Elevated interleukin‐18 levels in bronchoalveolar lavage fluid of patients with eosinophilic pneumonia

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Abstract
Background:  Interleukin (IL)‐18 can induce Th2 cytokine production particularly in collaboration with IL‐2. Accumulation of Th2 cells and increased levels of Th2 cytokines are found in bronchoalveolar lavage fluid (BALF) from patients with eosinophilic pneumonia (EP). To evaluate the role of IL‐18 in the pathogenesis of EP, we measured the concentration of IL‐2, IL‐12, IL‐18, and Th2 cytokines in BALF from patients with EP.Methods:  The concentrations of interferon (IFN)‐γ, IL‐2, IL‐5, IL‐10, IL‐12, IL‐13, and IL‐18 in BALF were measured in patients with idiopathic acute eosinophilic pneumonia (AEP), with idiopathic chronic eosinophilicpneumonia (CEP), with sarcoidosis and healthy volunteers (HV).Results:  The BALF concentrations of Th2 cytokines, IL‐5, IL‐10, and IL‐13, were higher in patients with EP than in sarcoidosis and control. The IL‐2 level in BALF was higher in EP than in sarcoidosis and control. The IL‐18 and IL‐12 (p40 + p70) levels were higher in patients with EP than sarcoidosis, while the level of IL‐12 (p70) was below the detection limit in patients with EP. There was a significant correlation between IL‐2 level and both IL‐5 and IL‐13 in BALF of patients with EP.Conclusions:  Our findings suggest that IL‐18 may contribute to Th2 cytokine‐dominant responses in patients with EP in collaboration with IL‐2.