Rapid decreases in donor-specific cytotoxic T lymphocyte precursor frequencies and graft outcome after liver and lung transplantation

Background. A decrease in donor-specific T cell precursor frequencies as se en late, one or more years, after transplantation is assumed to reflect tra nsplantation tolerance, a condition important for long term acceptance of t he allograft. However, such late decreases also occur in recipients that de veloped chronic transplant dysfunction questioning its relevance in transpl antation tolerance, We investigated whether early, i.e., the first 6 months , decreases in donor-specific T cell precursor frequencies reflect transpla ntation tolerance and predict graft outcome after liver and lung transplant ation. Methods. Donor and third party specific cytotoxic (CTLp) and helper T lymph ocyte precursor (Rnp) frequencies were analyzed in pretransplant and 1 (or 2) and 6-month blood samples taken from liver and lung recipients and were correlated with graft outcome. Results. In liver allograft recipients with good graft function (n = 7), me an donor-specific CTLp frequencies decreased as early as 1 month after tran splantation and remained low thereafter, In contrast, mean CTLp frequencies did not decrease in liver allograft recipients with chronic transplant dys function (n = 6). In lung allograft recipients, donor-specific CTLp frequen cies remained relatively high and frequencies were not different between re cipients without (n = 6) or with (n = 6) chronic transplant dysfunction. Do nor-specific HTLp frequencies did not change significantly after liver or l ung transplantation and did not differ between recipients without or with c hronic transplant dysfunction, Conclusions, An early decrease in donor-specific CTLp correlates with good graft outcome after liver transplantation. Such rapid decreases in alloreac tivity do not occur after lung transplantation illustrating the unique capa city of liver allografts to induce transplantation tolerance.