Studies (Xiao et al., 2008) show that both B cells and T cells formed aggregates in the synovium of inflamed joints and mediated the pathogenesis of RA, and B-cell-activating factor (BAFF, also named TNFSF13B, BLys) played a vital role in B-cell survival and maturation. Here, TNFSF13B is linked to rheumatoid arthritis.