Comparison of circulating fibrocytes from non-asthmatic patients with seasonal allergic rhinitis between in and out of pollen season samples.

BACKGROUND: Allergic rhinitis is a risk factor for asthma development. In asthma, fibroblast progenitors, fibrocytes, are increased in the blood and bronchial mucosa following allergen exposure. These cells may play a role in lower airways remodeling as observed in non-asthmatic subjects with allergic rhinitis. OBJECTIVE: To determine the influence of seasonal allergen exposure on blood circulating fibrocytes in allergic rhinitic subjects without asthma. METHODS: Non-asthmatic subjects with seasonal allergic rhinitis had blood sampling at baseline and at the peak of rhinitis symptoms. Cells were stained for fibrocyte markers (CD34, CD45, CXCR4, collagen I) and analyzed by flow cytometry. RESULTS: Data from 26 subjects (11M:15F) aged 29 ± 8 years were analysed. Compared to baseline, there was a significant decrease in blood fibrocytes during the pollen season in subjects sensitized to trees [median (25-75 percentile), 9.3 (6.4-20.7)% vs 7.0 (4.2-10.1)%, P = 0.007] and a significant increase in subjects sensitized to grass [12.7 (9.9-23.1)% vs 64.0 (57.6-73.6)%, P < 0.001] and ragweed [8.0 (7.4-10.8)% vs 48.2 (43.5-52.6)%, P < 0.001]. A significant decrease in CXCR4 mean fluorescence was also observed between the two visits [1814 (1261-2235) vs 1352 (814-1796) (arbitrary units), P = 0.02]. CONCLUSIONS AND CLINICAL RELEVANCE: These results contribute to document dynamic variations in blood fibrocytes' activation and migration into the airways following natural exposure to allergens. These findings may help identify one of the potential factors involved in the development of asthma in allergic rhinitic subjects.