to or interact with a BLAA target molecule can be accomplished by determining the activity of the target molecule For example, the activity of the target molecule can be determined by detecting induction of a cellular second messenger of the target (i e mtracellular Ca 2+ , diacylglycerol, IP 3 , etc ), detecting catalytic/enzymatic activity of the target an appropnate substrate, detecting the induction of a reporter gene (compπsing a BLAA-responsive regulatory element operatively linked to a nucleic acid encoding a detectable marker, e g , luciferase), or detecting a cellular response, for example, cell survival, cellular differentiation, or cell proliferation In yet another embodiment, an assay of the present invention is a cell-free assay compπsing contacting a BLAA polypeptide or biologically active portion thereof with a test compound and determining the ability of the test compound to bmd to the BLAA polypeptide or biologically active portion thereof Binding of the test compound to the BLAA polypeptide can be determined either directly or indirectly as descπbed above In one embodiment, the assay compπses contacting the BLAA polypeptide or biologically active portion thereof with a known compound which binds BLAA to form an assay mixture, contacting the assay mixture with a test compound, and determining the ability of the test compound to interact with a BLAA polypeptide, wherein determining the ability of the test compound to interact with a BLAA polypeptide compnses determining the ability of the test compound to preferentially bmd to BLAA or biologically active portion thereof as compared to the known compound In another embodiment, an assay is a cell-free assay compnsing contacting BLAA polypeptide or biologically active portion thereof with a test compound and determining the ability of the test compound to modulate (e g stimulate or inhibit) the activity of the BLAA polypeptide or biologically active portion thereof Determining the ability of the test compound to modulate the activity of BLAA can be accomplished, for example, by determining the ability of the BLAA polypeptide to bind to a BLAA target molecule by one of the methods descπbed above for determining direct binding In an alternative embodiment, determining the ability of the test compound to modulate the activity of BLAA can be accomplished by determining the ability of the BLAA polypeptide further modulate a BLAA target molecule. For example, the catalytic/enzymatic activity of the target molecule on an appropriate substrate can be determined as previously described. In yet another embodiment, the cell-free assay comprises contacting the BLAA polypeptide or biologically active portion thereof with a known compound which binds BLAA to form an assay mixture, contacting the assay mixture with a test compound, and determining the ability of the test compound to interact with a BLAA polypeptide, wherein determining the ability of the test compound to interact with a BLAA polypeptide comprises determining the ability of the BLAA polypeptide to preferentially bind to or modulate the activity of a BLAA target molecule. The cell-free assays of the present invention are amenable to use of both the soluble form or the membrane-bound form of BLAA. In the case of cell-free assays comprising the membrane-bound form of BLAA, it may be desirable to utilize a solubilizing agent such that the membrane-bound form of BLAA is maintained in solution. Examples of such solubilizing agents include non-ionic detergents such as n-octylglucoside, n-dodecylglucoside, n-dodecylmaltoside, octanoyl-N-methylglucamide, decanoyl-N-methylglucamide, Triton ® X-100, Triton ® X-114, Thesit ® , Isotridecypoly(ethylene glycol ether) n , N-dodecyl- N,N-dimethyl-3-ammonio-l -propane sulfonate, 3-(3-cholamidopropyl)dimethylamminiol- 1 -propane sulfonate (CHAPS), or 3-(3-cholamidopropyl)dimethylamminiol-2-hydroxy- 1 -propane sulfonate (CHAPSO). In more than one embodiment of the above assay methods of the present invention, it may be desirable to immobilize either BLAA or its target molecule to facilitate separation of complexed from uncomplexed forms of one or both of the proteins, as well as to accommodate automation of the assay. Binding of a test compound to BLAA, or interaction of BLAA with a target molecule in the presence and absence of a candidate compound, can be accomplished in any vessel suitable for containing the reactants. Examples of such vessels include microtiter plates, test tubes, and micro-centrifuge tubes. In one embodiment, a fusion protein can be provided that adds a domain that allows one or both of the proteins to be bound to a matrix. For example, GST-BLAA fusion proteins or GST-target fusion proteins can be adsorbed onto glutathione sepharose beads (Sigma Chemical, St. Louis, MO) or glutathione derivatized microtiter plates, that are then combined with the test compound or the test compound and either the non-adsorbed target protein or BLAA polypeptide, and the mixture is incubated under conditions conducive to complex formation (e g , at physiological conditions for salt and pH) Following incubation, the beads or microtiter plate wells are washed to remove any unbound components, the matnx immobilized in the case of beads, complex determined either directly or indirectly, for example, as descnbed above Alternatively, the complexes can be dissociated from the matnx, and the level of BLAA binding or activity determined using standard techniques Other techniques for immobilizing proteins on matπces can also be used in the screening assays of the invention For example, either BLAA or its target molecule can be immobilized utilizing conjugation of biotm and streptavidin Biotmylated BLAA or target molecules can be prepared from biotin-NHS (N-hydroxy-succmimide) using techniques well known in the art (e g , biotinylation kit, Pierce Chemicals, Rockford, 111 ), and immobilized in the wells of streptavidm-coated 96 well plates (Pierce Chemical) Alternatively, antibodies reactive with BLAA or target molecules, but which do not interfere with binding of the BLAA protein to its target molecule, can be denvatized to the wells of the plate, and unbound target or BLAA trapped in the wells by antibody conjugation Methods for detecting such complexes, in addition to those descnbed above for the GST-immobihzed complexes, include immunodetection of complexes using antibodies reactive with the BLAA or target molecule, as well as enzyme-linked assays that rely on detecting an enzymatic activity associated with the BLAA or target molecule In another embodiment, modulators of BLAA expression are identified m a method wherein a cell is contacted with a candidate compound and the expression of BLAA mRNA or polypeptide in the cell is determined The level of expression of BLAA mRNA or polypeptide in the presence of the candidate compound is compared to the level of expression of BLAA mRNA or polypeptide in the absence of the candidate compound The candidate compound can then be identified as a modulator of BLAA expression based on this companson For example, when expression of BLAA mRNA or polypeptide is greater (statistically significantly greater) in the presence of the candidate compound than m its absence, the candidate compound is identified as a stimulator of BLAA mRNA or polypeptide expression Alternatively, when expression of BLAA mRNA or polypeptide is less (statistically significantly less) in the presence of the candidate compound than in its absence, the candidate compound is identified as an inhibitor of BLAA mRNA or polypeptide expression. The level of BLAA mRNA or protein expression in the cells can be determined by methods described herein for detecting BLAA mRNA or protein. In yet another aspect of the invention, a BLAA polypeptide can be used as "bait proteins" in a two-hybrid assay or three hybrid assay (see, e.g., U.S. Pat. No. 5,283,317; Zervos et al. (1993) Cell 72:223-232; Madura et al. (1993) J Biol Chem 268:12046-12054; Bartel et al. (1993) Biotechniques 14:920-924; Iwabuchi et al. (1993) Oncogene 8:1693-1696; and Brent WO94/10300), to identify other proteins that bind to or interact with BLAA ("BLAA-binding proteins" or "BLAA-bp") and modulate BLAA activity. Such BLAA-binding proteins are also likely to be involved in the propagation of signals by the BLAA polypeptides as, for example, upstream or downstream elements of the BLAA pathway. The two-hybrid system is based on the modular nature of most transcription factors, which consist of separable DNA-binding and activation domains. Briefly, the assay utilizes two different DNA constructs. In one construct, the gene that codes for BLAA is fused to a gene encoding the DNA binding domain of a known transcription factor (e.g., GAL-4). In the other construct, a DNA sequence, from a library of DNA sequences, that encodes an unidentified protein ("prey" or "sample") is fused to a gene that codes for the activation domain of the known transcription factor. If the "bait" and the "prey" proteins are able to interact, in vivo, forming a BLAA-dependent complex, the DNA-binding and activation domains of the transcription factor are brought into close proximity. This proximity allows transcription of a reporter gene (e.g., LacZ) that is operably linked to a transcriptional regulatory site responsive to the transcription factor. Expression of the reporter gene can be detected and cell colonies containing the functional transcription factor can be isolated and used to obtain the cloned gene that encodes the protein which interacts with BLAA. In another embodiment, modulators of activity or latency of (i.e., the lack of activity) or predisposition to an immune response-associated disorder are identified wherein a test animal at increased risk for an immune response-associated disorder is administered with a test compound. The test animal of this embodiment recombinantly expresses a BLAA polypeptide The activity of said polypeptide is then measured in the test animal Next, the activity of the polypeptide is measured m a control animal that recombmantly expresses the polypeptide but that is not at an increased risk for an immune response-associated disorder Finally, expression in the test animal is compared to the expression in the control animal A difference in the test animal relative to the control animal indicates that the test compound is a modulation of activity or latency