FIGURE 1.

Co-stimulating influence of LPS on NK cell IFN-γ secretion. Human NK cells were stimulated for 18 h with cytokines and LPS. Supernatants were harvested and analyzed for IFN-γ by ELISA. Data are mean ± SD of triplicate wells in one representative individual experiment. *P < 0.05, ***P < 0.001, comparisons were shown between cells, stimulated by a cytokine with LPS, and cells, stimulated by the cytokine alone. (A) NK cells were incubated in the presence or absence of IL-2 (500 U/ml) or IL-12 (10 ng/ml) and LPS (5 μg/ml). Combination of IL-2 and IL-12 was used as a positive control. (B) NK cells were stimulated with IL-2 (500 U/ml) and different doses of LPS. Results of one experiment are shown from the group of experiments demonstrating an increase of IFN-γ secretion under LPS action (12 different donors). Other experiments showed similar effects but differed in IFN-γ level.