IFNG and infectious disease: IFN-gamma(IFN-γ), a cytokine produced by T lymphocytes and NK cells, plays a key factor in host defense response against infectious diseases caused by bacteria, fungi, and protozoa.[39] Known as “macrophage-activating factor,” IFN-γ not only acts as an antiviral factor, but also, recruits macrophages to secrete high-level pro-inflammatory cytokines, hence providing strong protection against intracellular pathogens.[40] The polarization of macrophages regulated by T cells, ILCs, and PSCs is activated to drive fibrosis, in which Th2 cells play a crucial role.