Elevated levels of antimicrobial peptides in bronchoalveolar lavage fluid in patients with chronic eosinophilic pneumonia.

BACKGROUND: Chronic eosinophilic pneumonia (CEP) is an idiopathic pulmonary disease. As the lung is in direct communication with the environment, inhaled antigen may activate immune mechanisms in the airway that may participate in the pathogenesis of idiopathic pulmonary diseases. Defensins are antimicrobial peptides that consist of alpha-defensin (HAD) in neutrophils and beta-defensin (HBD) in epithelial cells. Defensins act as innate immunity against pathogens acquired from the environment and as mediators to induce local inflammation.

OBJECTIVES: The aim of the present study was to determine whether immune mechanisms in the airway are induced in CEP patients.

METHODS: We measured BALF defensin levels in patients with CEP, acute EP (AEP) and drug-induced eosinophilic pneumonia (drug-EP). We also measured BALF levels of IL-5, GM-CSF, eotaxin and RANTES. These substances can recruit eosinophils.

RESULTS: BALF HAD levels were higher in patients with CEP than in those with drug-EP and normal controls. HBD-2 was detected in BALF of 10 of 11 CEP patients and in 3 of 5 AEP patients while its level was below detection in drug-EP patients and normal controls. BALF HBD-2 levels correlated with the proportion of lymphocytes in CEP patients.

CONCLUSION: The defensin-linked immune system is activated in CEP but not in drug-EP. This suggests that inhaled antigen(s) may be involved in the pathogenesis of CEP.