The monoclonal antibody 1.5D7 recognizes the disease associated isoform of the prion proteintermed PrPSc. Prion diseases, also known as spongiform encephalopathies, are a group ofneurodegenerative diseases that include BSE (bovine spongiform encephalopathy) in cattle, scrapiein sheep and CJD (Creutzfeldt-Jakob disease) in humans. The normal cellular form of the prionprotein is denoted as PrPC and is a constitutively expressed glycosylphosphatidylinositol anchoredprotein that has been shown to play a role in myelin formation. PrPC has an unstructured N-terminalpart and a C-terminal part consisting of three α -helices and two short β strands. Refolding of thenormal prion protein results in PrPSc, which has a tightly packed C-terminal part enriched in betasheets which is insoluble and resistant to digestion by proteases. Prion diseases are characterized bythe deposition of highly structured aggregates of PrPSc, astrocytosis, neuronal cell death andspongiform structures in the brain. These diseases can be sporadically (unknown cause), be inheriteddue to polymorphisms or mutations in the prion protein gene or be transmitted by an infectious particlewhich is believed to consist of PrPSc only. In order to study prion diseases the detection of PrPSc andthe ability to discriminate between the normal and disease associated PrP is of pivotal importance.The monoclonal antibody 1.5D7 can be used for the specific identification and characterization ofPrPSc in tissue sections by immunohistochemistry and PET-blot.