Figure 6. Curcumin suppresses NKG2D-mediated NKL cell line cytotoxicity. (A) NKL cells were cultured with C1R cells and C1R-MICA*004 transfectants at the indicated effector:target (E:T) ratios for 4 h. Cytotoxicity was assayed by flow cytometry after PKH67/7AAD staining. For blocking assays, NKL cells were incubated beforehand with anti-NKG2D blocking monoclonal antibody (10 μg/ml) for 30 min. Data are shown as means ± SD of two independent experiments in triplicate. (B) NKL cells were incubated in the absence or presence of curcumin (4 µM for 24 h) and cytolytic activity against C1R and C1R-MICA*004 cells was assessed at the indicated effector: target (E:T) ratios. The upper figure shows a representative experiment and the lower histogram represents means ± SD of three independent experiments performed in triplicate. *p < 0.05 comparison between untreated and curcumin- or anti-NKG2D-treated NKL cells against C1R-MICA*004 transfectants. ^#p < 0.05 C1R-MICA*004 compared with C1R cells.