DONOR-DERIVED HUMAN-LEUKOCYTE ANTIGEN CLASS-I PROTEINS IN THE SERUM OF HEART-TRANSPLANT RECIPIENTS

Background: Human leukocyte antigen class I proteins are expressed on most cell types in all organ allografts but are constituitively secret ed only by certain organs, for example, the liver. We hypothesized tha t detectable levels of donor-derived human leukocyte antigen proteins would be released from transplanted cardiac allografts only when the a llograft was immunologically stimulated, that is, during rejection and perhaps during viral infection. If so, then the release of donor huma n leukocyte antigen might be a noninvasive monitor of these events. Me thods: We used an enzyme-linked immunosorbent assay to detect donor-de rived human leukocyte antigen-A2 in the serum of 21 human leukocyte an tigen-A2 negative recipients of human leukocyte antigen-A2-positive he art transplants. The level of donor human leukocyte antigen-A2 during the first 100 days after transplantation was correlated with the clini cal status of the patient. Results: We found little or no donor human leukocyte antigen in the serum of heart transplant recipients whose po stoperative clinical course was unremarkable for infection or rejectio n. We did find donor-derived human leukocyte antigen in the serum of h eart transplant recipients transiently in the week immediately after t ransplantation, continuously from patients in whom chronic rejection w as developing, during cytomegalovirus infection, and during some, but not all, acute rejection episodes as determined by endomyocardial biop sy. Conclusions: These findings are consistent with the hypothesis tha t the donor human leukocyte antigen serum level reflects vascular dise ases, rather than myocardial disease in the transplanted heart. Theref ore, the serum level of donor human leukocyte antigen cannot be used a s a monitor of cellular infiltration and myocyte damage as currently a ssessed by endomyocardial biopsy but may be an early indicator of the development of vascular disease such as chronic rejection.