Adhesion molecule expression in local-macrophage-depleted rats bearing orthotopic corneal allografts.

Background: Rejection of corneal grafts is dependent on influx of T lymphocytes and macrophages. This process is partly regulated by adhesion molecules. Earlier investigations showed that corneal graft rejection in rats could be prevented by clodronate liposomes that selectively eliminate macrophages. In the present study the effect of macrophage depletion on adhesion molecule expression after corneal allotransplantation was investigated.
Methods: Orthotopic corneal allografts were performed, after which rats received subconjunctival injections with clodronate liposomes or remained untreated. On various postoperative days, grafted rats were killed and mid-eye sections were stained for expression of ICAM-1 (CD54) and beta(2)-integrins (CD18 and CD11b/c).
Results: In the clodronate liposome-treated group grafts were not rejected, while in untreated rats grafts had a mean survival time of 12 days. During the first postoperative days a slightly enhanced expression of ICAM-1 in the conjunctiva and allografted cornea of clodronate liposome-treated recipients was seen. On day 12, however, ICAM-1 expression was markedly downregulated in the allografts of this treated group. The expression of beta(2)-integrins was also significantly decreased in the allografts and recipient corneas of treated rats at this time point.
Conclusion: Prolonged corneal graft survival in rats, obtained via local depletion of macrophages, correlates with diminished expression of adhesion molecules.