Intracellular IFN-γ detection in CSA-exposed NK cells. NK cells were cultured with IL-2 (100 U/mL) and IL-15 (10 ng/mL) with and without CSA for 7 days and then IFN-γ production in NK cells was induced by culturing cells in IL-12 (10 ng/mL) and IL-18 (100 ng/mL) for 18 hours. Brefeldin A (10 μg/mL final concentration) was added for the last 4 hours. Samples were stained with CD56 first, permeabilized, and stained with IFN-γ. (A) Cells from a representative donor. (B) The percentage of IFN-γ–expressing cells from 8 consecutive donors. Black bars represent the mean. Statistics were calculated using the Wilcoxon signed rank test.