NK cell production of type 1 cytokines IFN-γ and TNF-β.

(A) IFN-γ protein was measured by ELISA in cell culture supernatants of freshly isolated CD56^bright and CD56^dim NK cells after culture with monokines or PMA plus ionomycin for 72 hours. CD56^bright NK cells produced significantly more IFN-γ in response to all positive stimuli; data represent the mean ± SEM of 5 to 10 donors (*P < .004; **P < .03). IL-12 or IL-15 alone induced minimal IFN-γ (less than 2 ng/mL) whereas no IFN-γ was detected in cultures with IL-18, IL-1β, PMA, or ionomycin alone (data not shown; sensitivity < 25 pg/mL). (B) CD56^bright NK cells also produced significantly more TNF-β protein after activation with monokines or PMA plus ionomycin (n = 3-5 donors per condition; **P < .03; ***P < .05). There was no detectable TNF-β protein with IL-12, IL-1β, IL-18, PMA, or ionomycin alone (data not shown; sensitivity less than 20 pg/mL). ■ indicates CD56^dim; ▪, CD56^bright.