Amyloid protein and neurofibrillary tangles coexist in the same neuron in Alzheimer disease.

In Alzheimer disease, paired helical filaments accumulate in the neuron, and amyloid fibers are found in the extracellular space in the neuropil and brain vessels. Amyloid and paired helical filaments are morphologically distinct. Although messenger RNA that encodes the amyloid has also been shown in several tissues, including brain, the intracellular expression of the protein has not been observed. By using monoclonal antibodies to a synthetic amyloid beta peptide, the present study demonstrates that amyloid reactivity is present in both Alzheimer patients and normal individuals in different types of neurons, including the neurons with the neurofibrillary tangles, but not in the tangle itself.