OBJECTIVESTo study the concentration, distribution and expression of IL-5 in nasal polyp tissues and explore its significance in micro-environment differentiation of eosinophil accumulation.

METHODSThe concentration and expression of IL-5 in nasal polyp tissues of 40 patients were determined by ELISA and immunohistochemistry and inferior turbinate mucosa from patients with nasal polyps and healthy volunteers were used as control.

RESULTSIL-5 concentration in polyp tissues was significantly higher than that in turbinate mucosa (P < 0.05). There was no significant difference in the turbinate mucosae between patients with nasal polyps and healthy volunteers (P > 0.05). IL-5 concentrations in polyp tissues were markedly higher in patients with allergic rhinitis compared with those without (P < 0.05). IL-5 concentrations had no correlation with age and sex (P > 0.05). 80.1% of the eosinophils were positive for IL-5 and 90.9% of IL-5 positive cells were eosinophils. Only 3.7% of lymphocytes and neutrophils were positive for IL-5; IL-5 was not detectable in epithelial cells. IL-5 expression in eosinophils of polyp tissues was remarkably stronger than that of the turbinate mucosa (P < 0.05); there was no significant difference in the the turbinate mucosae between patients with nasal polyps and healthy volunteers (P > 0.05). IL-5 expression of eosinophils in polyp tissue was significantly stronger in patients with allergic rhinitis compared with those without (P < 0.05). There was no significant difference in IL-5 expression in lymphocytes and neutrophils between polyp tissues and turbinate nasal mucosa (both P > 0.05).

CONCLUSIONIL-5 is the key cytokine in eosinophilic pathologic mechanisms in nasal polyp tissues.