Close interactions between sympathetic neural fibres and follicular dendritic cells network are not altered in Peyer’s patches and spleen of C57BL/6 mice during the preclinical stage of 139A scrapie infection

• Within mouse PP, as no close interactions between FDC and sympathetic neural fibres occurred, neuroinvasion process should not occur by direct contact between both cells.
• After oral inoculation of scrapie, the neuroimmune interface between FDC and the SNS within PP stays unchanged.
• Within mouse spleen, close interactions occur between FDC and sympathetic neural fibres.
• After intraperitoneal inoculation of scrapie, the in vivo neuroimmune interface between FDC and the SNS within the spleen stays unchanged.
• With age, the number of FDC–SNS close interactions in spleen of C57BL/6 mouse stays unchanged, but the proportion of FDC well innervated increases.

During preclinical stage of prion diseases, secondary lymphoid organs seem to play an important role in prion amplification prior the invasion of the associated peripheral nervous system. In mice, it was shown that the relative positioning of follicular dendritic cells (FDC) and sympathetic nervous system (SNS) affects the velocity of neuroinvasion following scrapie inoculation. In this study, we checked if scrapie infection, by oral or intraperitoneal route, could influence this neuroimmune interface between FDC and tyrosine hydroxylase (TH) positive neural fibres within Peyer’s patches (PP) and spleen of the C57BL/6 mouse strain. We concluded that, in vivo, scrapie 139A and ME7 strains do not modify FDC–SNS neuroimmune interface. However, age seems to alter this neuroimmune interface and thus could influence the neuroinvasion in prion pathogenesis.