Evidence for induction of localized amyloid deposits and neuritic plaques by an infectious agent.

Mice inoculated intracerebrally with mouse brain homogenate infected with a particular strain of scrapie agent developed amyloid and neuritic plaques and amyloid tubercles along the injection track, solid wall-like infiltrations at the injection site, or both. Our observations implicate an infections agent in the localized formation of the amyloid and the neuritic plaque--the leading pathological change found in normal elderly people and animals and in patients with senile dementia of the Alzheimer type. Further, these studies indicate that microglia appear to play a central role in the pathogenesis of amyloid formation and could be involved in the processing, production, and assembly of the fibers.