Interferon

Interferon, any of several related proteins that are produced by various types of cells in the body as a defensive response to viruses. Interferons are so-named because they interfere with viral replication. They are classified into three main types—type I, type II, and type III—based on their structure, the receptors they bind to, and their biological functions. Most nucleated cells are able to produce interferon, though specialized immune cells, including dendritic cells, T cells, and natural killer (NK) cells, are particularly important sources, depending on the type of interferon.

Functions

Interferons are produced mainly in response to viral infections, where they help limit viral replication by triggering the expression of antiviral genes in neighboring cells. Beyond antiviral activity, interferons also enhance immune surveillance by increasing antigen presentation, activating NK cells, and promoting the activity of macrophages and cytotoxic T cells.

Different types of interferons have specialized functions. Type I interferons, such as IFN‑α and IFN‑β, are key for early antiviral responses. Type II interferon, the only member of which is IFN‑γ, primarily regulates and activates immune cells to fight intracellular pathogens. Type III interferons, which include various subtypes of IFN‑λ, protect mucosal surfaces, such as the respiratory and gut linings. Together, interferons act as crucial messengers, coordinating innate and adaptive immunity while maintaining a balanced response to infections and other immune challenges.

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immune system: Interferons

Role in therapeutics

Interferons were discovered in 1957 by British bacteriologist Alick Isaacs and Swiss microbiologist Jean Lindenmann. Research conducted in the 1970s revealed that these substances could not only prevent viral infection but also suppress the growth of cancers in some laboratory animals. Hopes were raised that interferon might prove to be a wonder drug able to cure a wide variety of diseases, but its serious side effects, which include flulike symptoms of fever and fatigue as well as a decrease in the production of blood cells by the bone marrow, deflated expectations for its use against less serious diseases.

Despite these setbacks, in the 1980s IFN‑α came into use, in low doses, to treat hairy-cell leukemia (a rare form of blood cancer) and, in higher doses, to combat Kaposi sarcoma, which frequently appears in AIDS patients. IFN‑α also has been approved for treating the viral infections hepatitis B, hepatitis C (non-A, non-B hepatitis), and genital warts (condylomata acuminata). IFN‑β is mildly effective in treating the relapsing-remitting form of multiple sclerosis. IFN‑γ is used to treat chronic granulomatous disease, a hereditary condition in which white blood cells fail to kill bacteria.