The aim of our study was to determine whether some bacterial components as well as some proinflammatory cytokines can affect surface mast cell levels. By the use of flow cytometry technique, we documented that freshly isolated mature rat peritoneal mast cells do express surface TLR2 and TLR4 protein, but not CD14 molecules, and respond to stimulation with TLR2 and TLR4 ligands by cysteinyl leukotriene generation. The level of TLR2 protein is modulated by PGN and CCL5 treatment, but not by LPS, LAM, TNF, or IL-6. Surface mast cell TLR4 expression is affected by LPS, LAM, IL-6, and CCL5. Considering that TLR-mediated activation conditions not only engaged these cells in antibacterial defense and development of inflammation but also might influence allergic processes, our observations that surface TLR2 and TLR4 expression can be regulated both bacterial components and proinflammatory cytokines seem to be very intriguing and importance.

Nowadays there is more and more evidence that mast cells take part in antibacterial defence. Mast cells have the ability to kill bacteria via phagocytose-dependent or phagocytose-independent ways and express antimicrobial peptides that can directly kill pathogens at their site of entry. What is more, mast cells are capable of processing bacterial antigens for presentation through class I and II MHC molecules. Some data indicate that these cells can release various proinflammatory mediators in response to activation with bacteria and/or their products, however this information is still far from complete. Therefore, in this study we examined the ability of PGN from Staphylococcus aureus, LPS from Eschericha coli and LAM from Mycobacterium smegmatis to stimulate mature rat mast cell degranulation as well as cysteinyl LT generation. We also studied the influence of these bacterial components on mast cell migration. We found that PGN, LPS and LAM all failed to induce mast cell degranulation and histamine release. At the same time, activation of mast cells with these bacterial antigens resulted in generation and release of significant amounts of LT. Moreover, we documented that, even in the presence of laminin, none of the bacterial antigens used stimulated mast cell migration. However, PGN did induce migration of RANTES-primed mast cells, and LPS did stimulate mast cell migratory response after priming with IL-6. Our results show that PGN, LPS and LAM might be among the important bacterial antigens involved in mast cell activation during bacterial infection. Key words bacterial cell wall components, leukotrienes, mast cells.Mast cells are distributed throughout connective tissues and are particularly numerous beneath the subepithelial surface of the skin, in the respiratory system, in the gastrointestinal and genitourinary tracts, and adjacent to blood vessels and nerves. These cells are a potent source List of Abbreviations: BMMC, bone marrow-derived mast cells; BSA, bovine serum albumin; CBMC, cord blood-derived mast cells; cDMM, DMEM supplemented with 10% FCS, 10 μg/mL gentamicin and 2 mM

Mast cells are found in all tissues of the oral cavity and it is suggested that they take part in the development of oral inflammation. As Porhyromonas gingivalis is widely recognized as a major pathogen in the development and progression of gingivitis and periodontitis, the aim of our study is to determine the effect of P. gingivalis lipopolysaccharide (LPS) on mast cell degranulation, cysteinyl leukotriene (cysLT) generation, and migration, as well as Toll-like receptor (TLR)-2 and -4 expression. Experiments were carried out in vitro on rat peritoneal mast cells. LPS-induced mast cell histamine release was estimated by a spectrofluorometric method and cysLT generation by ELISA test. Mast cell migration in response to this antigen was examined according to Boyden's modified method and TLR expression was determined by flow cytometry. We found that P. gingivalis LPS did not induce mast cell degranulation and histamine release. However, activation of mast cells with this bacterial antigen resulted in generation and release of significant amounts of cysLTs. We also documented that LPS from P. gingivalis did not stimulate mast cell migration, even in the presence of laminin, whereas it strongly upregulated TLR2 and TLR4 expression on mast cells. Observations that P. gingivalis LPS activates mast cells to generate and release proinflammatory mediators such as cysLTs and modulates TLR2 and TLR4 expression indicates that these cells might be involved in the emergency of inflammatory processes evolved in response to P gingivalis infection.