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(ĭn'tərfēr`ŏn), any of a group of proteins produced by cells in the body in response to an attack by a virusvirus,
parasite with a noncellular structure composed mainly of nucleic acid within a protein coat. Most viruses are too small (100–2,000 Angstrom units) to be seen with the light microscope and thus must be studied by electron microscopes.
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. A cell infected by a virus releases minute amounts of interferons, which attach themselves to neighboring cells, prompting them to start producing their own protective antiviral enzymes. The result is impairment of the growth and replication of the attacking virus. Interferon has also been shown to have some antitumor properties. There are three known classes of interferons: alpha-, beta-, and gamma-interferons.

Although they were discovered in the 1950s, the medical use of interferons was impractical until the recombinant DNA techniques of genetic engineeringgenetic engineering,
the use of various methods to manipulate the DNA (genetic material) of cells to change hereditary traits or produce biological products. The techniques include the use of hybridomas (hybrids of rapidly multiplying cancer cells and of cells that make a
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 made it possible to mass produce them. Interferons used as drugs include alpha-interferon, for hepatitishepatitis
, inflammation of the liver. There are many types of hepatitis. Causes include viruses, toxic chemicals, alcohol consumption, parasites and bacteria, and certain drugs.
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 B and C, human papillomavirushuman papillomavirus
(HPV), any of a family of more than 60 viruses that cause various growths, including plantar warts and genital warts, a sexually transmitted disease. Detectable warts can be or removed, usually by chemicals, freezing, or laser, but often recur.
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, hairy-cell leukemialeukemia
, cancerous disorder of the blood-forming tissues (bone marrow, lymphatics, liver, spleen) characterized by excessive production of immature or mature leukocytes (white blood cells; see blood) and consequently a crowding-out of red blood cells and platelets.
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, and Kaposi's sarcomaKaposi's sarcoma
, a usually fatal cancer that was considered rare until its appearance in AIDS patients. First described by an Austro-Hungarian physician, Moritz Kaposi, in 1872, it appears in three forms and is characterized by vascular skin tumors.
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 (a cancer associated with AIDSAIDS
or acquired immunodeficiency syndrome,
fatal disease caused by a rapidly mutating retrovirus that attacks the immune system and leaves the victim vulnerable to infections, malignancies, and neurological disorders. It was first recognized as a disease in 1981.
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), and beta-interferon, for multiple sclerosismultiple sclerosis
(MS), chronic, slowly progressive autoimmune disease in which the body's immune system attacks the protective myelin sheaths that surround the nerve cells of the brain and spinal cord (a process called demyelination), resulting in damaged areas that are unable
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See also immunityimmunity,
ability of an organism to resist disease by identifying and destroying foreign substances or organisms. Although all animals have some immune capabilities, little is known about nonmammalian immunity.
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a protective protein manufactured by cells in mammals and birds and by cell cultures in response to their infection by viruses, suppressing the reproduction (replication) of the viruses in the cells.

Interferon was discovered in 1957 in the cells of infected chickens by the English scientists A. Isaacs and J. Lindenman. It was later discovered that the formation of interferon is also induced by bacteria, rickettsia, toxins, nucleic acids, and synthetic polynucleotides. Interferon is not an individual substance but a group of proteins of low molecular weight (25,000110,000). They are stable within a wide pH range, resistant to nucleases, and destroyed by proteolytic enzymes. The formation of interferon in the cells is due to the development of a virus in them—that is, it is a reaction of the cells to the penetration of foreign nucleic acid. Interferon is not found after the disappearance of the infecting virus from the cells or in normal cells. The mechanism of interferon’s action is different in principle from that of antibodies: it is not specific in relation to viral infections (it is active against a variety of viruses), and it does not neutralize the infectiousness of the virus, but suppresses the reproduction of the virus in the body by inhibiting the synthesis of the viral nucleic acids. Interferon is ineffective when it enters cells after a viral infection has already developed in them. Moreover, interferon is, as a rule, specific for the cells that form it; for example, the interferon of chicken cells is active in those cells only and does not inhibit the reproduction of a virus in rabbit or human cells. It has been suggested that it is not interferon itself that acts on the viruses, but rather another protein that is produced under its influence. Encouraging results have been obtained in testing interferon for the prevention and treatment of viral diseases (herpes infection of the eyes, influenza, cytomegaly). However, broad clinical use of interferon is limited by the difficulty of obtaining the preparation, the necessity for multiple injections, and its species specificity.


Solov’ev, V. D., and T. A. Bektimirov. Interferon v teorii i praktike meditsiny. Moscow, 1970.
Isaacs, A., and J. Lindenmann. “Virus Interference. I: The Interferon.” Proceedings of the Royal Society of London, series B:Biological Sciences, 1957, vol. 147, no. 927.
Vilček, I. Interferon. Vienna-New York, 1969.



A protein produced by intact animal cells when infected with viruses; acts to inhibit viral reproduction and to induce resistance in host cells.


Biochem any of a family of proteins made by cells in response to virus infection that prevent the growth of the virus. Some interferons can prevent cell growth and have been tested for use in cancer therapy
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