Definition of autoimmunity.The healthy human body is equipped with a powerful set of tools for resisting the onslaught of invading microorganisms (such as viruses, bacteria, and parasites). Unfortunately, this set of tools, known as the immune system, sometimes goes awry and attacks the body itself. These misdirected immune responses are referred to as autoimmunity, which can be demonstrated by the presence of autoantibodies or T lymphocytes reactive with host antigens. Definition of autoimmune disease.In general, autoimmune disorders occur more frequently in women than men and less frequently in children and the elderly. Autoimmunity is present in everyone to some extent. It is usually harmless and probably a universal phenomenon of vertebrate life. However, autoimmunity can be the cause of a broad spectrum of human illnesses, known as autoimmune diseases. |