complement system

Syllable breakdown

Dictionary meaning

a cascade of plasma proteins and cell surface receptors of the innate immune system that, when activated, amplify inflammatory responses, opsonise pathogens to enhance phagocytosis, recruit immune cells to sites of infection, and directly lyse microbial membranes through formation of the membrane attack complex; the complement system can be activated through three pathways — the classical pathway triggered by antibody-antigen complexes, the lectin pathway activated by carbohydrates on microbial surfaces, and the alternative pathway constitutively active at low levels — all converging on the cleavage of complement component C3 and subsequent downstream effector functions