Immunomodulatory effects of Treg and Th17 cells in parasitic infections and hygiene hypothesis

Abstract

The parasitic infection is still a severe public health problem in developing countries, which threatens people's health and social development. With the advances of molecular biology and immunology, more and more insights have been reached on the immunity and immunopathogenesis to parasitic infections. CD4+ T cells play a central role in the host's immunosurveillance and immunoregulation. Traditionally, naive CD4+ T cells are considered to be able to differentiate into Th1 and Th2 cell subsets both in vivo and in vitro. These Th1 and Th2 cells secret diverse cytokine profiles to exert different functions. Later, two new subsets of CD4+ T cells, Th17 and Treg cells, have been discovered. They are completely different from traditional Th1 and Th2 cells with independent differentiation and regulation mechanism. Ample studies suggest that Treg and Th17 cells play a key role in a variety of parasitic diseases. Furthermore, Treg and Th17 cells have been got increasing attention for their involvement in the hygiene hypothesis. Based on the current advances of researches of Treg and Th17 cells, we make a brief review about immunomodulatory effects of these two subsets in parasitic infections as well as the hygiene hypothesis.