Chemotactic Factors:C5a and MAC(C5b67)are both chemotactic.C5a is also a potent activator of neutrophils,and macrophages and thus amplifies nonspecific immunity.It also causes induction of adhesion molecules on vascular endothelial cells and hence promotes diapedesis. Opsonins:C3b and C4b on the surface of microorganisms attach to C receptor(CRI)on phagocytic cells and promote phagocytosis. activ e pr s of C activation:Degra cts of C3(iC3b,C3d and Ce)also bind to different cells by distinet receptors and modulate their functions In summary the complement system in is an important component of the nonspecific immune function and an adjunct to the specific immune system.It generates a number of products of biologic and pathophysiologic significance(Table 2). There are known genetic deficiencies of most individual complement components,but C3 deficiency is most serious and fatal.Complement deficiencies also occur in immune complex diseases(e.g SLE)and acute and chronic bacterial,viral and parasitic infections. Chemotactic Factors: C5a and MAC (C5b67) are both chemotactic. C5a is also a potent activator of neutrophils,and macrophages and thus amplifies nonspecific immunity. It also causes induction of adhesion molecules on vascular endothelial cells and hence promotes diapedesis. Opsonins: C3b and C4b on the surface of microorganisms attach to C_receptor (CR1) on phagocytic cells and promote phagocytosis. Other Biologically active products of C activation: Degradation products of C3 (iC3b, C3d and C3e) also bind to different cells by distinct receptors and modulate their functions. In summary the complement system in is an important component of the nonspecific immune function and an adjunct to the specific immune system. It generates a number of products of biologic and pathophysiologic significance (Table 2). There are known genetic deficiencies of most individual complement components, but C3 deficiency is most serious and fatal. Complement deficiencies also occur in immune complex diseases (e.g., SLE) and acute and chronic bacterial, viral and parasitic infections. 6