The role of complement in corneal allo- and xenograft rejection

Purpose. Complement mediated injury s an important component of hyperacute and acute rejection of transplanted organs. However, the role of complement m corneal graft rejection is unclear. The cornea! cell layets are known to express complement regulatory proteins, and complement activation is thought to be involved in cornea] neovascularization processes. The purp >se of our study was to define the role ot complement activation in corneal allô- and xenograft rejection using rat graft recipients which selectively lack the C6 componert of complement and therefore are unable to assemble the membrane attack comple ; (MAC). Methods. 3.5 mm full thickness penetrating ortholopic keratoplasties we-e performed from male BN rats (Group A. n=12), DA rats (Group B, n-12) and Hartley guinea pigs (Group C. n-12) into Cd deficient (C6-) and sufficient (C6+) PVC rats. Complement deficiency was confirmed by C6 ELISA. All transplants were performed with the same technique by the same surgeon. The running suture was not removed. Immunological rejection was defined as complete opacity of the donor cornea. Results. (A): In the BN to PVG combination 847r of grafts remained clear over an observ; tion period of 30 days, A transient rejection episode appeared in one PVG(C6+) at day 9, and in one PVG(C6-recipient at day 20 (B): 50% of DA grafts in C6(-> as well a, in C6( + ) PVG were rejected, the mean graft survival time (MST) in PVG(C6-) recipier b was slightly prolonged compared to the C6+ COntrols (17.7 ±06 Vf. 1$ 1 + 2.M. (C)- Xenograft rejection was markedly prolonged in PVG(C-) (12.7 ±0.6d} compared 10 FVG(Ct) recipients iti.25 ±0.9d). All Cd+ rejectors showed a stronger and faster novasculanzation than observed in C6(-) rats which never developed a complete gralî vascularizalion including the central graft. Preliminary data indicate that these effec.s are consistently increased in donor specific presensitized recipients. Conclusions, nhihition of MAC formation in C6 deficient recipients has a significant effect on the nost aggressive form of corneal rejection and neovasculariiation which is seen in xem>greafts. but a less apparent effect m corneal allografts.