IFn

Interferons, abbreviated IFN, are a group of signaling proteins produced by host cells in response to pathogens, especially viruses. They are important components of the innate immune response and help orchestrate the antiviral state in neighboring cells while also regulating the adaptive immune system. When released, interferons bind to specific cell surface receptors, activating the JAK-STAT signaling pathway and upregulating interferon-stimulated genes that inhibit viral replication and promote antigen presentation and immune cell activation.

There are three main families of human interferons: Type I (including IFN-α, IFN-β, and IFN-ω), Type II (IFN-γ), and Type III (IFN-λ). Type I signals through the IFNAR1/IFNAR2 receptor complex, Type II through IFNGR, and Type III through the IFNLR1/IL10RB complex. Interferons exert antiviral, antiproliferative, and immunomodulatory effects, enhancing natural killer cell activity, macrophage function, and expression of major histocompatibility complex molecules.

In medicine, recombinant interferons have been used to treat certain viral infections and cancers, notably IFN-α and IFN-β. Historically, they were used for hepatitis B and C and various hematologic malignancies; today most hepatitis C infections are treated with direct-acting antivirals, but interferons remain used in some contexts such as multiple sclerosis (IFN-β) and some rare conditions. Common side effects include flu-like symptoms, fatigue, cytopenias, liver enzyme elevations, and mood disturbances. Production of interferons for clinical use relies on recombinant DNA technology in bacterial or mammalian cell systems.

Interferons were first described in 1957 by Isaacs and Lindenmann, who observed that virus-infected cells could protect neighboring cells from infection, laying the groundwork for understanding the antiviral state.