Pretreatment with the IL-15/IL-15Rα complex restores iNKT cell responses in IL-15Rα^−/− mice. Analysis of iNKT cells producing IFN-γ after α-GalCer administration in IL-15Rα^−/− mice pretreated with or without the IL-15/IL-15Rα complex. (A) Representative histogram overlaying the percentage of hepatic iNKT cells producing IFN-γ from treated and untreated IL-15Rα^−/− mice. (B) Average percentage of iNKT cells in the liver and spleen expressing IFN-γ in response to α-GalCer in mice either pretreated or untreated with the IL-15/IL-15Rα complex. (C-D) Effect of IL-15 signaling on T-bet expression in IL-15Rα-deficient mice. The IL-15/IL-15Rα complex was injected into IL-15Rα^−/− mice; and one day later, T-bet expression in iNKT cells was analyzed by flow cytometry. (C) Representative histogram showing an overlay of the level of T-bet expressed in CD1d tetramer⁺ CD44^HighNK1.1⁺ cells isolated from liver of treated and untreated IL-15Rα^−/− mice. (D) Combined data are the average MFI of T-bet in CD44^HighNK1.1⁺ iNKT cells from the liver of IL-15/IL-15Rα complex-treated or untreated mice. (B,D) Data are generated from 2 independent experiments; n = 4 mice. Error bars represent SEM. *P < .05.