Innate Immunity in Alzheimer's Disease

The classical complement system. The nine major complement proteins participate in a series of reactions that involve proteolysis and specific intermolecular associations. Although an immune complex (e.g., antibody bound to the cell membrane of a pathogen, as shown) is the classical instigator of complement activation, C1q can in fact interact with other proteins—some of which are produced in pathological processes—to activate the C1 complex. Many additional factors, such as the C-reactive protein, facilitate the cascade of reactions.