Lymphocyte subtypes in asthma: relationship with the clinical status and bronchial hyperreactivity

To study the role of T lymphocytes in asthma and its relationship with clinical severity, atopic status and bronchial hyperreactivity (BHR), we have examined T cell populations in peripheral blood of 32 stable asthmatic (18 non atopic, 14 atopic) and 10 non atopic-non asthmatic person using flow cytometry. BHR was determined with histamine challenge test. The percentages of CD4+, CD8+ T lymphocytes, CD4/CD8 ratios, T cell activation markers (IL-2R, CD25; HLA-DR) were not different from control (p > 0.05). The percentage of CD16+ CD56+ cells were higher in peripheral blood of asthmatics (15.5% versus 9.3% p < 0.05). In the asthmatic group, there was inverse correlation between BHR and CD4/CD8 ratio (p < 0.05). The percentages of CD5+ T lymphocytes bearing activation marker CD25 significantly higher in severely asthmatics when compared with mild asthmatics (13.2 +/- 2.0 versus 7.8 +/- 1.1% p < 0.05). These results suggest that natural killer activity is increased in the asthmatics, severely asthmatics have more T lymphocytes bearing activation marker CD25 and BHR would be related with CD4/CD8 ratio rather than the other T lymphocytes subpopulations in peripheral blood.