a b s t r a c tAlthough the alimentary tract has been suggested as the most likely portal of entry in natural scrapie, a growing amount of data indicates that the respiratory system and more specifically the pharyngeal tonsils serve as a natural portal of entry for scrapie.This study describes for the first time the broad cell populations in the lymphoid compartment of pharyngeal tonsils and more specifically inside the lymphoid follicles where the scrapie agent accumulates during the period of latency.Follicular dendritic cells (FDCs), stromal cells located in the light zone of the germinal centre of lymphoid follicles, seem to be the principal causal factor in the accumulation of the infectious agent in transmissible spongiform encephalopathy (TSE) diseases. Knowing that efficient lymphoreticular prion propagation requires PrPc expression, we analysed the expression of PrPc with the mouse monoclonal antibody Pri 909 both in situ and on FDC-cluster-enriched cell suspensions.In situ, a positive staining was observed in the germinal centre of pharyngeal lymph follicles. The germinal centre labelling was due to the presence of a follicular dendritic network as revealed after immunogold staining of isolated FDC clusters. Our results suggest that the pharyngeal lymphoreticular system and more specifically PrPc expressing follicular dendritic cells could serve as a prion "reservoir" during the latency phase, thus playing a key role during the scrapie lymphoinvasion.

Lameness due to stifle and especially meniscal lesions is frequent in equine species. In humans, mechanoreceptors involved in proprioceptive function are well studied. Given the high incidence of meniscal injuries in horses, and the lack of information concerning them in equine menisci, our objective was to study these corpuscles in six healthy anterior horns of the equine medial meniscus, which is the most common localisation reported for equine meniscal injuries. Immunohistochemical stainings were performed using antibodies against high molecular weight neurofilaments and glial fibrillary acidic proteins. From a purely fundamental point of view, our work highlights for the first time the presence of Ruffini, Pacini and Golgi corpuscles in equine meniscus. They were found, isolated or in clusters and always located at the vicinity of blood vessels, at the level of the anterior horn of the equine medial meniscus. This morphological approach could serve as a basis for clinical studies, to evaluate the impact of these corpuscles on the poor sportive prognosis in equine meniscal tears.

Recent studies have established the involvement of nasal-associated lymphoid tissues, mainly the pharyngeal tonsil, in prion pathogenesis. However, the mechanisms of the associated neuroinvasion are still debated. To determine potential sites for prion neuroinvasion inside the ovine pharyngeal tonsil, the topography of heavy (200 kDa) and light (70 kDa) neurofilaments and of glial fibrillar acidic protein has been semi-quantitatively analysed inside the various compartments of the tonsil. The results show that the most innervated areas are the interfollicular area and the connective tissue located beneath the respiratory epithelium. The existence of rare synapses between follicular dendritic cells and nerve fibres inside the germinal centre indicates that this mechanism of neuroinvasion is possible but, since germinal centres of lymphoid follicles are poorly innervated, other routes of neuroinvasion are likely. The host PRNP genotype does not influence the pattern of innervation in these various tonsil compartments, unlike ageing during which an increase of nerve endings occurs in a zone of high trafficking cells beneath the respiratory epithelium. A minimal age-related increase of innervation inside the lymphoid follicles has also been observed. An increase in nerve fibre density around the lymphoid follicles, in an area rich in mobile cells such as macrophages and dendritic cells capable of capturing and conveying pathogen prion protein (PrPd), might ensure more efficient infectivity, not in the early phase but in the advanced phase of lymphoinvasion after the amplification of PrPd; alternatively, this area might even act as a direct site of entry during neuroinvasion.

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A number of immunological functions in CD4+ T cells are dependent on the circadian rhythm as we and others could previously demonstrate. Little is known about the underlying mechanisms. One possibility could be the circadian rhythm of the molecular clock in T cells. The molecular clock is known to control the circadian rhythm in the brain and several peripheral organs. To address this question we analyzed the expression of five clock genes (Bmal1, Per2, Cry1, Rev-erba, Dbp), the production of cytokines and the CD40L expression in CD4+ T cells from human volunteers. A total of 15 healthy young men were examined under defined conditions over 24 h in the sleep lab. Venous blood was drawn periodically every 3 h, CD4+ T cells were isolated. T cells were split: one fraction was used for the investigation of clock gene expression and the second fraction was polyclonally stimulated and analyzed applying FACS. We found that on average 32% of polyclonally stimulated highly purified CD4+ T cells express CD40L at 15:00 h whereas only 2% of the CD4+ T cells express CD40L at 6:00 h. Additionally there is also a strong rhythm for the production of INF-g. Furthermore, we have preliminary data demonstrating the rhythmic expression of the core clock genes Bmal1and Cry1 in CD4+ T cells. These findings demonstrate that highly purified CD4+ T cells have a strong functional circadian rhythm and that a possible underlying mechanism could be the molecular clock. It is well demonstrated that norepinephrine can influence the immune response [1]. We already demonstrated that in RA synovial tissue there are cells producing catecholamines. To study the role of local catecholamine production in the inflammatory process in arthritis. Synovial samples were obtained from 21OA and 10RA patients who underwent knee joint replacement. Synovial cells were cultured with reserpine (10-6 to 10-8 M), OR486 (10-5 or 10-6 M) or medium (control) for 24 h. TNF, IL-8 and IL-6 were determined by Luminex and ELISA. For in vivo experiments, collagen type-II arthritis in DBA-1J mice was elicited. Thirty-one days after arthritis induction, mice were injected with 300 mg/kg reserpine or with NaCl (control) in the dorsum of one hind paw. Arthritis score was daily evaluated until day 47. The blockade of catecholamine by reserpine 10-6 M caused a strong reduction of TNF both in OA and RA. IL-6 is significantly lower in reserpine-treated cells of OA, whereas there is a reduction of IL-8 production only in reserpine-treated RA cells. The effects on cytokines were even stronger if reserpine was used in combination with OR486, an inhibitor of catecholamine degradation. Also in vivo caused reserpine a strong anti-inflammatory effect. In fact, 16 days after reserpine treatment the clinical score was lower in reserpinetreated mice compared to controls. We hypothesize that the local production of catecholamines in the synovial tissue plays a crucial role in the inflammatory process in arthritis. Therefore, modulation of catecholamine release by reserpine could be useful in t...