Interleukin-5 modifies histamine release and leukotriene generation by human basophils in response to diverse agonists

Human interleukin 5 (IL5), known as a selective colony-stimulating factor of the eosinophil lineage and activator of mature eosinophils, also profoundly influences the mediator release profile of human basophils. IL5 by itself triggers neither granule release nor de novo synthesis of lipid mediators. However, at low concentrations (0.1-10 ng/ml), IL5 rapidly primes basophils for enhanced histamine release and leukotriene C4 (LTC4) generation in response to all established basophil agonists. LTC4 generation is more strongly affected by 11,5 than histamine release. In particular, IL5 renders basophils capable of producing large quantities of LTC4 in response to C5a, which, without the cytokine, induces histamine release only. Finally, IL5 renders basophils responsive to agonists (neutrophil-activating peptide 1 and C3a), which are otherwise inefficient triggers for basophil mediator release. The effects are similar to the recently established bioactivity of IIL3 on basophils, with the exception of its influence on IgE-dependent basophil activation, which is less pronounced. Thus, IL5 strongly modulates the function not only of eosinophils but also of basophils, the two major effector leukocyte types involved in allergic inflammatory processes, e.g., in asthma