Patient characteristics. (A) Patients were classified according to Durie and Salmon's staging system. (B) Malignant PCs obtained from BM samples of MM patients were selected by gating on CD38⁺CD138⁺ cells and an example is shown (P2). (C) NKG2D and DNAM-1 ligand expression was evaluated on malignant PCs from BM sample by gating on the CD38⁺CD138⁺ population. The mean fluorescence intensity (MFI) of each specific ligand subtracted from the MFI of isotype control antibody is reported.