Kidney-induced systemic tolerance of heart allografts in mice.

In swine and nonhuman primates, kidney allografts can induce tolerance of heart allografts, leading to their long-term, immunosuppression-free survival. We refer to this phenomenon as kidney-induced cardiac allograft tolerance (KICAT). In this study, we have developed a murine model for KICAT to determine the underlining cellular/molecular mechanisms. Here, we show that spontaneously accepted DBA/2J kidneys in C57BL/6 recipients induce systemic tolerance that results in the long-term acceptance of DBA/2J heart allografts but not third-party cardiac allografts. The state of systemic tolerance of hearts was established 2 weeks after transplantation of the kidney, after which time, the kidney allograft is no longer required. Depletion of Foxp3+ T cells from these mice precipitated rejection of the heart allografts, indicating that KICAT is dependent on Treg function. Acceptance of kidney allografts and cotransplanted heart allografts did not require the thymus. In conclusion, these data show that kidney allografts induce systemic, donor-specific tolerance of cardiac allografts via Foxp3 cells, and that tolerance is independent of the thymus and continued presence of the kidney allograft. This experimental system should promote increased understanding of the tolerogenic mechanisms of the kidney.