PRNP and scrapie: In contrast, PK treatment of the brain homogenate abrogated MBP-PrP detection (Fig. 6A, lanes marked PK) whereas immunodetection using monoclonal antibody 9A2 clearly shows the presence of PK-resistant PrPSc (Fig. 6A, right panel lane marked PK) in the scrapie positive brain homogenate.