miR-155 and BIC RNA expression in resting and IL-12 and/or IL-18–stimulated NK cells and NK subsets. CD56⁺ human NK cells were left unstimulated or stimulated with IL-12 (10 ng/mL), IL-18 (100 ng/mL) or combination of both for 18 hours after which pellets were collected and used to prepare RNA. miR-155 (A) and BIC (B) RNA expression were quantified by real-time RT-PCR. (C) Supernatants were analyzed for IFN-γ production by ELISA. (D) CD56^bright and CD56^dim NK cells were quantified for miR-155 expression by real-time RT-PCR. This experiment is representative of at least 4 such experiments performed with similar results.