Compositions and methods for treating immune related diseases.

Isolated PRO256 polypeptide having an amino acid sequence identity of at least 97% with respect to: (a) the amino acid sequence shown in FIG. 2 and reproduced below: (b) residues X to 529 of the amino acid sequence shown in claim 1, part (a); (C) residues 1 to Y of the amino acid sequence shown in claim 1, part (a), or (d) X to residue Y of the amino acid sequence shown in claim 1, part (a), wherein said sequence identity is determined using the ALIGN-2 computer program and wherein X is and Y is 36+ -5 465 + -5, and wherein said PRO256 polypeptide has the ability to stimulate T cell proliferation as it determined by testing mixed lymphocyte reaction (MLR) and / or the human Co-Stimulation assay.