IL-4Rα Expression by Bone Marrow-Derived Cells Is Necessary and Sufficient for Host Protection against Acute Schistosomiasis

IL 4 receptor α (IL-4Rα) expression by non-bone marrow (BM)-derived cells is required to protect hosts against several parasitic helminth species. In contrast, we demonstrate that IL-4Rα expression by BM-derived cells is both necessary and sufficient to prevent Schistosoma mansoni-infected mice from developing severe inflammation directed against parasite ova, whereas IL-4Rα expression by non-BM-derived cells is neither necessary nor sufficient. Chimeras that express IL-4Rα only on non-BM-derived cells still produce Th2 cytokines, but overproduce IL-12p40, TNF, and IFN-γ, fail to generate alternatively activated macrophages, and develop endotoxemia and severe hepatic and intestinal pathology. In contrast, chimeras that express IL-4Rα only on BM-derived cells have extended survival, even though the granulomas that they develop around parasite eggs are small and devoid of collagen. These observations identify distinct roles for IL-4/IL-13 responsive cell lineages during schistosomiasis: IL-4Rα-mediated signaling in non-BM-derived cells regulates granuloma size and fibrosis, whereas signaling in BM-derived cells suppresses parasite egg-driven inflammation within the liver and intestine.