Natural regulatory T cells and parasites: a common quest for host homeostasis

This review discusses the roles played by natural CD4(+)CD25(+) regulatory T cells (natural Tregs) during parasitic infections. Natural Tregs may limit the magnitude of effector responses, which may result in failure to adequately control infection. However, natural Tregs also help to limit collateral tissue damage caused by vigorous antimicrobial immune responses. We discuss the hypothesis that parasites have evolved means to manipulate the host's natural Treg population, thereby generating conditions that secure survival in their vertebrate host for an extended period of time.