An autoantibody is an antibody (a type of protein) produced by the immune system that acts against one or more of the individual's own proteins. Many autoimmune diseases are caused by autoantibodies.
The causes of autoantibody production are varied and not well understood. It is thought that some autoantibody production is due to a genetic predisposition combined with an environmental trigger, such as a viral illness or a prolonged exposure to certain toxic chemicals. There is generally not a direct genetic link however. While families may be susceptible to autoimmune conditions, individual family members may have different autoimmune disorders, or may never develop an autoimmune condition. Researchers believe that there may also be a hormonal component as many of the autoimmune conditions are much more prevalent in women of childbearing age. While the initial event that leads to the production of autoantibodies is still unknown, there is a body of evidence that autoantibodies may have the capacity to maintain their production. Source: Wikipedia
Also see :Lupus