of or predisposition to an immune response-associated disorder For example, an increase m expression in the test animal indicates that the test compound is a stimulator of an immune response-associated disorder Likewise, a decrease in the test animal indicates that the test compound is an inhibitor of an immune response- associated disorder The test animal may be a recombinant test animal that expresses a test protein transgene. as descnbed above, or expresses said transgene under the control of a promoter at increased lev els compared to a wild type test animal In this embodiment, the promoter is not the native promoter of the transgene This invention further pertains to novel agents identified by the above-descπbed screening assays and uses thereof for treatments as descnbed herein Detection Assays Portions or fragments of the cDNA sequences identified herein (and the corresponding complete gene sequences) can be used m numerous ways as polynucleotide reagents For example, these sequences can be used to (l) map their respective genes on a chromosome, and, thus, locate gene regions associated with genetic disease, and (n) identify an individual from a minute biological sample (tissue typing) These applications are descnbed in the subsections below Chromosome Mapping Once the sequence (or a portion of the sequence) of a gene has been isolated, this sequence can be used to map the location of the gene on a chromosome This process is called chromosome mapping Accordingly, portions or fragments of the BLAA sequences descnbed herein, can be used to map the location of the BLAA genes, respectively, on a chromosome The mapping of the BLAA sequences to chromosomes is an important first step in coπelating these sequences with genes associated with disease Bnefly, BLAA genes can be mapped to chromosomes by prepaπng PCR pπmers (preferably 15-25 bp in length) from the BLAA sequences Computer analysis of the BLAA, sequences can be used to rapidly select pnmers that do not span more than one exon in the genomic DNA, thus complicating the amplification process These pnmers can then be used for PCR screening of somatic cell hybnds containing individual human chromosomes Only those hybnds containing the human gene corresponding to the BLAA sequences will yield an amplified fragment Somatic cell hybnds are prepared by fusing somatic cells from different mammals (e g , human and mouse cells) As hvbπds of human and mouse cells grow and divide, they gradually lose human chromosomes in random order, but retain the mouse chromosomes By using media in which mouse cells cannot grow, because they lack a particular enzyme, but in which human cells can, the one human chromosome that contains the gene encoding the needed enzyme will be retained By using vanous media, panels of hybnd cell lines can be established Each cell line in a panel contains either a single human chromosome or a small number of human chromosomes, and a full set of mouse chromosomes, allowing easy mapping of individual genes to specific human chromosomes (D'Eustachio et al (1983) Science 220 919-924) Somatic cell hybnds containing only fragments of human chromosomes can also be produced by using human chromosomes with translocations and deletions PCR mapping of somatic cell hybnds is a rapid procedure for assigning a particular sequence to a particular chromosome Three or more sequences can be assigned per day using a single thermal cycler Using the BLAA sequences to design oligonucleotide pnmers, sublocahzation can be achieved with panels of fragments from specific chromosomes Fluorescence in situ hybndization (FISH) of a DNA sequence to a metaphase chromosomal spread can further be used to provide a precise chromosomal location in one step Chromosome spreads can be made using cells whose division has been blocked in metaphase by a chemical like colcemid that disrupts the mitotic spindle The chromosomes can be treated bnefly with trypsin, and then stained with Giemsa A pattern of light and dark bands develops on each chromosome, so that the chromosomes can be identified individually The FISH technique can be used with a DNA sequence as short as 500 or 600 bases However, clones larger than 1,000 bases have a higher likelihood of binding to a unique chromosomal location with sufficient signal intensity for simple detection. Preferably 1,000 bases, and more preferably 2,000 bases, will suffice to get good results at a reasonable amount of time For a review of this technique, see Verma et al , HUMAN CHROMOSOMES A MANUAL OF BASIC TECHNIQUES (Pergamon Press, New York 1988). Reagents for chromosome mapping can be used individually to mark a single chromosome or a single site on that chromosome, or panels of reagents can be used for marking multiple sites and/or multiple chromosomes. Reagents corresponding to noncodmg regions of the genes actually are preferred for mapping purposes Coding sequences are more likely to be conserved within gene families, thus increasing the chance of cross hybndizations duπng chromosomal mapping Once a sequence has been mapped to a precise chromosomal location, the physical position of the sequence on the chromosome can be correlated with genetic map data Such data are found, for example, in McKusick, MENDELIAN INHERITANCE IN MAN, available on-line through Johns Hopkins University Welch Medical Library) The relationship between genes and disease, mapped to the same chromosomal region, can then be identified through linkage analysis (co-inhentance of physically adjacent genes), descπbed in, for example, Egeland et al (1987) Nature, 325-783-787 Moreov er, differences in the DNA sequences between individuals affected and unaffected with a disease associated with the BLAA gene, can be determined If a mutation is observed in some or all of the affected individuals but not in any unaffected individuals, then the mutation is likely to be the causative agent of the particular disease. Companson of affected and unaffected individuals generally involves first looking for structural alterations in the chromosomes, such as deletions or translocations that are visible from chromosome spreads or detectable using PCR based on that DNA sequence Ultimately, complete sequencing of genes from several individuals can be performed to confirm the presence of a mutation and to distinguish mutations from polymorphisms. Tissue Typing The BLAA sequences of the present invention can also be used to identify individuals from minute biological samples In this technique, an individual's genomic DNA is digested with one or more restriction enzymes, and probed on a Southern blot to yield unique bands for identification The sequences of the present invention are useful as additional DNA markers for RFLP ("restriction fragment length polymorphisms," descπbed in U S Pat No 5.272.057) Furthermore, the sequences of the present invention can be used to provide an alternative technique that determines the actual base-by-base DNA sequence of selected portions of an individual's genome Thus, the BLAA sequences descnbed herein can be used to prepare two PCR pnmers from the 5' and 3' ends of the sequences These pnmers can then be used to amplify an individual's DNA and subsequently sequence it Panels of corresponding DNA sequences from individuals, prepared in this manner, can provide unique individual identifications, as each individual will have a unique set of such DNA sequences due to allelic differences The sequences of the present invention can be used to obtain such identification sequences from individuals and from tissue The BLAA sequences of the invention uniquely represent portions of the human genome Allelic vanation occurs to some degree in the coding regions of these sequences, and to a greater degree in the noncodmg regions It is estimated that allelic v aπation between individual humans occurs ith a frequency of about once per each 500 bases Much of the allelic vanation is due to single nucleotide polymorphisms (SNPs), which include restnction fragment length polymorphisms (RFLPs) Each of the sequences descπbed herein can, to some degree, be used as a standard against which DNA from an individual can be compared for identification purposes Because greater numbers of polymorphisms occur in the noncodmg regions, fewer sequences are necessary to differentiate individuals The noncodmg sequences of SEQ ID NO 1, SEQ ID NO 3. and SEQ ID NO 5 (SEQ ID NOs 8, 10, and 12, respectively) can comfortably provide positive individual identification with a panel of perhaps 10 to 1,000 pnmers that each yield a noncodmg amplified sequence of 100 bases If predicted coding sequences, such as those in SEQ ID NO 1 , 3, 5, 7, 9, and 1 1 are used, a more appropnate number of pnmers for individual positive identification would be 500-2000 Predictive Medicine The present invention also pertains to the field of predictive medicine in which diagnostic assays, prognostic assays, pharmacogenomics, and monitoring clinical tnals are used for prognostic (predictive) purposes to thereby treat an individual prophylactically Accordingly, one aspect of the present invention relates to diagnostic assays for determining BLAA polypeptide and/or nucleic acid expression as well as BLAA activity, m the context of a biological sample (e g , blood, serum, cells, tissue) to thereby determine whether an individual is afflicted with a disease or disorder, or is at nsk of developing a disorder, associated w ith abeπant BLAA expression or activity The invention also provides for prognostic (or predictive) assays for determining whether an individual is at πsk of developing a disorder associated with BLAA polypeptide or nucleic acid expression or activity For example, mutations in a BLAA gene can be assayed in a biological sample Such assays can be used for prognostic or predictive purpose to thereby prophylactically treat an individual pπor to the onset of a disorder charactenzed by or associated with BLAA polypeptide or nucleic acid expression or activity Another aspect of the invention provides methods for determining BLAA polypeptide or nucleic acid expression or BLAA activity m an individual to thereby select appropnate therapeutic or prophylactic agents for that individual (refeπed to herein as "pharmacogenomics") Pharmacogenomics allows for the selection of agents (e g , drugs) for therapeutic or prophylactic treatment of an individual based on the genotype of the