T cells in sputum of asthmatic patients are activated independently of disease severity or control

Background T cells play an important role in bronchial asthma. Although airway CD4+ T cells have been extensively studied previously, there are hardly any studies relating CD8+ T cell activation and disease symptoms. Objectives The aim of this study was to analyse the association between T cell activation in induced sputum T cells and asthma severity and control; and to evaluate T cell subpopulations in the same subgroups. Methods Fifty allergic asthmatic patients were recruited and lung function testing was performed. Airway cells were obtained by sputum induction via inhalation of hypertonic saline solution. CD3, CD4, CD8, CD28, CD25 and CD69 were studied by flow cytometry in whole induced sputum and peripheral blood cells. Results Total induced sputum T cells and CD8+ T cells had a higher relative percentage of the activation markers CD25 and CD69 in comparison with peripheral blood. In sputum, the relative percentage of CD25 was higher in CD4+ T cells when compared to CD8+ T cells and the reverse was true regarding CD69. However, neither disease severity nor control were associated with the relative percentage of CD25 or CD69 expression on T cells in sputum. Conclusions Both CD4+ and CD8+ T cells are activated in the lungs and peripheral blood of asthmatic patients. However, with the possible exception of CD69+ CD8+ T lymphocytes in the sputum, there is no association between T cell activation phenotype in the target organ and disease severity or control.