Detection of the complement (CD21)/Epstein-Barr virus receptor in human lacrimal gland and ocular surface epithelia

CD21, the receptor for the C3d complement fragment, has been reported to be the Epstein-Barr virus (EBV) receptor in B lymphocytes and cultured squamous epithelial cells. This receptor has previously been found to be expressed in the epithelia of nonocular mucosal-associated lymphoid tissues (MALT) which are also sites of persistent EBV infection. We recently found evidence of persistent EBV infection in human ocular MALT and hypothesized that the epithelia in these tissues may also express the complement (C3d)/EBV receptor. To test this hypothesis, histologic sections of human lacrimal gland, ocular surface tissue (conjunctiva, limbus, and cornea), and conjunctival impression cytology specimens were stained by immunohistochemical techniques using three different anti-CD21 monoclonal antibodies (HB-5, B2, OKB7). HB-5 stained lacrimal gland ductal and all ocular surface epithelia, except limbus. B2 stained lacrimal gland ductal and limbal epithelia, and OKB7 stained only the limbal and corneal epithelia. The intensity of limbal and corneal epithelial staining with all anti-CD21 antibodies correlated with the level of epithelial differentiation, with the weakest staining noted in the cells which are thought to be the stem and transient amplifying cells of the cornea. These results suggest that external ocular tissues, similar to other MALT, have CD21-positive epithelia which may be potential targets for EBV infection.