The complement system is a component of the immune system that consists of a series of small proteins found in the blood, generally synthesized by the liver. These proteins circulate as inactive precursors and become activated in response to a pathogen or tissue damage. Activation of the complement system can occur through three pathways: the classical, lectin, and alternative pathways. These pathways converge at the cleavage of complement component C3, leading to a cascade that results in inflammation, opsonization, and the formation of the membrane attack complex.
