immune disorders
Autoimmune Disorders
Causes of Autoimmune Disorders
Autoimmune reactions can be triggered in several ways: A normal body substance is altered, for example, by a virus, a drug, sunlight, or radiation. The altered substance may then appear foreign to the immune system. For example, a virus can infect and thus alter cells in the body. The virus-infected cells stimulate the immune system to attack. A foreign substance that resembles a natural body substance may enter the body. The immune system may inadvertently target the similar body substance as well as the foreign substance. For example, the bacteria that cause strep throat have an antigen that is similar to an antigen in human heart cells. Rarely, the immune system attacks a person's heart after strep throat (this reaction is part of Rheumatic Fever ). The cells that control antibody production—for example, B cells (a type of white blood cell)—may malfunction and produce abnormal antibodies that attack some of the body's cells. T cells , another type of white cell that are involved in the immune response, may also malfunction and damage the body's cells. A substance in the body that is normally confined to a specific area (and thus is hidden from the immune system) is released into the bloodstream. For example, a blow to the eye can cause the fluid in the eyeball to be released into the bloodstream. The fluid stimulates the immune system to identify the eye as foreign and attack it. Why something triggers an autoimmune reaction or disorder in one person (and not another) is usually unknown. However, heredity is sometimes involved. Some people have genes that make them slightly more likely to develop an autoimmune disorder. This slightly increased susceptibility to an autoimmune disorder, rather than the disorder itself, is inherited. In susceptible people, a trigger, such as a viral infection or tissue damage, may cause the disorder to develop. Many autoimmune disorders are more common among women. 