Figure 3.

Activation of NK cells in IL-15^−/− mice strictly depends on IL-12. C57BL/6 WT, IL-15^−/− or IL-18^−/− mice were injected i.v. with 1×10⁷ L. infantum promastigote parasites or PBS. (A) Intracellular IL-12 p40/p70 expression in splenic mDC (CD11b^intCD11c^hi cells) taken from WT and IL-15^−/− mice at 12 or 24 h after infection and cultured in vitro for 4 h in medium. Three independent experiments with two to three mice per group. Each diamond represents a single mouse; the mean is given as horizontal line. (B) Intracellular IFN-γ protein expression in NK cells taken from WT, IL-15^−/− or IL-18^−/− mice 12 h after infection and co-cultured for 4 h in vitro with YAC-1 cells; 30 min before injection of parasites or PBS IL-12 p40-neutralizing mAb or rat IgG control Ab were applied i.p. Mean±SEM of two independent experiments with two mice per group. Significant differences by Mann–Whitney test between anti-IL-12p40 and control IgG treatment are indicated as ^*p<0.05; between WT and IL-15^−/− or IL-18^−/− NK cells as ^♯p<0.05.