IFNG and infection: Our ex vivo model by no means solves the question of what prompts a cyst to reactivate; however, in the context of TE (absence of IFNγ) and during initial infection, the developmental pathway uncovered by this ex vivo model suggests that the parasite is pre-programmed to undertake two important functions: (i) amplify parasite burden to maximize dissemination and (ii) seed tissues with cysts that will continue transmission (see the model in Fig. 8).