Elevated concentrations of defensins in bronchoalveolar lavage fluid in diffuse panbronchiolitis

Human neutrophils contain three isoforms of antimicrobial and cytotoxic peptides in the azurophil granules, which belong to a family of mammalian neutrophil peptides named defensins. Here we investigate the role of these peptides in diffuse panbronchiolitis (DPB). Defensins (human neutrophil peptide-1, -2 and -3) were measured by radioimmunoassay in bronchoalveolar lavage fluid (BALF) of 30 patients with DPB, 16 patients with idiopathic pulmonary fibrosis (IPF) and 15 healthy adults. The concentration of defensins was higher in BALF of patients with DPB than in patients with IPF and healthy subjects. DPB and IPF patients also had significantly higher plasma concentrations of defensins than controls. In patients with DPB, BALF concentration of defensins correlated significantly with neutrophil count or BALF concentration of interleukin (IL)-8. Immunohistochemistry of open-lung biopsy specimens from four DPB patients showed localization of defensins in neutrophils and mucinous exudate in the airways, and on the surface of bronchiolar epithelial cells. In vitro studies showed an enhanced extracellular release of defensins following stimulation of neutrophils with phorbol myristate acetate, N-formyl-methionyl-leucyl-phenyalamine, and human recombinant IL-8. Treatment of DPB with macrolides for 6 months significantly reduced neutrophil count and concentrations of defensins and IL-8 in BALF. Our results indicate accumulation of neutrophil-derived defensins in the airway in diffuse panbronchiolitis, and suggest that defensins may be a marker of neutrophil activity in this disease.