IL21 and inflammatory response: While parasite burdens were comparable between wild-type mice and mice lacking a functional IL-21/IL-21R signaling axis (Il21r−/−), the lack of a functional IL-21/IL-21R signaling pathway in Il21r−/− mice infected with S. mansoni led to diminished TH2-dependent immunopathology in those mice, as evidenced by attenuated formation of granulomatous inflammation and liver fibrosis (Pesce et al., 2006).