Figure 2.

Rapid IFN-γ production in response to T. gondii requires IL-12 and IL-18. (a) Percent of IFN-γ⁺ cells amongst total viable CD3^–NKp46⁺ cells in the spleen 24 h after B6 mice were injected i.v. with 10⁷ T. gondii ME49 tachyzoites. Some mice received an i.p. injection of 200 µg mAb against IL-18 and/or IL-12 immediately after injection of T. gondii. (b) Serum concentrations of IL-18, IL-12p70 and IFN-γ at various time points after B6 mice were injected i.v. with 10⁷ T. gondii ME49 tachyzoites. (c) Percent of IFN-γ⁺ cells amongst total viable CD3^–NKp46⁺ cells in the spleen 24 h after B6 or Il18^−/− mice were injected i.v. with 10⁷ T. gondii ME49 tachyzoites. Some mice received an i.p. injection of 200 µg mAb against IL-12 immediately after injection of T. gondii. (d) Serum concentrations of IL-18 24 h after B6 or Il18^−/− mice were injected i.v. with 10⁷ T. gondii ME49 tachyzoites. Some mice received an i.p. injection of 200 µg mAb against IL-12 immediately after injection of T. gondii. (e) Serum concentrations of IFN-γ 24 h after B6 or Il18^−/− mice were injected i.v. with 10⁷ T. gondii ME49 tachyzoites. Some mice received an i.p. injection of 200 µg mAb against IL-18 and/or IL-12 immediately after injection of T. gondii. (f) Serum concentrations of IL-12 24 h after B6 or Il18^−/− mice were injected i.v. with 10⁷ T. gondii ME49 tachyzoites. Some mice received an i.p. injection of 200 µg mAb against IL-18 and/or IL-12 immediately after injection of T. gondii. Results are presented as individual data points (a,c,d,e,f) or as means ± SEM (b) of 4–15 mice per group from at least two pooled independent experiments. Statistical analyses: One-way ANOVA followed by Dunnett’s multiple comparison test. Significant differences are indicated by asterisks: *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001.