IL-3, IL-5, and GM-CSF exert various overlapping functions in basophils. We investigated the receptor expression profiles and concentration-dependent effects of IL-3, IL-5, and GM-CSF on several basophil functions in comparison with their effects on eosinophils. The order of the receptor expression levels was IL-3Ralpha > IL-5Ralpha > GM-CSFRalpha in basophils and IL-5Ralpha greater than or equal to GM-CSFRalpha > IL-3Ralpha in eosinophils. Compared with eosinophils, basophils expressed a much higher level of IL-3Ralpha and similar levels of IL-5Ralpha and GM-CSFRalpha. The order of potency was IL-3 > IL-5 = GM-CSF for degranulation, survival, and CD11b expression in basophils, and IL-5 = GM-CSF greater than or equal to IL-3 for survival and CD11b expression in eosinophils. However, IL-3 induced CD69 expression preferentially in basophils. Our results indicate that IL-3 is the most potent activator of human basophils, and that the rank order of potency of hemopoietic growth factors virtually corresponded to their receptor expression levels in both cell types. (C) 2003 Elsevier Science (USA). All rights reserved.