The complement system is a group of proteins which plays a major role in the processing and removal of microorganisms and tissue breakdown products from the circulation and extracellular spaces. The system is activated by a wide range of targets, and activation leads to the production of opsonins, chemotaxis of granulocytes, cell lysis and other biological activities. Inappropriate overactivation of the system contributes to inflammatory tissue damage in the host, while inadequate activation leads to accumulation of immune complexes and other debris in the circulation, and susceptibility to...