Argyrophilic structures stimulate glial reactions in neurofibrillary tangles and senile plaques.

Neurofibrillary tangles (NFT) and senile plaques (SP) contain various pathological structures, and the majority of these pathological structures are argyrophilic. To investigate the glial reactions of the argyrophilic substance, we performed immunohistochemistry for microglia or for astroglia after Gallyas-Braak staining, which is one of the most sensitive silver impregnation techniques detecting argyrophilic structures in NFT and SP. We found that extracellular argyrophilic structures in NFT and SP showed glial reactions, and we observed reactive microglia in the center of NFT and SP in contrast to astroglia, which were situated in the periphery. These findings suggest that the exposed argyrophilic components in the extracellular space stimulate both glial reactions, but that there is a striking difference in localization between microglia and astroglia.