Monoclonal antibodies show that neurofibrillary tangles and neurofilaments share antigenic determinants

Neurofibrillary tangles are a prominent feature in the pyramidal cells of the hippocampus and in neurones of the cerebral cortex of people suffering from senile dementia of the Alzheimer type (SDAT) 1 . Similar neuronal changes also occur in elderly Down's syndrome patients and to a lesser degree in intellectually normal old people 2 . The tangles are composed of bundles of paired helically twisted 10–13 nm filaments (PHF) 3,4 , which may be either neurofilaments 3 or microtubules 5 . Attempts to isolate tangles from postmortem material have met with some success 6 but there is disagreement over the molecular weight ( M r ) of presumptive PHF proteins enriched in these fractions, with conflicting claims of 50,000 (refs 6,7) and 20,000 (ref. 8). Initially it seemed that the 50,000- M r putative PHF protein and tubulin cross-react 9,10 but this result may have been a serological artefact, due to tangle-associated material in preparations of microtubule proteins used as immunogen and as test antigen 11 . We have used monoclonal antibodies to show here that neurofilament antigens are present in neurofibrillary tangles.