Figure 1.

Schematic representation of the effectors and regulators of the complement cascade. Complement is initiated by three distinctive pathways: the classical (blue arrows), the lectin (green arrows), and the alternative (brown arrows) pathways. All three pathways converge in the formation of C3 and C5 convertases, which in turn generate the inflammation modulators C3a and C5a. The terminal steps, which culminate in the assembly of the membrane attack complex (MAC), are common to the three pathways. Inhibitory proteins of the three pathways are shown in red boxes.