IFNG and protozoa infectious disease: Other types of immune cells have been reported to produce IFN-γ during protozoal infection (Figure 2); for example, natural killer T (NKT) cells were shown to secrete IFN-γ in the liver of P. yeolii-infected mice [34,35] and a significant proportion of γδ T cells and αβ T cells were reported to produce IFN-γ in the peripheral blood of Plasmodium-infected children [36,37,38].