Bronchial hyperresponsiveness in seasonal allergic rhinitis patients is associated with increased IL-18 during natural pollen exposure

BackgroundThe mechanism of bronchial hyperresponsiveness (BHR) is not certain in seasonal allergic rhinitis (SAR) patients.ObjectiveWe aimed to investigate the effects of natural pollen exposure on IL-18 and its relationship with BHR.MethodsThirty-two SAR patients with grass pollen sensitivity, 14 nonallergic rhinitis (NAR) patients and 17 normal-controls were included. Sixteen SAR patients had BHR during pollen season and off-season. Serum IL-18 levels were measured in SAR patients during pollen season between May-August and off-season between November-February. IL-18 levels were measured in NAR patients and normal controls once.ResultsDuring pollen season, SAR patients with BHR had significantly increased levels of IL-18 than those without BHR (279.2 ± 161.1 versus 145.3 ± 101.0 pg/ml, p = 0.012). Serum IL-18 levels were not different between SAR patients with and without BHR during off-season (233.8 ± 139.7 versus 183.2 ± 162.9 pg/ml, p = 0.16). Serum IL-18 levels in SAR patients during pollen season (212.3 ± 148.8 pg/ml) and off-season (208.5 ± 151.5 pg/ml) were not different than those NAR patients (224.8 ± 180.1 pg/ml, p = 0.98 and p = 1.0, respectively) and normal controls (174.8 ± 76.0 pg/ml, p = 0.60 and p = 0.76, respectively).ConclusionThe results suggested us that BHR in SAR patients is associated with increased IL-18 during natural pollen exposure.

► IL-18 levels are increased in patients with bronchial hyperresponsiveness (BHR). ► This relationship is not seen during off-season. ► Allergen exposure may be the cause of seasonal relationship between IL-18 and BHR.