[Dynamics of CD4⁺ T cell subsets and their roles in schistosome infections: a review]

Schistosomiasis is a chronic helminthic disease that affects about two hundred millions of people in the world. The pathogenesis of schistosome infection is primarily due to hepatic and intestinal granuloma formation around deposited eggs and subsequent fibrosis. It is known that CD4⁺ T cell subsets play critical roles in the host immunity and immunopathogenesis to schistosome infections, in which T helper 1 (Th1) and Th2 cells are major effector T cell subsets, whereas T regulatory (Treg) cells exert immunosuppressive roles in general. The recently discovered Th17 cells are also actively involved in the immune responses to the infection. During the infection, these T cell subsets cross-talk and exhibit different kinetics and roles in the control and regulation of infection progress and fibrosis. This review summarizes current findings of Th1, Th2, Th17 and Treg cells and their effector cytokines in schistosome infection.