Lectin binding and endocytosis at the apical surface of human airway epithelia

The specificity of lectin binding to distinct saccharides makes them valuable reagents for investigation and identification of cells within complex tissues and potentially for delivery of agents into cells. Therefore we examined lectin binding to airway epithelia. We used an in vitro model of primary cultures of well-differentiated human airway epithelia and applied the lectins to the apical surface of living epithelia. This approach limited binding specifically to the extracellular surface of the apical membrane. Of 32 lectins studied, we found 15 that bound to the apical membrane. The pattern varied from diffuse binding to the surface of nearly all the cells, to binding to a small subset of the cells. Our data combined with earlier studies identify lectins that may be used to detect specific populations of epithelial cells. Because lectins may be used to deliver a variety of agents, including gene transfer vectors, to airway cells, we examined endocytosis of lectins. We found that several lectins bound to the apical surface were actively taken up into the cells. These data may be of value for studies of airway epithelial structure and may facilitate the targeting of the epithelial apical surface.