Ultrastructural visualization of lectin receptors in normal and injured epithelium of the rabbit cornea

Lectin receptors of the rabbit corneal epithelium were investigated ultrastructurally using gold-conjugated lectins. Corneal epithelium with an intact mucous layer was readily labeled with wheat-germ agglutinin (WGA), whereas after mechanical or chemical removal of the mucus, labeling was minimal, suggesting that the lectin receptors were located mainly in the mucus. Corneal epithelium subjected to slight superficial injury was also labeled with WGA. In this case, however, the gold particles were in close contact with the cell membrane of injured and/or newly exposed cells. In the more injured cells, gold particles were seen in the cytoplasm as well. Labeling with WGA indicates the presence of sialyl residues, known to be attachment sites for Pseudomonas aeruginosa. The results suggest a protective role of mucus against infection. The association of WGA lectin receptors with the plasma membrane of compromised corneal epithelial cells may help to explain the mechanism of bacterial invasion of the cornea, e.g., in overnight wear of contact lenses with insufficient oxygen transmissibility.