INDUCTION OF LEUKOCYTE RECRUITMENT AND BRONCHIAL HYPERRESPONSIVENESS IN THE GUINEA-PIG BY AEROSOL ADMINISTRATION OF INTERLEUKIN-2

Exposure of guinea pigs to an aerosol of human recombinant interleukin -2 (IL-2; 30 mu g) resulted in an increase in the numbers of eosinophi ls and macrophages recovered from bronchoalveolar lavage fluid (BALE) 24 h later. This was accompanied by a bronchial hyperresponsiveness to intravenous acetylcholine. In guinea pigs sensitized to ovalbumin, ex posure to IL-2 caused an increase in the number of macrophages, but no t eosinophils in BALE and bronchial hyperresponsiveness to acetylcholi ne did not develop. In guinea pig skin, intradermal injection of IL-2 (10(-14) to 10(-9) mol/site) had no effect on In-111-eosinophil accumu lation, measured over 3 h, suggesting that IL-2 does not act directly to recruit eosinophils. The hypothesis that IL-2 may be acting via rel ease of interleukin-5 (IL-5) was tested using an antibody to IL-5 (TRF K-5; 1 mg/kg). Treatment with TRFK-5 Ih before exposure to IL-2 aeroso l had no effect on the numbers of macrophages or eosinophils recovered from BALE 24 h later, although there was a tendency for reduced bronc hial hyperresponsiveness to acetylcholine. These results suggest that (1) IL-2 is not a directly acting chemoattractant for eosinophils in t he guinea pig, (2) the action of IL-2 to increase bronchial hyperrespo nsiveness is also indirect, partly via generation of IL-5, and (3) imm unological sensitization alters the response of both eosinophils and b ronchial smooth muscle to IL-2.