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

Abstract
Background: Local antigen presentation may be necessary for both primary and recall T‐cell responses to grass pollen in hay fever patients. We examined the effect of seasonal allergen exposure on nasal mucosal antigen‐presenting cell (APC) populations and the effects of topical corticosteroid therapy. Methods: Nasal biopsies were collected from 46 grass pollen‐sensitive seasonal rhinitis patients before the grass‐pollen season. A second biopsy was collected during the pollen season, when patients had received 6 weeks' treatment with either fluticasone propionate (200 µg, twice daily) or placebo. Cell populations in biopsy sections were quantified by immunocytochemistry. Results: Significant increases in submucosal and epithelial CD1a+ Langerhans cells, but not CD68+ macrophages or CD20+ B cells, were observed during the pollen season. Seasonal increases in CD1a+ Langerhans cells were inhibited by corticosteroid therapy. Conclusions: Recruitment of CD1a+ Langerhans cells to the nasal mucosa during natural seasonal allergen exposure may contribute to local T cell responses. Topical corticosteroids may act, at least in part, by inhibiting effective allergen presentation to T cells through inhibition of recruitment of Langerhans cells to the nasal mucosa.

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