Signal transduction pathway for type I IFNs and a summary of key ISG effects on the virus and mucosal immune response during influenza. Type II IFN (IFN-γ) binds IFNGR1 and IFNGR2 heterodimer receptor on the cell surface, which leads to activation of JAK1 and JAK2, STAT dimerization, and phosphorylation with transcriptional activation of ISGs with the GAS element. Type III IFNs (IFN-λ1, -λ2, and -λ3) signal via ligand binding to IFNLR1 and IL-10R2 subunits of the cell surface receptor, activation of JAK1 and Tyk2 with similar downstream signaling pathways as the type I IFNs. ISGs can be either discrete or common sets for the different IFN families. Biological properties of type I, type II, and type III IFNs as identified in T and B cells [33–39] do not represent an exhaustive list.
