Increased numbers of circulating donor-specific T helper lymphocytes after human heart valve transplantation.

Implantation of cryopreserved human donor heart valves for either congenital or acquired cardiac disease has been performed since the last three decades. Although the clinical outcome is good, long-term valve degeneration resulting in dysfunction has been observed. A specific immunological response of the recipient against the allograft has been proposed as one of the factors involved in this process. Helper T lymphocytes play an important intermediate role in cellular and humoral immune response. Increasing numbers of circulating donor-specific helper T lymphocytes precursors (HTLp) correlate with graft rejection after organ transplantation. To investigate whether cryopreserved human donor heart valves are able to induce a donor-specific T helper response, we monitored the HTLp frequencies (HTLpf) in peripheral blood samples of 13 patients after valve allograft transplantation by use of a limiting dilution assay followed by an interleukin-2 bioassay. Prior to transplantation, HTLpf specific for donor and third-party antigens showed individual baseline levels. After allografting, the antidonor frequencies significantly increased in 11 of the 13 patients (P = 0.02). This was not found for stimulation with third-party spleen cells (P = 0.68), which indicates a donor-specific response. Maximal donor-specific HTLpf were already found at 1--2 months after operation. Valve allograft transplantation induces an increase in the numbers of donor-specific HTLp in peripheral blood of the patients. Analogous to organ transplantation, these HTLp may play a crucial role in events that lead to valve damage. Therefore, monitoring of HTLp in peripheral blood samples might be informative for donor valve degeneration (rejection) and subsequently valve allograft failure.