Interleukin-2 Activates Human Peripheral Blood Eosinophils

The effect of interleukin (IL)-2 on eosinophil survival and mediator release was investigated in vitro. Human peripheral blood eosinophils were isolated and purified from mildly atopic donors and cultured on albumin-coated wells with different concentrations of IL-2, interferon (IFN)-γ, and granulocyte–macrophage colony stimulating factor (GM-CSF) and their viability was evaluated after 4 days in culture. Eosinophils were cultured with IL-2 (1000 u/ml), IFN-γ (1000 u/ml), or GM-CSF (10 ng/ml) for 18 h, or with platelet activating factor (PAF) (10−6 M) for 20 min, and the release of eosinophil peroxidase (EPO) and IL-6 was measured. Nedocromil sodium (10−5 M) was added with each of the above cytokines to study the inhibitory effect of this drug on EPO release. A significant increase of EPO release was induced by IL-2, IFN-γ, and GM-CSF after 18 h in culture. IL-2 as well as IFN-γ induced a significant IL-6 release from eosinophils. Nedocromil sodium significantly inhibited EPO release from eosinophils induced by IL-2 or PAF. These results show that IL-2 can activate peripheral blood eosinophils to release granule mediators (EPO) and cytokines (IL-6). Taken together with the presence of IL-2 receptors on eosinophils, we conclude that IL-2 is an important mediator in allergic inflammation and a possible target for pharmacological modulation.