individual (e g , the genotype of the individual examined to determine the ability of the individual to respond to a particular agent ) Yet another aspect of the invention pertains to momtonng the influence of agents (e g , drugs, compounds) on the expression or activity of BLAA in clinical tnals These and other agents are descπbed in further detail in the following sections Diagnostic Assays An exemplary method for detecting the presence or absence of BLAA in a biological sample in olves obtaining a biological sample from a test subject and contacting the biological sample with a compound or an agent capable of detecting BLAA polypeptide or nucleic acid (e g , mRNA, genomic DNA) that encodes BLAA polypeptide such that the presence of BLAA is detected in the biological sample An agent for detecting BLAA mRNA or genomic DNA is a labeled nucleic acid probe capable of hybπdizmg to BLAA mRNA or genomic DNA. The nucleic acid probe can be, for example, a full-length BLAA nucleic acid, such as the nucleic acid of SEQ ID NO- 1, 3, 5, 7, 8, 9, 10, 11, or 12, or a portion thereof, such as an oligonucleotide of at least 15, 30, 50, 100, 250 or 500 nucleotides in length and sufficient to specifically hybπdize under stπngent conditions to BLAA mRNA or genomic DNA Other suitable probes for use in the diagnostic assays of the invention are described herein An agent for detectmg BLAA polypeptide is an antibody capable of binding to BLAA protein, preferably an antibody with a detectable label Antibodies can be polyclonal, or more preferably, monoclonal An intact antibody, or a fragment thereof (e g , Fab or F(ab') 2 ) can be used. The term "labeled", with regard to the probe or antibody, is intended to encompass direct labeling of the probe or antibody by coupling (i e , physically linking) a detectable substance to the probe or antibody, as well as indirect labeling of the probe or antibody by reactiv lty with another reagent that is directly labeled. Examples of indirect labeling include detection of a pπmary antibody using a fluorescently labeled secondary antibody and end-labeling of a DNA probe with biotm such that it can be detected with fluorescently labeled streptavidin The term "biological sample" is intended to include tissues, cells and biological fluids isolated from a subject, as well as tissues, cells and fluids present within a subject. That is, the detection method of the invention can be used to detect BLAA mRNA, polypeptide, or genomic DNA in a biological sample in vitro as well as in vivo For example, in vitro techniques for detection of BLAA mRNA include Northern hybπdizations and in situ hybndizations In vitro techniques for detection of BLAA polypeptide include enzyme linked immunosorbent assays (ELISAs), Western blots, lmmunoprecrpitations and lmmunofluorescence In vitro techniques for detection of BLAA genomic DNA include Southern hybπdizations Furthermore, in vivo techniques for detection of BLAA protein include introducing into a subject a labeled anti-BLAA antibody For example, the antibody can be labeled with a radioactive marker whose presence and location in a subject can be detected by standard imaging techniques In one embodiment, the biological sample contains protein molecules from the test subject Alternatively, the biological sample can contain mRNA molecules from the test subject or genomic DNA molecules from the test subject A preferred biological sample is a peπpheral blood leukocyte sample isolated by conventional means from a subject In another embodiment, the methods further involve obtaining a control biological sample from a control subject, contacting the control sample with a compound or agent capable of detecting BLAA polypeptide, mRNA, or genomic DNA, such that the presence of BLAA polypeptide, mRNA or genomic DNA is detected m the biological sample, and companng the presence of BLAA polypeptide. mRNA or genomic DNA in the control sample with the presence of BLAA polypeptide, mRNA or genomic DNA in the test sample The invention also encompasses kits for detecting the presence of BLAA in a biological sample For example, the kit can compπse a labeled compound or agent capable of detecting BLAA polypeptide or mRNA in a biological sample, means for determining the amount of BLAA in the sample, and means for companng the amount of BLAA in the sample with a standard The compound or agent can be packaged in a suitable container The kit can further compnse instructions for using the kit to detect BLAA polypeptide or nucleic acid Prognostic Assays The diagnostic methods descπbed herein can furthermore be utilized to identify subjects having or at nsk of developing a disease or disorder associated with aberrant BLAA expression or activity For example, the assays descπbed herein, such as the preceding diagnostic assays or the following assays, can be utilized to identify a subject having or at πsk of developing an immune response-associated disorder associated with BLAA polypeptide or nucleic acid expression or activity such as cancers, infectious diseases, autoimmune disorders, and complications associated with transplantation Alternatively, the prognostic assays can be utilized to identify a subject having or at nsk for developing a disease or disorder Thus, the present invention provides a method for identifying a disease or disorder associated with abeπant BLAA expression or activity in which a test sample is obtained from a subject and BLAA polypeptide or nucleic acid (e g , mRNA, genomic DNA) is detected, wherein the presence of BLAA polypeptide or nucleic acid is diagnostic for a subject having or at πsk of developing a disease or disorder associated with aberrant BLAA expression or activity As used herein, a "test sample" refers to a biological sample obtained from a subject of interest For example, a test sample can be a biological fluid (e g , serum), cell sample, or tissue Furthermore, the prognostic assays descπbed herein can be used to determine whether a subject can be administered an agent (e g , an agonist, antagonist, peptidomimetic, protein, peptide. nucleic acid, small molecule, or other drug candidate) to treat a disease or disorder associated with abenant BLAA expression or activity For example, such methods can be used to determine whether a subject can be effectively treated with an agent for a disorder, such as cancer, infectious disease, autoimmune disorders, and complications associated with transplantation Thus, the present invention provides methods for determining whether a subject can be effectively treated with an agent for a disorder associated with aberrant BLAA expression or activity in which a test sample is obtained and a BLAA polypeptide or nucleic acid is detected (e g , wherein the presence of a BLAA polypeptide or nucleic acid is diagnostic for a subject that can be administered the agent to treat a disorder associated with abenant BLAA expression or activity ) The methods of the invention can also be used to detect genetic lesions m a BLAA gene, thereby determining if a subject with the lesioned gene is at nsk for a disorder charactenzed by abenant cell proliferation and/or differentiation In vanous embodiments, the methods include detectmg, in a sample of cells from the subject, the presence or absence of a genetic lesion charactenzed by at least one of an alteration affecting the integnty of a gene encoding a BLAA polypeptide, or the mis-expression of the BLAA gene For example, such genetic lesions can be detected by ascertaining the existence of at least one of (1) a deletion of one or more nucleotides from a BLAA gene, (2) an addition of one or more nucleotides to a BLAA gene, (3) a substitution of one or more nucleotides of a BLAA gene, (4) a chromosomal reanangement of a BLAA gene, (5) an alteration in the level of a messenger RNA transcnpt of a BLAA gene, (6) aberrant modification of a BLAA gene, such as of the methylation pattern of the genomic DNA, (7) the presence of a non-wild type splicing pattern of a messenger RNA transcnpt of a BLAA gene, (8) a non-wild type level of a BLAA polypeptide, (9) allelic loss of a BLAA gene and ( 10) inappropriate post-translational modification of a BLAA polypeptide As descπbed herein, there are a large number of assay techniques known in the art which can be used for detecting lesions in a BLAA gene A prefeπed biological sample is a penpheral blood leukocyte sample isolated by conventional means from a subject However, any biological sample containing nucleated cells may be used, including, for example, buccal mucosal cells In certain embodiments, detection of the lesion involves the use of a probe/pπmer in a polymerase chain reaction (PCR) (see, e g , U S Pat Nos 4,683,195 and 4,683,202), such as anchor PCR or RACE PCR, or, alternatively, in a hgation chain reaction (LCR) (see, e g , Landegran et al (1988) Science 241 1077-1080, and Nakazawa et al (1994) PNAS 91 360-364), the latter of which can be particularly useful for detecting point mutations in the BLAA-gene (see Abravaya et al (1995) Nucl Acids Res 23 675-682) This method can include the steps of collecting a sample of cells from a patient, isolating nucleic acid (e g , genomic, mRNA or both) from the cells of the sample, contacting the nucleic acid sample with one or more pnmers that specifically hybndize to a BLAA gene under conditions such that hybπdization and amplification of the BLAA gene (if present) occurs, and detecting the presence or absence of an amplification product, or detecting the size of the amplification product and companng the length to a control sample It is anticipated that PCR and/or LCR may be desirable to use as a preliminary amplification step in conjunction with any of the techniques used for detectmg mutations descnbed herein Alternative amplification methods include self sustained sequence replication (Guatelh et al , 1990, Proc Natl Acad Sci USA 87 1874-1878), transcnptional amplification system (Kwoh, et al , 1989, Proc Natl Acad Sci USA 86 1173-1177), Q-Beta Rephcase (Lizardi et al, 1988, BioTechnologv 6 1 197), or any other nucleic acid amplification method. followed by the detection of the amplified molecules using techniques well known to those of skill in the art These detection schemes are especially useful for the detection of nucleic acid molecules if such molecules are present m very low numbers In an alternativ e embodiment, mutations in a BLAA gene from a sample