A naturally produced chemical released by the body in response to viral infections. Interferon can be artificially produced and used as a form of immunotherapy.A biological response modifier (a substance that can improve the body’s natural response to infections and other diseases). Interferons interfere with the division of cancer cells and can slow tumor growth. There are several types of interferons, including interferon-alpha, -beta, and -gamma. The body normally produces these substances. They are also made in the laboratory to treat cancer and other diseases. Alpha-interferons may control symptoms of carcinoid syndrome and produce objective biochemical responses (greater than 50% suppression of 5-HIAA).