ICAM-1 expression in upper respiratory mucosa is differentially related to eosinophil and neutrophil inflammation according to the allergic status.

BACKGROUND: Chronic non-infectious sinusitis is an inflammatory disease sharing numerous features with both allergic and non-allergic rhinitis and asthma.

METHODS: In an attempt to analyse the underlying mechanisms of sinus and nasal inflammation, we assessed ICAM-1 immunoreactivity on maxillary sinus, nasal polyp and turbinate biopsies obtained surgically from 21 patients with sinusitis and chronic allergic rhinitis (AR), 23 patients with sinusitis and chronic non-allergic rhinitis (NAR) and 17 non-atopic control subjects. We compared ICAM-1 expression with both eosinophil (EG1) and neutrophil (NP57 elastase) infiltrates.

RESULTS: In nasal turbinates and polyps, ICAM-1 was broadly distributed within the epithelium, on ciliated and basal epithelial cells and in the submucosa on endothelial and inflammatory cells. ICAM-1 was rarely expressed in the mucosa of the sinus, compared with polyps (P < 0.01) and turbinates (P < 0.0001). Submucosal and epithelial eosinophils were increased in both sinus and nasal biopsies from AR by comparison with NAR (P=0.003 and P=0.02) and non-atopic control subjects (P<0.0001 and P=0.014). Submucosal and epithelial neutrophil numbers were increased in the two chronic rhinitis groups and correlated with ICAM-1 submucosal expression in NAR only (P<0.01). On the other hand, epithelial eosinophil numbers correlated with ICAM-1 epithelial expression in AR only (P = 0.002).

CONCLUSION: This study further characterizes sinus and nasal granulocyte inflammation in chronic non-infectious sinusitis and rhinitis and suggests a differential role for ICAM-1 in neutrophil and eosinophil recruitment according to the allergic status.