Human and mouse brain proteins immunoblotted with mAbs to PrPc raised in this study. Prnp−/−, PrP knockout mice; H, I, U, diglycosylated,monoglycosylated, unglycosylated full-length PrP; I trunc and U trunc, monoglycosylated and unglycosylated truncated PrP. mAbs 8H4 and 6G9 react with all PrP forms while mAb 5B2 only reacts with the full-length forms. mAb 6G9 fails to recognize the diglycosylated forms. None of the mAbs react with any protein from the brain of PrP−/− mice which does not express PrP.