New evidence of inflammation in asthma

Abstract

T lymphocytes play a central role in the development of airway inflammation.2 They are present in increased numbers in the airways of patients with fatal asthma3 or in patients with asthma of variable aetiology including occupational asthma.4 Most bear CD4 receptors while CD8 positive cells are more rarely identified, even during exacerbations of asthma.5 T cells are likely to play a role in controlling the chronic inflammation of asthma. Using in situ hybridisation, the Th2 phenotype of T cells has been observed in cells recovered by bronchoalveolar lavage (BAL) from patients with asthma. After allergen challenge, many allergen specific T cells in bronchial biopsy specimens or BAL fluid are of the Th2 phenotype.6 Eosinophils are a major target of Th2 cytokines and their number is increased in the airways of asthmatic subjects. In asthma these cells are also activated and release high levels of several mediators such as eosinophilic cationic protein, growth factors,7 and metalloproteases. These cells are therefore able to play an important part in both airway inflammation and remodelling. A recent study has suggested that the presence of eosinophilic inflammation is associated with markers of airway remodelling such as increased levels of transforming growth factor (TGF)β expression and a thickened basement membrane.8