Ultrastructural localization of Alzheimer amyloid beta/A4 protein precursor in the cytoplasm of neurons and senile plaque-associated astrocytes.

The ultrastructural localization of amyloid beta/A4 protein precursor (APP) in the brains of control and Alzheimer's disease patients was examined immunohistochemically using antisera against the N and C termini of APP. In both control and Alzheimer brains, immunoreaction for APP was seen in the cytoplasm of most neurons, on plasma membranes, outer membrane of mitochondria, granular substance and neurofilaments. Cell bodies and foot processes of astrocytes, containing glial filaments, were also labeled. In primitive and classic type senile plaques, APP immunoreaction products were localized in the astroglial processes that surrounded the amyloid mass of the senile plaques. Swollen degenerating neurites in the senile plaques were also labeled. Amyloid fibrils were negative with APP antisera.