IFITM3 and viral load: As an IFN-stimulated gene, the main function of IFITM3 is to inhibit viral infections, which is well supported by the wide range of viruses under IFITM3 restriction, vulnerability of IFITM3 KO mice to lethality with influenza virus infection, as well as the association of IFITM3 polymorphisms in humans with higher susceptibility to viral diseases (37, 52, 53, 54, 55).