Neurofibrillary tangles of Alzheimer disease share antigenic determinants with the axonal microtubule-associated protein tau (tau).

The relationship of the neurofibrillary tangle, found in Alzheimer disease and aged brains, to normal or abnormal cytoskeletal proteins remains elusive. Although immunohistochemical studies have yielded disparate results, most antigenic determinants localized to neurofibrillary tangles are cytoskeletal constituents normally present in neuronal perikarya or dendrites. We report light and electron microscopic immunolabeling of neurofibrillary tangles by a monoclonal antibody to the microtubule-associated protein tau (tau). Dephosphorylation of tissue slices not only increased the number of tau-positive tangles but also produced marked positive immunoreactivity of neuritic plaques. The localization of tau, an axonal protein, to neurofibrillary tangles in the perikaryon in particular suggests that abnormal synthesis, modification, or aggregation of tau may induce aberrant cytoskeletal--cell organelle interactions, subsequent interference with axonal flow, and resultant tangle formation.