Amyloidoses of the nervous system in the transmissible dementias.

The transmissible spongiform encephalopathies, both in humans and in animals, are neurodegenerative diseases which do not evoke an immune response in the host. The search for the etiological agent has led to the prion hypothesis, which proposes that a host-encoded protein may be the causal agent itself or a part of it. In humans, a low percentage of these transmissible encephalopathies are familial. Investigations centered on the understanding of the pathogenesis of the transmissible spongiform encephalopathies have implications, not only in basic sciences, but in clinical medicine as well.