CREATION OF THE "THYMOHEART" ALLOGRAFT

Background. A state of tolerance may be more easily achieved if fully vascularized and functional donor thymus is transferred to the recipient at the time of whole organ transplantation. Methods. A composite "thymoheart" allograft was created by implanting autologous thymus into a donor heart 60-90 days before organ procurement. Successful intracardiac engraftment of autologous thymus was documented by histology and by flow cytometric analysis. Results. Histology of the thymic autografts at explantation revealed viable thymus with preservation of normal thymic architecture. Cells retrieved from thymic autografts 60 days after implantation exhibited the same MHC class I and class II staining profiles by flow cytometry as cells taken from the residual native thymus. Conclusion. We have created a novel composite organ that confers vascularized and functional donor thymus to heart allograft recipients at the time of transplantation without affecting cardiac function.