Effects of allergen challenge on eosinophils, eosinophil cationic protein, and granulocyte-macrophage...

Allergen inhalation challenge is associated with increases in eosinophil number and activation, and provides a useful model for investigating airway inflammation in asthma. Limited information, however, is available on the effect of allergen challenge on cytokines regulating eosinophil function. We investigated allergen-induced changes in eosinophil number and activation and in granulocyte-macrophage colony-stimulating factor (GM-CSF), a cytokine known to regulate eosinophil function in vitro. Seven subjects with mild atopic asthma and late asthmatic responses completed diluent- and allergen-inhalation challenges. Blood, bronchoalveolar lavage fluid (BALF), and biopsy samples were collected 24 h after challenge. Allergen inhalation caused a significant increase in eosinophils in BALF and biopsy samples. Eosinophil activation, as assessed by secretion of eosinophil cationic protein, and GM-CSF levels were significantly increased in BALF and bronchoalveolar lavage (BAL) cells. Allergen inhalation did not cause a significant change in eosinophil activation in biopsy tissue but did result in a significant decrease in GM-CSF in the tissue. Significant correlations were shown between the concentration of GM-CSF in BALF and the percentage of BAL eosinophils (Rs = 0.75, p = 0.05), severity of the late asthmatic response, and number of BAL eosinophils (Rs = 0.82, p = 0.02). A trend was seen between the late response and the concentration of GM-CSF in BALF. These results are consistent with the hypothesis that eosinophils, regulated by GM-CSF, contribute to allergen-induced decreases in airway function.