IRF7 and infection: Most of the well-studied ISGs—such as Protein Kinase R (PKR), 2’-5’-Oligoadenylate Synthetase 1 (OAS1), IRF7, and RNAseL—require activation by infection-dependent signals, whereas select other ISGs—such as IRF1—are synthesized in a constitutively active form [10,277,278,279].