Flow cytometric analysis of lymphocytes and lymphocyte subpopulations in induced sputum from patients with asthma

Abstract

Study objectives were to compare the numbers of lymphocytes and lymphocyte subpopulations in induced sputum from asthmatic patients and from healthy subjects, and to determine the effect of inhaled anti-asthmatic steroid therapy on these cell numbers. Hypertonic saline inhalation was used to non-invasively induce sputum samples in 34 patients with bronchial asthma and 21 healthy subjects. The sputum samples were reduced with dithioerythritol and absolute numbers of lymphocytes and lymphocyte subpopulations were assessed by direct immunofluorescence and flow cytometry. To assess the effect of beclomethasone dipropionate (BDP) on induced sputum, numbers of lymphocytes and lymphocyte subpopulations in sputum also were evaluated after 4 weeks of BDP inhalation treatment in seven asthmatic patients. An adequate sample was obtained in 85.3% of patients with asthma and in 79.2% of the healthy subjects. Induced sputum from patients with asthma had increased numbers of lymphocytes (P = 0.009); CD4+ cells (P = 0.044); CD4+ cells-bearing interleukin-2 receptor (CD25; P = 0.016); and CD4+ cells bearing human histocompatibility leukocyte antigen (HLA)-DR (P = 0.033). CD8+ cells were not increased in asthmatic patients. In patients treated with inhaled steroids, numbers of lymphocytes, CD4+ cells, CD25-bearing CD4+ cells and HLA-DR-bearing CD4+ cells in sputum decreased from pretreatment numbers (P = 0.016, 0.002, 0.003 and 0.002, respectively). Analysis of lymphocytes in induced sputum by flow cytometry is useful in assessing bronchial inflammation, and activated CD4+ lymphocytes may play a key role in the pathogenesis of airway inflammation in bronchial asthma.

Keywords

• bronchial asthma
• CD4-positive lymphocyte
• flow cytometry
• induced sputum
• interleukin-2 receptor