Pretransplant Xenogeneic Blood Transfusions Reduce the Humoral Response in a Mouse‐to‐Rat Heart Transplantation Model

A mouse heart transplanted to a rat is rejected promptly 3 days after transplantation, independent of whether cyclosporin A (CyA) is used as an immunosuppressant or not. Adding a short course of deoxyspergualin (DSG) initially, in addition to continuous CyA treatment, results in long‐term graft survival and permits retransplantation during CyA monotherapy. In this paper, we have explored the possibility of substituting the initial heart transplant with blood transfusions. Lymphocyte‐enriched blood transfusions combined with CyA and an initial course of DSG proved to lower or eliminate the haemagglutinating antibody titre normally seen in acute vascular xenorejection. The therapy, however, did not prolong the mean survival of the cardiac xenograft, but the same treatment protocol could result in either hyperacute rejection or prolonged survival of up to 11 days. In conclusion, this and earlier studies propose that a humoral unresponsiveness can be induced if the recipient vascular circulation is exposed to a xenoantigen in a mouse‐to‐rat combination.