Characteristic PrPSc deposition patterns in classical and atypical/Nor98 scrapie: The same lymph follicle in the tonsil of a sheep with classical scrapie is shown stained either with the PET blot method (a) or conventional immunohistochemistry (b) (both mAb P4, bars = 250 μm). In the cervical spinal cord segment of a sheep with atypical/Nor98 scrapie (c) stained with the PET blot method (mAb P4, bar = 800 μm) synaptic PrPSc aggregates are present in the substantia gelatinosa (vertical arrow) and granular PrPSc in the corticospinal tract (horizontal arrows). In the cerebellar cortex of a classical scrapie sheep stained with the PET blot (d) complex PrPSc deposits are visible. Glia-associated PrPSc deposits take a stellate form in the molecular layer (mAb P4, bar = 150 μm; M = molecular layer, P = layer of Purkinje cells, G = granular cell layer). In the majority of the atypical/Nor98 scrapie sheep the cerebellar cortices show a more intense staining of the molecular layer than the granular layer (e) (PET blot, mAb P4; bar 600 μm). Intraneuronal, perineuronal and glia-associated PrPSc aggregates (f) in the reticular formation of a classical scrapie sheep (PET blot, mAb P4; bar = 50 μm). Tissue sections derived from sheep with the genotypes VRQ/ARH (a,b), AHQ/AHQ (c,e) and ARQ/ARQ (d,f).