B-lymphocyte stimulator (BLyS, CD257, also known as B-cell activating factor (BAFF)) (Schneider et al, 1999) and A proliferation-inducing ligand (APRIL, CD256) stimulate the growth of primary myeloma cells (Moreaux et al, 2004; Novak et al, 2004). Here, TNFSF13B is linked to plasma cell myeloma.