Expression of HLA by the human trabecular meshwork and corneal endothelium

By using immunohistochemical techniques, we demonstrated that HLA class I (A, B and C) and HLA class II (DR), the major histocompatibility antigens in man, are expressed constitutively by cells of the trabecular meshwork/Schlemm's canal system and corneal endothelium, as well as by the conjunctival epithelium, Langerhans cells, vascular endothelium and uvea. Because clinical studies indicate that these antigens are involved in mediating corneal graft rejection and possibly in glaucomatous disease of the eye, the presence of both class I and II HLA in the corneal endothelium and in the trabecular cells has important implications for an understanding of immune disorders in the anterior segment of the eye. The presence of HLA on trabecular cells raises the possibility that these antigens potentiate the recognized role of Langerhans cells at the limbus and that they participate in, and/or regulate, the maintenance and defense of the aqueous outflow pathway. Our findings also open up the possibility of using HLA as a genetic marker in the determination of susceptibility to these disorders in man.