Effects of TGF‐β on Eosinophil Chemotaxis

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Abstract
Transforming growth factor-beta (TGF-beta), which can decrease the effects of interleukin (IL)-3, IL-5 and granulocyte-macrophage colony-stimulating factor (GM-CSF) on eosinophil viability, has been shown to be chemotactic for neutrophils. However, there is little information on its effects on eosinophil chemotaxis. Because TGF-beta has recently been found in increased concentrations in asthmatic sputum, we investigated whether TGF-beta could influence eosinophil migration and eosinophil viability. Purified eosinophils from normal donors were incubated with increasing concentrations of TGF-beta. Chemotaxis was measured with a modified Boyden chamber technique. In addition, eosinophils were incubated for 96 h with either IL-3, IL-5 or GM-CSF (1 ng/ml) together with increasing concentrations of TGF-beta. Eosinophil viability was then determined with propidium jodide and flow cytometry. Eosinophil chemotaxis was significantly increased in the presence of TGF-beta in concentrations between 10(-9) and 10(-4) microg/ml. The optimal concentration of TGF-beta in this assay was between 10(-9) and 10(-8) microg/ml. The chemotactic effect of TGF-beta diminished when higher as well as lower concentrations (between 10[-12] and 10[-3] microg/ml) were employed. In contrast, inhibition of eosinophil survival induced by IL-3, IL-5 and GM-CSF reached its maximum at concentrations of TGF-beta between 10(-4) and 10(-3) microg/ml. From these data we conclude that TGF-beta in low concentrations can induce eosinophil chemotaxis whereas higher concentrations reduce eosinophil survival mediated by IL-3, IL-5 and GM-CSF.

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