Tubuloreticular structures in microglial cells, pericytes and endothelial cells in Alzheimer's disease.

In two of six brain biopsies of patients with Alzheimer's disease (AD), tubuloreticular structures (TRS) were observed in the distended endoplasmic reticulum of microglial cells, endothelial cells of vessels, and pericytes. In the microglial cells that produce amyloid fibrils, TRS were found in the cytoplasmic channels, which were filled with newly formed amyloid fibrils. Co-localization of TRS and newly formed amyloid fibrils in the same cellular compartment strengthens the hypothesis that amyloid fibrils are formed in the endoplasmic reticulum of microglial cells. Formation of TRS in microglial cells, pericytes, and endothelial cells of vessels probably reflects local or systemic alpha-interferon production. In some cells, this pathological process coexists with the second type of pathological changes: formation of amyloid fibrils.