Inhibitory effect of 15d-PGJ₂ on IFN-γ production in NK92 cells. (A-B) Inhibition of IL-2-induced IFN-γ production by 15d-PGJ₂ but not ciglitazone in NK92 cells. NK92 cells were pretreated with either 15d-PGJ₂ (2 μM) or ciglitazone (2 μM) or drug vehicle for 30 minutes and then further incubated with IL-2 (200 U/mL) for 3 hours (A) or 6 hours (B). Supernatant was collected at each time point or treatment for measurement of IFN-γ by ELISA. Data represent the average from 3 different experiments (mean ± SE). Statistically significant changes compared with control samples are indicated with an asterisk (P < .05). (C) Effect of 15d-PGJ₂ on IL-2-induced IFN-γ mRNA in NK92 cells. NK92 cells were pretreated with different doses of 15d-PGJ₂ for 1 hour and then with IL-2 (200 U/mL) for an additional 2 hours. Total RNA was extracted and subjected to RPA analysis as described in “Materials and methods.” The IFN-γ mRNA levels were presented as arbitrary units that were derived from average normalization densitometry values of each IFN-γ band by corresponding GAPDH band.