B-cell maturation protein, which binds the tumor necrosis factor family members BAFF and APRIL, is dispensable for humoral immune responses

B cell maturation protein (BCMA) is a member of the tumor necrosis factor ( TNF) receptor family and is expressed in B lymphocytes. BCMA binds two TNF family members, BAFF and APRIL, that stimulate cellular proliferation. RAFF in particular has been shown to influence B-cell survival and activation, and transgenic mice overexpressing BAFF have a lupus like autoimmune disord er. We have inactivated BCMA in the mouse germ line. BCMA(-/-) mice have no rmal B-cell development, and the life span of mutant B lymphocytes is compa rable to that of wild-type B cells. The humoral immune responses of BCMA(-/ -) mice to T-cell-independent antigens as well as high and low doses of T-c ell-dependent antigens are also intact. In addition, mutant mice have norma l splenic architecture, and germinal centers are formed during an ongoing i mmune response. These data suggest a functional redundancy of BCMA in B-cel l physiology that is probably due to the presence of TACI, another TNF rece ptor family member that is expressed on B cells and that can also bind BAFF and APRIL.