Interleukin 10 production by CD4 T cells may help to control immunopathology and limit symptoms of infection (10), as suggested by murine models of malaria and other parasitic infections such as Leishmania and toxoplasmosis, where IL10 production from T helper cell (Th1) IFNγ-producing CD4 T cells is essential for dampening inflammatory responses, preventing disease (5, 11, 12), and protecting from IFNγ-dependent, TNFα-mediated pathology (13). This evidence concerns the gene IL10 and toxoplasmosis.