IMMUNE REGULATION AND TOLERANCE II

J. Wang, P. Urbanellis, I. Shalev, W. He, O.A. Adeyi, M.J. Phillips, D.R. Grant, G.A. Levy
University Of Toronto Transplant Institute, University Health Network, Toronto/CANADA

Body: Introduction: Organ transplantation is one of the most challenging and complex areas of modern medicine. Tolerance - the stable maintenance of good allograft function without continuing need for immunosuppressive drugs could eliminate the adverse events associated with immunosuppression. The broad application of tolerance strategies to clinical transplantation will be dependent on identifying assays or markers that are predictive of the tolerance state. In this study, our objective was to identify differentially regulated proteins that can be served as potential biomarkers for tolerance and rejection. Methods: We used a fully MHC-mismatched murine heterotopic heart transplant model, in which a state of tolerance can be induced by rapamycin, to study the proteome profiles of tolerant and rejecting grafts. Soluble proteins were extracted from transplanted hearts and separated by 2D gel electrophoresis. The 2D gel images of naive control hearts, rejecting hearts and tolerant hearts were compared using Bio-Rad 2D image analysis software. Differentially regulated protein spots were analyzed, quantified, and further identified by MALDI-TOF. Results: Nineteen proteins were up-regulated at least 2-fold in tolerant heart compared to naive and rejecting hearts. Among these proteins, 5 proteins are subunits of proteasome or proteasome activator complex, suggesting a proteasome involvement in regulating cell death that may contribute to the tolerance of the graft. Six up-regulated proteins are structural proteins, such as vimentin, actin, cofilin, gelsolin, and tubulin that are involved in maintaining and enhancing the tolerant heart function. Metabolic proteins and enzymes that are involved in ATP synthesis and electron transfer pathway were among the 19 proteins that were down-regulated in tolerant hearts. The down-regulation of these proteins confirmed an impaired function of the heterotopically transplanted hearts. Five proteins including two heat shock proteins were up-regulated by at lease 2-fold in rejecting hearts, but not in naive and tolerant hearts. Conclusion: Our results demonstrate quantitative proteomics as a robust analytical tool for the identification of potential biomarkers for tolerance and rejection.

Disclosure: All authors have declared no conflicts of interest.