Mechanism of concordant corneal xenograft rejection in mice: synergistic effects of anti-leukocyte function-associated antigen-1 monoclonal antibody and FK506.

Abstract

The mechanisms of corneal xenogeneic immunoreaction, as well as the potential role of immunosuppressive therapy in the suppression of corneal xenograft rejection, have not been thoroughly explored. BALB/c mice who received orthotopic corneal transplants (Lewis rats donors) were administered intraperitoneally anti-leukocyte function associated antigen-1 (LFA-1) monoclonal antibody (mAb) or FK506 (3 mg/kg/day) or both of these immunosuppressants during a 12-day postoperative period. Histological (hematoxylin-eosin stain) and immunohistochemical evaluations of enucleated eyes were performed. Humoral immune response and delayed-type hypersensitivity (ear-swelling assay) were evaluated. The mean (+/-SD) graft survival time in the untreated control, FK506-treated, anti-LFA-1 mAb-treated, and combined-treatment groups was 5.8+/-0.8, 9.4+/-4.0, 8.7+/-5.0, and 67.7+/-16.4 days, respectively. In the untreated control group, mouse IgG, IgM, and C3 were expressed on the rat corneal grafts during the early postoperative phase. Flow cytometry studies revealed high titers of xenoreactive IgG and IgM antibodies. T helper 1 cytokines were expressed on xenografted corneal beds, and delayed-type hypersensitivity was induced. However, local expression of IgM, C3 and T helper 1 cytokines, serum antibodies of IgG and IgM, and delayed-type hypersensitivity were suppressed in the anti-LFA-1 mAb- plus FK506-treated group. Both humoral and cell-mediated immune reaction play an important role in the initial rejection in rat-to-mouse corneal xenotransplantation. The treatment with anti-LFA-1 mAb in combination with FK506 synergistically suppresses concordant corneal xenogeneic reaction.