Survival in high-risk eyes of epithelium-deprived orthotopic corneal allografts reconstituted in vitro with syngeneic epithelium.

Abstract

In low-risk eyes of mice, most of the composite corneal grafts composed of syngeneic epithelium layered on allogeneic stroma and endothelium are accepted indefinitely. The study was undertaken to determine the fate of similar composite corneal grafts placed in high-risk mouse eyes. Epithelium-deprived allogeneic corneas (C57BL/6) were reconstituted in vitro with BALB/c epithelium, and then transplanted orthotopically into high-risk eyes of BALB/c mice. Graft survival was assessed clinically and evaluated histologically. Acquisition of donor-specific delayed hypersensitivity (DH) was also assessed in recipient mice. Recipients bearing healthy composite grafts were immunized subcutaneously with injected C57BL/6 spleen cells at 2 or 8 weeks after grafting, after which the fate of the grafts was evaluated. Virtually all epithelium-deprived corneal allografts reconstituted in vitro with normal BALB/c corneal epithelium survived indefinitely when placed in high-risk eyes of BALB/c mice. Recipients of these composite grafts failed to acquire donor-specific DH when tested at both 2 and 8 weeks after grafting. Moreover, these recipients did not acquire the capacity to actively suppress donor-specific DH. Within 1 to 3 weeks of sensitization of recipient mice with spleen cells of donor origin, healthy composite grafts in residence for 2 or 8 weeks were rejected. Replacement of donor epithelium with syngeneic epithelium protects orthotopic allogeneic corneal grafts (stroma plus endothelium) placed in high-risk eyes from sensitizing their recipients and from immune-mediated rejection. Recipients of composite corneal grafts containing syngeneic epithelial layers act as though they are immunologically ignorant of the graft's presence.