Background: Decreased in vitro T cell alloreactivity, demonstrated by decreased frequencies of peripheral blood donor-specific T cell precursors, may reflect a tolerant state after transplantation and lower the risk for development of chronic graft dysfunction. It is unknown whether a decrease in donor-specific T cell frequencies also occurs after clinical lung transplantation and if such a decrease lowers the risk for bronchiolitis obliterans syndrome (BOS), a hallmark of chronic graft dysfunction. Therefore, we compared changes in posttransplant donor-specific cytotoxic T lymphocyte (CTLp) and helper T lymphocyte precursor (HTLp) frequencies in lung allograft recipients with good graft function and in recipients with BOS.
Methods: Donor and third party specific CTLp and HTLp frequencies were determined by limiting dilution assay in pre- and posttransplant (1 year) peripheral blood samples of lung allograft recipients with good graft function (n = 13) and BOS (n = 10).
Results: In recipients with good graft function, mean donor-specific CTLp frequencies decreased after transplantation (183 vs. 16 precursors before and after transplantation, respectively). Additionally, HTLp frequencies decreased but this was not specific for donor alloantigens because third party-specific HTLp frequencies decreased also. Surprisingly, recipients with BOS also showed a decrease in mean donor-specific CTLp frequencies after transplantation (332 vs. 49 precursors before and after transplantation, respectively). Again, HTLp frequencies decreased nonspecifically.
Conclusions: We conclude that donor-specific CTLp frequencies decrease after lung transplantation, but that this does not result in transplantation tolerance protecting the lung against the development of chronic graft dysfunction.