Higher priming concentration of IL-12 induced higher miR-132, -212, and -200a levels and more efficient suppression of IFN-γ production in subsequent IL-12 challenge. (A) NK cells were primed with 0, 0.1, 1, or 10 ng/mL IL-12 (1′ IL-12) continuously for 24 hours in the presence of IL-2, washed twice with PBS, and challenged with 0, 0.1, 1, or 10 ng/mL of IL-12 (2′ IL-12) for another 8 hours in the presence of IL-2. The expression of IFN-γ was measured by flow cytometry. (B) NK cells were primed with 0, 0.1, 1, or 10 ng/mL IL-12 (1′ IL-12) continuously for 24 hours in the presence of IL-2, washed twice with PBS, and challenged with 10 ng/mL of IL-12 (2′ IL-12) for another 8 hours in the presence of IL-2. The IFN-γ levels in the medium were quantified by ELISA. (C) NK cells were treated as in panel B, qRT-PCR analysis of total small RNA for miR-132, miR-212 and miR-200a expression analysis in total small RNA. The results are mean ± SEM of representative experiment with NK cells from 3 different donors. *P < .05, **P < .01 versus IL-12–unprimed cells.