cell can be identified by alterations in restriction enzyme cleavage patterns For example, sample and control DNA is isolated, amplified (optionally), digested with one or more restπction endonucleases, and fragment length sizes are determined by gel electrophoresis and compared Differences in fragment length sizes between sample and control DNA indicates mutations in the sample DNA Moreover, the use of sequence specific nbozymes (see, for example, U S Pat No 5,493.531) can be used to score for the presence of specific mutations by development or loss of a πbozyme cleavage site In other embodiments, genetic mutations in BLAA can be identified by hybπdizmg a sample and control nucleic acids, e g , DNA or RNA, to high density anays containing hundreds or thousands of oligonucleotides probes (Cronm et al (1996) Human Mutation 7 244-255, Kozal et al (1996) Nature Medicine 2 753-759) For example, genetic mutations in BLAA can be identified in two dimensional anays containing light-generated DNA probes as descπbed in Cronin et al above Bnefly, a first hybndization anay of probes can be used to scan through long stretches of DNA in a sample and control to identify base changes between the sequences by making linear anays of sequential overlapping probes This step allows the identification of point mutations This step is followed by a second hybπdization anay that allows the charactenzation of specific mutations by using smaller, specialized probe anays complementary to all vanants or mutations detected Each mutation anay is composed of parallel probe sets, one complementary to the wild-type gene and the other complementary to the mutant gene In yet another embodiment, any of a vanety of sequencing reactions known in the art can be used to directly sequence the BLAA gene and detect mutations by companng the sequence of the sample BLAA with the conesponding wild-type (control) sequence Examples of sequencing reactions include those based on techniques developed by Maxim and Gilbert (1977) PNAS 74 560 or Sanger (1977) PNAS 74 5463 It is also contemplated that any of a vanety of automated sequencing procedures can be utilized when performing the diagnostic assays (Naeve et al , (1995) Biotechniques 19 448), including sequencing by mass spectrometry (see, e g , PCT International Publ No WO 94/16101, Cohen et al (1996) Adv Chromatogr 36 127-162, and Gπffin et al (1993) Appl Biochem Bwtechnol 38 147-159) Other methods for detecting mutations in the BLAA gene include methods m which protection from cleavage agents is used to detect mismatched bases in RNA RNA or RNA/DNA heteroduplexes (Myers et al (1985) Science 230 1242) In general, the art technique of "mismatch clea age" starts by providing heteroduplexes of formed by hybndizing (labeled) RNA or DNA containing the wild-type BLAA sequence with potentially mutant RNA or DNA obtained from a tissue sample The double-stranded duplexes are treated with an agent that cleaves smgle-stranded regions of the duplex such as which will exist due to basepair mismatches between the control and sample strands For instance, RNA/DNA duplexes can be treated with RNase and DNA/DNA hybnds treated with SI nuclease to enzymatically digesting the mismatched regions In other embodiments, either DNA/DNA or RNA DNA duplexes can be treated with hydroxylamine or osmium tetroxide and with pipendme in order to digest mismatched regions After digestion of the mismatched regions, the resulting material is then separated by size on denatunng polyacrylamide gels to determine the site of mutation See, for example, Cotton et al (1988) Proc Natl Acad Sci USA 85 4397, Saleeba et al (1992) Methods Enzvmol 217 286-295 In an embodiment, the control DNA or RNA can be labeled for detection In still another embodiment, the mismatch cleavage reaction employs one or more proteins that recognize mismatched base pairs m double-stranded DNA (so called "DNA mismatch repair" enzymes) m defined systems for detecting and mapping point mutations in BLAA cDNAs obtained from samples of cells For example, the mutY enzyme of E coli cleaves A at G/A mismatches and the thymidine DNA glycosylase from HeLa cells cleaves T at G/T mismatches (Hsu et al (1994) Carcinogenesis 15 1657-1662) According to an exemplary embodiment, a probe based on a BLAA sequence, e g , a wild-type BLAA sequence, is hybπdized to a cDNA or other DNA product from a test cell(s) The duplex is treated with a DNA mismatch repair enzyme, and the cleavage products, if any, can be detected from electrophoresis protocols or the like See, for example, U S Pat No 5,459,039 In other embodiments, alterations in electrophoretic mobility will be used to identify mutations in BLAA genes For example, single strand conformation polymorphism (SSCP) may be used to detect differences in electrophoretic mobility between mutant and wild type nucleic acids (Onta et al (1989) Proc Natl Acad Sci USA 86 2766, see also Cotton (1993) Mutat Res 285 125-144, Hayashi (1992) Genet Anal Tech Appl 9 73-79) Smgle-stranded DNA fragments of sample and control BLAA nucleic acids will be denatured and allowed to renature The secondary structure of single-stranded nucleic acids vanes according to sequence, the resulting alteration in electrophoretic mobility enables the detection of even a single base change The DNA fragments may be labeled or detected with labeled probes The sensitivity of the assay may be enhanced by using RNA (rather than DNA), in which the secondary structure is more sensitive to a change in sequence In one embodiment, the subject method utilizes heteroduplex analysis to separate double stranded heteroduplex molecules on the basis of changes in electrophoretic mobility (Keen et al (1991) Trends Genet 7 5) In yet another embodiment the movement of mutant or wild-type fragments in polyacrylamide gels containing a gradient of denaturant is assayed using denatunng gradient gel electrophoresis (DGGE) (Myers et al (1985) Nature 313 495) When DGGE is used as the method of analysis, DNA will be modified to insure that it does not completely denature, for example by adding a GC clamp of approximately 40 bp of high-melting GC-nch DNA by PCR In a further embodiment, a temperature gradient is used m place of a denatunng gradient to identify differences in the mobility of control and sample DNA (Rosenbaum and Reissner (1987) Bιoph\s Chem 265 12753) Examples of other techniques for detecting point mutations include, but are not limited to, selective oligonucleotide hybπdization, selective amplification, or selective pπmer extension For example, oligonucleotide pnmers may be prepared in which the known mutation is placed centrally and then hybndized to target DNA under conditions that permit hybndization only if a perfect match is found (Saiki et al (1986) Nature 324 163), Saiki et al (1989) Proc \atl Acad Sci USA 86 6230) Such allele specific oligonucleotides are hybndized to PCR amplified target DNA or a number of different mutations when the oligonucleotides are attached to the hybndizing membrane and hybndized with labeled target DNA Alternatively, allele specific amplification technology that depends on selective PCR amplification may be used in conjunction with the instant invention Oligonucleotides used as pnmers for specific amplification may carry the mutation of interest in the center of the molecule (so that amplification depends on differential hybπdization) (Gibbs et al (1989) Nucleic Acids Res 17 2437-2448) or at the extreme 3' end of one pπmer where, under appropnate conditions, mismatch can prevent, or reduce polymerase extension (Prossner (1993) Tibtech 1 1 238) In addition it may be desirable to introduce a novel restnction site in the region of the mutation to create cleavage-based detection (Gaspanm et al (1992) Mol Cell Probes 6 1) It is anticipated that m certain embodiments amplification may also be performed using Taq hgase for amplification (Barany ( 1991 ) Proc Natl Acad Sci USA 88 189) In such cases, hgation will occur only if there is a perfect match at the 3' end of the 5' sequence, making it possible to detect the presence of a known mutation at a specific site by looking for the presence or absence of amplification The methods descnbed herein may be performed, for example, by utilizing pre-packaged diagnostic kits compπsing at least one probe nucleic acid or antibody reagent descπbed herein, which may be conveniently used, e g , in clinical settings to diagnose patients exhibiting symptoms or family history of a disease or illness involving a BLAA gene Furthermore, any cell type or tissue, preferably penpheral blood leukocytes, in which BLAA is expressed may be utilized in the prognostic assays descπbed herein However, any biological sample containing nucleated cells may be used, including, for example, buccal mucosal cells Pharmacogenomics Agents, or modulators that have a stimulatory or inhibitory effect on BLAA activity (e g , BLAA gene expression), as identified by a screening assay descπbed herein can be administered to individuals to treat (prophylactically or therapeutically) disorders (e g , cancer, infectious disease, autoimmune disorders, and complications associated with transplantation) associated with abenant BLAA activity In conjunction with such treatment, the pharmacogenomics (z e , the study of the relationship between an individual's genotype and that individual's response to a foreign compound or drug) of the individual may be considered Differences in metabolism of therapeutics can lead to severe toxicity or therapeutic failure by altenng the relation between dose and blood concentration of the pharmacologically active drug Thus, the pharmacogenomics of the individual permits the selection of effective agents (e g , drugs) for prophylactic or therapeutic treatments based on a consideration of the individual's genotype Such pharmacogenomics can further be used to determine appropriate dosages and therapeutic regimens Accordingly, the activity of BLAA polypeptide, expression of BLAA nucleic acid, or mutation content of BLAA genes in an individual can be determined to thereby select appropnate agent(s) for therapeutic or prophylactic treatment of the individual Pharmacogenomics deals with clinically significant hereditary variations in the response to drugs due to altered drug disposition and abnormal action in affected persons See g , Eichelbaum, Clin Exp Pharmacol Physwl, 1996, 23 983-985 and