Immunosuppressive effect of total body irradiation and cyclosporine A on graft survival and the lymphatic system in a cardiac hamster-to-rat transplantation model.

The aim of the study was to evaluate the effect of total body irradiation (TBI) and cyclosporine A (CyA) on graft survival and the lymphatic system in a concordant hamster-to-rat heart transplantation model, and to compare these effects with those of total lymphoid irradiation (TLI). Preoperatively TBI was given as a single dose of 5 Gy, CyA was given intramuscularly at a dose of 10 mg/kg/day. TBI prolonged graft survival to seven days. Combined TBI and CyA prolonged graft survival to ten days. The effect of TBI on graft survival, total white blood cell count (WBC) and differential counts was reproducible but not as distinct as the effect of TLI. Analysis of changes in WBC and differential counts combined with the morphology of the grafts at rejection and of spleens from TBI- and CyA-treated animals indicates a reproducible immunosuppressive effect of TBI and a severe type of acute humoral rejection with vasculitis and cellular infiltrates dominated by macrophages and neutrophilic granulocytes. In conclusion, we find TBI a simple pretreatment which may be useful in combination with other immunosuppressive treatment as preoperative induction and depletion therapy.