Leukocyte antigen CD37 (CD37) is also known as Tetraspanin-26 (Tspan-26) and TSPAN26,which is a member of the transmembrane 4 superfamily or tetraspanin family. Most of these members are cell-surface proteins that are characterized by the presence of four hydrophobic domains. The proteins encoded by CD37 gene mediate signal transduction events that play a role in the regulation of cell development, activation, growth and motility. CD37 is a cell surface glycoprotein that is known to complex with integrins and other transmembrane 4 superfamily proteins. CD37 may play a role in T-cell-B-cell interactions.