Autoantibodies are immunoglobulins that directly target proteins or cellular components that occur normally in oneself. The body’s growth, development and survival are maintained by an intact autoimmune tolerance mechanism, and the normal immune response has a protective defense, i.e., it does not react to its own tissues and components. Once the integrity of auto-tolerance is destroyed, the body sees its own tissues and components as “foreign bodies”, and auto-immune reactions occur, producing auto-antibodies. However, if the titer of autoantibodies exceeds a certain level, it may cause damage to the body and induce disease. Autoimmune reactions can be triggered in several ways: substances (hidden antigens) that are normally strictly confined to a specific site in the body (isolated from the immune system) are released into the systemic circulation. For example, the atrial fluid of the eye is normally confined to the eye and when it enters the bloodstream during ocular trauma, the immune system reacts to it; alteration of a substance in the normal organism, such as a virus, drug, sunlight or radiation alters the structure of a protein so that it looks like a foreign substance; the immune system, in response to a foreign substance similar to its own, mistakenly attacks the self-substance as if it were also foreign. Abnormalities in some functions of the cells that control antibody production; for example, cancerous B lymphocytes can produce abnormal antibodies that attack red blood cells.