Friendly Fire – an introduction to autoimmune disease

 Autoimmunity is a blanket term describing pathologies where the immune system attacks its host body. The typical paradigm is that the immune system protects us from foreign invaders- pathogens looking for a niche to colonize. In autoimmune disease, the immune system mistakes our body’s tissues for a target- and harms them. Whether due to a break in tolerance, consequences of molecular mimicry, or due to epitope spreading, autoimmune disease covers a wide range of pathologies, ranging in severity from mild to lethal.

Autoimmune disease can target nearly any organ and system in the body. There are over 80 documented types of autoimmune disease, disorder, or syndrome. Multiple sclerosis, for example, targets the myelin that insulates nerves. In type I diabetes (diabetes mellitus) T cells destroy the pancreatic cells that produce insulin. Sjogren’s Syndrome targets the glands that produce saliva and tears, causing severe and chronic dry eyes and dry mouth. Celiac disease causes damage to the lining of the intestines because of antibodies against a protein found in wheat, barley and rye (gluten) that cross-react with the intestines. Rheumatoid arthritis attacks the joints- especially the hand, fingers, and toe joints. Vitiglio causes the destruction of melanocytes, the cells that give skin darker color, causing white patches of skin to appear.

Each individual autoimmune disease has its own mechanism and preferred targets, but they share some commonalities. Women present with autoimmune disorders at nearly twice the rate of men – 6.4% of women versus 2.7% of men. The attack by the immune system can cause pain, redness, and swelling in the targeted organs and systems of the body. Many autoimmune diseases are mediated by antibodies that bind to our own tissue, making them a target for other immune cells such as macrophages and T cells. Autoimmune diseases are generally chronic, and managed via medication, lifestyle alterations, and other medical interventions.

The precise etiology of most autoimmune conditions remains undetermined, but a combination of genetics and environment are likely to influence the type and severity of autoimmunity.

Dr. Kerry Maxine Leehan is a AAAS Science and Technology Policy Fellow at the Millennium Challenge Corporation in Washington DC. Dr. Leehan is a human immunologist with a special interest in T cells and autoimmune disease and holds a PhD in Pathology and an MS in Microbiology & Immunology.

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