Immunologic basis for autoimmunity and the potential influences of xenobiotics

Autoimmune disease may take a variety of forms ranging from organ-specific to systemic disorders. Such diseases are believed to be precipitated by a breakdown of tolerance and a failure of the immune system to discriminate effectively between 'self' and 'non-self'. Susceptibility to autoimmunity is determined by both heritable traits and environmental factors, and in this context there has been considerable interest in the influences that exposure to drugs and chemicals may have on the initiation and/or progression of autoimmune diseases. In this article we introduce the adaptive immune system and the concepts of tolerance to 'self' and autoimmunity. In addition, the mechanisms through which immunological tolerance may be compromised are considered.