Peripheral clearance of amyloid β peptide by complement C3-dependent adherence to erythrocytes

Brain deposits of amyloid β peptide (Aβ) have been a diagnostic hallmark of Alzheimer's disease (AD) for nearly a century. Recent studies have demonstrated that Aβ is also present in peripheral blood. Here, we present evidence that circulating Aβ42 is subject to complement C3b-dependent adherence to complement receptor 1 (CR1) on erythrocytes, a classical set of mechanisms by which pathogens and proteins recognized as foreign are cleared from the bloodstream. Levels of Aβ42 targeted by this pathway differ significantly in AD compared to mild cognitive impairment and nondemented elderly controls.