Diffuse panbronchiolitis (DPB) is a chronic airway disorder exclusively seen in Japan, characterized by chronic inflammation of the respiratory bronchioles leading to air flow obstruction. Although the pathogenesis of the disorder is unknown, current studies based on bronchoalveolar lavage (BAL) have implied an important role of neutrophil-mediated inflammation as a characteristic pathological feature of the disease. Interleukin 8 (IL-8), a cytokine with potent chemotactic activity for neutrophils, has been proven to have close association with many inflammatory disorders. In this study, neutrophil chemotactic activity (NCA) and IL-8 were measured in the BAL fluid in eight patients with DPB to examine the roles of IL-8 in the neutrophil recruitment to the lower respiratory tract in DPB. Significantly higher levels of NCA and IL-8 were demonstrated in the BAL fluid of DPB patients (71.6 +/- 3.6%, 491.9 +/- 48.0 pg/ml, respectively) compared with that of chronic bronchitis (CB) patients (24.8 +/- 2.8%, 54.1 +/- 13.9 pg/ml, p < 0.001) and of healthy control subjects (7.0 +/- 0.9%, 14.2 +/- 3.9 pg/ml, p < 0.001). The IL-8 values were positively correlated with the NCA in the BAL fluid of DPB patients. Treatment with anti-IL-8 could significantly inhibited the NCA. These results suggest that IL-8 plays an important role in the recruitment of neutrophils to the lower respiratory tract in DPB.