Increased rejection of corneal allografts which lack Fas-ligand expression

Purpose: Recent studies have demonstrated that the cornea expresses significant levels of Fas-ligand, which may play a dominant role in the maintenance of immune privilege. This immune privilege has been cited as one of the contributing factors in the remarkable success of corneal allograft transplantation. Thus, we wished to determine the role that Fas-ligand plays in corneal allograft rejection. Methods: Orthotopic corneal transplants were performed by placing either C57BL/6 (Fas-ligand⁺) or C57BL/6-g/d (Fas-ligand^-) corneas on BALB/c recipient mice. These grafts were then evaluated for rejection. Results: The incidence for rejection of C57BL/6 (Fas-ligand⁺) corneal allografts was, as has been previously described, 60%. The incidence for rejection of C57BL/6-g/d (Fas-ligand^-) corneal allografts was >90%. In addition, the opacity scores for BALB/c mice engrafted with C57BL/6-g/d corneas were significantly higher (3.3 vs. 2.5) than those for mice which were engrafted with normal C57BL/6 corneas. Studies are ongoing to define the nature of this increased corneal allograft rejection. Conclusions: The absence of functional Fas-ligand on donor allogeneic corneas leads to increased incidence and severity of rejection. This suggests that the success seen in corneal allograft transplantation may in part be due to the presence of Fas-ligand on corneas.