Skip to main content
. Author manuscript; available in PMC: 2012 Oct 1.
Published in final edited form as: Curr Opin Immunol. 2011 Sep 15;23(5):573–582. doi: 10.1016/j.coi.2011.08.009

Figure 1. Signaling pathways involved in the induction and action of interferon.

Figure 1

(left) Nucleic acid sensors that respond to viral infection detect viral nucleic acids as foreign, thereby leading to the production and action of IFN. Sensors include the RIG-I and MDA5 cytosolic helicases and their mitochondrial membrane-associated adaptor IPS-1; the Toll-like receptor TLR3 that acts through the TRIF adaptor; TLRs 7, 8 and 9 that act through the MyD88 adaptor; and, RNA polymerase III that acts through IPS-1. RIG-I, MDA5 and TLR3 sense dsRNA, and pol III senses cytosolic dsDNA to produce dsRNA. TLRs 7 and 8 sense ssRNA, and TLR9 CpG-rich DNA. These nucleic acid sensors trigger antiviral innate immunity through activation of factors that lead to transcriptional activation of IFN production. (right) Signaling by types I, II and III interferons through the canonical JAK-STAT pathway is illustrated, leading to the transcriptional activation of IFN-stimulated genes. Among the IFN-induced gene products are ADAR1 and PKR, both of which bind dsRNA and possess enzymatic activity, one (PKR) regulated by dsRNA and the other (ADAR1) utilizing dsRNA as a substrate. Adapted from Samuel [26].