The complement system is a network of small proteins in the blood, primarily synthesized by the liver, that circulate as inactive precursors until activated by specific triggers. Proteolytic activation initiates a cascade that amplifies the immune response and culminates in formation of the membrane attack complex, which can lyse target cells. Complement component 3 (C3) is central to this process. Cleavage of C3 by C3 convertase generates C3b and iC3b, with C3b driving inflammation and covalently binding to microbial surfaces to promote opsonization.
