Background: Due to many geological reasons arsenic (As) appears in water, food and soil in Bijar, Kordistan province. As-contaminated water and food lead to major health problems in human and animals. Determination of As in water, hair and urine biomarkers in the region revealed a huge exposure of inhabitants to the As; this can deteriorate health effects of the exposed people. These geogenic As is able to disregulate the immune system through immune-sensor molecules like surface receptors of immune cells, such as TLRs etc. By far the most pivotal cells in the induction of immune responses are dendritic cells (DCs); they specifically dictate T-cell polarisation depending on the nature of the encountered antigens and environmental cues. There is countless information on As chemistry, but the information on the effect of As on immune-sensor molecules in DCs is little. Objectives: The main goal of this study was to examine the effect of As on the gene and protein expression of key immunosensor molecules, TLR2 and TLR4, in monocyte-derived DCs (MoDCs) of healthy humans, and eventually to get insight into how this dangerously toxic element disturbs the immune system. Methods: To elucidate the effect of As on the function of DCs, the MoDCs were generated from blood samples of 6 healthy individuals (age 21-27 years). In general, production of MoDCs from adhered monocytes yielded >90% CD11c+ DC, with >93% viability. The ability of the As to affect the immunosensor molecules was investigated in DCs culture system using primary cells, MoDCs. In the cell culture media the generated MoDCs were then exposed to 0ng/ml (control group) and 20ng/ml (treatment group) of As for 2 h. The RNA were extracted from treated and control MoDCs and subjected for cDNA synthesis and then used for qPCR using primers specific for TLR2 and TLR4. Protein expression of TLR2 and TLR4 in MoDCs upon stimulation of the the cells with As for 2 h was assessed by two-color flow cytometry method; briefly, the pure control and As-exposed MoDCs stained with FITC-anti-TLR2 and PE-anti-TLR4. A minimum of 10,000 MoDCs was acquired for each sample. Protein expression of the TLR2 and TLR4 was eventually expressed in terms of mean fluorescence intensity. Results and conclusion: This study focused the in vitro effects of a minimal geogenic level of As on some key TLRs in human MoDCs. Analyses of the results from qPCR showed that As significantly increased (P<0.05) both TLR2 and TLR4 transcripts in human MoDCs. Moreover, As significantly up-regulated expression of TLR2 and TLR4 proteins in human MoDCs. When exposed to As for 2h, the observed over-expression of each TLRs mRNA in the MoDCs was similar to what was observed in the TLRs proteins. Apart from the observed effects of As on TLR2/TLR4 in human MoDCs, in porcine in vitro model we also observed that As interferes with antigen presenting capacity and maturation of MoDCs (unpublished data). It might therefore be likely that induction of immunodisregulation, immunotoxicity and thus (non)infectious diseases in chronically As-exposed people are highly likely. Our research in this area is still ongoing.

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