Background: 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.
Objectives: 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.
Methods: 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.
Results: 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.
Conclusions: 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.