Figure 4. Immunohistochemistry, double labelling for PrP^Sc (brown colour) and nerves (PGP, red colour).

Scrapie inoculated sheep. A, B. In the germinal centres (GC), a few nerve fibres were present in close association with cells strongly immunolabelled for PrP^Sc (A; inset). In some areas, the lymphoid nodules were separated from the PALS by a narrow rim of spindle-shaped cells (A, B; arrowheads) with PrP^Sc labelling mostly confined to the nodule side of the rim. In the PALS, nerves were most abundant around the arteriole (a), sometimes with PrP^Sc-labelled granules close to the nerve fibres (A; arrow). Among the lymphoid cells of the PALS, a few nerve fibres and small granules labelled for PrP^Sc were generally not co-localised. In the red pulp (A; RP) and the marginal zone (B; MZ), longitudinally and cross-sectioned small nerve fibres (B; white arrows) were abundant. C. High power view of B, showing the PALS-germinal centre transition (arrowheads), PGP labelled nerve fibres (white arrows) and PrP^Sc (black arrows). D. In the marginal zone, the nerve fibres (white arrow) were often close to numerous small granules labelled for PrP^Sc (black arrows). Bars, 100 µm (A, B), 10 µm (C, D). Nuclei were stained with haematoxylin.