Interferon

a class of small protein and glycoprotein cytokines (15–28 kD) produced by T cells, fibroblasts, and other cells in response to viral infection and other biological and synthetic stimuli

Description
Interferons bind to specific receptors on cell membranes; their effects include inducing enzymes, suppressing cell proliferation, inhibiting viral proliferation, enhancing the phagocytic activity of macrophages, and augmenting the cytotoxic activity of T lymphocytes. Interferons are divided into five major classes (&#945;, &#946;, &#947;, &#964;, and &#969;) and several subclasses (indicated by Arabic numerals and letters) on the basis of physicochemical properties, cells of origin, mode of induction, and antibody reactions. Since the development of recombinant DNA technology, interferons began to play an important role in the treatment not only of viral infections but also of certain malignancies. Commercially available interferons are produced by genetically altered colonies of Escherichia coli or Chinese hamster ovary cells, or are induced by controlled viral infection in pooled human leukocytes. The &#945; interferons have found the widest application in medicine. (The spelling '&#945;' is used with respect to naturally occurring interferons; in compliance with international conventions for generic drug names, the spelling alfa appears in names of pharmaceutical formulations.) The &#945; interferons are used in the treatment of chronic hepatitis B and hepatitis C, hairy cell leukemia, chronic myelogenous leukemia, AIDS-related Kaposi sarcoma, malignant melanoma, condylomata acuminata and recurrent respiratory papillomatosis due to human papillomavirus, and infantile hemangiomatosis. About 50% of patients treated for chronic hepatitis B with interferon-alfa show disappearance of hepatitis Be antigen (HBeAg) and reversion of alanine aminotransferase to normal. The response rate in chronic hepatitis C is lower (15–25%), but better results are achieved by using more aggressive therapy (daily rather than thrice weekly administration) and continuing it longer (a minimum of 12 months). Modified formulations of interferon-alfa conjugated with polyethylene glycol (PEG), have yielded promising results in hepatitis C with once-a-week dosing. The &#946; interferons reduce clinical recurrences and progression of myelin damage in multiple sclerosis. &#947; interferon is effective in retarding tissue changes in osteopetrosis and systemic scleroderma and in reducing the frequency and severity of infections in chronic granulomatous disease. Administration of interferons is parenteral (intravenous, intramuscular, subcutaneous, intranasal, intrathecal, or intralesional) and several weeks of treatment may be required before clinical response is noted. More than 50% of patients experience a flu-like syndrome of fatigue, myalgia, and arthralgia. Gastrointestinal and CNS side effects are also common, and marrow suppression may occur with prolonged treatment.