RESUMO
BACKGROUND: Xenotrasplantation is a possible alternative for organ shortage in clinical transplantation, but hyperacute xenograft rejection has been a big huddle. Pre-existing natural xenoreactive antibodies and consequent activation of the complement system are thought to play major roles in hyperacute rejection. To set a monitorig test for the hyperacute rejection in xenotransplantation, we optimised a complement hemolytic assay and evaluated its in-vitro precisions and clinical implications. METHODS: Complement hemolytic activities of normal human sera on rabbit or porcine red blood cells (RBCs) in each gelatin veronal buffer with or without dextrose were compared to retrieve optimal conditions for assay. The precision and activity range of normal human sera were evaluated at a given optimum condition. And we also assayed complement hemolytic activities of the sera obtained from various models of xenotransplantated animal, and assessed its association with other clinical parameters. RESULTS: The assay with rabbit RBCs in gelatin veronal buffer containing dextrose showed linear hemolytic reactions in the broadest range of serum dilutions with the least background hemolysis. Its intra- and inter-assay coefficient variation was 1.3% and 8.1%, respectively. The complement hemolytic activity was dependent on the serum levels of C3 and IgM. Severe hyperacute rejection in lung xenotransplantation was accompanied with a rapid decline of serum complement hemolytic activities compared to the basal level. CONCLUSIONS: The complement hemolytic assay using rabbit red cells has a clinically acceptable range of precision, and seems to be useful for the evaluation of hyperacute rejection in clinical xenotransplantation.