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Background: Peripheral tolerance can be mediated by extrathymic Aire-expressing cells (eTACs) and lymph node stromal cells (LNSCs) have recently been shown to induce T-cell tolerance by ectopically expressing and presenting range of peripheral tissue antigens (PTAs). New evidence shows that all types of LNSCs-including fibroblastic reticular cells, follicular DCs, and lymphatic endothelial cells-express PTAs. Ectopic expression of genes encoding PTAs in lymph nodes (LN) controlled by transcriptional regulators Aire and deformed autoregulatory factor 1 (Deaf1). Therefore, the aim of our study was to determine the effect of the levels of Deaf1 and Aire mRNA expression on the nature of Foxp3 + Treg cells differentiation during experimental STZ-induced diabetes mellitus (EDM) in rats pancreatic lymph nodes (PLN). Methods. To determine the level of mRNA Deaf1 and Aire expression was performed RT-PCR in real-time by thermocycler CFX96™ Real-Time PCR Detection Systems. The relative level of gene expression were studied with rat reference genes GAPDH by the method ΔΔ Ct. Statistical analysis were conducted using available software «Bio-Rad СFX Manager 3.1». The Foxp3 +immunopositive lymphocytes were determined using an indirect immunofluorescence technique with using a monoclonal rat antibody. Results: Development of EDM was accompanied by decreased the expression levels of the transcriptional regulator Deaf1 and Aire in rats PLN. So, Deaf1 expression is decreased 4,2-fold in rats PLN with 3-week EDM and 2,5fold in rats with 5-week EDM. Aire expression is decreased 2-fold in rats PLN with 3-week EDM and 50-fold in rats with 5-week EDM. Reduced Deaf1 and Aire mRNA expression during EDM associated with an decreased of total amount of Treg in the PLN, led to changes of distribution into individual classes of FoxP3 + lymphocytes and FoxP3 concentration in immunopositive cells. Conclusions: development of EDM due to a breakdown in peripheral immune tolerance. This contributes to progression of diabetes mellitus.

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The change of the expression of a variety of pattern-recognizing receptors: membrane and endosomal Toll-like receptors, cytoplasmic NOD-like receptors, viral RNA sensors such as the RIGlike receptors may play a critical role in the development of the type 1 diabetes mellitus (DM). The purpose of the thesis was to find out the pattern of distribution of TLR2+-, TLR4+-, NOD2+- and RIGI+-lymphocytes in pancreatic lymph nodes of rats with experimental streptozotocin-induced diabetes after introduction of metformin. The indirect immunofluorescence method with the use of monoclonal or polyclonal antibodies to the respective pattern-recognizing receptors was used to identify the immunopositive lymphocytes. The development of diabetes is accompanied by the change in the number of immunopositive lymphocytes, and the introduction of metformin to diabetic rats changes the number of lymphocytes and affects the density and concentration of receptors of innate immunity.