Abstract:

Objective To observe the survival of corneal xenograft of swine-rhesus monkey corneal xenotransplantation after the rhesus monkeys were preconditioned using cyclophosphamide(Cyc) and the following donor bone marrow transplantation(BMT), and discuss the mechanism of immune tolerance. Methods The donor corneas of 3 months old Wuzhishan pig(WZSP) were grafted orthotopically into rhesus recipients. Eighteen rhesus monkeys were divided into three groups randomly. Group 1 received BMT preconditioning using Cyc for one time, group 2 received BMT preconditioning using Cyc for two times and Group 3 received preconditioning with cyc without BMT. The survival status of the xeno-grafts were evaluated by slit-lamp microscopy. Mixed lymphocyte reactivity(MLR) was used to examine the specific immune reactivity of recipient to donor, the lymphocyte, the immunoglobulins and complements in the blood of the recipients were detected before and after keratoplasty at different time points. Two recipients in each group were sacrificed for corneal histopathological staining one month after transplantation. Results The mean survival time was(36.0±4.7 ) days in group 1, (32.8±6.4) days in group 2 and (17.7±3.2 ) days in group 3. MLR showed that the specific immune reactivity of group 1 and 2 was depressed to donor spleen cells after BMT, but there was no significant difference in group 3. The concentrations of immunoglobulins IgG, IgA, IgM and complement C3, C4 were increased 1~2 weeks after surgery in all groups. After corneal transplantation, the lymphocytes in the control group did not change significantly, while in groups 1 and 2, CD4⁺ T cells were gradually reduced and CD8⁺ T cells increased. Histopathological examination showed that corneal xenografts were infiltrated with inflammatory cells in group 3, the corneal endothelia were destroyed and exudative membranes were attached onto the endothelium of the grafts with acidophil infiltration. In groups 1 and group 2, there were only minimal inflammatory cells infiltration in the corneal xeno-grafts, the cornea was intact and no exudative membrane appeared, meanwhile no acidophil infiltration was found. Conclusion The survival time of the xenograft could be prolonged significantly in the recipient rhesus monkeys preconditioned using Cyc and following donor BM. The specific immune reactivity to donor was also depressed. The rejection of xenotransplantation was related to both cellular immunity and humoral immunity.

Key words: corneal xenotransplantation, bone marrow transplantation, immune tolerance, chimera