Abstract
Interferons (IFNs) are signaling proteins that play fundamental roles during health and disease. Although types I, II, and III IFNs are structurally and functionally different, all IFNs signal via an intricate network of Janus kinases, named after the Roman god of time and duality. IFNs are characterized by activities that vary over time and can lead to opposing outcomes. IFNs have protective roles during bacterial, viral, and fungal infections but can also drive numerous inflammatory and autoimmune diseases. In this review, we provide an overview of the cellular and molecular mechanisms governing IFN induction and responses, emphasizing their roles in infections, tumorigenesis, and inflammatory, autoimmune, and genetic diseases, with particular attention to mucosal tissues. Overall, we spotlight how the balanced production of distinct members of the IFN families over time is necessary to exert their protective functions and the detrimental consequences for the host when this balance is lost.