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