Coated viruses also can be bound by complement receptors on inflammatory cells including neutrophils and macrophages, and this leads to their destruction by phagocytosis or by release of toxic mediators. Complement facilitates clearance of immune complexes from the body . Deficiency in complement components that comprise C1, C2 or C4 can predispose a person to the autoimmune disease, lupus erythematosis . This is because when autoimmune complexes are formed, the classical pathway cannot generate C3b to opsonize the complexes. There are only about 100 CR1 molecules on each RBC surface, but there are so many RBCs, they can carry a lot of immune complexes.
Complement plays a major role in the inflammatory response .
These components are potent mediators called anaphylatoxins that bind to receptors on mast cells and basophils and stimulate release of histamine . C5b67 all contribute to inflammation by indicing extravasation of monocytes and neutrophils. Deficiencies in complement components or in regulators of complement can cause a number of serious diseases or susceptibilities C3 deficiencies are the most severe. Without C3, the MAC cannot be activated. Other deficiences make a person susceptible to specific problems.