Airway eosinophilia and airway hyperreactivity are parallel rather than sequential events in the guinea-pig.

It is known that eosinophil activation in the airways is associated with epithelial damage in both guinea-pigs and man and it has been presumed that airway hyperreactivity arises in consequence of these events. However, infusion of (+/- )isoprenaline induces airway hyperreactivity in the guinea-pig despite a reduction of eosinophil numbers in the airway lumen, whilst rh-GM-CSF or rh-IL3 induce eosinophilia of the airways without attendant airway hyperreactivity. These findings complement earlier studies which showed that airway hyperreactivity in sensitized animals reacting to inhaled allergen could not be correlated with the number of eosinophils in the airway lumen.