IL4R and infection: Collectively, we conclude that it is a Lyz2lo IL-4Rα+ Arg1+ population of F4/80hiCD11bhi macrophages that is critically involved in the suppression of fibrosis in chronic schistosomiasis, while the Lyz2hi IL-4Rα+ population of mature resident macrophages controls the magnitude of the egg-induced inflammatory response at both acute and chronic time points post-infection.