Epithelial cells potentially contribute to airways inflammation by antigen presentation and the production of proinflammatory cytokines. This study investigated the immunocytochemical localization of interleukin-8 (IL-8), granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-1 receptor (IL-1R Type I), tumor necrosis factor-alpha receptor (TNF-alpha R; 55kD), and human leukocyte antigen-DR (HLA-DR) on epithelial cells obtained by nasal brushing from 10 patients with allergic rhinitis in season and 15 healthy, nonallergic subjects. Six of the 15 nonallergic asymptomatic subjects had macroscopic evidence of nasal mucosal inflammation, and their brushings contained more than 10% neutrophils ("subclinical inflammation"). In normal control subjects, 8 +/- 7.5% of epithelial cells stained for HLA-DR, approximately one quarter stained for IL-8 and GM-CSF, and about one third stained positive for IL-1R and TNF-alpha R. The findings in subjects with allergic rhinitis in season and with subclinical neutrophilia were similar, and the numbers of cells staining for HLA-DR expression correlated with both neutrophil and lymphocyte content. These findings further support the conclusion that epithelial cells can contribute to inflammatory processes in the nasal mucosa. The findings emphasize the need to identify asymptomatic nasal mucosal inflammation in studies of the nasal mucosa.