Innate immunity to Toxoplasma gondii infection

Toxoplasma gondii is a protozoan parasite of global importance. In the laboratory setting, T gondii is frequently used as a model pathogen to study mechanisms of T helper 1 (T(H)1) cell-mediated immunity to intracellular infections. However, recent discoveries have shown that innate type 1 immune responses that involve interferon-gamma (IFN gamma)-producing natural killer (NK) cells and neutrophils, rather than IFN gamma-producing T cells, predetermine host resistance to T gondii. This Review summarizes the Toll-like receptor (TLR)-dependent mechanisms that are responsible for parasite recognition and for the induction of IFN gamma production by NK cells, as well as the emerging data about the TLR-independent mechanisms that lead to the IFN gamma-mediated elimination of T. gondii.