Role of NKG2D in antileukemia activity of HLA-matched CD56⁺ cells. (A) CFU-GM colony inhibition assay of CD34⁺ CML cells from patient 2 by IL-2⁺IL-15–stimulated HLA-matched CD56⁺ cells in the presence or absence of anti-NKG2D mAb. IL-2⁺IL-15–stimulated HLA-matched PBLs served as a control. (B) CFU-GM colony inhibition assay of CD34⁺ CML cells from patient 14 by IL-2–stimulated HLA-matched CD56⁺ cells in the presence or absence of anti-NKG2D mAb. IL-2–stimulated HLA-matched CD56^- cells and HLA-mismatched CD56⁺ cells were used as negative or positive controls, respectively. Error bars indicate plus or minus SD.