BLOOD CD25+CD4+ T CELLS PHENOTYPE AND REGULATION ASSOCIATED MOLECULES IN “OPERATIONALLY TOLERANT” VERSUS CHRONIC REJECTION HUMAN KIDNEY RECIPIENTS.

Abstract

O351* Aims: Withdrawal (because of PTLD or non compliance) of immunosuppression (IS) in long term graft recipients usually results in a rejection. However some recipients referred as “operationally tolerant” keep a good and stable graft function following withdrawal. We analysed some key molecules linked to immune regulation in CD4+ and CD8+ blood T cells of these patients (6.3± 3.3 years following IS withdrawal) in comparison with kidney recipients. Methods: Four groups of individuals have been studied: a) “operationally tolerant” kidney recipients with a good and stable functional graft, drug free (DF-Tol) for more than 3 years, b) patients with histologically documented chronic rejection (CR) c) recipients with stable long term graft function under classical therapy (Sta) and, d) healthy individuals. Real-time PCR and cytofluorimetry were used to analyse a panel of molecules linked to immune regulation or activation, Th1/Th2 cytokines and chemokine receptors in CD4+/CD8+ blood T cell populations. T cell proliferative response was studied after anti-CD3/anti-CD28 antibodies stimulation. Results are quantified by [3H] thymidine incorporation. Results: CR recipients displayed less circulating CD4+CD25+ cells than DF-Tol patients and healthy individuals (10.4±4.9%, 19.9±5.2%, 17.4±7.5% respectively, p<0.05). These CD4+CD25+ were CD103, GITR, CCR4 and CTLA4 positive but these markers were not significantly increase in CD4+CD25+ of any studied groups. CD4+ and CD8+ cells in DF-Tol patients displayed a more FOXP3 transcript levels compared to CR patients (p= 0.0043 and p=0.026 respectively). However these levels were not higher than Sta patients and healthy individuals. No difference was observed for PD1, TGFβ, IL-2 and perforin transcripts between the different groups and Th1/Th2 chemokine receptor proteins CXCR3, CCR5, CCR9, CCR7. Finally, CD8+ and CD4+ T cells in all groups (DF-Tol, Sta, CR patients and healthy individuals) equally responded to a polyclonal anti-CD3/anti-CD28 stimulation (with and without IL-2), suggesting that blood T cells of tolerant recipients were not anergic or hyporesponsive. Conclusions: Drug free “operationally tolerant” patients exhibited a similar number of CD4+CD25+ blood T cells, a similar FOXP3 transcript level in both CD4+ and CD8+ T peripheral cells and a normal proliferative response compared to Sta patients and healthy individuals. In contrast, blood of CR patients displayed a significant defect in CD4+CD25+ T cells and higher significant decrease of FOXP3 transcript accumulation suggesting a lack of potentially regulatory mechanisms in these patients contrasting with normal levels in DF-Tol patients.