Do tonsilar FDCs express PrPc in sheep?

(1)

Do tonsilar FDCs express PrPC in sheep?

Toppets V.1_{, Piret J.}1_{, Minne M.}1_{, Gabriel A.}2_{, Jacqmot O.}2_{, Grobet L.}1_{, Antoine N.}1

1. Department of Morphology and Pathology, Laboratory of Animal Histology and Embryology, Faculty of Veterinary Medicine, University of Liege, Belgium

2. Department of Morphology and Pathology, Laboratory of Animal Anatomy, Faculty of Veterinary Medicine, University of Liege, Belgium

Introduction

In 2007, two cases of natural scrapie were confirmed on sheep flocks in the south of Belgium. Always fatal, this endemic disease is associated with the accumulation of a pathogen prion protein (PrPSc) in the lymphoreticular system prior to neuroinvasion. PrPSc is generated by the transconformational change of a host cellular protein: PrPC. Studies on the kinetic of prion propagation reveal that the oral route is the main route of entrance of the pathogen agent.

Results

Discussion/Conclusion

These results support the hypothesis that ovine FDCs could retain and replicate the pathogenic agent and could play a key role during the lymphoinvasion phase of the disease. However, could they play a role in the dissemination of the pathogen through the nervous system? Analysis of innervation pattern of these lymph organs is now in progress to study potent neuro-immune connections in germinal centers.

FDCs immunostained with FDC-B1 were located in the germinal center of a lymphoid follicle in a palatine tonsil. Gx100.

Pri 909 positive immune cells were also localized in the germinal center. Gx100.

Confocal microscopy highlighted a perfect superposition of both markers. Gx100.

Cytospin of ovine FDCs cluster. Immunostaining with FDC-B1 revealed a positive FDC surrounded by negative B cells .

Counterstaining with hematoxylin. Gx1000.

PrPC expression inside an ovine FDC cluster. Immunostaining with Pri 909 as primary antibody. Gx3000.

Superposition of the pictures obtained after confocal analysis reveals that ovine FDCs

co-express PrPC and FDC-B1. GX3000.

Objective

Because infection is localized in tonsils at early time point of the disease, those organs and their draining lymph nodes appear to be of strong interest in the study of immune cells implicated in prion retention. Although the key role of FDCs in other prion diseases has been clearly demonstrated, their implication in natural scrapie must be confirmed.

Material and methods

Palatine and pharyngeal tonsils were removed from sheeps 6 to 8 months old and cryosections were processed for immunostainings. The labelling of FDCs was performed by the use of FDC-B1. Cellular prion protein expression was revealed with PrPC specific antibodies.