Effects of ibuprofen and IL-1Ra on the production of IL-6 in MEF cells. A, constitutive secretion of IL-6 was measured in the absence or presence of the IL-1Ra. IL-1Ra was added to the cultures of IL-18Rα ko cells at 10 μg/ml, and after 20 h, levels of IL-6 were measured. In cultures without IL-1Ra (−), the level of IL-6 was set at 100%, and the mean percentage change of parallel cultures with IL-1Ra was calculated. Data are mean ± S.E. percentage change from three independent experiments. ***, p < 0.001 compared with cultures without IL-1Ra. B, constitutive production of IL-6 in WT, IL-18 ko, and IL-18Rα ko MEF cells in the absence and presence of ibuprofen (10 μm) after 20 h of incubation. C, each of the MEF strains were stimulated with IL-1β (1 ng/ml) in the absence or presence of ibuprofen (ibu; 10 μm). After 20 h, levels of IL-6 were measured in the supernatants. Note the break in the IL-18Rα bar. B and C, the data are mean ± S.E. of three independent experiments. *, p < 0.05; **, p < 0.01; ***, p < 0.001 comparing cultures with ibuprofen with those without.