TNFRSF13B and plasma cell myeloma: The BAFF signaling pathway overall has a similar structure in NP and RP, with myeloid cells being the primary secretors of the ligand TNFSF13B, and the memory and naive B-cells populations being the primary receivers through receptors TNFRSF13B and TNFRSF13C. Elevated serum levels of TNFSF13B have been noted previously in MM patients30, and BAFF signaling can have pro-proliferative effects on myeloma cell lines31,32.