OBJECTIVES: To study the concentration, distribution and expression of IL-5 in nasal polyp tissues and explore its significance in micro-environment differentiation of eosinophil accumulation. METHODS: The 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. RESULTS: IL-5 concentration in polyp tissues was significantly higher than that in turbinate mucosa (P 0.05). IL-5 concentrations in polyp tissues were markedly higher in patients with allergic rhinitis compared with those without (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). IL-5 expression of eosinophils in polyp tissue was significantly stronger in patients with allergic rhinitis compared with those without (P 0.05). CONCLUSION: IL-5 is the key cytokine in eosinophilic pathologic mechanisms in nasal polyp tissues.
