The effect of natural pollen exposure on eosinophil apoptosis and its relationship to bronchial hyperresponsiveness in patients with seasonal allergic rhinitis

Background: Limited data suggest that there is increased eosinophilic inflammation in the airways of patients with seasonal allergic rhinitis (SAR) during pollen season even if they do not have asthma. Objective: To investigate the effect of natural pollen exposure on inflammatory cells and apoptosis of eosinophils and its association with bronchial hyperresponsiveness (BHR) during and out of pollen season in SAR patients sensitized to only grass pollens. Methods: Forty SAR patients and 10 patients with nonallergic rhinitis (NAR) from Ankara, Turkey, were recruited to participate in the study. Two induced sputum samples were taken from SAR patients during pollen season (May-June) and out of pollen season (November-January), but only 1 induced sputum sample was taken from NAR patients. Slides of induced sputum were evaluated by 2 cytologists with the use of light microscopy after cytocentrifuged and dyed with May-Grunwald-Giemsa stain. Induced sputum samples were sufficient for differential cell counts in 14 SAR and 7 NAR patients. Results: Eosinophil counts in SAR patients were statistically higher in pollen season (19.4% +/- 16.2%) compared with out of season (4.6% +/- 6.9%, P = .003) and with NAR patients (4.7% +/- 9.5%, P = .01). The apoptotic eosinophil counts in SAR patients were statistically higher out of pollen season (3.0% +/- 4.5%) than in pollen season (0.38% 0.80%, P = .02) and higher than those of NAR patients (0.14% +/- 0.26%, P = .005). The apoptotic ratio was statistically higher after pollen season compared with pollen season (0.720% +/- 0.394% vs 0.044% +/- 0.116%, P = .002). Blood eosinophil counts of SAR patients were increased during the pollen season (364 +/- 187/mm(3)) compared with out of season (278 219/mm(3), P = .04) and with NAR patients (85 +/- 54/mm(3), P = .001). The number of SAR patients who had BHR during the pollen season (7/14) was higher than the number who had BHR out of season (2/14, chi(2) = 4.2, P = .04). Conclusion: Our data indicate that changes in eosinophil counts and eosinophil apoptosis may be related to the changes of natural pollen exposure and seasonal changes of BHR in SAR patients.