Effect of macrolides on the expression of HLA-DR and costimulatory molecules on antigen-presenting cells in nasal polyps.

To clarify the basis of macrolide therapy for improvement of chronic sinusitis, we investigated the effect of macrolides on the expression of HLA-DR and costimulatory molecules such as CD54 and CD80 on macrophages in nasal polyps. Nasal polyps taken from 54 patients who had or had not been treated with macrolides were immunohistochemically studied. The percentages of CD68-positive macrophages expressing HLA-DR or CD54 were not significantly different between patients treated with macrolides and those not treated with macrolides. However, among patients exhibiting no atopic predisposition, the number of CD80-positive macrophages was higher in patients treated with macrolides than in those not treated. In addition, the percentage of CD80-positive macrophages was negatively correlated with the percentage of infiltrating eosinophils in the polyps. These results demonstrate that macrophages act as antigen-presenting cells, expressing both major histocompatibility complex II and costimulators, and that the expression of CD80 may play a key role in the immune responses occurring in a nasal polyp. Macrolides may modulate the mucosal immune responses through CD80 expression.