The above three pathways produce C3 convertase and C5 convertase, which can cleave the central complement components C3 and C5, respectively, and generate effector molecules [13]. Anaphylatoxins, including C3a and C5a, are important potent pro-inflammatory molecules that attract and activate immune cells. Opsonin C3b (or C4b) is deposited on the surface of pathogens or injured cells, and mediates immune adhesion and opsonization or induces cytolysis through the membrane attack complex (MAC). The MAC consists of C5b, C6, C7, C8, and C9, which can directly lyse targeted pathogens or damaged autologous cells [14,15].
