Characterization of lymphocyte subsets in the lungs of smokers and patients with COPD

Background: COPD is characterized by chronic inflammation in the lungs. CD8+ T cells but in more severe disease also CD4+ T cells, have been implicated in the pathogenesis. T cell maturation entails distinct stages which can be identified based on their expression of the surface markers CD45RA and CD27. By combining these markers it is possible to distinguish naive and memory/effector subpopulations. We investigated whether these T cell subpopulations in bronchoalveolar lavage (BAL) differ in COPD patients compared to smokers with normal lung function and never-smokers. Methods: Bronchoscopy and BAL was performed on 24 never-smokers, 20 smokers with normal lung function and 20 COPD patients (14 smokers and 6 ex-smokers). The frequencies of major lymphocyte subsets and the differentiation status of CD4+ and CD8+ T cells were analyzed by flow cytometry. Results: There were higher percentages of CD8+ T cells in smokers and CD56+ T cells in smokers and COPD patients compared to never-smokers (p Conclusions: The higher percentages of cytotoxic T cells in smokers and COPD patients may be related to smoking-induced tissue damage. The increased percentage of central memory cells in COPD smokers suggests an ongoing immune response. Smoking cessation resulted in a normalization of CD4+ central/effector memory cells in BAL, indicating a reversibility of smoke-induced changes.