CD257/BAFF

CD257, known as BAFF (B cell activating factor) or TNFSF13B, is a TNF family cytokine that exists as a membrane-bound and a soluble proteolytically cleaved form. It assembles into homotrimers and, unusually for the family, can also form virus-like 60-mer assemblies that enhance receptor clustering. BAFF binds three receptors, BAFF-R, TACI, and BCMA, and selectively promotes the maturation, survival, and antibody production of B cells. Excess BAFF allows autoreactive B cells to escape tolerance checkpoints, and elevated levels are associated with systemic lupus erythematosus, Sjogren's syndrome, and other autoimmune conditions; belimumab, an anti-BAFF antibody, is approved for lupus treatment. Recombinant CD257/BAFF is widely used in B cell culture and receptor-binding assays.