ACTIVATION OF THE IMMUNE SYSTEM IN PATIENTS AFTER CRYOPRESERVED HUMAN CARDIAC VALVE TRANSPLANTATION.

Abstract

105 In clinical application of cryopreserved human cardiac allograft valves HLA-matching is not performed and immunosuppression is not routinely administered. Recently, in vitro studies have demonstrated that endothelial cells obtained from these cryopreserved human cardiac valves express HLA class I and II antigens and that they are able to induce lymphoproliferation. In addition, graft infiltrating cells obtained from valve allograft explants showed donor-specific cytotoxicity. In serum of patients after cryopreserved human cardiac valve transplantation donor-specific antibodies could be detected between 1-13 months after the operation. This indicates that after cryopreservation donor valves remain immunogenic. The reason for early valve allograft degeneration and dysfunction could be immunological. After organ transplantation cytotoxic T-lymphocytes (CTL) with high avidity for donor antigens are regarded as the major effector cells causing graft rejection. It is unknown whether these cells play a role in the allo-response against cryopreserved human cardiac valves. Therefore, we investigated by limited dilution analysis whether the frequency of CTL with high avidity for donor antigens increases in peripheral blood of patients after allogenic cardiac valve transplantation. From three patients, 4 to 6 peripheral blood samples were obtained during eighteen months after transplantation. By addition of anti-CD8 monoclonal antibodies in the cytotoxic phase of the assay, the CTL with high avidity (no inhibition) could be distinguished from those with low avidity (inhibition) for donor antigens. In the blood samples of the first patient the donor-specific CTL frequency increased from 31±5/106 cells prior to transplantation (day 0) to 72±10 in the blood sample 272 days after transplantation and it remained high (61±9 on day 398). The percentage CTL with high avidity increased from < 10% to 80±8%. In the second and third patient a similar increase was found. Patient 2: 11±3/ < 10% (day 0), via 70±7/ 86±8% (day 140) to 155±18/ 59±6% (day 469) and patient 3: 18±3/ < 10% (day 0) to 54±7/ 21±4% (day 28). Donor-specific allo-antibodies were also found in the sera of these patients. We have shown the induction of high-avidity CTL in the peripheral blood after transplantation of cryopreserved human cardiac valves. The observed proportion of these high-avidity CTL indicates the clinical relevance of the allo-reactivity against these valves.