During the acute phase, CD8 T cells primarily via the production of IFN-γ and possibly TNF-α and cytotoxicity-associated molecules such as perforin and granzyme B inhibit parasite replication and cause conversion of the parasite from tachyzoite stage to bradyzoite stage. IFN-γ elicits the production of NO, ROS and IDO and activates p47GTPases that augment parasite clearance. During the chronic phase, CD8-produced IFN-γ and possibly TNF-α is vital for maintaining the parasites in the encysted stage.
IDO: Indoleamine 2,3-deoxygenase; iNOS: Inducible nitric oxide synthetase; ROS: Reactive oxygen species.