The effects of two anti-CD18 antibodies on antigen-induced airway hyperresponsiveness and leukocyte accumulation in the guinea pig.

Guinea pigs sensitized to ovalbumin develop airway eosinophilia and bronchial hyperresponsiveness to acetylcholine and histamine 24 h after ovalbumin challenge. We have used two different antibodies to the leukocyte integrin CD18 (R15.7 and 6.5E) to study the link between eosinophilia and the development of bronchial hyperresponsiveness. In this model, both these antibodies reduced, to a similar degree, the number of eosinophils recovered from bronchoalveolar lavage fluid, although the eosinophil numbers in lung tissue were not reduced. However, only R15.7 reduced bronchial hyperresponsiveness. The results suggest that the CD18 integrin is involved in the recruitment of leukocytes to the airways, but increased numbers of eosinophils in lavage fluid are not an essential correlate of bronchial hyperresponsiveness in this model.