The protein encoded by this gene is a member of the transmembrane 4 superfamily, also known as the tetraspanin family.;Most of these members are cell-surface proteins that are characterized by the presence of four hydrophobic domains.;The proteins mediate signal transduction events that play a role in the regulation of cell development, activation,;growth and motility. This encoded protein is a cell surface glycoprotein that is known to complex with integrins. It;contributes to the transduction of CD2-generated signals in T cells and natural killer cells and has been suggested to;play a role in growth regulation. Familial deficiency of this gene has been linked to an immunodeficiency associated;with recurrent infectious diseases caused by bacteria, fungi and viruses. Alternative splicing results in multiple;transcript variants encoding the same protein.