Investigations for effects of toxins from gram pozitive bacteria on toll-like receptors of mesenchymal stem cells.

Investigations for effects of toxins from gram pozitive bacteria on toll-like receptors of mesenchymal stem cells.Toll-like receptors (TLRs) are members of pattern recognition receptors that recognize pathogen-associated molecular patterns (PAMP) as an important component of innate immune responses. TLR expression by various cells of the innate immune system has been well characterized. However, there is some controversial information pertaining TLR expression by bone marrow-derived mesenchymal stem cells (BMSCs). The purpose of this study was to investigate the effects of Diphtheria toxin and Staphylococcal enterotoxin B (SEB) on TLR expression by human bone marrow-derived mesenchymal stem cells (hBMSCs).MTT assay was used to determine viability of hBMSCs that were exposed to different concentrations of toxins for 24 hours.TLR expression was explored using TLR-specific antibodies by flow cytometry.Diphtheria toxin did not affect TLR expression at all. However, SEB changed TLR expression in a dose dependent fashion. For example, while 30 µg/ml SEB increased expression of TLR-1, SEB at the concentrations of both 3 µg/ml and 30 µg/ml increased expression of both TLR-2 and TLR-3. SEB did not affect expression of the other TLRs.First of all, the results of this study have suggested that SEB could be involved in regulation of TLR-1, TLR-2, and TLR-3 expression by hBMSCs. Secondly, these findings indicate a novel discovery since no literature pertaining effects of SEB on TLR expression by hBMSCs. Therefore, further investigations are needed to make a final definitive conclusions about the regulatory roles of SEB on TLR expression particularly by hBMSCs.