Immunosuppressive cells express CD38 and are sensitive to daratumumab. G-MDSCs (CD11b⁺CD14^–HLA^–DR^–CD15⁺CD33⁺) were generated from 6-day cocultures with healthy donor PBMCs and myeloma cell lines as previously described. G-MDSCs were sorted and evaluated for CD38 expression (red represents the isotype control and blue indicates the CD38⁺ staining) and (A) sensitivity to isotype or (B) daratumumab-mediated ADCC/CDC. (C) Bregs express CD38 and, when stimulated, (D) produced IL-10. (E) CD38⁺ Bregs decreased and remained depleted following daratumumab treatment.