Cellular markers of inflammation in the airways of allergic sheep with and without allergen-induced late responses.

Allergic sheep respond to inhaled Ascaris suum antigen either with an acute bronchoconstriction alone (acute responders, AR) or both an acute and late bronchoconstriction (dual responders, DR). In this study, we determined if: (1) inflammatory cell composition of bronchoalveolar lavage (BAL) obtained during the late response differs between DR and AR; (2) the difference in inflammatory cells is dependent on the prechallenge BAL cell composition; and (3) drugs that block late airway responses also modify this airway inflammation. Antigen challenge caused significant immediate mean increases in specific lung resistance (SRL) both in DR (n = 28) and in AR (n = 14), but only DR had a late increase in SRL. There were no differences between the two groups in total cell returns or in the percentage of neutrophils in BAL 7.5 to 8 h after challenge, but DR had a 3.5-fold increase (p less than 0.05) in the percentage of eosinophils. Methylprednisolone succinate (15 mg/kg intravenously) given to DR (n = 7) 3 h after antigen challenge blocked the late airway response and the eosinophil response. When BAL was performed both before and after (i.e., 7.5 to 8 h) antigen challenge, similar results were observed: AR (n = 7) and DR (n = 14) exhibited characteristic airway responses. No significant differences in prechallenge BAL cell composition were observed between AR and DR; after challenge both groups showed increases in neutrophils, but only the DR showed an increase (p less than 0.05) in eosinophils. Pretreatment of DR with the antiallergic agents (cromolyn sodium or nedocromil sodium aerosol, 20 mg) blocked the immediate and late responses and the late increase in BAL eosinophils.(ABSTRACT TRUNCATED AT 250 WORDS)