Immune rejection of allogeneic amniotic epithelium transplanted in the eyes of presensitized recipients

Abstract

Abstract: : Purpose: We and others have been reported that allogeneic amniotic membrane displays low immunogenicity and often fails to sensitize their recipients after transplantation. The purpose of this study was to evaluate the capacity of amniotic epithelium to be a target of alloimmune rejection. Methods: Normal BALB/c mice were immunized subcutaneously with 10 X 10⁶ C57BL/6 spleen cells. One week later, segments of freshly isolated amniotic epithelium from enhanced green fluorescence protein (EGFP) mice (C57BL/6 background) were transplanted in corneas or into the anterior chamber (AC) of these presensitized BALB/c mice. Normal BALB/c mice were used as control recipients of GFP positive amniotic epithelium allografts. Graft–bearing eyes were removed at 4, 7, 10, 14, 21, 28 and 56 days, and frozen tissue sections were prepared. Fluorescence microscopy was used to observe GFP positive donor cells. Expression of CD4 and CD8 on infiltration leukocytes was examined immunohistochemically using anti–CD4 and anti–CD8 antibodies. Results: In normal recipients, GFP positive cells were present in corneal stroma at 14 days after allogeneic GFP positive amniotic epithelium grafting in corneas. Moreover, a large number of GFP positive cells were retained in the anterior chamber for more than 56 days without evidence of inflammation after grafting into AC. On the other hand, GFP positive cells were disappeared within 10 days in corneas and in AC in the pre–sensitized recipients. An accumulation of CD4 positive and CD8 positive cells was found at the graft site, and these T cells were also seen in neovessels in the cornea and in iris and ciliary body in these presensitized recipients. Conclusions: The present study clearly demonstrates that allogeneic amniotic epithelium is vulnerable to immune rejection in specifically sensitized recipients. It is suggested that amniotic epithelium is able to display alloantigens to be a target of immune rejection.

Keywords: transplantation • anterior chamber • immune tolerance/privilege