Preliminary results of intrathymic injection of donor cells to prevent acute rejection in human heart transplantation.

In rodents, the intrathymic injection of donor cells or major histocompatibility complex peptides induces indefinite survival of a subsequent allograft with little or no immunosuppression. Here, experiments have been performed in two patients with cardiac transplantation to establish (1) the safety and tolerability of the intrathymic injection of donor leukocytes at the time of transplant surgery and (2) whether conventional immunosuppression interfered with the process of the thymic recognition of alloantigens. It was shown that the intrathymic inoculation of donor cells is safe and can be done without undesired effects. However, the procedure, as performed, did not protect from acute graft rejection. There are data enough to attribute the failure of the thymus technique in these two patients to the concomitant use of immunosuppressants. The results of this study are relevant for future trials aimed at finding the appropriate experimental conditions for the use of the thymic approach in human organ transplantation.