Immunocytochemical characterization of glial fibrillary tangles in Alzheimer's disease brain

Neurofibrillary tangle is a major cytoskeletal pathology in Alzheimer's disease brains, and has been considered to develop exclusively in neuronal cells. We examined brains with Alzheimer's disease and observed argyrophilic fibrillary tangles not only in cortical neurons but also in subcortical glial cells in the frontal and temporal white matter. The tangles in glial cells were immunolabeled by antibodies against tau and ubiquitin, and double immunocytochemistry analyzed by confocal laser scanning microscopy demonstrated that the cytoplasms of tangle-bearing glia were labeled by antibodies against transferrin and 2'3'-cyclic nucleotide 3'-phosphohydrolase. Ultrastructurally, they were made up of bundles of straight filaments 16 nm in diameter and constricted filaments. These results indicate that fibrillary tangles resembling neurofibrillary tangles may develop in oligodendrocytes in brains with Alzheimer's disease and are distinguishable from glial cytoplasmic inclusions observed in multiple system atrophy brains. We referred to them as glial fibrillary tangles. Glial fibrillary tangles commonly occurred in this disease condition, and glial cells might be involved under the pathological processes similar to neuronal cells.