The study investigates the effects of overexpressing BAFF, a new member of the TNF family, in transgenic mice. BAFF binds to B cells and promotes their growth. Mice transgenic for BAFF exhibit increased numbers of mature B and effector T cells, and develop autoimmune-like manifestations, including high levels of rheumatoid factors, circulating immune complexes, anti-DNA autoantibodies, and Ig deposition in the kidneys. These findings suggest that dysregulation of BAFF expression may play a critical role in the development of autoimmune diseases. The study also examines the cellular and molecular mechanisms underlying these autoimmune manifestations, including the expansion of B cell compartments, altered lymphoid organ architecture, and the presence of autoantibodies. The results provide insights into the etiology of autoimmune disorders and potential therapeutic strategies.The study investigates the effects of overexpressing BAFF, a new member of the TNF family, in transgenic mice. BAFF binds to B cells and promotes their growth. Mice transgenic for BAFF exhibit increased numbers of mature B and effector T cells, and develop autoimmune-like manifestations, including high levels of rheumatoid factors, circulating immune complexes, anti-DNA autoantibodies, and Ig deposition in the kidneys. These findings suggest that dysregulation of BAFF expression may play a critical role in the development of autoimmune diseases. The study also examines the cellular and molecular mechanisms underlying these autoimmune manifestations, including the expansion of B cell compartments, altered lymphoid organ architecture, and the presence of autoantibodies. The results provide insights into the etiology of autoimmune disorders and potential therapeutic strategies.