Prolongation of rat heart allografts by donor-specific blood transfusion treated with ultraviolet irradiation

The effect of donor-specific blood transfusion was compared to that of UVB-irradiated donor-specific blood transfusion on heart allograft survival in inbred rats with major histocompatibility differences. In one series ACI rats received heterotopic heart grafts from Lewis rats and 1 mL transfusion of donor-type blood at 1, 2, and 3 weeks prior to the transplantation. Fifty percent of the grafts were permanently accepted (survival greater than 200 days). Following UVB-irradiated donor-specific blood transfusion, 55% of the grafts survived indefinitely. In a mixed lymphocyte reaction ACI lymphocytes are weak responders to Lewis lymphocytes. In another series, Lewis rats received ACI hearts. Donor-specific transfusions at 1, 2, and 3 weeks prior to transplantation did not significantly alter the survival of heart allografts. Lewis lymphocytes react strongly to ACI stimulator cells in a mixed lymphocyte reaction. However, when the donor blood was UVB-irradiated prior to transfusion, the ACI allograft survival was significantly prolonged in this ACI-to-Lewis strain combination. When Lewis rats received W/F hearts following either donor-specific or UVB-irradiated donor-specific transfusions, the hearts' survival was similarly and significantly prolonged, but did not become permanent. Mixed lymphocyte reaction reveals that the stimulation index of Lewis lymphocytes against W/F lymphocytes is greater than that of ACI versus Lewis, but is less than that between Lewis responder cells against ACI stimulators. Thus, donor-specific transfusion prolongs heart allograft survival in most rat combinations, but is most striking in combinations where the mixed lymphocyte reaction shows the lowest stimulation index. The addition of UVB-irradiation to donor-specific transfusion significantly increases heart allograft survival only in the ACI to Lewis strain combination, which has a high stimulation index in the MLR. This suggests that pre-treatment with UVB-irradiated donor-specific transfusion may increase the beneficial effect of such transfusions on graft survival in strong responders and totally histoincompatible donor-recipient combinations.