Macrophages on the Nasal Mucosal Surface in Provoked and Naturally Occurring Allergic Rhinitis

Macrophages are the most common cell type residing in the lumen of the lower airways. However, very little is known about the presence and putative pathogenic implications of macrophages in the upper airways. Using specific immunohistochemical techniques, the presence of and changes in macrophage density were studied before and after allergen exposure in the laboratory and during natural allergen exposure of subjects with seasonal allergic rhinitis. the monoclonal antibody EBM 11 combined with the alkaline phosphatase-anti-alkaline phos-phatase-technique was applied on cytospin-prepared slides. in the challenge experiment, 0.5 + 0.2%(mean ± SEM; n=10)of the total cell numberwere positive for the EBM II marker before challenge, thereby not differing from the controls (0.2 ± 0.2%; mean ± SEM; n=3). Local allergen challenge induced an increase of these cells to a peak of 1.3+0.4% after 4 (p < 0.05). During seasonal exposure there was also a similar increase, from 0.7 ± 0.2 to 1.3 ± 0.3% (p < 0.05; n = 11) in placebo-treated patients and from 0.7 ± 0.2 to 1.6 + 0.4% (p < 0.05; n = 11) in patients treated with topical glucocorticoids. There was, however, no direct relationship between nasal symptoms and number of macrophages present on the mucosal surface. the study indicates that macrophages are involved in the inflammatory processes of allergic rhinitis.