CD79 is a disulfide-linked heterodimer composed of an alpha chain (CD79a) and a beta chain (CD79b) that associates non-covalently with membrane immunoglobulin to form the B cell receptor (BCR) complex. Its expression is restricted to B lymphocytes first appearing on the surface at the pro-B cell stage and remaining through all stages of B cell differentiation prior to plasma cells. Crosslinking of the BCR leads to B cell activation. The monoclonal antibody CB3-1 reacts with the beta chain of CD79.