Figure 1: Scheme of immune responses during lethal P. yoelii 17XL and nonlethal P. yoelii 17XL infection: DC: dendritic cell; Th: helper T cell (CD4+ T cells); Tr1, IL-10-producing CD4+ T cells; Treg, regulatory T cells; CTL, cytotoxic T cells (CD8+ T cells). In a lethal P. yoelii 17XL infection, Tr1 are induced. IL-10 inhibits proinflammatory cytokine production for parasite killing, producing high levels of parasitemia and the death of mice. Tr1 are also induced in nonlethal Py 17XNL as well as lethal Py 17XL infection. However, parasite killing occurs during nonlethal Py 17XNL infection. When IL-10 is ineffective (depletion or deficiency of IL-10 or the blockade of IL-10 receptor) in mice infected with nonlethal Py 17XNL or lethal Py 17XL, excessive inflammation is induced in association with the development of hepatic pathology.