The Role Of CD4～+CD25～(high) Regulatory T Cell In Allogeneic Hematopoietic Stem Cell Transplantation

Objective:(1)To explore the reconstitution of CD4⁺CD25^high regulatory T cells earlyafter allogeneic hematopoietic stem cell transplantation(allo-HSCT).(2)To evaluate the roleof CD4⁺CD25^high regulatory T cells in the development of acute Graft-versus-hostdisease(aGVHD) and chronic Graft-versus-host disease(cGVHD).Methods:(1)Twenty-seven patients undergoing allo-HSCT were enrolled in this study.Collect donor graft and periperal blood of recipients at different time after transplant-ation(at 2 weeks, 1 month, 2 month, 3 month post-transpant respectively). TheCD4⁺CD25⁺ T cells and CD4⁺CD25^high T cells subpopulations ratios in CD4⁺ Tlymphocytes (CD4⁺CD25⁺/CD4⁺, CD4⁺CD25^high/CD4⁺) of the donor graft and recipentsperipheral blood were detected with the Flowcytometry, and the expression of FOXP3 genewere analyzed with Real-time PCR assays to study the early reconstitution dynamics ofCD4⁺CD25^high regulatory T cells following allogeneic stem cell transplantation.(2)Thirteen aGVHD and five cGHVD patients were enrolled in this study. Flowcytometrywere performed to detect the CD4⁺CD25⁺/CD4⁺ and the CD4⁺CD25^high/CD4⁺ ratios inperiperal blood at the onset of aGVHD and cGVHD, and when aGVHD was controlled.Real-time PCR assays were performed to analyze the expression of FOXP3 gene ofmononuclear cells in the peripheral blood. To study the correlations of CD4⁺CD25^highregulatory T cells with aGVHD and cGVHD.Results:(1)In without aGVHD group, the CD4⁺CD25⁺/CD4⁺ and CD4⁺CD25^high/CD4⁺ratios exhibited a similar change: the CD4⁺CD25⁺/CD4⁺ ratio increased significantly at 2weeks post-transplant, and the CD4⁺CD25^high/CD4⁺ ratio was significantly higher than thehealthy-control (P=0.003, 0.002), at 1month and 2～3 month post-transplant, both of the two ratios decreased (P＜0.05) ; the expression of FOXP3 increased significantly early aftertransplantation: at 2 weeks post-transplant, the FOXP3 expression of the peripheralmononuclear cells increased significantly than that of the donor grafts (P=0.025) , at 1 monthpost-transplant its expression also increased than the 2 weeks' level (P=0.007) ;while itremained below the healthy-control level within 3 months after transplantation(P＜0.05) .Compared with the without-aGVHD group, the CD4⁺CD25^high/CD4⁺ ratio inaGVHD-group also increased significantly together with the CD4⁺CD25⁺/CD4⁺ ratio, but theexpression of FOXP3 remained lower after transplantation (P＜0.05) and lower than theaGVHD-group at 1month and 2～3month post-transplant. (2)At the onset of aGVHD, theCD4⁺CD25⁺/CD4⁺ and the CD4⁺CD25^high/CD4⁺ ratios were both higher than the healthycontrol and without-aGVHD group (P＜0.05) ,but the expression of FOXP3 were lower thanthat of healthy control and without-aGVHD group (P＜0.05);when aGVHD was controlled, theexpression of FOXP3 raised compared with that at the onset of aGVHD (P=0.025), also theCD4⁺CD25^high/CD4⁺ ratio exhibited an increase tendency (P=0.050); at the onset of cGVHD,both of the CD4⁺CD25⁺/CD4⁺ ratio and the CD4⁺CD25^high/CD4⁺ ratio had no difference withthat of healthy control and without-cGVHD patients, while the expression of FOXP3 inperipheral blood mononuclear cells were lower than the healthy control (P=0.003).Conlusion:(1) The CD4⁺CD25^high regulatory T cells subpopulations can undergo asignificant expansion early after transplantation,but its complete reconstitution is a slowprocess.(2) The lower number of CD4⁺CD25^high regulatory T cells and/or their lowerexpression of FOXP3 gene may contribute to the development of aGVHD. (3) To monitorthe expression of FOXP3 and the change of CD4⁺CD25^high T cells subsets ratio in theperipheral blood may be helpful for the clinical diagnosis and treatment of GVHD.