HLA-E expression in BMMCs from patients with MM. BMMCs were isolated from the BM of 6 patients with active MM who were treatment naïve. (A) Representative gating strategy for BM cell populations from patient 4. (B) Representative dot plot showing CD38 and CD138 subpopulations (left), and overlay histograms of HLA-E staining using mAb 3D12 (PE-conjugated, middle) and mAb 4D7 (APC-conjugated, right) in CD38^–CD138^– (gray), CD38⁺CD138^– (red), and CD38⁺CD138⁺ (blue) subpopulations. (C-D) Box plots summarizing HLA-E staining GMFI across the subpopulations for all 6 patients with MM using 3D12 (C) and 4D7 (D) antibodies. Cells (5 × 10⁵) were stained with BV780-conjugated anti-CD38 and fluorescein isothiocyanate-conjugated anti-CD138 antibodies (5 μg/mL each). Data were acquired using a CytoFLEX flow cytometer and analyzed with Kaluza software. FSC-A, forward scatter area; GMFI, geometric mean fluorescence intensity; ns, not significant; PE, fluorescent dye R-phycoerythrin; SSC-A, side scatter area.