STAT1 and parasitic infectious disease: During intracellular parasitic infections such as those caused by Leishmania mexicana, Trypanosoma cruzi, and Toxoplasma gondii, STAT1 leads to cellular Th1 responses through proinflammatory cytokines such as gamma interferon (IFN-γ) and M1 macrophage polarization, which have been associated with resistance to these infections [4,5,6].