Dynamic Changes Of Regulatory T Cells In BALB/c Mice By Trichloroethylene

BackgroundTrichloroethylene（TCE）is an organic solvent in industry, mainly used as cleaningand degreasing agents for metal parts and electronic components in hardware,electronics, toy industry, etc. The rising number of Occupational DermatitisMedicamentosa-like of Trichloroethylene (ODMLT) patients in our country has becomethe outstanding health hazards of workers exposed to TCE. There were many studies onthe pathogenesis of ODMLT, which considered it as delayed-type hypersensitivitymediated by T lymphocyte. Although most researches on inflammatory mechanism hadbeen carried out, the study on the regulatory mechanism of immunologic injury inducedby TCE has just started. Regulatory T cell is an new T cell population different fromTh1and Th2, and play an important role in the immune suppression or immunetolerance, mainly by the secretion of IL-10and(or) TGF-β.ObjectiveTo explore the dynamic changes of CD4+CD25+Foxp3+Treg cells in spleen ofTCE-induced mice by flow cytometrytechnology, and measure the level of TGF-β andIL-10in skin and sera at different time points, providing a theoretical basis forillustrating the hazards and mechanisms of ODMLT and countermeasures of TCE.MethodEighty healthy female BALB/c mice in6to8weeks, were randomly divided intoblank control group and TCE treatment group. Establish a BALB/c mice sensitizedmodel, observe and record the of tested part of the mice skins. At24h after the lastchallenge, the TCE treatment group, according to the sensitization status and thematerial collection points (on the1st day,2nd day,3rd day,7th day,14th day after thelast challenge, the blood samples, skin tissues and spleens were aseptically collected,respectively), was divided into sensitized1d group, sensitized2d group, sensitized3d group, sensitized7d group, sensitized14d group and unsensitized1d group,unsensitized2d group, unsensitized3d group, unsensitized7d group, unsensitized14dgroup. PBMCs of spleen were stained with fluorochrome-conjugated mAbs andanalyzed by flow cytometry. Detection of TGF-β and IL-10in sera was examined byenzyme-linked immunosorbent assays. Expression of TGF-β and IL-10in skin wasexamined by immunohistochemical technique.Result1. Sensitization rateIn the skin sensitization test, the control group showed no erythema or edema.Twenty-seven of seventy-five mice in TCE treatment group showed erythema or edema.Sensitization rate was36%.2. The proportion of spleen Treg cellsThe proportion of CD4~+CD25~+Foxp3~+Treg in sensitized2d or3d group wassignificantly higher than that in control group or sensitized1d group. It had reached thehighest level in sensitized3d group, which no statistically significant differencecompared with sensitized2d group. Sensitized7d or14d group was significantly lowerthan sensitized2d or3d group. At the same material collection point, the proportion ofCD4~+CD25~+Foxp3~+Treg in sensitized2d or3d group was significantly higher thanthat in the corresponding unsensitized group.3. Level of IL-10and TGF-β in seraThe levels of IL-10in all sensitized groups were significantly higher than that ofcontrol group. The level of IL-10in sensitized groups showed an ‘first upward and thendownward’ trend. It had reached the highest level in sensitized3d group, and sensitized2d3d,7d, or14d group was significantly higher than sensitized1d group. At the samematerial collection point, the level of IL-10in sensitized group was higher than that inunsensitized group, and the difference was not statistically significant but theunsensitized14d group.The level of TGF-β in sensitized1d,2d,3d, or14d groups was significantly higherthan that in control group. Sensitized3d,7d, or14d group was lower than sensitized1d group, and the difference was statistically significant. Sensitized3d or7d group waslower than sensitized2d group, and the difference was statistically significant. At thesame material collection point, the level of TGF-β in sensitized group was respectivelyhigher than unsensitized group, but only in sensitized2d group there was an statisticallysignificant difference compared with unsensitized2d group (P <0.05).4. Level of IL-10and TGF-β in skinsThe level of IL-10in sensitized1d,2d, or3d group was significantly higher thanthat of control group. The level of IL-10in sensitized1d,2d, or3d group wassignificantly higher than sensitized7d or14d group. At the same material collectionpoint, the level of IL-10in sensitized1d,2d, or3d group was significantly higher thanthat in the corresponding unsensitized group.The level of TGF-β in sensitized1d,2d,3d, or7d group was significantly higherthan that in control group. Sensitized2d or3d group was higher than sensitized1dgroup, and the difference was statistically significant. Sensitized7d or14d group wassignificantly lower than sensitized3d group. Sensitized7d was significantly higher thansensitized14d group which was to a minimum. At the same material collection point,the level of TGF-β in sensitized1d,2d, or7d group was significantly higher than that inthe corresponding unsensitized group.Conclusion1. TCE can cause sensitive effect on BALB/c mice with proper dose,at this experimentcondition, the sensitive rate is36%.2. The level of CD4+CD25+Foxp3+Treg cells and its related cytokines IL-10、TGF-βshowed statistical significannce between sensitized and non-sensitized groups, they mayparticipate in the formation of TCE-induced cutaneous sensitized reaction and plays animportant role in DMLT.