(A) PBMCs from healthy donors were stimulated with IL-12, IL-15, and IL-18 for 24 hours, and the frequency of CD38+ iNKT cells was measured by flow cytometry (n = 10, paired t test). (B) Frequency of CD38+ iNKT cells after stimulation of PBMCs from healthy donors (n = 15) with IL-12, IL-15, and IL-18 or a combination of all 3 for 24 hours (1-way ANOVA, **P < 0.01). (C) CD1d mean fluorescence intensity (MFI) of various PBMC subsets was analyzed by flow cytometry. A representative experiment from 5 healthy donors is shown. (D and E) Healthy donor PBMCs were stimulated for 24 hours with 100 U/ml IFN-α2 or 1000 U/ml IFN-λ3 or were left untreated, followed by analysis of CD1d MFI of monocytes. Groups were compared by paired t test.