CD38 and plasma cell myeloma: Daratumumab also acts on immune-suppressive cells, such as CD38 + regulatory T cells (Tregs), regulatory B cells (Bregs), and myeloid-derived suppressor cells, leading to the activation of cytotoxic CD8 + T cells and CD4 + helper T cells.[19] Consequently, daratumumab indirectly contributes to the elimination of multiple myeloma cells by modulating the immune response.