IFN-γ production by NK cells from NOD/SCID mice. (A) FACS sorter-purified CD56⁺ NK cells from BM of growth factor (GF)–treated NOD/SCID mice (I: n = 3), NK cells generated in vitro within 4 weeks from BM of GF-treated (II: n = 3) and untreated control (III: n = 5) NOD/SCID mice, and purified NK cells isolated from human PB mononuclear cells (IV: n = 2) were stimulated with medium containing IL-2 (□) or IL-12 and IL-18 (▪) for 36 hours. Synthesis of IFN-γ was measured by intracellular FACS analysis, and the mean ± SEM percentages of IFN-γ⁺ NK cells are shown. (B) Representative FACS pictures of IFN-γ–producing NK cells generated in cultures II, III, and IV are shown. Numbers represent the percentages of total cells in culture.