Recently, Foxp3− IL-10-producing Th1 cells (type 1 regulatory; Tr1), rather than thymus-derived FoxP3+ CD4+ regulatory T (Treg) cells, have also been recognized to play important roles in determining the outcome of protozoan parasitic diseases, including malaria, leishmaniasis and toxoplasmosis (26–29). The gene discussed is CD4; the disease is malaria.