Presented at:
World Transplant Congress 2006
Boston, MA, July 22-27, 2006
Indices of tolerance: interim report
Hernandez-Fuentes MP, Sawitszki B, Sagoo P, Flavia R, Jimenez E, , Perucha E, Le Moine A, Craciun L, Peters B, Braudeau C, Brouard S, Trzonkowski P, Warnecke G, Chapman S, Libin M, Warrens A, Goldman M, Volk H-D, Soulillou JP, Janssen U, Wood K, Lechler RI.
King's College London, United Kingdom; Imperial College London, United Kingdom; Universite Libre Bruxelles, Belgium; Charite Medical Hospital, Berlin, Germany; INSERM U437, Nantes, France; Miltenyi Biotech GmbH, Germany; Oxford University, United Kingdom.
This multi-centre study is aimed at finding specific immunological characteristics which identify tolerance, by in vitro immunological monitoring of 4 groups of renal transplant recipients; Stable renal function with (1) CNI or (2) non-CNI based immunosuppression, patients undergoing (3) chronic rejection (CR) and (4) drug-free tolerant recipients.
Quantitative assessments of donor-specific responses are obtained by IFNg ELISpot and CFSE analysis. Donor and 3rd party stimulation of directly and indirectly primed responder cells is also assessed by real time-PCR analysis of TH1/TH2 cytokines and FoxP3. CD4+CD25+ depletion from responder populations in these assays is used to detect donor-specific Treg-mediated suppression. Quantitative-PCR analysis of a panel of tolerance and rejection associated genes is performed on recipient PBMCs. Combined with other approaches used to examine these same patients (trans-vivo DTH, micro-array, TCR-Landscaping) this study may provide an immunological 
fingerprint
of the tolerant state.
Interim data shows that ELISpot can be effectively used to detect donor-specific hyporesponsiveness and donor-specific regulation of indirect allo-responses, where regulation is also detectable by RT-PCR cytokine analysis. By q-PCR analysis of PBMCs, there appears to be no clear correlation between the expression of single genes and tolerance versus rejection. However analysis of FoxP3 and a-Mannosidase expression as a ratio does appear to distinguish tolerant from CR patient groups, where CR patients display a significantly lower ratio and conversely, tolerant patients show a higher ratio compared to stable transplant recipients.
Donor-specific assays can provide an insight into the generation and regulation of recipient responses following transplantation. Preliminary q-PCR analysis shows it can be used to distinguish tolerant patients, with the potential to indicate patients where immunosuppression withdrawal may be possible.