T CELL DIVERSITY AND FUNCTIONAL BIOLOGY

H.A. Nafady hego¹, Y. Li¹, S. Sakaguchi², S. Uemoto¹, T. Koshiba^1
1Hepatopancreatobillary Surgery And Liver Transplantation, Kyoto University Hospital, Kyoto/JAPAN, ², Institute for Frontier Medical Science, Kyoto University, Kyoto/JAPAN

Body:
Introduction:It has been recently shown that CD4⁺CD25⁺regulatory T (Tregs) express low levels of IL-7Rα, In this study we tried to assess the relevant clinical role ofCD4⁺CD25⁺ IL-7R ^{α low} cells in controlling immune responses directed to a living donor liver transplant (LDLT) in children. Methods: The peripheral blood monocular cells were derived from pediatric LDLT patients who could successfully stop immunosuppression(IS) (Tol n=22). CD4⁺CD25⁺ IL-7Rα^low was phenotyped by FACS analysis and isolated by a cell sorter .The results were compared with those of patients failed tostop IS due to rejection (Intol n=18), patients during the weaning process (Weaning n=10) and age-matched healthy volunteers (Healthy n=11). Results: After transplantation the frequency ofCD25⁺ IL-7Rα^low within CD4+ cells decreased in Intolerant group with no difference among the other groups (Intol, Tol, Weaning and Healthy; 5.2%, 7.6%, 7.2% and 8.9%:Intol vs. Tol, weaning and Healthy; p<0.001, p=0.003 and p<0.001).Intriguingly FOXP3 expression is up regulated in CD4⁺CD25⁺ IL-7Rα^low in Tolerance andweaning patients after transplantation and failed to increase in Intolerant patients (Intol, Tol, weaning and Healthy; 57.4%, 69%, 75.6% and 45.6%: Intol vs. Tol and weaning p=0.03 and 0.004 and Tolvs. Healthy p<0.001. (figure 1) CD4 proliferation on direct alloresponses was determined in MLR. CD4 proliferative response after stimulation by irradiated PBMCs from donor was significantly lower than that after stimulation by irradiated PBMCs from 3^rd party, Regulation of CD4 proliferation by CD4⁺CD25⁺ IL-7Rα^low cells was quantified both by their depletion from CD4⁺ cells. After depletion we detected a significant increase in CD4 proliferation directed to donor antigen in Tol (p=0.004) which reflected the regulatory capacity of these cells.(figure 2) the data represented as %increase = (cpm CD4 after depletion of Treg) - (cpm CD4) (cpm CD4 after depletion of Treg)Conclusion : Up to our knowledge this is the first report illustrating; up regulation of FOXP3 (the key Regulatory marker) in CD4⁺CD25⁺IL-7Rα^- in operational tolerant after pediatric LDLT and the contribution of this finding as a significant Surrogate markers for selecting the Tx patients for the safe and successful weaning from IS.

Disclosure: All authors have declared no conflicts of interest.