Linder, Clin Chem, 1997, 43 254-266 In general, two types of pharmacogenetic conditions can be differentiated Genetic conditions transmitted as a single factor alteπng the way drugs act on the body (altered drug action) or genetic conditions transmitted as single factors altenng the way the body acts on drugs (altered drug metabolism) These pharmacogenetic conditions can occur either as rare defects or as polymorphisms For example, glucose-6-phosphate dehydrogenase (G6PD) deficiency is a common inherited enzymopathy in which the main clinical complication is haemolysis after ingestion of oxidant drugs (anti-malanals, sulfonamides, analgesics, mtrofurans) and consumption of fava beans As an illustrati e embodiment, the activity of drug metabolizing enzymes is a major determinant of both the intensity and duration of drug action The discovery of genetic polymorphisms of drug metabolizing enzymes (e g , N-acetyltransferase 2 (NAT 2) and cytochrome P450 enzymes CYP2D6 and CYP2C19) has provided an explanation as to why some patients do not obtain the expected drug effects or show exaggerated drug response and senous toxicity after taking the standard and safe dose of a drug These polymorphisms are expressed m two phenotypes in the population, the extensive metabolizer (EM) and poor metabolizer (PM) The prevalence of PM is different among different populations For example, the gene coding for CYP2D6 is highly polymorphic and several mutations have been identified in PM, which all lead to the absence of functional CYP2D6 Poor metabohzers of CYP2D6 and CYP2C19 quite frequently expenence exaggerated drug response and side effects when they receive standard doses If a metabolite is the active therapeutic moiety, PM show no therapeutic response, as demonstrated for the analgesic effect of codeine mediated by its CYP2D6-formed metabolite morphine The other extreme are the so called ultra-rapid metabohzers who do not respond to standard doses Recently, the molecular basis of ultra-rapid metabolism has been identified to be due to CYP2D6 gene amplification Thus, the activity of BLAA polypeptide, expression of BLAA nucleic acid, or mutation content of BLAA genes in an individual can be determined to thereby select appropriate agent(s) for therapeutic or prophylactic treatment of the individual In addition, pharmacogenetic studies can be used to apply genotypmg of polymorphic alleles encoding drug-metabohzmg enzymes to the identification of an individual's drug responsiveness phenotype This knowledge, when applied to dosmg or drug selection, can avoid adverse reactions or therapeutic failure and thus enhance therapeutic or prophylactic efficiency when treating a subject with a BLAA modulator, such as a modulator identified by one of the exemplary screening assays described herein Monitoring of Effects During Clinical Trials Momtoπng the influence of agents (e g , drugs, compounds) on the expression or activity of BLAA (e g , the ability to modulate abenant cell proliferation and/or differentiation) can be applied not only in basic drug screening, but also in clinical tnals For example, the effectiveness of an agent determined by a screening assay as descπbed herein to increase BLAA gene expression, protein levels, or upregulate BLAA activity, can be monitored in clinical trails of subjects exhibiting decreased BLAA gene expression, protein levels, or downregulated BLAA activity Alternatively, the effectiveness of an agent determined by a screening assay to decrease BLAA gene expression, protein levels, or downregulate BLAA activity, can be monitored in clinical trails of subjects exhibiting increased BLAA gene expression, protein levels, or upregulated BLAA activity In such clinical tnals, the expression or activity of BLAA and, preferably, other genes that have been implicated m, for example, an immune response-associated disorder can be used as a "read out" or markers of the immune responsiveness of a particular cell For example, and not by way of limitation, genes, including BLAA, that are modulated in cells by treatment with an agent (e g , compound, drug or small molecule) that modulates BLAA activity (e g , identified in a screening assay as descπbed herein) can be identified Thus, to study the effect of agents on cellular proliferation disorders, for example, in a clinical tπal, cells can be isolated and RNA prepared and analyzed for the levels of expression of BLAA and other genes implicated m the disorder The levels of gene expression (i e , a gene expression pattern) can be quantified by Northern blot analysis or RT-PCR, as descnbed herein, or alternatively by measuring the amount of protein produced, by one of the methods as descnbed herein, or by measunng the levels of activity of BLAA or other genes In this way, the gene expression pattern can serve as a marker, indicative of the physiological response of the cells to the agent Accordingly, this response state may be determined before, and at vanous points dunng, treatment of the individual with the agent In one embodiment, the present invention provides a method for monitoπng the effectiveness of treatment of a subject with an agent (e g , an agonist, antagonist, protein, polypeptide. peptidomimetic, nucleic acid, small molecule, or other drug candidate identified by the screening assays descnbed herein) compnsing the steps of (ι) obtaining a pre-administration sample from a subject pπor to administration of the agent, (u) detecting the level of expression of a BLAA polypeptide, mRNA, or genomic DNA in the preadmimstration sample, (in) obtaining one or more post-administration samples from the subject, (zi ) detecting the level of expression or activity of the BLAA polypeptide, mRNA, or genomic DNA in the post-administration samples, (v) companng the level of expression or activity of the BLAA polypeptide, mRNA, or genomic DNA m the pre-administration sample with the BLAA polypeptide, mRNA, or genomic DNA in the post administration sample or samples, and (vή alteπng the administration of the agent to the subject accordingly For example, increased administration of the agent may be desirable to increase the expression or activity of BLAA to higher levels than detected. ι e , to increase the effectiveness of the agent Alternatively, decreased administration of the agent may be desirable to decrease expression or activity of BLAA to lower levels than detected, ι e , to decrease the effectiveness of the agent Methods of Treatment The present invention provides for both prophylactic and therapeutic methods of treating a subject at nsk of (or susceptible to) a disorder or having a disorder associated with abenant BLAA expression or activity Disorders Diseases and disorders that are charactenzed by increased (relative to a subject not suffenng from the disease or disorder) levels or biological activity may be treated with therapeutics that antagonize (i e , reduce or inhibit) activity Therapeutics that antagonize activity may be administered in a therapeutic or prophylactic manner Therapeutics that may be utilized include, but are not limited to, (i) an aforementioned polypeptide, or analogs, deπvatives, fragments or homologs thereof, (it) antibodies to an aforementioned polypeptide, (in) nucleic acids encoding an aforementioned polypeptide, (zv) administration of antisense nucleic acid and nucleic acids that are "dysfunctional" (/ e due to a heterologous insertion within the coding sequences of coding sequences to an aforementioned polypeptide) that are utilized to "knockout" endogenous function of an aforementioned peptide by homologous recombination (see, e g Capecchi, 1989, Science 244 1288-1292), or (v) modulators ( i e , inhibitors, agonists and antagonists, including additional polypeptide mimetic of the invention or antibodies specific to a peptide of the invention) that alter the interaction between an aforementioned polypeptide and its binding partner Diseases and disorders that are charactenzed by decreased (relative to a subject not suffenng from the disease or disorder) levels or biological activity may be treated with therapeutics that increase (z e , are agonists to) activity Therapeutics that upregulate activity may be administered in a therapeutic or prophylactic manner Therapeutics that may be utilized include, but are not limited to, an aforementioned polypeptide, or analogs, deπvatives, fragments or homologs thereof, or an agonist that increases bioavailabihty Increased or decreased levels can be readily detected by quantifying polypeptide and/or RNA, by obtaining a patient tissue sample (e g from biopsy tissue) and assaying it in vitro for RNA or peptide levels, structure and/or activity of the expressed polypeptides (or mRNAs of an aforementioned polypeptide) Methods that are well-known within the art include, but are not limited to, immunoassays (e g by Western blot analysis, mimunoprecipitation followed by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis, lmmunocytochemistry, etc ) and/or hybndization assays to detect expression of mRNAs (e g , Northern assays, dot blots, in situ hybndization, etc ) Prophylactic Methods In one aspect, the invention provides a method for preventing, in a subject, a disease or condition associated w ith an abenant BLAA expression or activity, by admimstenng to the subject an agent that modulates BLAA expression or at least one BLAA activity Subjects at πsk for a disease that is caused or contnbuted to by abenant BLAA expression or activity can be identified by, for example, any or a combination of diagnostic or prognostic assays as described herein Administration of a prophylactic agent can occur pπor to the manifestation of symptoms characteπstic of the BLAA abenancy, such that a disease or disorder is prevented or, alternatively, delayed in its progression Depending on the type of BLAA abenancy, for example, a BLAA agonist or BLAA antagonist agent can be used for treating the subject The appropnate agent can be determined based on screening assays described herein The prophylactic methods of the present invention are further discussed m the following subsections Therapeutic Methods Another aspect of the invention pertains to methods of modulating BLAA expression or activity for therapeutic purposes The modulatory method of the invention involves contacting a cell with an agent that modulates one or more of the activities of BLAA polypeptide activity associated