BAFF, a novel ligand of the tumor necrosis factor family, stimulates B cell growth

Members of the tumor necrosis factor (TNF) family induce pleiotropic biolog ical responses, including cell growth, differentiation, and even death. Her e we describe a novel member of the TNF family, designated BAFF (for B cell activating factor belonging to the TNF family), which is expressed by T ce lls and dendritic cells. Human BAFF was mapped to chromosome 13q32-34. Memb rane-bound BAFF was processed and secreted through the action of a protease whose specificity matches that of the furin family of proprotein proprotei n convertases. The expression of BAFF receptor appeared to be restricted to B cells. Both membrane-bound and soluble BAFF induced proliferation of ant i-immunoglobulin M-stimulated peripheral blood B lymphocytes. Moreover, inc reased amounts of immunoglobulins were found in supernatants of germinal ce nter-like B cells costimulated with BAFF. These results suggest that BAFF p lays an important role as costimulator of B cell proliferation and function .