Interleukin-6 expression in chronic sinusitis: colocalization of gene transcripts to eosinophils, macrophages, T...

Chronic sinusitis in allergic (ACS) and nonallergic (NCS) patients is characterized by persistent inflammation and subepithelial fibrosis of the sinus mucosa. The inflammatory infiltrate is rich in T lymphocytes, monocyte/macrophages, plasma cells, and eosinophils. Th2-type cytokines are thought to regulate inflammatory cell recruitment, activation, survival, and the release of tissue-damaging mediators. Interleukin-6 is a proinflammatory Th2-type cytokine that stimulates fibroblast proliferation and collagen synthesis. Expression of interleukin-6 has been reported in pulmonary fibrosis and a number of other conditions associated with fibrotic tissue changes. In vitro studies have indicated that interleukin-6 is produced by macrophages, T cells, eosinophils, mast cells, and other cell types. Here we examined interleukin-6 messenger RNA and immunoreactivity in the sinus epithelium and subepithelium of subjects with ACS and NCS by in situ hybridization and immunocytochemistry, performed on sinus biopsy and polyp sections obtained from patients. Nasal turbinate biopsy specimens from normal volunteers were used as controls. Interleukin-6 messenger RNA and immunoreactivity were expressed by a significantly greater proportion of epithelial and subepithelial cells in ACS and NCS subjects than in normal controls. There was no difference in epithelial or subepithelial interleukin-6 expression between ACS and NCS patients. Colocalization studies revealed that macrophages, T cells, eosinophils, and mast cells are sources of interleukin-6 messenger RNA in ACS and NCS. The numbers of interleukin-6 messenger RNA-positive cells coexpressing immunoreactivity for the mast-cell marker were significantly greater in ACS than in NCS subjects. The results of this study suggest a role for interleukin-6 in the inflammatory response of chronic sinusitis.