T-cell cytokine profile evaluated at the single cell level in BAL and blood in allergic asthma

Atopic asthma is characterized by bronchial mucosal inflammation, involving eosinophils, mast cells, and lymphocytes. It has been suggested that the development and maintenance of this allergic inflammation is due to T-lymphocyte activation with predominant production of the cytokines interleukin 4 (IL-4) and IL-5. To address the ability of peripheral blood and bronchoalveolar lavage T-cells to generate IL-2, IL-4, or interferon gamma (IFN-gamma), we have employed a flow cytometric method which permits analysis of cytokine production at the single cell level within 5 h of obtaining cell samples. When stimulated with PMA and ionomycin, there was a greatly increased percentage of IFN-gamma-producing cells among bronchoalveolar lavage (BAL) T-cells from the subjects with asthma (median 74%), compared with atopic and nonatopic controls (35 and 43%, respectively; P>0.01). The proportion of BAL T-cells producing IL-4 was small (median 1.7%, range 0 to 7.8% in the asthmatic group). In all three groups, the proportion of BAL T-cells producing IL-2 or IFN-gamma was increased compared with T-cells from peripheral blood. There was no significant difference between the three groups in the percentage of BAL T-cells producing IL-2, or in the percentage of peripheral blood T-cells producing IFN-gamma, IL-2 or IL-4. These findings indicate that IL-4 production is confined to a relatively small proportion of airway and blood T-cells and that there is selective enhancement of IFN-gamma production by airway T-cells in asthma.