Eosinophil infiltration is related to increased expression of vascular cell adhesion molecule-1 in nasal polyps

Endothelial adhesion molecules are important in the recruitment of leukocytes to inflammatory sites. Nasal polyps characteristically contain a leukocyte infiltrate in which eosinophils often are remarkably prominent. We have studied whether this feature is related to a particular profile of adhesion molecules on the local microvascular endothelium. Nasal polyps were obtained from 15 patients. Mucosal biopsy specimens of the lower and the middle turbinate from the same patients as well as from three control subjects served as reference tissue. Expression of endothelial adhesion molecules and the relative numbers of eosinophils and neutrophils were examined by two- and three-color immunofluorescence staining. Both the number of eosinophils and the proportion of vessels positive for vascular cell adhesion molecule-1 (VCAM-1) were significantly increased in nasal polyps compared with the turbinate mucosa of the same patients (P = 0.008 and P = 0.001, respectively). By contrast, the number of neutrophils and the relative expression of E-selectin and intercellular adhesion molecule-1 were similar at both tissue sites. Furthermore, the relative number of eosinophils in nasal polyps was well correlated (rs = 0.73, P = 0.006) with the percentage of vessels positive for VCAM-1, but this was not true for neutrophils. Taken together, this direct in situ observation strongly supports the crucial role suggested for VCAM-1 in human eosinophil extravasation at inflammatory sites.