Interferons (IFNs) can be devided in three classes, Type I, II and III. Type I IFNs are created when the cell surface or specific receptors recognize microbial products; these are structural homologues of one another which bind the same receptor. Binding to this receptor leads to an activation of kinases which regulate the phosphorylation and therefore activation of some STAT proteins (see PW for details). There is only 1 Type II interferon, INF-gamma, consisting of two subunits (R1 and R2), which associate with Jak 1 and 2, respectively. Activation of Jak1 and Jak2 leads to phosphorylation of STAT1, which ultimately binds to IFN-gamma-activated sequence (GAS) elements, regulating the transcription of genes. Type III interferons are considered a protein family of 4, which bind to a different receptor compared to Type I interferons, however they trigger the same STAT1+2 phosphorylation reactions as TypeI IFNs. aeb e65 d7e aeb d7e type II interferon signaling pathway PW:0000896 Pathway Ontology type I interferon signaling pathway PW:0000895 Pathway Ontology signaling pathway PW:0000003 Pathway Ontology 21372217 PubMed Direct effects of type I interferons on cells of the immune system. Clin Cancer Res 2011 Hervas-Stubbs S Perez-Gracia JL Rouzaut A Sanmamed MF Le Bon A Melero I 15864272 PubMed Mechanisms of type-I- and type-II-interferon-mediated signalling. Nat Rev Immunol 2005 Platanias LC 30936491 PubMed Decoding type I and III interferon signalling during viral infection. Nat Microbiol 2019 Mesev EV LeDesma RA Ploss A