In situ expression of the cell adhesion molecules in bronchial tissues from asthmatics with air flow limitation: in vivo evidence of VCAM- 1/VLA-4 interaction in selective eosinophil infiltration

Eosinophils play a critical role in the pathogenesis of bronchial asthma by releasing various mediators. To understand the mechanisms of eosinophil migration to the site of inflammation, we examined the expression of adhesion molecules in the bronchial tissues of asthmatic subjects with air flow limitation. By immunohistochemical analysis, Mac-1, LFA-1, and VLA-4 were strongly positive in eosinophils and mononuclear cells infiltrated in the bronchial mucosa and submucosa. Their number was significantly increased compared with those in control tissue. Immunolocalization for ICAM-1, the ligand of Mac-1 and LFA-1, was detected in the endothelial cells of capillaries and venules, in the mononuclear cells in submucosa, and in the basal layer of the epithelium. Endothelial cells in capillaries and venules were also strongly positive for VCAM-1, the ligand of VLA-4. Immunolocalization for E-selectin was detected in some endothelial cells in capillaries and venules in bronchial submucosa, whereas there were very few positive cells in the bronchial tissues from control subjects. In situ hybridization demonstrated ICAM-1 mRNA expression in the endothelial cells and mononuclear cells in bronchial submucosa. Immunoelectron microscopy for ICAM-1, VCAM-1, and E-selectin demonstrated de novo synthesis of these molecules and their expression along the luminal cell membrane of endothelial cells. These results suggested that ICAM-1, VCAM-1, and E-selectin were newly synthesized prior to spontaneous asthma attacks, and that their expression, particularly that of VCAM-1, may play a key role in eosinophil infiltration into the airway.