This gene encodes a type I membrane glycoprotein containing two extracellular immunoglobulin domains; a transmembrane and a cytoplasmic domain. This gene is expressed by various cell types; including B cells; a subset of T cells; thymocytes; endothelial cells; and neurons. The encoded protein plays an important role in immunosuppression and regulation of anti-tumor activity. Alternative splicing results in multiple transcript variants encoding different isoforms.