EFFECTS OF ALLERGEN CHALLENGE ON EOSINOPHILS, EOSINOPHIL CATIONIC PROTEIN, AND GRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR IN MILD ASTHMA

Allergen inhalation challenge is associated with increases in eosinoph il number and activation, and provides a useful model for investigatin g airway inflammation in asthma. Limited information, however, is avai lable on the effect of allergen challenge on cytokines regulating eosi nophil function. We investigated allergen-induced changes in eosinophi l number and activation and in granulocyte-macrophage colony-stimulati ng factor (GM-CSF), a cytokine known to regulate eosinophil function i n vitro. Seven subjects with mild atopic asthma and rate asthmatic res ponses completed diluent- and allergen-inhalation challenges. Blood, b ronchoalveolar lavage fluid (BALF), and biopsy samples were collected 24 h after challenge. Allergen inhalation caused a significant increas e in eosinophils in BALF and biopsy samples. Eosinophil activation, as assessed by secretion of eosinophil cationic protein, and GM-CSF leve ls were significantly increased in BALF and bronchoalveolar lavage (BA L) cells. Allergen inhalation did not cause a significant change in eo sinophil activation in biopsy tissue but did result in a significant d ecrease in GM-CSF in the tissue. Significant correlations were shown b etween the concentration of GM-CSF in BALF and the percentage of BAL e osinophils (Rs = 0.75, p = 0.05); severity of the late asthmatic respo nse, 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 ate consistent with the hypothesis that eosinophils, r egulated by GM-CSF, contribute to allergen-induced decreases in airway function.