Presented at:
9th Congress of the British Transplantation Society
Seattle, Washington, March 29-31, 2006
Indices of immunological tolerance in renal transplantation: Interim analysis
Hernandez-Fuentes MP, Sagoo P, Jimenez-Vera E, Rovis F, Waters J, Hilton R, Warrens AN, Lechler R
King's College London; Imperial College, London
Induction of tolerance is a desired long-term outcome for renal transplant patients. However, in order to manipulate the immune response to achieve tolerance, we first need to identify the specific immunological characteristics which describe the tolerant phenotype. This ongoing study scrutinizes the cellular basis of tolerance in terms of specific anti-donor responses and regulatory activity of CD4+CD25+ Tregs in 4 specific groups (n=20 per group) of renal transplant recipients: (1) stable renal function with a non-CNI-based immunosuppressive therapy; (2) stable renal function with a CNI based therapy; (3) patients undergoing chronic rejection; and (4) drug-free tolerant recipients. Quantitative assessments of recipient reponses to donor and 3rd party antigends were made by IFNγ and IL-4 ELISPOT analysis. Donor-specific responses generated by the indirect pathway were prepared by stimulating recipient PBMCs with a preparation of solublized donor membrane proteins. Frequencies of direct parthway donor-reactive CD8 and CD4 T cells were studied by stimulation with APCs prified from donor PBMCs or spleen. Direct pathway T cell responder frequencies were also estimated by CFSE analysis. Depletion of CD4+CD25_ cells from responder populations in ELISPOT and CFSE assays further allowed detection of Treg-mediated regulation of anti-donor responses.
Interim data analysis shows that using these assays, donor-specific hypo and hyper-responsiveness is detected, along with donor-specific Treg activity. By performing these assays in parallel on each patient group, we aim to detect immunological differences which may govern the tolerant state. We expect that with more patients analysed by the study endpoint, a clinically important answer should be obtained. Donor-specific assays developed for this study provide an insight into the development of recipient responses following transplantation and will help to elucidate the governing role of Tregs in immune tolerance and chronic rejection. In addition, combined with data from molecular and genetic studies (in vivo DTH, microarray, TCR-landscaping) on these same patients, this data should significantly frther our understanding of regulatory mechanisms and provide and immunological 'fingerprint' of tolerance.