Eosinophils in nasal polyps and nasal mucosa: an immunohistochemical study.

Immunohistochemical staining was performed at the time of endoscopic sinus surgery (ESS), after 6 months, and after 1 year on nasal polyps and biopsy specimens of the macroscopically unaffected mucosa of the middle and inferior turbinate bones of 46 patients with nasal polyps. During the follow-up period the patients were treated with topical corticosteroids. At time of ESS significantly more BMK13+ and EG1+ (pan eosinophil markers) and EG2+ (activation marker) eosinophils were found in the polyps than in the macroscopically unaffected mucosa of the middle and inferior turbinate bones of the patients. In the middle and inferior turbinate bones of 10 healthy subjects no EG2+ (activated) eosinophils were detected, whereas low-to-moderate numbers of BMK13+ and EG1+ eosinophils were seen in these specimens. This emphasizes that eosinophils play a role in the pathogenesis of nasal polyps. Compared with numbers at ESS, after 6 months and 1 year of follow-up, lower numbers of BMK13+, EG1+, and especially of EG2+ eosinophils were found in recurrences of polyps and in the macroscopically unaffected mucosa of the middle and inferior turbinate bones of the patients. The decrease in number of EG2+ (activated) eosinophils is an indication of a reduced local inflammatory reaction, and could be an important factor in postponement of recurrences of nasal polyps.