Chemical and immunological heterogeneity of fibrillar amyloid in plaques of Alzheimer's disease and Down's syndrome brains revealed by confocal microscopy

Am J Pathol. 1995 Aug;147(2):503-15.


Amyloid beta peptides (A beta) are deposited in the brains of Alzheimer's disease (AD) and elderly Down's syndrome (DS) patients in a variety of amyloid plaques. Among these are classical plaques composed of a spherical core and corona. Analyzing AD tissue sections single and double stained with anti-A beta antibodies and thioflavin S (thioS) by bright field, fluorescence, and confocal microscopy revealed that spherical plaque cores consist of a thioS-positive center and an anti-A beta antibody immunoreactive rim. This indicates that there is a fibrillar form of amyloid that is thioS positive but not immunoreactive with anti-A beta antibodies. In contrast, classical plaques in DS patients have irregular cores that are thioS positive as well as anti-A beta immunoreactive. In addition, a subset of plaques in both DS and AD patients have a distinct "fibrous" appearance when stained with thioS, but are amorphous when immunostained. These findings suggest that anti-A beta antibodies and thioS stain similar; as well as different forms of fibrillar amyloid. A beta may become thioS positive by interacting with one or more of its known molecular chaperons, and this may be important for the pathogenesis of AD, given that thioS-positive A beta deposits are associated with neuritic and synaptic damage.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Aged
  • Aged, 80 and over
  • Alzheimer Disease / metabolism*
  • Alzheimer Disease / pathology*
  • Amyloid / immunology*
  • Amyloid / metabolism*
  • Brain / metabolism
  • Brain / pathology
  • Down Syndrome / metabolism*
  • Down Syndrome / pathology*
  • Humans
  • Microscopy, Confocal
  • Microscopy, Fluorescence
  • Middle Aged


  • Amyloid