EFFECT OF ANTIGEN ON THE GLYCOCONJUGATE PROFILE OF TRACHEAL SECRETIONS AND THE EPITHELIAL GLYCOCALYX IN ALLERGIC SHEEP

To characterize the glycoconjugate composition of tracheal secretions and the apical glycocalyx of the tracheal epithelium under baseline co nditions and after antigen challenge, sheep allergic to Ascaris suum w ere intubated with a double-balloon nasotracheal tube to create a trac heal chamber. After an initial tracheal lavage, the animals were eithe r 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 th e animals were killed. An enzyme-linked lectin assay and lectin histoc hemical analysis were used to characterize carbohydrate residues in ly ophilized, resuspended tracheal secretions and the apical glycocalyx o f the tracheal epithelium, respectively. Eight lectins were used to de tect GalNAc, alpha-Gal, beta-Gal, alpha-Fuc, (1-3)Man, alpha-Man/Glu, alpha-Man, and alpha-(2-3)sialyl residues. The amounts of total nondia lyzable solids, proteins, and lipids in tracheal secretions were appro ximately twice as high after exposure to A. suum than after exposure t o PBS. All carbohydrate residues were present in tracheal secretions a fter exposure to PBS and A. suum, but the reactivity was higher after exposure to A. suum for beta-Gal (+125%), alpha-Man/Glu (+150%), alpha -(1-3)Man (+287%), alpha-(2-3)sialyl (+353%), and alpha-Man (+448%) (p < 0.05). Likewise, the apical glycocalyx contained all carbohydrate r esidues after exposure to PBS and A. suum; afer exposure to A. suum, t he reactivity was greater for alpha-GalNAc (+18%), alpha-(2-3)sialyl ( +90%), beta-Gal(1-3)GalNAc (+433%), and alpha-(1-3)Man (+482%) (p < 0. 05). There were no differences in other carbohydrate residues in eithe r tracheal secretions or the apical glycocalyx. These antigen-induced changes in the respective glycoconjugate profiles of tracheal secretio ns and the apical glycocalyx of the tracheal epithelium could have an effect on airway defenses, including bacterial adhesion to the epithel ium.