Tumor necrosis factor receptor superfamily member 17 (TNFRSF17), also known as B-cell maturation antigen (BCMA), is a single-pass type III membrane protein. It is the receptor for TNFSF13B/BLyS/BAFF and TNFSF13/APRIL, promoting B-cell survival and playing a role in the regulation of humoral immunity. Additionally, BCMA activates NF-kappa-B and JNK signaling pathways. Its expression has been detected in immune organs and mature B cell lines, but not in T-cells or monocytes. Although some cell surface expression has been observed, BCMA appears to be primarily localized to the Golgi compartment. Its interaction with APRIL or BAFF has been shown to stimulate IgM production in peripheral blood B cells and enhance the survival of cultured B cells. The identification of BCMA as an NF-kappaB-activating receptor for TALL-1 provides potential targets for drug development against certain immunodeficient or autoimmune diseases. Furthermore, it represents a target of donor B-cell immunity in myeloma patients who respond to donor lymphocyte infusion (DLI). Antibody responses to cell-surface BCMA may directly contribute to tumor rejection in vivo.