MAMMALIAN CELL SURFACE ANTIGENS; RELATED REAGENTS

1 . A substantially pure or recombinant 312C2 protein or conservatively modified variants thereof, said protein:

a) is expressed on activated T cells; or

b) specifically binds to antibodies generated against SEQ ID NO: 2 or 4.

2 . A protein or peptide of claim 1 , selected from the group consisting of:

a) a natural protein from a warm blooded animal selected from the group of birds and mammals, including a rodent or primate;

b) a protein or peptide:

i) comprising at least one polypeptide segment of at least 14 amino acids of SEQ ID NO: 2;

ii) comprising at least one polypeptide segment of at least 14 amino acids of SEQ ID NO: 4; or

iii) which is not glycosylated;

iv) which is in a buffered solution;

v) which is attached to a solid substrate;

vi) which exhibits a plurality of epitopes from SEQ ID NO: 2 or 4;

vii) which is detectably labeled;

viii) which is a synthetic polypeptide;

ix) which is conjugated to a chemical moiety;

x) which is a 5-fold or less substitution from a natural sequence; or

xi) which is a deletion or insertion variant from a natural sequence.

3 . A protein or peptide of claim 1 , comprising a sequence from the extracellular or the intracellular portion of a 312C2.

4 . A fusion protein comprising a peptide of claim 1 .

5 . A sterile composition comprising the protein of claim 1 , and a pharmaceutically acceptable carrier.

6 . An antibody which specifically binds a protein or peptide of claim 1 .

7 . An antibody of claim 6 , wherein:

a) said 312C2 is a mammalian protein, including a mouse or human;

b) said antibody is raised against a purified peptide sequence of SEQ ID NO: 2 or 4;

c) said antibody is a monoclonal antibody;

d) said antibody is detectably labeled;

e) said antibody is attached to a solid substrate;

f) said antibody is in a sterile composition; or

g) said antibody is in a buffered composition.

8 . A method of purifying a 312C2 protein or peptide from other materials in a mixture comprising contacting said mixture to an antibody of claim 6 , and separating bound 312C2 from other materials.

9 . An isolated or recombinant nucleic acid capable of encoding a protein or peptide of claim 1 .

10 . A nucleic acid of claim 9 , wherein said nucleic acid:

a) encodes a sequence of SEQ ID NO: 2 or 4;

b) comprises a sequence of SEQ ID NO: 1 or 3; or

c) encodes a sequence from an extracellular domain of a natural 312C2;

d) encodes a sequence from an intracellular domain of a natural 312C2;

e) attached to a solid substrate;

f) is detectable labeled; or

g) is in a sterile composition.

11 . An expression or replicating vector of claim 9 .

12 . A kit comprising:

a) a substantially pure 312C2 or fragment of claim 1 ;

b) an antibody or receptor which specifically binds a 312C2; or

c) a nucleic acid encoding a 312C2 or peptide.

13 . A method for detecting in a sample the presence of a 312C2 nucleic acid, protein, or antibody, comprising testing said sample with a kit of claim 12 .

14 . A method of modulating the physiology of a cell comprising contacting said cell with:

a) a substantially pure 312C2 or fragment of claim 1 ;

b) an antibody or binding partner which specifically binds a 312C2; or

c) a nucleic acid encoding a 312C2 or peptide.

15 . The method of claim 14 , wherein said cell is a T cell and said modulating of physiology is:

a) apoptosis of said T cell; or

b) activation of said T cell

16 . A method of claim 14 , wherein said cell is in a tissue and/or in an organism.

17 . A method of expressing a 312C2 comprising expressing a nucleic acid of claim 9 .

18 . A cell, tissue, organ, or organism comprising a nucleic acid of claim 9 .

19 . A recombinant nucleic acid comprising sequence at least about 70% identity over a stretch of at least about 30 nucleotides to a 312C2 nucleic acid sequence of SEQ ID NO: 1 or 3.

20 . A nucleic acid of claim 19 , further encoding a polypeptide comprising at least about 60% identity over a stretch of at least about 20 amino acids to a 312C2 sequence of SEQ ID NO: 2 or 4.

21 . A method of treating a host mammal having an abnormal immune response by administering to said mammal an effective dose of:

a) an antibody or binding partner which binds specifically to a 312C2;

b) a substantially pure 312C2 protein or peptide thereof; or

c) a nucleic acid encoding a 312C2 peptide.

22 . The method of claim 21 , wherein said abnormal immune response is characterized by:

a) a T-cell immune deficiency;

b) chronic inflammation; or

c) tissue rejection.