How immunization works remains uncertain. Multiple mechanisms have been suggested, including stimulation of antibody-induced phagocytosis of plaque deposits as well as induction of cell-mediated immune responses. Anti-Aβ antibodies might also directly disrupt existing aggregates, impede the formation of new aggregates, or neutralize toxic soluble species of Aβ. Peripheral administration of anti-Aβ antibodies has also been shown to induce massive increases in plasma Aβ,96,100 suggesting that passive immunization may promote an efflux of Aβ out of the brain into what has been called a peripheral sink. These mechanisms as well as others have recently been reviewed.97,101
