Do microglial cells phagocyte the beta/A4-amyloid senile plaque core of Alzheimer disease?

We performed EM, immuno-EM and light microscope immunohistochemistry studies on the topographic and functional relationships between microglial cells and amyloid senile plaque core in Alzheimer's disease. Microglial cells with cytologic characteristics of phagocytic function were associated to amyloid fibrils and to other neuropathological degenerative processes. On the periphery of the amyloid plaque core, microglial cells contain intracytoplasmic bundles of membrane bound fibrils. These fibrils, like plaque core fibrils, are immunodecorated. Immunostaining was observed neither in secretory organelles nor in hyalaplasm. Preamyloid deposits in superficial layers were not associated to microglial cells. These data lead us to conclude that the microglial cells participate to phagocytosis of beta/A4 amyloid and do not secrete this substance in Alzheimer's disease.