IL-5 synthesis is upregulated in human nasal polyp tissue.

BACKGROUND

In most nasal polyps, tissue eosinophilia is a striking finding, the pathologic mechanism of which is not understood.

OBJECTIVE

This study was performed to investigate a possibly distinct cytokine and chemokine pattern that could explain the characteristic tissue eosinophilia in nasal polyps.

METHODS

Polyps from 23 patients and turbinate tissue from 18 control subjects were investigated. The cytokine protein content (IL-1 beta, IL-3, IL-4, IL-5, IL-6, IL-8, IL-10, tumor necrosis factor-alpha, granulocyte-macrophage colony-stimulating factor, IL-1RA, RANTES, GRO-alpha) of tissue homogenates was measured by ELISA. Immunohistochemistry was performed in selected samples to detect IL-5+, major basic protein-positive, and EG2+ cells.

RESULTS

IL-5 was detectable in only one sample of tissue from 18 control subjects but was found in 18 of 23 nasal polyps. Immunohistochemistry revealed an abundant number of IL-5+ cells, of which 69.5% could be identified as eosinophils by morphology. IL-6, IL-8, IL-10, tumor necrosis factor-alpha, GRO-alpha, and RANTES were detected in all specimens, without significant differences between groups (p > or = 0.05), whereas significnatly higher concentrations of IL-1 beta and IL-1RA were found in turbinate mucosa (p < or = 0.05). IL-3 was not detectable: granulocyte-macrophage colony-stimulating factor could only occasionally be found.

CONCLUSION

This study indicates that IL-5 plays a key role in the pathophysiology of eosinophilic nasal polyps and may be produced by eosinophils.