Autoimmune disorders

Autoimmune disorders are conditions in which a person's immune systemattacks the body's own cells, causing tissue destruction. Autoimmunity is accepted as the cause of a wide range of disorders and is suspected to be responsible for many more. Autoimmune diseases are classified as either general, inwhich the autoimmune reaction takes place simultaneously in a number of tissues, or organ specific, in which the autoimmune reaction targets a single organ.

To understand autoimmune disorders, it is helpful to understand the workingsof the immune system. The purpose of the immune system is to defend the bodyagainst attack by infectious microbes (germs) and foreign objects. When the immune system attacks an invader, it is very specific--a particular immune system cell will only recognize and target one type of invader. To function properly, the immune system must not only develop this specialized knowledge of individual invaders, it must also learn how to recognize and not attack cellsthat belong to the body itself.

Every cell carries protein markers on its surface that identify it in one oftwo ways: what kind of cell it is (e.g. nerve cell, muscle cell, blood cell,etc.) and to whom that cell belongs. These markers are called major histocompatability complexes (MHCs). When functioning properly, cells of the immune system will not attack any other cell with markers identifying it as belongingto its own body.

If the immune system cells do not recognize the cell as "self," they attach themselves to it and put out a signal that the body has been invaded. This inturn stimulates the production of substances such as antibodies that engulf and destroy the foreign invaders. In the case of autoimmune disorders, the immune system cannot distinguish between "self" cells and invader cells. As a result, the same destructive operation is carried out on the body's own cells that would normally be carried out on bacteria, viruses, and other such harmful entities.

The reasons why immune systems become dysfunctional in this way is not well understood. However, most researchers agree that a combination of genetic, environmental, and hormonal factors play a role.

Autoimmune disorders include the systemic lupus erythematosus, rheumatoid arthritis, Goodpasture's syndrome, Grave's disease, Hashimoto's thyroiditis, pemphigus vulgaris, myasthenia gravis, scleroderma (also called CREST syndrome),autoimmune hemolytic anemia, autoimmune thrombocytopenic purpura, polymyositis, dermatomyositis, pernicious anemia, Sjögren's syndrome, ankylosing spondylitis, and vasculitis. Type I diabetes mellitus may be caused by an antibody that attacks and destroys the islet cells of the pancreas that produce insulin. Symptoms these above disorders vary widely.

The principle tool used to diagnose autoimmune diseases is antibody testing.These tests measure the level of antibodies found in the blood and determineif they react with specific antigens that would give rise to an autoimmune reaction.

Treatment of autoimmune diseases is specific to the disease, and usually concentrates on alleviating symptoms rather than correcting the underlying cause.Another aspect of treatment is controlling the inflammatory and proliferative nature of the immune response. This is generally accomplished with two types of drugs. Steroid compounds are used to control inflammation. The proliferative nature of the immune response is controlled with immunosuppressive drugs. These drugs work by inhibiting the replication of cells and, therefore, also suppress non-immune cells. Both drug therapies have potentially serious side effects.

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