THE EFFECT OF SEGMENTAL BRONCHOPROVOCATION WITH ALLERGEN ON AIRWAY LYMPHOCYTE FUNCTION

We hypothesized that allergen-induced airway eosinophilia is linked to activation or recruitment of T cells in the airway and generation of interleukin-5 (IL-5). To evaluate this hypothesis, we performed bronch oscopy with segmental antigen bronchoprovocation in 12 atopic subjects . Bronchoalveolar lavage (BAL) was done 5 min and 48 h after challenge with saline or antigen. Airway cells were isolated and then stimulate d ex vivo with a T-cell mitogen, phytohemagglutinin (PHA), and cytokin e release was determined. Cells retrieved from the saline-challenged s egment secreted principally interferon-gamma (IFN-gamma) and IL-2. In contrast, cells obtained 48 h after allergen challenge secreted high l evels of IL-5 and small but increased amounts of IL-4, IL-10, and gran ulocyte-macrophage colony-stimulating factor (GM-CSF). Although CD4(+) T cells were a major source of IL-5, there were no significant change s in the relative proportion of CD4(+) cells in response to bronchopro vocation. Additionally, ex vivo secretion of IL-5 by airway cells corr elated closely with amounts of IL-5 and eosinophils present in the bro nchoalveolar lavage fluid (BALF). These observations suggest that foll owing exposure to allergen, airway T cells are functionally but not ph enotypically different from resident airway T cells, and that T cells within the airway contribute to eosinophilic airway inflammation throu gh the secretion of IL-5.