Zonal variation of HLA expression on human cornea epithelium.

Seven human corneas were studied, using the enzyme-linked immunosorbent assay (ELISA) technique, for expression of human leukocyte antigens (HLA) class-I and class-II antigens on the epithelial cells of the central 8-mm corneal button and the remaining corneal periphery and limbus. The antigenicity was compared with that of Raji and Daudi cell lines, which served as controls. It was demonstrated that the epithelium of the two corneal parts shows a high expression of HLA class-I antigens, albeit not as strong as that found in the control cell lines. On the other hand, HLA class-II antigens were found only in the limbal-peripheral area. Expression of the HLA class-I antigens was weaker in the central portion of the cornea. It is proposed that the absence of HLA class-II antigens expression in the central portion of the cornea offers an additional explanation for the greater success of small corneal grafts, since the recognition step necessary for the immunological response is lacking.