| Abstract: | This study was aimed at ascertaining whether long-term graft survival was achievable with short term cyclosporine (CsA) therapy or with subtherapeutic doses of CsA in rats conditioned with blood transfusions (BT) combined with CsA. Previous studies had shown that donor-specific transfusions combined with a short course of CsA interacted synergistically, resulting in considerable prolongations of ACI and BUF grafts in LEW hosts receiving no postoperative treatment. The donor-specific depression of alloreactivity was confirmed in the present study by showing a depression of mixed-lymphocyte reaction (MLR) reactivity as well as of humoral antidonor responses in BT-CsA conditioned rats. The effects of postoperative CsA were then studied in recipients conditioned with BT-CsA or BT alone. ACI and BUF cardiac graft survival in LEW hosts conditioned with BT and treated with a five-day postoperative course of CsA (20 mg/kg/day) were indistinguishable from graft survival in untransfused hosts (ACI: 35.6 +/- 15.5 vs. 38.8 +/- 7.4; BUF: 58.4 +/- 39.8 vs. 48.0 +/- 21.7) indicating no interaction between BT and CsA under these conditions. In contrast, the effect of a post-operative five-day course of CsA (10 mg/kg/day) was extended by conditioning the recipients with donor-specific BT and CsA (ACI:41.7 +/- 7.0 vs. 27.4 +/- 11.6; P less than 0.05). More remarkably, a thirty-day course of subtherapeutic doses of CsA (2.5 mg/kg/day) resulted in long-term prolongation (greater than 100 days) of ACI grafts in a large proportion of hosts conditioned with donor-specific BT and CsA, while the majority of controls conditioned with nonspecific BT and CsA or CsA alone rejected their grafts within three weeks (P less than 0.01). The possible mechanisms of this phenomenon are discussed. |
