Autoimmune Disease: Mechanisms

The immune system specifically recognizes and eliminates foreign agents thereby protecting the host against infection. During maturation of the immune system, immune cells that react against self-tissues are eliminated providing an immune system that is ‘tolerant’ to self. Historically, autoimmunity or reactivity of the immune system to self-antigenswas thought of as an aberrant response.More recently, researchers have realized that autoimmunity is a natural phenomenon, with self-reactive antibodies and autoimmune cells present in all normal individuals. Antiself responses are usually generated in the process of mounting an immune response to foreign antigens, but autoimmune disease results only if autoimmunity is poorly regulated. A combination of genetic predisposition and environmental factors contribute to the development of autoimmune disease. Although individual autoimmune diseases are relatively uncommon, as a group they affect approximately 5–8% of the population in the United States and are the third most common category of disease in industrialized countries following cardiovascular disease and cancer. Because many autoimmune diseases start at a relatively young age and continue throughout life, they have a disproportionate affect on public health with an estimated annual cost of over 100 billion dollars in the United States alone. Furthermore, most autoimmune diseases are chronic in nature requiring a lifetime of care. Understanding the mechanisms that lead to dysregulation of the immune response resulting in autoimmune disease is necessary to develop better therapies to treat and possibly even prevent these diseases.