Effect of antigen on the glycoconjugate profile of tracheal secretions and the epithelial glycocalyx in allergic sheep

Abstract

To characterize the glycoconjugate composition of tracheal secretions and the apical glycocalyx of the tracheal epithelium under baseline conditions and after antigen challenge, sheep allergic to Ascaris suum were intubated with a double-balloon nasotracheal tube to create a tracheal chamber. After an initial tracheal lavage, the animals were either exposed to intratracheally nebulized phosphate-buffered saline (PBS) (3 ml, n = 6) or A. suum antigen (251,000 protein nitrogen units in 3 ml of PBS, n = 6). Tracheal lavage was repeated 2 hours later, and the animals were killed. An enzyme-linked lectin assay and lectin histochemical analysis were used to characterize carbohydrate residues in lyophilized, resuspended tracheal secretions and the apical glycocalyx of the tracheal epithelium, respectively. Eight lectins were used to detect GalNAc, α-Gal, β-Gal, α-Fuc, (1-3)Man, α-Man/Glu, α-Man, and α-(2-3)sialyl residues. The amounts of total nondialyzable solids, proteins, and lipids in tracheal secretions were approximately twice as high after exposure to A. suum than after exposure to PBS. All carbohydrate residues were present in tracheal secretions after exposure to PBS and A. suum, but the reactivity was higher after exposure to A. suum for β-Gal ( +125%), α-Man/Glu ( +150%), α-(1-3)Man ( +287%), α-(2-3)sialyl ( +353%), and α-Man ( +448%) ( p < 0.05). Likewise, the apical glycocalyx contained all carbohydrate residues after exposure to PBS and A. suum; afer exposure to A. suum, the reactivity was greater for α-GalNAc ( +18%), α-(2-3)sialyl ( +90%), β-Gal(1-3)GalNAc ( +433%), and α-(1-3)Man ( +482%) ( p < 0.05). There were no differences in other carbohydrate residues in either tracheal secretions or the apical glycocalyx. These antigen-induced changes in the respective glycoconjugate profiles of tracheal secretions and the apical glycocalyx of the tracheal epithelium could have an effect on airway defenses, including bacterial adhesion to the epithelium. (J A LLERGY C LIN I MMUNOL 1994;93:585-93.)