with the cell An agent that modulates BLAA polypeptide activity can be an agent as described herein, such as a nucleic acid or a protein, a naturally-occurnng cognate hgand of a BLAA polypeptide, a peptide, a BLAA peptidomimetic, or other small molecule In one embodiment, the agent stimulates one or more BLAA polypeptide activity Examples of such stimulatory agents include active BLAA polypeptide and a nucleic acid molecule encoding BLAA that has been introduced into the cell In another embodiment, the agent inhibits one or more BLAA polypeptide activity Examples of such inhibitory agents include antisense BLAA nucleic acid molecules and anti-BLAA antibodies These modulatory methods can be performed in vitro (e g , by culturmg the cell with the agent) or, alternatively, in vivo (e g , by admimstenng the agent to a subject) As such, the present invention provides methods of treating an individual afflicted with a disease or disorder charactenzed by abenant expression or activity of a BLAA polypeptide or nucleic acid molecule In one embodiment, the method involves admimstenng an agent (e g , an agent identified by a screening assay descnbed herein), or combination of agents that modulates (e g , upregulates or downregulates) BLAA expression or activity In another embodiment, the method involves admimstenng a BLAA polypeptide or nucleic acid molecule as therapy to compensate for reduced or abenant BLAA expression or activity Stimulation of BLAA activity is desirable in situations in which BLAA is abnormally downregulated and/or in which increased BLAA activity is likely to have a beneficial effect One example of such a situation is where a subject has a disorder charactenzed by abenant cell proliferation and or differentiation (e g , cancer) Another example of such a situation is where the subject has an immune response-associated disorder (e g , autoimmune disorders, infectious diseases, and complications associated with transplantation) In one embodiment, this invention involves a method of treating a pathological state m a mammal compπsing admimstenng a therapeutic amount of a polypeptide that is at least 95% identical to a polypeptide with an amino acid sequence of SEQ ID NO 2 or SEQ ID NO 4, or a biologically active fragment thereof An alternative embodiment involves admimstenng to a subject an antibody that selectively binds to a BLAA polypeptide, and fragments, homologs, analogs, and deπvatives thereof Determination of the Biological Effect of the Therapeutic In vaπous embodiments of the present invention, suitable in vitro or in vivo assays are utilized to determine the effect of a specific therapeutic and whether its administration is indicated for treatment of the affected tissue In vanous specific embodiments, in vitro assays may be performed with representative cells of the type(s) involved in the patient's disorder, to determine if a given therapeutic exerts the desired effect upon the cell type(s) Compounds for use in therapy may be tested m suitable animal model systems including, but not limited to rats, mice, chicken, cows, monkeys, rabbits, and the like, pπor to testing in human subjects Similarly, for in vivo testing, any of the animal model system known in the art may be used pnor to administration to human subjects Malignancies An aforementioned BLAA polypeptide may be involved in the regulation of cell proliferation Accordingly, therapeutics of the present invention may be useful in the therapeutic or prophylactic treatment of diseases or disorders that are associated with cell hyperprohferation and/or loss of control of cell proliferation (e g , cancers, malignancies and tumors) For a review of such hyperprohferation disorders, see e g Fishman, et al , 1985 MEDICINE 2nd ed , J B Lippincott Co , Philadelphia. PA Therapeutics of the present invention may be assayed by any method known within the art for determining efficacy in treating or preventing malignancies and related disorders Such assays include, but are not limited to, in vitro assays utilizing transformed cells or cells denved from the patient's tumor, as well as in vivo assays using animal models of cancer or malignancies Potentially effective therapeutics are those that, for example, inhibit the proliferation of tumor-denved or transformed cells in culture or cause a regression of tumors in animal models, in companson to the controls In the practice of the present invention, once a malignancy or cancer has been shown to be amenable to treatment bv modulating (z e , inhibiting, antagonizing, or agonizing) activity, that cancer or malignancy may subsequently be treated or prevented by the administration of a therapeutic that serves to modulate polypeptide function Disorders related to organ transplantation BLAA has been implicated in disorders related to organ transplantation, in particular, but not limited to, organ rejection Therapeutics of the invention, particularly those that modulate (or supply) activity, may be effective in treating or preventing diseases or disorders related to organ transplantation Therapeutics of the invention (particularly therapeutics that modulate the levels or activity of an aforementioned protein) can be assayed by any method known in the art for efficacy in treating or preventing such diseases and disorders related to organ transplantation Such assays include in vitro assays for using cell culture models as descnbed below, or in vivo assays using animal models of diseases and disorders related to organ transplantation, see e g , below Potentially effective therapeutics, for example, but not by way of limitation, reduce immune rejection responses m animal models m companson to controls Accordingly, once diseases and disorders related to organ transplantation are shown to be amenable to treatment by modulation of activity, such diseases or disorders can be treated or prevented by administration of a therapeutic that modulates activity T lymphocyte Growth and Activation Cell Proliferation/Differentiation Activity The BLAA polypeptide disclosed in the instant invention is a new B7 family member B7 family members, such as B7-1 and B7-2, are members of the immunoglobuhn superfamily and bind to activated T lymphocytes and provide regulatory signals for T lymphocyte cell growth than activation Immune Stimulating or Suppressing Activity A BLAA polypeptide of the present invention may also exhibit immune stimulating or immune suppressing activity, including without limitation the activities for which assays are descnbed herein A protein may be useful m the treatment of various immune deficiencies and disorders (including severe combined immunodeficiency (SCID)), e g , in regulating (up or down) growth and proliferation of T and or B lymphocytes, as well as effecting the cytolytic activity of NK cells and other cell populations These immune deficiencies may be genetic or be caused by v iral (e g , HIV) as well as bactenal or fungal infections, or may result from autoimmune disorders More specifically, infectious diseases causes by vital, bactenal, fungal or other infection may be treatable using a polypeptide of the present invention, including infections by HIV, hepatitis viruses, herpesviruses, mycobactena, Leishmama species, malaπa species, and vanous fungal infections such as candidiasis Of course, in this regard, a polypeptide of the present invention may also be useful where a boost to the immune system generally may be desirable, z e in the treatment of cancer Autoimmune disorders which may be treated using a polypeptide of the present invention include, for example, connective tissue disease, multiple sclerosis, systemic lupus erythematosus, rheumatoid arthπtis, autoimmune pulmonary inflammation, Guillain-Bane syndrome, autoimmune thyroiditis, insulin dependent diabetes melhtus, myasthenia gravis, graft-versus-host disease and autoimmune inflammatory eye disease Such a polypeptide of the present invention may also to be useful in the treatment of allergic reactions and conditions, such as asthma (particularly allergic asthma) or other respiratory problems Other conditions, in which immune suppression is desired (including, for example, organ transplantation), may also be treatable using a polypeptide of the present invention Using the polypeptide of the invention to modulate immune responses in a number of vvavs Down regulation may be in the form of inhibiting or blocking an immune response already m progress or may involve preventing the induction of an immune response The functions of activated T cells may be inhibited by suppressing T cell responses or by inducing specific tolerance in T cells, or both Immunosuppression of T cell responses is generally an active, non-antigen-specific, process which requires continuous exposure of the T cells to the suppressive agent Tolerance, which involves inducing non-responsiveness or energy m T cells, is distinguishable from immunosuppression in that it is generally antigen-specific and persists after exposure to the tolenzing agent has ceased Operationally, tolerance can be demonstrated by the lack of a T cell response upon re-exposure to specific antigen in the absence of the tolenzing agent Down regulating or preventing one or more antigen functions (including without limitation B lymphocyte antigen functions (such as, for example, B7)), e g , preventing high level lymphokine synthesis by activated T cells, will be useful in situations of tissue, skin and organ transplantation and in graft-versus-host disease (GVHD) For example, blockage of T cell function should result in reduced tissue destruction in tissue transplantation Typically, in tissue transplants, rejection of the transplant is initiated through its recognition as foreign by T cells, followed by an immune reaction that destroys the transplant The administration of a molecule which inhibits or blocks interaction of a B7 lymphocyte antigen with its natural hgand(s) on immune cells (such as a soluble, monomeπc form of a peptide having B7-2 activity alone or in conjunction with a monomenc form of a peptide having an activity of another B lymphocyte antigen (e g , B7-1, B7-3) or blocking antibody), pnor to transplantation can lead to the binding of the molecule to the natural hgand(s) on the immune cells without transmitting the conespondmg costimulatory signal Blocking B lymphocyte antigen function m this matter prevents cytokme synthesis by immune cells, such