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

Background: Natural exposure to pollen provokes an increase in airway respo nsiveness in nonasthmatic subjects with seasonal allergic rhinitis, This na tural exposure map induce inflammatory cell recruitment and cytokine releas e, leading to lower airway inflammation. Objective: The aim of this study was to characterize loner airway inflammat ion in nonasthmatic pollen-sensitive subjects. Methods: We performed immunohistochemical tests on bronchial biopsy specime ns from subjects with rhinitis who had no past or current history of asthma to evaluate cytokine expression and inflammatory cell numbers and activati on both in and out of the pollen season. Results: The number of CD4(+), CD8(+), and CD45RO(+) lymphocyte subpopulati ons mere significantly higher during the pollen season compared with the ou t-of-season period (P <.14), Furthermore, EG1(+) cells tended to increase a fter natural pollen exposure (P =.06), The number of IL-5(+) cells increase d significantly after natural exposure to pollen compared with out-of-seaso n numbers (P <.01), This increase in IL-5 expression was correlated with th e numbers of CD3(+), CD4(+), CD45RO(+), and EG1(+) cells. The numbers of tr yptase-positive, IFN-gamma (+), and IL-4(+) cells did not change after natu ral exposure. Conclusion: This study showed that natural pollen exposure was associated w ith an increase in lymphocyte numbers, eosinophil recruitment, and IL-5 exp ression in the bronchial mucosa of nonasthmatic subjects with allergic rhin itis.