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

Brain deposits of amyloid (3 peptide (A(3) have been a diagnostic hallmark of Alzheimer's disease (AD) for nearly a century. Recent studies have demonstrated that A(3 is also present in peripheral blood. Here, we present evidence that circulating A(342 is subject to complement Cab-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 A(342 targeted by this pathway differ significantly in AD compared to mild cognitive impairment and nondemented elderly controls. (c) 2005 Elsevier Inc. All rights reserved.