TNFRSF13B and plasma cell myeloma: Osteoclasts contribute to an immunosuppressive environment by the production of A proliferation-inducing ligand (APRIL), which is the ligand for B cell maturation antigen (BCMA) that is expressed on virtually all myeloma cells, and for transmembrane activator and calcium modulator and cyclophilin ligand interactor (TACI) that is expressed on myeloma cells and Tregs.