Apotosis of mature B cells.

Antigen receptor (BCR) transduces either pro-apoptotic or anti-apoptotic signals of mature B cells depending on the nature of stimuli. Mature B cells also undergo apoptosis by signaling through CD95. Those apoptotic signals through BCR or CD95 are blocked by various transmembrane signaling such as those via CD40, BCR, CD21 and IL-4 receptor, presumably generated by interaction with T helper cells or the components of innate immunity such as complements. Induction of B cell apoptosis and its regulation are likely to play important roles in humoral immunity. Indeed, spontaneous models as well as patients of systemic autoimmune diseases show defects in apoptosis of mature B cells mediated by BCR or CD95.