The effect of cyclosporine, total lymphoid irradiation, and cobra venom factor on hyperacute rejection.

Transplantation into sensitized recipients is contraindicated due to the potential for hyperacute rejection. In order to study the mechanism of hyperacute rejection and the role of immunosuppression in the face of presensitization, we evaluated the effect of total lymphoid irradiation, cyclosporine, and cobra venom factor, alone and in combination, on hyperacute rejection of heterotopic rat heart allografts. Lewis rats were sensitized to strongly RT-1-incompatible ACI rats by three successive skin grafts. Heart allografts were then performed, and survived for a mean period of 15.7 +/- 7.4 hours. Neither preoperative treatment of hypersensitized rats with total lymphoid irradiation alone nor with cyclosporine (5 mg/kg/day) resulted in a prolongation of survival (20.4 +/- 16.6 hours and 35.6 +/- 6.2 hours, respectively). However, complement depletion using cobra venom factor significantly prolonged mean graft survival time to 114.4 +/- 31.0 hours (p less than 0.05). Cyclosporine (10 mg/kg/day) also significantly prolonged survival to 149 +/- 29 hours (p less than 0.01), but did not lower the antibody or complement levels. The addition of total lymphoid irradiation or cyclosporine to treatment with cobra venom factor did not result in longer survival than cobra venom factor alone. In conclusion, cobra venom factor and cyclosporine delay but do not prevent hyperacute rejection, while total lymphoid irradiation has no observable effect on hyperacute rejection.