Frequency and characterization of antigen-specific IL-4- and IL-13- producing basophils and T cells in peripheral blood of healthy and asthmatic subjects.

Abstract

Both basophils and T cells are known to secrete IL-4 and IL-13 after activation with either nonspecific stimuli or specific antigen, but the relative contribution of these 2 cell types to overall cytokine production is unclear. To further characterize basophil cytokine production and compare it with that of T cells, we examined the frequency of IL-4- and IL-13-producing basophils and T cells in human PBMCs by means of flow cytometry after activation in allergic asthmatic and normal subjects. PBMCs obtained from whole blood after Percoll gradient were activated with specific antigen or ionomycin and fixed. PBMCs were made permeable; stained with antibodies to IgE, CD3, and either IL-4 or IL-13; and analyzed by means of flow cytometry. Preformed cytokines were not detected in unactivated basophils. After ionomycin activation, 60% to 90% of basophils from both control and allergic asthmatic subjects expressed IL-4 and IL-13. Specific antigen induced cytokine expression by 10% to 20% of basophils from the asthmatic group only. After specific antigen activation, basophils accounted for 4 times more IL-4-producing cells than did T cells. IL-4 and IL-13 production at 2 hours was exclusively from basophils. After allergen activation, CD40 ligand was upregulated on a subset of peripheral blood basophils. These data demonstrate that basophils are the predominant peripheral blood cells that express IL-4 and IL-13 in the first 6 hours after antigen activation and strengthen the putative role of basophils both in IgE production and in the generation of allergic inflammation.