as T cells, and thus acts as an immunosuppressant Moreover, the lack of co stimulation may also be sufficient to energize the T cells, thereby inducing tolerance in a subject Induction of long-term tolerance by B lymphocyte antigen-blocking reagents may avoid the necessity of repeated administration of these blocking reagents To achieve sufficient immunosuppression or tolerance m a subject, it may also be necessary to block the function of B lymphocyte antigens The efficacy of particular blocking reagents m preventing organ transplant rejection or GVHD can be assessed using animal models that are predictive of efficacy m humans Examples of appropriate systems which can be used include allogeneic cardiac grafts in rats and xenogeneic pancreatic islet cell grafts in mice, both of which have been used to examine the lmmunosuppressive effects of CTLA4Ig fusion proteins in vivo as descπbed in Lenschow et al , Science 257 789-792 (1992) and Turka et al , Proc Natl Acad Sci USA, 89 1 1 102-1 1105 (1992) In addition, munne models of GVHD (see Paul ed , FUNDAMENTAL IMMUNOLOGY, Raven Press, New York, 1989, pp 846-847) can be used to determine the effect of blocking B lymphocyte antigen function in vivo on the development of that disease Blocking antigen function may also be therapeutically useful for treating autoimmune diseases Many autoimmune disorders are the result of inappropriate activation of T cells that are reactive against self tissue and which promote the production of cytokines and auto- antibodies involved in the pathology of the diseases Preventing the activation of autoreactive T cells may reduce or eliminate disease symptoms Administration of reagents which block costimulation of T cells by disrupting receptor hgand interactions of B lymphocyte antigens can be used to inhibit T cell activation and prevent production of auto-antibodies or T cell-denved cytokines which may be involved in the disease process Additionally, blocking reagents may induce antigen-specific tolerance of autoreactive T cells which could lead to long-term relief from the disease The efficacy of blocking reagents in preventing or alleviating autoimmune disorders can be determined using a number of well-charactenzed animal models of human autoimmune diseases Examples include munne expenmental autoimmune encephalitis, systemic lupus erythematosis in MRL/lpr/lpr mice or NZB hybnd mice, munne autoimmune collagen arthπtis, diabetes melhtus in NOD mice and BB rats, and munne expenmental myasthenia gravis (see Paul ed , FUNDAMENTAL IMMUNOLOGY, Raven Press, New York, 1989, pp 840-856) Upregulation of an antigen function (preferably a B lymphocyte antigen function), as a means of up regulating immune responses, may also be useful in therapy Upregulation of immune responses may be in the form of enhancing an existing immune response or eliciting an initial immune response For example, enhancing an immune response through stimulating B lymphocyte antigen function may be useful in cases of viral infection In addition, systemic vital diseases such as influenza, the common cold, and encephalitis might be alleviated by the administration of stimulatory forms of B lymphocyte antigens systemically Alternatively, anti-viral immune responses may be enhanced in an infected patient by removing T cells from the patient, costimulatmg the T cells in vitro with viral antigen-pulsed APCs either expressing a peptide of the present invention or together with a stimulatory form of a soluble peptide of the present invention and remtroducing the in vitro activated T cells into the patient Another method of enhancing anti-vital immune responses would be to isolate infected cells from a patient, transfect them with a nucleic acid encoding a protein of the present invention as described herein such that the cells express all or a portion of the protein on their surface, and reintroduce the transfected cells into the patient The infected cells would now be capable of dehvenng a costimulatory signal to, and thereby activate, T cells in vivo In another application, up regulation or enhancement of antigen function (preferably B lymphocyte antigen function) may be useful in the induction of tumor immunity Tumor cells (e g , sarcoma, melanoma, lymphoma, leukemia, neuroblastoma, carcinoma) transfected with a nucleic acid encoding at least one peptide of the present invention can be administered to a subject to overcome tumor-specific tolerance m the subject If desired, the tumor cell can be transfected to express a combination of peptides. For example, tumor cells obtained from a patient can be transfected ex vivo with an expression vector directing the expression of a peptide having B7-2-hke activity alone, or in conjunction with a peptide having B7-l-lιke activity and or B7-3-hke activity The transfected tumor cells are returned to the patient to result in expression of the peptides on the surface of the transfected cell Alternatively, gene therapy techniques can be used to target a tumor cell for transfection in vivo The presence of the peptide of the present invention having the activity of a B lymphocyte antιgen(s) on the surface of the tumor cell provides the necessary costimulation signal to T cells to induce a T cell mediated immune response against the transfected tumor cells In addition, tumor cells which lack MHC class I or MHC class II molecules, or which fail to reexpress sufficient amounts of MHC class I or MHC class II molecules, can be transfected with nucleic acid encoding all or a portion of (e g , a cytoplasmic-domam truncated portion) of an MHC class I α chain protein and β2 microglobuhn protein or an MHC class II a chain protein and an MHC class II β chain protein to thereby express MHC class I or MHC class II proteins on the cell surface Expression of the appropnate class I or class II MHC in conjunction with a peptide having the activity of a B lymphocyte antigen (e.g., B7-1 , B7-2, B7-3) induces a T cell mediated immune response against the transfected tumor cell. Optionally, a gene encoding an antisense construct which blocks expression of an MHC class II associated protein, such as the invariant chain, can also be cotransfected with a DNA encoding a peptide having the activity of a B lymphocyte antigen to promote presentation of tumor associated antigens and induce tumor specific immunity. Thus, the induction of a T cell mediated immune response in a human subject may be sufficient to overcome tumor-specific tolerance in the subject. The activity of a polypeptide of the invention may, among other means, be measured by the following methods: Suitable assays for thymocyte or splenocyte cytotoxicity include, without limitation, those descnbed In: CURRENT PROTOCOLS IN IMMUNOLOGY. Coligan et al, eds. Greene Publishing Associates and Wiley-Interscience (Chapter 3, Chapter 7); Herrmann et al, Proc Natl Acad Sci USA 78:2488-2492, 1981 ; Herrmann et al, J Immunol 128: 1968-1974, 1982; Handa et al, J Immunol 135: 1564-1572, 1985; Takai et al, J Immunol 137:3494-3500, 1986; Takai et al., J Immunol 140:508-512, 1988; Herrmann et al, Proc Natl Acad Sci USA 78:2488-2492, 1981 ; Herrmann et al, J Immunol 128: 1968-1974, 1982; Handa et al., J Immunol 135: 1564-1572, 1985; Takai et al, J Immunol 137:3494-3500, 1986; Bowman et al, J Virology 61 : 1992-1998; Takai et al, J Immunol 140:508-512, 1988; Bertagnolli et al, Cell Immunol 133 :327-341 , 1991 ; Brown et al. , J Immunol 153:3079-3092, 1994. Assays for T-cell-dependent immunoglobuhn responses and isotype switching (which will identify, among others, proteins that modulate T-cell dependent antibody responses and that affect Thl/Th2 profiles) include, without limitation, those described in: Maliszewski, J Immunol 144:3028-3033, 1990; and Mond and Brunswick In: CURRENT PROTOCOLS IN IMMUNOLOGY. Coligan et al, (eds.) Vol 1 pp. 3.8.1-3.8.16, John Wiley and Sons, Toronto 1994. Mixed lymphocyte reaction (MLR) assays (which will identify, among others, proteins that generate predominantly Thl and CTL responses) include, without limitation, those described In: CURRENT PROTOCOLS IN IMMUNOLOGY. Coligan et al, eds. Greene Publishing Associates and Wiley-Interscience (Chapter 3, Chapter 7); Takai et al, J Immunol 137:3494-3500, 1986; Takai et al, J Immunol 140:508-512, 1988; Bertagnolli et al, J Immunol 149:3778-3783, 1992. Dendritic cell-dependent assays (which will identify, among others, proteins expressed by dendritic cells that activate naive T-cells) include, without limitation, those described in: Guery et al, J Immunol 134:536-544, 1995; Inaba et al, JExp Med 173:549-559, 1991 ; MacaXo a et al, J Immunol 154:5071-5079, 1995; Porgador et al, JExp Med 182:255-260, 1995; Nair et al., J Virol 67:4062-4069, 1993; Huang et al, Science 264:961-965, 1994; Macatonia et al, J Exp Med 169: 1255-1264, 1989; Bhardwaj et al, J Clin Investig 94:797-807, 1994; and Inaba et al, JExp Med 172:631-640, 1990. Assays for lymphocyte survival/apoptosis (which will identify, among others, proteins that prevent apoptosis after superantigen induction and proteins that regulate lymphocyte homeostasis) include, without limitation, those described in: Darzynkiewicz et al, Cytometry 13:795-808, 1992; Gorczyca et al, Leukemia 7:659-670, 1993; Gorczyca et al. , Cancer Res 53: 1945-1951 , 1993; Itoh et al , Cell 66:233-243, 1991 ; Zacharchuk, J Immunol 145:4037-4045, 1990; Zamai et al, Cytometry 14:891 -897, 1993; Gorczyca et al, Internat J Oncol 1 :639-648, 1992. Assays for proteins that influence early steps of T-cell commitment and development include, without limitation, those described in: Antica et al, Blood 84: 1 1 1-1 17, 1994; Fine et al.. Cell Immunol 155: 1 1 1-122, 1994; Galy et al. Blood 85:2770-2778, 1995; Toki et al , Proc Nat Acad Sci USA 88:7548-7551 , 1991. Other Activities A polypeptide of the invention may also exhibit one or more of the following additional activities or effects: inhibiting the growth, infection or function of, or killing, infectious agents, including, without limitation, bacteria, viruses, fungi and other parasites; effecting (suppressing or enhancing) bodily characteristics, including, without limitation, height, weight, hair color, eye color, skin, fat to lean ratio or other tissue pigmentation, or organ or body part size or shape (such as, for example, breast augmentation or diminution, change in bone form or shape); effecting biorhythms or circadian cycles