Classical pathway (of complement activation)
Chapter: 2
The first pathway of complement activation that was discovered. It requires antibody fixation, after which the cascade of complement proteins is sequentially activated, beginning with C1, to produce a variety of proinflammatory mediators, chemotactic factors, and the constellation of activated complement proteins that, together, form the "membrane attack complex". The latter, as the name implies, injures and increases the permeability of cell membranes.