Immunosuppressive effect of bovine seminal ribonuclease on a model of corneal transplantation in rabbit

Background: Bovine seminal ribonuclease (BS RNase) was determined to have a specific suppressive effect on the proliferation of T lymphocytes in vitro. Its immunosuppressive effect was proven in skin grafting in mice as well. Methods: The immunosuppressive effect of BS RNase was evaluated in tissue cultures and on a model of corneal transplantation in rabbits. The penetration of BS RNase into the anterior chamber was detected by immunoblotting of anterior chamber fluid obtained from animals treated either topically or subconjunctivally. Results: In vitro blastic transformation of mouse T lymphocytes was significantly inhibited by BS RNase (concentrations 15-250 mu g/ml). No such effect was observed on B lymphocytes. In the rabbit model of corneal graft rejection, BS RNase injected subconjunctivally pro longed mean graft survival time significantly (33.4 days) compared with placebo (salt solution; MST 17.7 days). No BS RNase was detected by immunoblotting in anterior chamber fluid after either topical or subconjunctival application, Conclusion: BS RNase showed significant immunosuppressive effect both in the blastic transformation test and in the rabbit high-risk model of corneal transplantation. Negative results of anterior chamber fluid immunoblotting indicate poor absorption of the drug.