Abstract
Abstract: :
Purpose: Class Ib molecules encoded in the major histocompatibility complex are expressed on the placenta and have been implicated in the immune privilege that protects the fetus from immune rejection by the maternal immune system. Niederkorn et al have previously described expression of the murine MHC Class Ib molecule Qa-2 on ocular parenchymal cells. We wished to determine the presence and level of expression of another murine MHC Class Ib molecule, Qa-1, on cells that surround the immune privileged anterior chamber of the eye. Methods: Transformed cell lines from murine corneal epithelium, endothelium, and keratocytes were examined by RT-PCR and immunocytochemistry for the transcription and expression of Qa-1 and Qa-2. Primary cultured iris and ciliary body cells and freshly explanted lens were also evaluated. Results: Intense transcription and surface expression of Qa-1 were detected constitutively on cells of corneal epithelium, endothelium, and keratocytes, and on epithelial cells of iris, ciliary body, and lens. Qa-1 expression was significantly more intense than that of Qa-2. Conclusions: Qa-1, the murine homologue of HLA-E, is highly expressed in the anterior segment of the eye. Since both Qa-1 and HLA-E have been documented to inhibit NK cells, cytotoxic T cells, and CD4+ T cells, their expression in the eye may protect ocular cells from cell-mediated cytotoxicity and contribute to the immunosuppressive environment that produces ocular immune privilege.
Keywords: immune tolerance/privilege • anterior chamber • cornea: basic science