Lectin binding sites on the surfaces of the pneumonocytes in human neonatal lung

The surface coating of the pneumonocytes in human neonatal lung was studied by means of an electron microscope technique. Slices of aldehyde-fixed lung tissue were labelled with a horseradish peroxidase conjugate of one of the following lectins: Dolichos biflorus lectin, Triticum vulgaris lectin, Canavalia ensiformis lectin (concanavalin A), Limulus polyphemus lectin, Lotus tetragonolobus lectin and Arachis hypogaea lectin. The tissue slices were then incubated in a diaminobenzidine-hydrogen peroxide medium and then postfixed in an osmium tetroxide solution. It was found that the type I and type II pneumonocytes were strongly labelled with the lectins of Triticum vulgaris, Canavalia ensiformis, Limulus polyphemus and Arachis hypogaea. The type I pneumonocytes were also strongly labelled with Dolichos biflorus lectin but the staining of type II cells was relatively weak with this agent. Neither type of epithelial cell was labelled with Lotus tetragonolobus lectin conjugate. These results suggest that the surface coating of the pneumonocytes in human neonatal lung contains the following carbohydrate groups: N-acetylgalactosamine, N-acetylglucosamine, alpha-D-mannose, beta-D-galactose and sialic acid.