| Objective This study was designed to investigate the effect of the pathway of B7/CD28 and CD4+CD25+ regulatory T cells on the recipient immunoloregulation in the model of SD to Wistar rat cardiac allotransplantation. The mechanisms of rejection in allotransplantation will be explored in the model.Materials and methods CD4+CD25+ regulatory T cells were isolated from Wistar rat splenocytes and peripheral lymphnodes by using magnetic cell sorting system (negative selection and positive selection). The purity of isolated CD4+CD25+ regulatory T cells was detected by flow cytometry.Donor(SD rat) and recipient(Wistar rat) were divided randomly into four groups. Group A(no treatment): The heart from SD rat was transplanted into the abdomen of Wistar rat without any pre-treatment; Group B(B7-2 mAb Group ): Tolerance was induced in Wistar rats by injecting 1mg B7-2 mAb in abdomen when doing heterotopic transplantation; Group C (control group): 1x 106 fresh CD4+CD25+ regulatory T cells were infused intravenously into the caudal vein of each Wistar rat 1 day before transplantation; Group D (experimental group): the recipients were injected with 1x 106 CD4+CD25+ fresh regulatory T cells 1 day before transplantation and 1mg B7-2 mAb on the day of transplantation. The mean survival time (MST) of grafted heart,the content of CD4+CD25+ regulatory T cells in peripheral blood,the optical density(OD) of mixed lymphocyte reaction (MLR), the expression of IL-2,TGF-β1 and the pathology were observed.Results (1)MST:Group A: 7.5±1.7d; Group B: 48.3±7.6d; Group C: 68.5±5.6d; Group D: 84.3.6±5.1d.The MST of Group B,Group C and group D were longer than group A, P<0.05. Group C> GroupB ,P >0.05.The MST of Group D > Group C,and P<0.05. (2)The quantity of Wistar rat blood CD4+CD25+ regulatory T cells after transplantation: Group B was lower than group A,(P<0.05). Group C and group D were higher than groupA,(P<0.05).Group C was lower than group D.(P<0.05). (3) The results of MLR: Group A:1.08±0.04; Group B:0.77±0.05; Group C: 0.68±0.05; Group D: 0.57±0.05. The optical density (OD) of group C and group D was much lower than group A, P<0.05. MLR of group D was lower than group B,group C , P<0.05 (4)The expression of IL-2: The level of IL-2 was higher when the grafts rejected than that before transplantation in group A, P<0.05.In group D,expression of IL-2 was not greater than those in na?ve Wistar rats,P >0.05.IL-2 after grafting in group D is lower than that in both of group B and group C, P<0.05.(5)The expression of TGF-β1:When the grafts rejected,the TGF-β1 level of group A was not higher than that before transplantation,P >0.05. In group D, TGF-β1 was strongly expressed on week 1,4 and 6 after grafting, P<0.05. TGF-β1 after grafting in group D is much higher than those in group B,C and P<0.05.Conclusions 1,Injecting B7-2mAb can block the pathway of B7/CD28.Secretion of IL-2 is inhibited, while expression of TGF-β1 is increased. It helps to induce immune tolerance.2,Infusing fresh CD4+CD25+ regulatory T cells can precipitate Th1 and Th2 cell respondence to immune deviation.Secretion of IL-2 is inhibited, while expression of TGF-β1 is increased. It helps to induce immune tolerance.3,Injecting B7-2mAb affiliacted with Infusing fresh CD4+CD25+ regulatory T cells can induce immune tolerance better in this experiment.4,Injecting B7-2mAb can inhibit the generation of CD4+CD25+ regulatory T cells,increase their inhibitory function by TGF-β1. |
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