HLA class I and II surface expression on myeloma patient and HV bone marrow cells. Quantification of HLA surface expression was performed using a bead-based flow cytometric assay. (A) HLA class I and (B) HLA-DR expression on CD38⁺CD138⁺ primary myeloma cells compared with autologous CD34⁺CD38⁻ HPCs, CD19⁺CD20⁺ B cells, and CD3⁺ T cells. (C) HLA class I and (D) HLA-DR expression on primary MM cells compared with bone marrow–derived plasma cells of HVs. n.s., not significant; *P < .05; **P < .01; ***P < .001.