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The exact cause of autoimmune disorders is unknown. As a result, the body sets off a reaction that destroys normal tissues. When you have an autoimmune disorder, your immune system does not distinguish between healthy tissue and potentially harmful antigens.

The immune system produces antibodies against these antigens that enable it to destroy these harmful substances. Examples include bacteria, viruses, toxins, cancer cells, and blood and tissue from outside the body. The blood cells in the body's immune system help protect against harmful substances.
