[Encephalopathy caused by prions].

The concept of prion encephalopathy has emerged from such previous notions as slow virus infections, spongiform encephalopathies or transmissible dementias. The term prion (Prusiner, 1982) is now used in preference to unconventional agents. Proteins and genes of prions have recently been identified by molecular biology. Exactly how prion proteins are amplified in cells is still unknown. It has been demonstrated that amyloid deposits in scrapie-infected brain, Creutzfeldt-Jakob, Gerstmann-Straüssler and Kuru diseases are composed of prion proteins. Prion encephalopathies are good models to study some immunopathological mechanisms observed in the central nervous system in degenerative diseases or ageing.