Type I and Type III interferon signaling pathway (IFN-I and IFN-III pathway (non-standard; no widely accepted abbreviation specifically for the combined pathway))

The Type I and Type III interferon signaling pathways mediate the cellular response to interferons—cytokines rapidly produced in response to viral and other microbial infections. Type I interferons (notably IFN-α and IFN-β) act through the ubiquitously expressed Type I interferon receptor (IFNAR1/IFNAR2), whereas Type III interferons (primarily IFN-λ) signal via a receptor (IFNLR1/IL10R2) mainly found on epithelial cells. Both receptor types activate the JAK-STAT pathway, leading to the formation of the ISGF3 transcriptional complex and subsequent induction of hundreds of interferon-stimulated genes (ISGs) that restrict viral replication, modulate cell proliferation, and shape immune responses. Type III interferons are central to maintaining mucosal barrier integrity, providing targeted antiviral defense with reduced inflammation—a feature that distinguishes them from the more broadly acting, and sometimes more inflammatory, Type I interferons. These pathways are major therapeutic targets in infectious disease, cancer, autoimmune disorders, and beyond. Drugs that agonize or inhibit these pathways are active areas of clinical development. However, harnessing these pathways therapeutically requires careful modulation, since excessive or mis-timed activation can result in immunopathology or suppression of essential immune responses[1][2][3][4][5][6][7].

Other names

IFN-I/IFN-III pathwayInterferon alpha/beta/lambda signalingInterferon-stimulated gene (ISG) responseJAK-STAT interferon pathway

Activation of JAK-STAT pathway: IFNs bind their receptors (IFNAR or IFNLR1/IL10R2), initiating JAK-STAT signaling, leading to transcription of ISGs that exert antiviral, antiproliferative, and immunomodulatory effects. Direct antiviral activity: Induction of ISGs impedes viral replication, assembly, and release. Immunomodulation: Effects on inflammatory and immune cell recruitment can either promote or reduce inflammation.