Recruitment of CD1a+Langerhans cells to the nasal mucosa in seasonal allergic rhinitis and effects of topical corticosteroid therapy

Background: Local antigen presentation may be necessary for both primary an d recall T-cell responses to grass pollen in hay fever patients. We examine d the effect of seasonal allergen exposure on nasal mucosal antigen-present ing cell (APC) populations and the effects of topical corticosteroid therap y. Methods: Nasal biopsies were collected from 46 grass pollen-sensitive seaso nal rhinitis patients before the grass-pollen season. A second biopsy was c ollected during the pollen season, when patients had received 6 weeks' trea tment with either fluticasone propionate (200 mug, twice daily) or placebo. Cell populations in biopsy sections were quantified by immunocytochemistry . Results: Significant increases in submucosal and epithelial CD1a+ Langerhan s cells, but not CD68+ macrophages or CD20+ B cells, were observed during t he pollen season. Seasonal increases in CD1a+ Langerhans cells were inhibit ed by corticosteroid therapy. Conclusions: Recruitment of CD1a+ Langerhans cells to the nasal mucosa duri ng natural seasonal allergen exposure may contribute to local T cell respon ses. Topical corticosteroids may act, at least in part, by inhibiting effec tive allergen presentation to T cells through inhibition of recruitment of Langerhans cells to the nasal mucosa.