This gene is a member of the immunoglobulin superfamily and encodes a protein which transmits an inhibitory signal to T cells. The protein contains a V domain，a transmembrane domain，and a cytoplasmic tail. Alternate transcriptional splice variants，encoding different isoforms，have been characterized. The membrane-bound isoform functions as a homodimer interconnected by a disulfide bond，while the soluble isoform functions as a monomer. Mutations in this gene have been associated with insulin-dependent diabetes mellitus，Graves disease，Hashimoto thyroiditis，celiac disease，systemic lupus erythematosus，thyroid-associated orbitopathy，and other autoimmune diseases. [provided by RefSeq，Jul 2008]