Abstract
Objective: T lymphocytes have a central regulatory role in the pathogenesis of asthma. The objective of this study was to characterize immunologically the activation stage of asthma and the functional profile of lymphocytes from induced sputum, with particular emphasis on γδ T cells.Methods: Induced sputum was collected from 10 patients with acute exacerbation of asthma, and from healthy controls. The expression of activation markers on freshly isolated induced sputum lymphocytes and T-cell subsets was analyzed by double immunofluorescent staining and flow cytometry. Fas ligand (FasL) was determined by reverse transcriptase-polymerase chain reaction analysis. The phenotype of γδ T-cell subpopulations was tested by A13 and BB3 monoclonal antibodies. In this context, the functional profile of γδ T cells was tested in a chromium releasing test.Results: A significantly decreased proportion of αβ T cells and an increased proportion of γδ T cells, CD56+ cells and CD8+ γδ T cells were found in asthma patients compared with healthy controls. In asthmatic patients, there is a significantly increased proportion of T cells expressing CD69 and CD25 antigen. After stimulation of γδ T cells, an increased expression of intracellular tumour necrosis factor-α, interleukin (IL)-4 and IL10 cytokines were found at higher levels than controls. Interferon-γ was observed at similar levels in asthma patients and healthy controls. Freshly isolated T-cell receptor (TCR) γδ+ cells exhibited an increased percentage of FasL in our patient group. FasL mRNA was detected in (TCR) γδ+ cells before and after IL2 stimulation. (TCR) γδ+ cells were cytotoxic against the K562 cell line. This natural killer activity was mediated by the A13-positive subpopulation.Conclusion: The presence of cytokines producing γδ cells in induced sputum of asthmatic patients is consistent with regulatory activities. These cells display also cytotoxic function.