Prions 。Infectious proteins Inherited and transmissible by ingestion,transplant, surgical instruments 。 Spongiform encephalopathies:Sheep scrapie, Creutzfeldt-Jakob disease,Gerstmann-Straussler- Scheinker syndrome,fatal familial insomnia,mad cow disease PrPC,normal cellular prion protein,on cell surface PrPsc,scrapie protein,accumulate in brain cells forming plaques• Infectious proteins • Inherited and transmissible by ingestion, transplant, & surgical instruments • Spongiform encephalopathies: Sheep scrapie, Creutzfeldt-Jakob disease, Gerstmann-Sträussler￾Scheinker syndrome, fatal familial insomnia, mad cow disease • PrPC, normal cellular prion protein, on cell surface • PrPSc, scrapie protein, accumulate in brain cells forming plaques Prions