CD4 and infection: Consequently, in this study we generated CD4+ T cell-specific IL-4Rα−/− (LckcreIL-4Rα−/lox) mice (23) and iLckcreIL-4Rα−/lox mice that lack IL-4Rα on both CD4 and CD8 T cells (33) to determine the temporal role of IL-4 signaling via CD4+ and CD8+ T cells on the progression of VL infection.