or rhythms; effecting the fertility of male or female subjects; effecting the metabolism, catabolism, anabolism, processing, utilization, storage or elimination of dietary fat, lipid, protein, carbohydrate, vitamins, minerals, cofactors or other nutntional factors or component(s), effecting behavioral charactenstics, including, without limitation, appetite, libido, stress, cognition (including cognitive disorders), depression (including depressive disorders) and violent behaviors, providing analgesic effects or other pam reducing effects, promoting differentiation and growth of embryonic stem cells in lineages other than hematopoietic lineages, hormonal or endocπne activity, in the case of enzymes, correcting deficiencies of the enzyme and treating deficiency-related diseases, treatment of hyperprohferative disorders (such as, for example, psonasis), lmmunoglobuhn-hke activity (such as, for example, the ability to bmd antigens or complement), and the ability to act as an antigen in a vaccine composition to raise an immune response against such protein or another matenal or entity which is cross-reactive with such protein The present invention is not to be limited in scope by the specific embodiments described herein Indeed, vanous modifications of the invention in addition to those descnbed herein will become apparent to those skilled in the art from the foregoing descnption and accompanying figures Such modifications are intended to fall within the scope of the appended claims The contents of all references, patents and published patent applications cited throughout this application are hereby incorporated by reference EQUIVALENTS It is to be understood that while the invention has been descπbed in conjunction with the detailed description thereof, the foregoing descnption is intended to illustrate and not limit the scope of the invention, which is defined by the scope of the appended claims Other aspects, advantages, and modifications are within the scope of the following claims

Claims: We Claim An isolated nucleic acid molecule encoding a B lymphocyte activation antigen ("BLAA"), wherein said molecule compπses a nucleotide sequence encoding a polypeptide having a sequence that is at least 95% identical to SEQ ID NO 2, SEQ ID NO 4, or SEQ ID NO 6, or the complement of said nucleic acid molecule The nucleic acid molecule of claim 1, wherein said molecule hybπdizes under stnngent conditions to a nucleic acid sequence complementary to a nucleic acid molecule comprising the sequence of nucleotides of SEQ ID NO 1, SEQ ID NO 3. or SEQ ID NO 5, or the complement of said nucleic acid molecule The nucleic acid molecule of claim 1 , wherein said nucleotide sequence encodes a human BLAA The nucleic acid molecule of claim 1, wherein said molecule encodes a polypeptide compnsing the ammo acid sequence of SEQ ID NO 2, SEQ ID NO 4, or SEQ ID NO 6, or an amino acid sequence compπsing one or more conservative substitutions m the amino acid sequence of SEQ ID NO 2, SEQ ID NO 4, or SEQ ID NO 6 The nucleic acid molecule of claim 1. wherein said molecule encodes a polypeptide comprising the ammo acid sequence of SEQ ID NO 2, SEQ ID NO 4, or SEQ ID NO 6, or the complement of said nucleic acid molecule An oligonucleotide of less than 100 nucleotides in length and compnsing at least 6 contiguous nucleotides of SEQ ID NO 1 , SEQ ID NO 3, SEQ ID NO 5. SEQ ID NO 7, SEQ ID NO 8, SEQ ID NO 9, SEQ ID NO 10, SEQ ID NO 11, or SEQ ID NO 12, or a complement thereof A vector compnsing the nucleic acid molecule of claim 1 The vector of claim 7. wherein said vector is an expression vector The vector of claim 7, further comprising a regulatory element operably linked to said nucleic acid molecule An isolated polypeptide at least 80% identical to a polypeptide selected from the group consisting of (a) a polypeptide comprising an ammo acid sequence of SEQ ID NO 2, SEQ ID NO 4, or SEQ ID NO 6, (b) a fragment of a polypeptide comprising an ammo acid sequence of SEQ ID NO 2, SEQ ID NO 4, or SEQ ID NO 6, wherein the fragment compnses at least 6 contiguous ammo acids of SEQ ID NO 2, SEQ ID NO 4, or SEQ ID NO 6, (c) a denvative of a polypeptide compπsing an amino acid sequence of SEQ ID NO 2, SEQ ID NO 4, or SEQ ID NO 6, (d) an analog of a polypeptide compnsing an ammo acid sequence of SEQ ID NO 2, SEQ ID NO 4. or SEQ ID NO 6, (e) a homolog of a polypeptide compnsing an amino acid sequence of SEQ ID NO 2, SEQ ID NO 4, or SEQ ID NO 6, (f) a naturally occurπng allelic vanant of a polypeptide compnsing an amino acid sequence of SEQ ID NO 2, SEQ ID NO 4, or SEQ ID NO 6, wherein the polypeptide is encoded by a nucleic acid molecule that hybπdizes to a nucleic acid molecule of SEQ ID NO 1 , SEQ ID NO 3, or SEQ ID NO 5 under stnn λ tgent conditions The polypeptide of claim 10, wherein the polypeptide, or fragment thereof, has human B lymphocyte activation antigen B7-hke activity An antibody that selectively binds to the polypeptide of claim 10 A method of producing the polypeptide of claim 10, said method compnsing the step of cultunng a host cell under conditions in which the nucleic acid molecule is expressed A method of detecting the presence of the polypeptide of claim 10 in a sample, the method compnsing contacting the sample with a compound that selectively binds to the polypeptide of claim 10 and determining whether the compound bound to the polypeptide of claim 10 is present in the sample A method of detecting the presence of the nucleic acid molecule of claim 1 in a sample, the method compπsing contacting the sample with a nucleic acid probe or pπmer that selectively binds to the nucleic acid molecule of claim 1 and determining whether the nucleic acid probe or pnmer bound to the nucleic acid molecule of claim 1 is present m the sample A method for modulating the activity of the polypeptide of claim 10, the method compnsing contacting a cell sample compnsing the polypeptide of claim 10 with a compound that binds to said polypeptide m an amount sufficient to modulate the activity of the polypeptide A method of treating or preventing an immune response-associated disorder, said method compnsing admimstenng, to a subject, in which such treatment or prevention is desired, an effective amount of a therapeutic selected from the group consisting of (a) the nucleic acid of claim 1 , (b) the polypeptide of claim 10, and (c) the antibody of claim 12, wherein said therapeutic is administered in an amount sufficient to treat said immune response-associated disorder in said subject A pharmaceutical composition compnsing a therapeutically or prophylactically effective amount of a therapeutic selected from the group consisting of (a) the nucleic acid of claim 1 , (b) the polypeptide of claim 10, and (c) the antibody of claim 12, and a pharmaceutically acceptable earner A kit compnsing, in one or more containers, a therapeutically or prophylactically effective amount of the pharmaceutical composition of claim 18 The use of a therapeutic in the manufacture of a medicament for treating a syndrome associated with a human disease, the disease compnsing an immune response- associated disorder, wherein said therapeutic is selected from the group consisting of (a) the nucleic acid of claim 1, (b) the polypeptide of claim 10, and (c) the antibody of claim 12 A method for screening for a modulator of activity or of latency or predisposition to an immune response-associated disorder, the method compnsing (a) admimstenng a test compound to a test animal at increased nsk for an immune response-associated disorder, wherein said test animal recombmantly expresses a BLAA polypeptide, (b) measunng expression of the activity of said polypeptide m said test animal, (c) measuπng the activity of said polypeptide in a control animal that recombmantly expresses said polypeptide and is not at increased πsk for an immune response-associated disorder, and (d) comparing expression of said polypeptide in said test animal and said control animal, wherein a change in the activity of said polypeptide m said test animal relative to said control animal indicates that the test compound is a modulator of activity or latency of or predisposition to an immune response-associated disorder The method of claim 21, wherein said test animal is a recombinant test animal that expresses a test protein transgene or expresses said transgene under the control of a promoter at an increased lev el relative to a wild-type test animal, and wherein said promoter is not the nativ e promoter of said transgene -A method for determining the presence of or predisposition to a disease associated with altered levels of a BLAA polypeptide of claim 10, the method comprising (a) measuπng the amount of the polypeptide in a sample from a mammalian subject, and (b) companng the amount of said polypeptide in step (a) to the amount of the polvpeptide present in a control sample. wherein an alteration in the le el of the polypeptide in step (a) as compared to the control sample indicates a disease condition A method for determining the presence of or predisposition to a disease associated with altered levels of a BLAA nucleic acid of claim 1, the method compnsing (a) measuπng the amount of the nucleic acid in a sample from a mammalian subiect. and (b) compaπng the amount of the nucleic acid in step (a) to the amount of the nucleic acid present in a control sample, wherein an alteration in the level of the nucleic acid in step (a) as compared to the control sample indicates a disease condition A method of treating a pathological state in a mammal, the method compπsing admimstenng to the subject a polypeptide of claim 10, in an amount to alleviate the pathological state A method of treating a pathological state in a mammal, the method compnsing admimstenng to a subiect. the antibody of claim 12 in an amount sufficient to alleviate the pathological state

Inventors: CARULLI JOHN, DE FOUGEROLLES ANTONIN, GREEN CYNTHIA, HESSION CATHERINE, KOTELIANSKI VICTOR, CARULLI, JOHN, DE FOUGEROLLES, ANTONIN, GREEN, CYNTHIA, HESSION, CATHERINE, KOTELIANSKI, VICTOR
Applicants: BIOGEN INC, CARULLI JOHN, CURAGEN CORP, FOUGEROLLES ANTONIN DE, GREEN CYNTHIA, HESSION CATHERINE, KOTELIANSKI VICTOR, BIOGEN, INC., CARULLI, JOHN, CURAGEN CORPORATION, DE FOUGEROLLES, ANTONIN, GREEN, CYNTHIA, HESSION, CATHERINE, KOTELIANSKI, VICTOR
Application year: 2000
Main classification: C12N15
IPC codes: A61K38, C07K14, C12N15