interferon

Interferons are signaling proteins released by host cells in response to pathogens, particularly viruses. They belong to the cytokine family and help establish an antiviral state in neighboring cells while modulating the immune response. They are produced by many cell types, including virus-infected cells and certain immune cells, and can act in autocrine and paracrine fashions.

Humans recognize three main classes of interferons: Type I (including IFN-α, IFN-β, and IFN-ω), Type II (IFN-γ), and Type III (IFN-λ). Each class signals through a distinct receptor complex and activates the JAK-STAT signaling pathway, leading to the transcription of interferon-stimulated genes that inhibit viral replication and influence immune cell activity.

The antiviral state induced by interferons encompasses inhibition of viral protein synthesis, degradation of viral RNA, increased expression of MHC class I molecules, and enhanced antigen presentation. Interferons also promote natural killer cell activity and modulate dendritic cell function, thereby bridging innate and adaptive immunity.

Interferons have therapeutic uses through recombinant proteins. They have been employed to treat certain viral infections and cancers, such as IFN-α for hepatitis B and historically for hepatitis C, and IFN-β for relapsing-remitting multiple sclerosis. IFN-γ is used for selected immune deficiencies and chronic granulomatous disease. Treatments can cause flu-like symptoms, fatigue, and cytopenias, and patient responses vary.

Interferons were discovered in 1957 by Isaacs and Lindenmann. Modern production relies on recombinant DNA technology, enabling large-scale manufacture in bacterial or mammalian cells for clinical use.