BCL-2 is the founding member of the Bcl-2 family of regulator proteins that regulate cell death (apoptosis), by either inhibiting (anti-apoptotic) or inducing (proapoptotic) apoptosis. It is involved in both immunoglobulin synthesis (mutations result in CVID), lymphocyte development and the establishment of central and peripheral tolerance. BCL-2 deficiency in mice leads: accelerated lymphoid cell death in thymus and spleen, polycystic kidney, hair hypopigmentation, and distorted small intestine and postnatal growth retardation. Here, BCL2 is linked to polycystic kidney disease.