Cumulative and daily IFN-γ production and survival of purified CD3⁻CD56⁺ human NK cells. (A) Cumulative NK cell IFN-γ production in the presence of 15 ng/mL IL-15 alone (•) or IL-15 and 3 ng/mL IL-12 (▪). (B) Cumulative NK cell IFN-γ production in the presence of 15 ng/mL IL-2 alone (•) or IL-2 and IL-12 (▪). (C) NK cell daily IFN-γ production in the presence of 15 ng/mL IL-15 alone (•) or IL-15 and 3 ng/mL IL-12 (▪). (D) NK cell daily IFN-γ production in the presence of 15 ng/mL IL-2 alone (•) or IL-2 and IL-12 (▪). (E) Enumeration of viable NK cells as determined by vital dye exclusion assay in the presence of IL-15 alone (•), or IL-15 and IL-12 (▪). (F ) Enumeration of viable NK cells in the presence of IL-2 alone (•), or IL-2 and IL-12 (▪). Results represent the mean cell count for duplicate wells, with <15% standard deviation. Four independent experiments showed similar results. Results were generally more pronounced in the CD3⁻CD56^{bright +} subset of NK cells.