Claudin expression in follicle-associated epithelium of rat Peyer's patches defines a major restriction of the paracellular pathway.

AIM: Members of the tight junction protein family of claudins have been demonstrated to specifically determine paracellular permeability of the intestinal epithelium. In small intestinal mucosa, which is generally considered to be a leaky epithelium, Peyer's patches are a primary part of the immune system. The aim of this study was to analyse the tight junctional barrier of follicle-associated epithelium covering Peyer's patches (lymphoid follicles). METHODS: Employing small intestinal tissue specimens of male Wistar rats, electrophysiological analyses including the Ussing chamber technique, marker flux measurements and one-path impedance spectroscopy were performed. Morphometry of HE-stained tissue sections was taken into account. Claudin expression and localization was analysed by immunoblotting and confocal laser scanning immunofluorescence microscopy. RESULTS: Almost twofold higher parameters of epithelial and transepithelial tissue resistance and a markedly lower permeability for the paracellular permeability markers 4 and 20 kDa FITC-dextran were detected in follicle-associated epithelium compared to neighbouring villous epithelium. Analysis of claudin expression and localization revealed a stronger expression of major sealing proteins in follicle-associated epithelium, including claudin-1, claudin-4, claudin-5 and claudin-8. Therefore, the specific expression and localization of claudins is in accordance with barrier properties of follicle-associated epithelium vs. neighbouring villous epithelium. CONCLUSION: We demonstrate that follicle-associated epithelium is specialized to ensure maximum restriction of the epithelial paracellular pathway in Peyer's patches by selective sealing of tight junctions. This results in an exclusive transcellular pathway of epithelial cells as the limiting and mandatory route for a controlled presentation of antigens to the underlying lymphocytes under physiological conditions.

Argyrophilic proteins of nucleolar organizer regions and proliferative activity of cells in squamous cell carcinoma of the lung.

Argyrophilic proteins associated with nucleolar organizer regions (Ag-NOR proteins) and Ki-67 antigen were analyzed in 118 samples of squamous cell carcinoma of the lungs. Tumors with low and high content of Ag-NOR proteins and Ki-67 index were selected. It was found that the content of Ag-NOR proteins correlated with some clinical and morphological parameters (indexes T and N, tumor size less and more that 3 cm, stage of the disease, and tumor differentiation degree) and survival rate. High survival was associated with low content of Ag-NOR proteins and Ki-67 index and low survival correlated with high content of Ag-NOR proteins and Ki-67 index, while intermediate survival was associated with opposite values of Ag-NOR protein content and Ki-67 index. The tumor size, parameter N, and the content of Ag-NOR proteins had independent effects on patient's survival. In patients with squamous cell carcinoma of the lung without metastases in lymph nodes, survival correlated with the content of Ag-NOR proteins; in patients without metastases, survival correlated with tumor size.