What is autoimmunity?
The term autoimmunity is commonly employed to describe conditions in which self-tolerance is broken and an individual becomes the victim of his or her own immune response. Just like immunity to foreign antigens, autoimmune disorders are antigen-driven processes that are characterized by specificity, high affinity, and memory. However, an autoimmune process involves the immune system’s recognition of an antigen, either foreign or self, that is then followed by an assault on its own self-antigens (i.e., autoantigens). Typically, these processes develop in an individual who previously displayed tolerance to the same antigens that are now targeted by the immune response. Therefore, most autoimmune processes are better described not simply as an absence of tolerance but as a loss of previously established tolerance. Clinically, autoimmunity can be divided into two categories:
• Organ-specific autoimmunity: defined as an immune response against a single autoantigen or a restricted group of autoantigens within a given organ (e.g., myasthenia gravis [antibodies to acetylcholine receptor]).
• Systemic autoimmunity: defined as an immune response against multiple autoantigens resulting in clinical manifestations in multiple organs (e.g., systemic lupus erythematosus [SLE]).