Autoantibodies to complement components

The complement system is a major component of innate immunity. Under normal conditions the contribution of the complement system is beneficial, but wh en inappropriately activated it may cause damage to the host and under cert ain conditions it may even be the target of an autoantibody response. Autoa ntibodies directed against individual complement components, convertases, c omplement regulators and complement receptors have been described. The pres ence of autoantibodies in individuals may be associated with manifestations of disease, but only for some autoantibodies have clear causal relations b een described. Autoantibodies against complement components can even be pre sent in healthy individuals, indicating that the development of pathology m ost likely requires the simultaneous action of multiple processes. Since au toantibodies against complement components may cause depletion of circulati ng complement levels, leading to a secondary complement deficiency, it is i maginable that this process leads to an increased susceptibility to infecti ons. In the present review, we describe autoantibodies against complement c omponents and their subsequent effects. (C) 2001 Elsevier Science Ltd. All rights reserved.