Mechanisms of allergy
Cytokine expression in the lower airways of nonasthmatic subjects with allergic rhinitis: Influence of natural allergen exposure,☆☆

https://doi.org/10.1067/mai.2000.110100Get rights and content

Abstract

Background: Natural exposure to pollen provokes an increase in airway responsiveness in nonasthmatic subjects with seasonal allergic rhinitis. This natural exposure may induce inflammatory cell recruitment and cytokine release, leading to lower airway inflammation. Objective: The aim of this study was to characterize lower airway inflammation in nonasthmatic pollen-sensitive subjects. Methods: We performed immunohistochemical tests on bronchial biopsy specimens from subjects with rhinitis who had no past or current history of asthma to evaluate cytokine expression and inflammatory cell numbers and activation both in and out of the pollen season. Results: The number of CD4+, CD8+, and CD45RO+ lymphocyte subpopulations were significantly higher during the pollen season compared with the out-of-season period (P < .04). Furthermore, EG1+ cells tended to increase after natural pollen exposure (P = .06). The number of IL-5+ cells increased significantly after natural exposure to pollen compared with out-of-season numbers (P < .01). This increase in IL-5 expression was correlated with the numbers of CD3+, CD4+, CD45RO+, and EG1+ cells. The numbers of tryptase-positive, IFN-γ+, and IL-4+ cells did not change after natural exposure. Conclusion: This study showed that natural pollen exposure was associated with an increase in lymphocyte numbers, eosinophil recruitment, and IL-5 expression in the bronchial mucosa of nonasthmatic subjects with allergic rhinitis. (J Allergy Clin Immunol 2000;106:904-10.)

Section snippets

Subject selection and evaluation

Twelve subjects 21 to 35 years of age with a history of recurrent seasonal pollen-induced rhinitis but no past or current history of asthma took part in the study. All had positive allergic skin test responses to tree, grass, and/or ragweed pollen. Six subjects were also sensitized to house dust, although they had minimal symptoms out of the pollen season. All subjects were nonsmokers who had no other respiratory conditions apart from their allergic rhinitis, and none had used anti-inflammatory

Change in airway responsiveness

We recruited 12 subjects: two did not agree to the second bronchoscopy, and bronchial biopsy specimens from two others were not adequate. The final study population consisted of 8 subjects (2 female and 6 male subjects). These subjects with rhinitis had normal pulmonary functions (Table I).

. Subject characteristics

Empty CellSexAge (y)FEV1 (% predicted)FVC (% predicted)
1F22109113
2M21142136
3M35116109
4M279095
5M20117113
6F31106103
7M23111103
8M3510499
Mean ± SEM27 ± 2112 ± 5108 ± 5

FVC, Forced vital capacity.

The

Discussion

This study showed that there is an inflammatory response in the bronchial mucosa of nonasthmatic subjects with allergic rhinitis and suggests that this inflammation is increased after natural exposure to pollen. This inflammatory burst is characterized by a significant increase in the number of CD4+ and CD8+ lymphocytes, memory cells, and eosinophils, as well as increased IL-5 expression. The number of IL-5+ cells was correlated with the numbers of CD3+, CD4+, CD45RO+, and EG1+ cells,

Acknowledgements

We thank Sylvie St-Martin and Doris Cantin for technical assistance and Gene Bourgeau for revising the manuscript.

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    Supported by the Centre québécois d’excellence en santé respiratoire FRSQ-Glaxo-Wellcome. Dr Chakir holds an FRSQ scholarship.

    ☆☆

    Reprint requests: Jamila Chakir, PhD, Centre de recherche de l’Hôpital Laval, 2725 Chemin Sainte-Foy, Sainte-Foy, Quebec, Canada G1V4G5.

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