Activated microglial cells are colocalized with perivascular deposits of amyloid-beta protein in Alzheimer's disease brain

Background and Purpose Microglial cells are present in the center of senile plaques (SPs) in Alzheimer's disease (AD) brain. Such a localization of microglial cells suggests that they are involved in the deposition or the clearance of amyloid-beta protein (A beta) in the brain. We examined their association with another type of parenchymal A beta deposit, which is termed the perivascular deposits of A beta (PA beta). Methods Thick sections from AD brain were stained with a three-color immunofluorescence method that labeled A beta, activated microglial cells, and vascular endothelial cells simultaneously. Results Three-dimensional observation under a laser scanning microscope confirmed that perivascular aggregates of activated microglial cells were colocalized with PA beta. Conclusions Microglia occur in association with both SPs and PA beta, suggesting that they play important roles in the metabolism of A beta in AD brain.