Research Of The PD-1~+CD8~+ Tregs In The Chronic Rejection Of Mice Heterotopia Tracheal Allograft

Objective: This study was undertaken to establish a mouse model for chronic rejection of ectopic tracheal transplantation,assess the level of PD-1+CD8+Tregs expression on D28 postoperatively and discuss the mechanism.Methods: 60 mice were randomized(n = 20/group)to experimental,intervention and control group,with 10 donors and 10 recipients in each group.In the experimental and the intervention group the donors were BALB/C mice while the recipients were C57BL/6 mice.In the control group the donors and recipients were all C57BL/6 mice.Cyclosporine was applied in the intervention group.Dorsal subcutaneous transplantations in the recipients were accomplished with grafts being donors’ tracheae which were extracted on D28 postoperatively.The expression of PD-1+CD8+Tregs was assessed by using hematoxylin-eosin(HE)staining,immunohistochemical method and Double immunofluorescence staining.Results: The operation was successfully completed,and the postoperative activity of the recipient mice was no obvious abnormality.Experimental group and intervention group graft epithelial cell necrosis,completely visible obvious fibrosis organization,lumen blocking rate is about 78±11%,61±13%,control group graft organizational structures closing to normal,with the rate of lumen blocking being about 33.8±17%.After allotransplantation,the thickness of the tube wall was higher than the isoplastic graft,and the difference was statistically significant P<0.05(P=0.006,P=0.03),and the rejection resulted in thickening of the tube wall and the occurrence of lumbar obstruction.Flow index of nonparametric tests suggest statistical significance between three groups no significant P > 0.05(P = 0.32,0.81),while the rejection led to obvious lumens article fiber hyperplasia of sample material,but the wall deformation was not serious with no obvious lumen occlusion happening.The expression of PD-1 in the experimental group was strongly positive,and the expression of CD8+ was strongly positive.The control group was weakly positive staining of PD-1 and CD8+ weak positive staining.The expression of PD-1 in the experimental group was positive,and the expression of CD8+ was positive,and the statistical significance was significant.The expression of PD-1+CD8+Tregs in the experimental group and the intervention group was higher than that of the same group(control group),but the statistical significance of the non-parametric test indicated no significant.In the intervention group,PD-1+CD8+Tregs/CD8+T percentage was higher than the other two groups,the statistical significance was significant(P<0.05).Conclusion: The model of chronic rejection of ectopic trachea transplantation in mice was successfully established,and PD-1+CD8+Tregs may play a protective role in the chronic rejection reaction,and cyclophosphamide may be negatively regulated by PD-1+CD8+Tregs.