miR-155 expression in IL-18Rα^high and IL-18Rα^low NK cells stimulated by IL-12 plus IL-18. (A) Freshly isolated CD56⁺ human NK cells were stimulated with IL-12 (10 ng/mL), IL-18 (100 ng/mL) or their combination for 48 hours after which cells were analyzed by FACS for expression of IL-18Rα. A nonreactive directly conjugated isotype-identical Ab was used as a control. (B) Percent and MFI of IL-18Rα expression from 6 different donors are summarized. (C) NK cells activated for 24 hours with IL-12 plus IL-18 were FACS sorted for IL18Rα^high and IL18Rα^low expression, and quantified for miR-155 and (D) IFN-γ mRNA expression by real-time RT-PCR. This experiment is representative of at least 4 experiments performed with similar results.