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Autoimmunity occurs when the immune system reacts to proteins in the body instead of just foreign proteins. This can cause autoimmune diseases such as type 1 diabetes, rheumatoid arthritis, and lupus. The causes of autoimmunity are unknown, but theories suggest that exposure to fetal proteins during pregnancy or reduced exposure to nonself proteins due to increased hygiene may play a role.
When the immune system is functioning normally, the body develops a state of tolerance in response to its own proteins. In some cases, however, a state of autoimmunity can develop, in which the immune system recognizes and reacts to one or more proteins in the body. When this happens, the immune reaction that develops can have a serious impact on your health.
The immune system has evolved a highly specialized response that recognizes and destroys foreign proteins and organisms. In this regard, the immune system only distinguishes between “self” and “non-self.” The proteins that are produced by the body are autonomous and trigger a state of immunological tolerance; the proteins of viruses, bacteria, parasites, plants, animals and other humans are non-self and can potentially trigger an immune response.
Immune tolerance is a state in which the immune response is actively suppressed towards proteins of the self. In some situations, however, the body may develop an immune response, rather than tolerance, to one or more self proteins. This self-directed immune response is called autoimmunity.
The best-known autoimmune diseases include type 1 diabetes and rheumatoid arthritis, as well as multiple sclerosis and lupus. Either way, the symptoms of autoimmune disease are caused when the immune system attacks the proteins of the self. The resulting immune response can cause tissue destruction, chronic inflammation, and other debilitating symptoms.
In the case of type 1 diabetes, for example, immune cells destroy the insulin-producing cells in the pancreas, leading to the need for an external source of insulin. In contrast, rheumatoid arthritis is the result of a cellular immune response to joint tissue that causes chronic pain and inflammation. Systemic lupus occurs when the body makes autoimmune antibodies that react to a type of protein found in almost every cell in the body. This form of the disease can be particularly dangerous, with the ability to affect organs, joints, muscles and blood.
While the general causes of autoimmunity are unknown, a number of theories attempt to explain the development patterns of autoimmune diseases in populations. One theory is based on the fact that women are more likely to develop autoimmunity than men and furthermore that pregnancy increases a woman’s risk of developing an autoimmune disease. According to this theory, this risk increases because women are exposed to fetal proteins across the placental barrier during pregnancy, which could disrupt tolerance to autonomic proteins.
Another theory attempts to explain why the incidence of autoimmune diseases has increased in many Western countries in recent decades. The hygiene hypothesis explains that increased attention to hygiene led to reduced exposure to nonself proteins and a reduced opportunity for the immune system to “learn” how to distinguish between self and nonself. There is some evidence for this theory in the fact that autoimmunity is much more prevalent in the Western world than in countries where one or more infectious diseases are endemic to the population.
