Abstract
Research findings increasingly support the view that eosinophils are important in the pathogenesis of asthma. Because eosinophils are under the control of cytokines, we measured eosinophil viability enhancing activity (EVEA) in bronchoalveolar lavage (BAL) fluids from patients who had symptomatic asthma (n=40), asymptomatic asthma (n=9), and patients with diseases other than asthma (n=3) . The BAL fluids from 15 symptomatic asthmatics showed increased EVEA. High levels of EVEA in four BAL fluid samples were almost completely blocked by an anti-interleukin (IL) -5 monoclonal antibody, and the remaining activity was blocked by anti-granulocyte-macrophage colony-stimulat-ing factor (GM-CSF) and/or an anti-IL-3 antibody. These findings suggest that EVEA in asthma is mediated mainly by IL-5, with lesser contributions from GM-CSF and IL-3. To determine when each eosinophil active cytokine appeared, we measured EVEA in BAL fluid samples from patients who had allergic rhinitis and had undergone segmental bronchoprovocation (SBP) with ragweed extract. Twenty-four hours after SBP, EVEA in BAL fluid was mostly due to IL-5; 48 hours after SBP, EVEA was mainly due to IL-5 with lesser contributions from GM-CSF, and IL-3. Thus, IL-5 is the predominant eosino-phil-active cytokine in asthma and may play a key role in the pathophysiology of eosinophil-associated airway inflammation.
