Figure 3.

Purified NK cells do not produce IFN-γ in response to fluA. NK cells were isolated from PBMCs by negative selection and incubated under different conditions, followed by intracellular staining for IFN-γ. Displayed in the bar graphs are frequencies of IFN-γ⁺ cells in the CD56^bright perforin^– (left panels) and CD56^dim perforin⁺ (right panels) NK cell subsets. (A) PBMCs or purified NK cells from 3 donors (nos. 1–3) were incubated with fluA for 17 hours. (B) PBMCs or purified NK cells from a fourth donor were incubated with fluA for 17 hours. Purified NK cells were also incubated with recombinant IFN-γ (100 ng/ml) in the presence of fluA, or with recombinant IL-12 (100 ng/ml) and IL-2 (250 U/ml), for 17 hours.