Transcript Diapositive 1

Are CNA.42 and FBC-B1 directed against
ovine follicular dendritic cells?
Toppets V., J. Piret, M. Minne, L. Grobet and Antoine N.
Faculty of Veterinary Medicine, Department of Morphology and Pathology, Laboratory of Animal Histology and Embryology,
University of Liege, Belgium.
Introduction
Like the variant of Creutzfeldt Jakob (vCJD) in human and bovine spongiform encephalopathy (BSE) in cattle, natural
scrapie in sheep is a transmissible spongiform encephalopathy (TSE) caused by prions (PrPSc). The presence of PrPSc
at early time points in tonsils suggests that tonsillar biopsies could have a role in the diagnosis at the preclinical stage
of the disease. In lymph organs, follicular dendritic cells (FDCs) seem to be the major site of cellular prion protein
expression and the principal site of infectious agent accumulation.
Objective
In this study, we compare the ability of FDC B1 and CNA.42 monoclonal antibodies to recognize ovine FDCs.
Material and Methods
Palatine and pharyngeal tonsils were removed from 4 - 6 month old sheep and processed for classical histology,
immunocytochemistry and confocal analysis.
Results
With FDC B1, the fluorescence microscopy analysis reveals a clearly positive network inside the germinal center of both
immunostained tonsils whereas CNA.42 only reacts with pharyngeal tonsil follicular dendritic network.
Hematoxylin Eosin Stainings
FBC B1 Immunostainings
CNA.42 Immunostainings
Pharyngeal
Tonsils
Palatine
Tonsils
Conclusions
FDC network
negative labelling
►Lympho epithelial tissue, ►respiratory epithelium,►epidermoid epithelium , ► follicles, ► mantle zone, ► germinal center, ► crypt.
These results allow us to postulate that the antigen recognised by CNA.42 is not expressed by follicular dendritic cells
from all lymph organs. Obtained negative stainings must thus be interpreted with full knowledge of the facts. The antigen
detected by FDC B1 seems to be more ubiquitous.
Perspectives
Other lymph organs, such as lymph nodes from digestive and respiratory tracts, will be studied to inquire whether the
observation is organ specific or not. Similarly, palatine and pharyngeal tonsils from other species will also be compared.