Immunologic Mechanisms of Corneal Allografts Reconstituted from Cultured Allogeneic Endothelial Cells in an Immune-Privileged Site

Abstract

To analyze outcomes and immunologic features after cultured corneal endothelial cell (CEC) transplantation in a murine model. CEC-deprived BALB/c corneas were reconstituted in vitro with an immortalized C3H-CEC cell line and then transplanted orthotopically into recipient BALB/c mice with experimental bullous keratopathy. Graft survival rates, donor-specific delayed hypersensitivity (DTH), and mixed lymphocyte reactions were evaluated in recipient mice after grafting. Fates of CEC transplantation were assessed after adoptive transfer, regrafting, and immunization with C3H splenocytes. Chimeric CEC allografts composed of cultured allogeneic CECs did not provoke rejection reaction, DTH, or mixed-lymphocyte reactions, unlike the high rejection rate that occurred in full-thickness corneal allografts. Adoptive transfer of splenocytes from mice that had accepted chimeric CEC allografts did not increase the graft survival rate after full-thickness corneal transplantation, and the rejection rate of a second full-thickness graft was not improved in these mice, suggestive of no active immunosuppression. Pre-sensitization by subcutaneous injection of splenocytes with the same haplotype as cultured CECs induced systemic DTH to the same allogeneic antigens but did not promote the rejection of chimeric CEC allografts, suggesting that chimeric CEC allografts are ignored by the host immune system. These findings indicate that immunologic ignorance rather than active immunosuppression is important for the rejection-free acceptance of chimeric CEC allografts. Transplantation of corneal grafts formed with allogeneic CECs could be an ideal treatment strategy to overcome postoperative rejection.