CD38 and plasma cell myeloma: We recently reported results in a small patient population treated with monotherapy, which demonstrated the immunomodulatory effects of daratumumab: (1) expansion of cytotoxic T cells; (2) reduction of immune suppressive cells, including CD38+ myeloid-derived suppressor cells, regulatory B cells, and a subpopulation of regulatory Tregs (CD4+CD25+CD127dim), to promote T-cell activity against myeloma cells; and (3) increase in T-cell repertoire clonality, reduction of NK cells, and downregulation of CD38 on target cells [11, 30].