Long-term survival in lung transplantation is limited by the development of obliterative bronchiolitis, a condition characterised by inflammation, epithelial injury, fibroproliferation and obliteration of bronchioles leading to airflow obstruction. To investigate the role of the bronchial epithelium in the pathogenesis of obliterative bronchiolitis the current study aimed to establish primary bronchial epithelial cell cultures (PBEC) from lung allografts.Four to six bronchial brushings were obtained from sub-segmental bronchi of lung allografts. Cells were seeded onto collagen-coated plates and grown to confluence in bronchial epithelial growth medium.Bronchial brushings (n533) were obtained from 27 patients. PBECs were grown to confluence from 12 out of 33 (39%) brushings. Failure to reach confluence was due to early innate infection. Bacteria were usually isolated from both bronchoalveolar lavage and culture media, but a separate population was identified in culture media only.Primary culture of bronchial epithelial cells from lung transplant recipients is feasible, despite a high rate of early, patient-derived infection. Latent infection of the allograft, identified only by bronchial brushings, may itself be a persistent stimulus for epithelial injury. This technique facilitates future mechanistic studies of airway epithelial responses in the pathogenesis of obliterative bronchiolitis.

Mechanisms other than classical alloimmunity are implicated in the pathogenesis of bronchiolitis obliterans syndrome (BOS). It was hypothesised that antimicrobial peptides (AMPs), elements of the innate immune response, have a role in BOS pathogenesis.Pulmonary expression of the neutrophil-derived AMPs human cathelicidin (hCAP)-18/LL-37 and a-defensins (human neutrophil peptides (HNP) 1-3), and the epithelial cell-derived AMPs human b-defensin (hBD)-2, elafin and secretory leukoprotease inhibitor (SLPI) were measured in stable lung transplant recipients and those with BOS. The relationship between airway pathogens and AMP levels was examined.Bronchoalveolar lavage (BAL) was performed on 44 lung transplant recipients (30 stable, 14 with BOS). BAL was cultured for pathogens and ELISA for AMPs was performed. The presence of airway pathogens was associated with significantly increased levels of neutrophil-derived and epithelial-derived AMPs. When patients without pathogens in BAL fluid were analysed, eight recipients with BOS had elevated hCAP-18/LL-37 and HNP 1-3 compared with 25 stable recipients. hBD-2 and elafin levels were comparable in BOS and stable recipients, but SLPI levels were reduced in BOS.Bronchiolitis obliterans syndrome is associated with elevated airway human cathelicidin 18/ LL-37 and human neutrophil peptides 1-3 from activated neutrophils, even in the absence of pathogens. Together with reduced airway secretory leukoprotease inhibitor this may favour nonalloimmune airway injury with reduced antiprotease defence and increased neutrophil degranulation.

Bronchiectasis is a chronic debilitating condition with considerable phenotypic diversity. A vicious cycle of infection and inflammation exists in damaged airways with patients suffering from persistent cough, purulent sputum production, recurrent chest infections and general malaise. The associated burden of disease in terms of increased morbidity, reduced quality of life and the socioeconomic cost of long-term management is significant. Further research is essential to improve our understanding of the development and progression of this disease. This article reviews what is currently known about bronchiectasis, its pathophysiology, aetiology and management strategies.

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