Basic And Clinical Research Of Induced CD4⁺CD25^high Regulatory T Cells Following Transplant

Lymphocytes that respond to alloantigens after transplantation have the potential to develop into not only effector lymphocytes attacking the allograft,but also.into an inhibitory population of T cells termed CD4⁺CD25^highTreg cells. Previous studies showed that CD4⁺CD25^highTreg cells played a key role in peripheral tolerance following organ transplantation.In this study,we were interested in understanding the biology and function of CD4⁺ CD25^highTreg,and the mechanism to induce tolerance in transplant recipients.First,we determine the phenoty of the purified CD4⁺CD25^highTreg cells. Immunomagnetically purified CD4+CD25+T cells colocalized within the CD4⁺ CD25 high population sorted from PBMCs using FACS in kidney recipients. FOXP3 RNA and protein were expressed at low levels in non-CD4⁺ and CD4⁺CD25^- cells,T-cell subsets,but at relatively higher levels in purified CD4+CD25+T-cell subsets.Second,we tracked CD4⁺CD25^highTreg peri-transplantation.After transplant, CD4⁺CD25^highTreg cells were induced and expanded in the periphery and that they readily accumulated in the allograft after transplantation,retaining their alloreactivity,their homing and expansion capabilities,and their suppressive efficacy in vivo.Furthermore,significant inhibition of induced CD4⁺CD25^-T cells was seen in cultures where PBMCs from recipients were mixed together as the stimulating antigens at a 1:8 ratio of conventional T cells:Treg cells.Third,we clarify the hypothesis that peripheral blood imbalances between cytopathic cells and Tregs would resulted in acute rejection and also be associated with outcome of acute rejection.Levels of Treg cells were significantly increased in patients with acute rejection(8.779%±2.614%)compared with stable allograft function(7.543%±2.527%)(p=0.043).Levels of CD4⁺CD25^highTreg were not statistically different in both groups with successful reversal and without(P=0.38).The rate of CD8⁺T cells per CD4⁺CD25^highTregs in patients with acute rejection(9.229%±2.826%)was nearly identical to that of recipients with stable kidney function(7.578%±1.468%).However,recipients with successful reversal acute rejection showed significantly lower ratio of CD8+T cells per CD4+CD25^highTregs compared with recipients without reversal(P=0.01).Fourth,we clarified the effect of the anti-CD25 monoclonal antibody (anti-CD25mAb)induction therapy on CD4⁺CD25^highTreg cells.Compared with the control group,recipients with anti-CD25mAb injection had significantly lower percentage of CD4⁺CD25^highin total CD4⁺ cells(1.13%±0.13%vs1.94%±0.22%, P=0.00;3.75%±0.28%vs7.11%±0.51%,P=0.00)on day 3,17 after transplantation.While,the percentage was not significantly different on day 10, 27(3.72%±0.19%vs 4.36%±0.28%,P=0.08;7.84%±0.35%vs 8.56%±0.36%, P=0.16).However,there was not obvious difference in Foxp3 expression level and function of the CD4⁺CD25^highTreg cells at the different time point after transplant.Conclusions:1.CD4⁺CD25^highTreg cells are consistent with the current description of Treg following transplant.2.Induced CD4⁺CD25^highTreg cells could regulate immune responses and induce tolerance to alloantigens in vivo following solid-organ transplantation.3.Increased CD4+CD25^highTreg cells in patients correlated with acute rejection,and low CD8⁺T cells/CD4⁺CD25^highTreg as a predictor of acute rejection reversal.4.The short-term treatment with anti-CD25mAb might not prevent the production,proliferation and function of neogenetic CD4⁺CD25^highTreg cells in organ transplant.