Abstract
Purpose: :
Limbal allogeneic transplantation is indicated as a form of treatment for bilateral limbal stem cell deficiency, but it is characterized by a high risk of graft rejection. We have established an experimental model of orthotopic limbal transplantation, in order to investigate immune response to limbal graft and to assess the immunosuppressive effects of anti-CD4 and anti-CD8 treatment.
Methods: :
Orthotopic limbal transplantation was performed in BALB/c mice; the donors used were C57BL/6 mice in the allogeneic group and BALB/c mice in the syngeneic group. Limbal grafts and recipient's cornea were observed and scored clinically for edema, neovascularization and opacity. The intragraft cytokine response (IL-2, IFN-g, IL-4, IL-10), the expression of gene for inducible nitric oxide synthesis (iNOS), and survival of graft donor cells in the limbus and in the cornea were detected by Real-time PCR. The allogeneic graft recipients were treated with monoclonal antibodies (mAb) anti-CD4 and anti-CD8.
Results: :
The high intragraft expression of genes for IL-2, IFN-g and iNOS has revealed a dominant Th1 type of immune response after limbal allotransplantation. The donor limbal cells and donor-derived cells on the corneal surface disappeared within 14 days. This cellular rejection correlated with the clinical manifestations of the rejection as determined by the appearance of the graft and by corneal opacity. While syngeneic limbal grafts survived indefinitely, limbal allografts in untreated recipients were rejected in 9.5 ± 1.6 days (mean ± SD). Treatment of limbal allograft recipients with mAb anti-CD4 considerably postponed the onset of rejection, decreased the clinical signs of rejection and significantly (P < 0.001) prolonged limbal allograft survival. In contrast to anti-CD4 treatment, the elimination of CD8 positive cells with mAb anti-CD8 did not have a significant effect on limbal allograft survival.
Conclusions: :
Allogeneic limbal grafts do not enjoy immune privilege of the eye, and are rejected promptly by the Th1 type of immune response involving CD4 positive cells and nitric oxide produced by macrophages. Anti-CD4 treatment thus represents a promising immunosuppressive approach after limbal allotransplantation.
Keywords: transplantation • cytokines/chemokines • immunomodulation/immunoregulation