Cytokine, << SY tuh kyn, >> is a type of protein produced by certain cells of the body. Cytokines play an important role in the immune system, where they are produced mostly by white blood cells, also called leukocytes. There are a wide variety of cytokines. They have many functions. Some cytokines play roles in cellular growth and differentiation, the process by which cells develop into different types. Other cytokines function in inflammation and tissue repair. Cytokines often act as a signal in triggering an immune response to infections. An immune response is the process by which the body produces disease-fighting cells and antibodies (disease-fighting proteins).
Cytokines activate other cells by binding to specific structures called receptors on their surfaces. One group of cytokines, called chemokines, plays a key role in directing leukocytes to the site of inflammation or infection. Other cytokines initiate the series of biological changes that cause fever. Still other cytokines widen blood vessels. The widening makes it easier for cells and fluids to pass into tissues to fight infection or begin healing. Certain cytokines aid in the response to an infection by attracting and activating immune system cells or by causing them to reproduce and spread.
Physicians may administer cytokines to patients to treat certain cancers and other conditions. One type of cytokine, called alpha interferon, is used to treat several diseases, including hepatitis types B and C. Beta interferon is used to treat some forms of multiple sclerosis. However, interferon treatment can have serious side effects.
See also Immune system (The immune response) ; Interferon ; Tumor necrosis factor (TNF) .
