In
autoimmune diseases, the body's immune system becomes unable to control immune responses against its own "self" substances,
causing tissue destruction and malfunction. This leads to a number of chronic and life-threatening diseases.
Autoimmune diseases are characterized by the presence of
antibodies and T-cells against "self" components, called autoantibodies and autoreactive T-cells.
A healthy person produces autoantibodies as a normal part of aging and during viral and bacterial infections. Excessive autoimmune responses are prevented by the deletion of autoreactive cells during immune system development and by cellular and cytokine (immune system "hormones") networks. When these controls fail, or the person is exposed to environmental or other agents, an autoimmune disease may result. Studies have shown that individuals likely to develop autoimmune diseases may be identified by the presence of autoantibodiesÑfor example, the presence of anti-islet cells or anti-insulin antibodies in combination with other tests may help to predict the onset of diabetes.
There are two types of autoimmune diseases: non-organ-specific and organ-specific. In non-organ-specific autoimmune diseases the immune system attacks many organs, causing systemic diseases such as rheumatoid arthritis, systemic lupus erythematosus, Sjogren syndrome, scleroderma, polymyositis and dermomyositis, ankylosing spondylitis, and rheumatic fever. Organ-specific autoimmune diseases are known for virtually every organ; among the most common are insulin-dependent diabetes, thyroid diseases (Graves disease and Hashimoto thyroiditis), Addison disease, and some kidney and lung diseases. Some neurological diseases such as multiple sclerosis and myasthenia gravis may also be considered autoimmune diseases because they are characterized by antibodies and T-cells that react with "self" components. Some diseases of the eye (uveitis), skin (psoriasis), liver (forms of hepatitis and cirrhosis), gut (celiac disease, inflammatory bowel disease) and reproductive systems (male and female infertility) may result from predominantly autoimmune responses. Autoimmune processes stimulated by viral infections including the HIV virus (see AIDS) frequently affect platelets and lymphocytes. Autoimmune phenomena may also accompany certain cancers or be precipitated by exposure to some chemicals.
The origin of autoimmune diseases is not known. Most occur in females, and some have a genetic component, recurring in families. Immune response genes appear to confer particular susceptibility. Most likely, development of an autoimmune disease requires both a genetic susceptibility and additional stimuli such as exposure to pathogens or toxins.
Autoimmune diseases are chronic illnesses that can be life-threatening. Treatment strategies, although limited by a present lack of a fundamental understanding of disease mechanisms, begin with the management of loss of function and pain. Removal of toxic antibodies, called plasmapheresis, may be helpful in diseases such as myasthenia gravis. Drug therapy includes corticosteroids, chloroquine derivatives, and small doses of antimetabolic or anticancer drugs. Other treatments include drugs that target immune system cells, such as the cyclosporines.