[Inhibitory effect of TGF-beta 1 on cytokine-enhanced eosinophil survival].

TGF-beta 1 has many biological activities in various cell types and is regarded as a multifunctioning regulator of cell growth. We studied the effect of TGF-beta 1 on cytokine-enhanced eosinophil survival in vitro. Eosinophils were purified from patients with mild atopic dermatitis by Percoll density gradient centrifugation and the CD16 negative selection/immunomagnetic beads technique. Eosinophil purity was greater than 95%. The purified eosinophils were incubated in the presence of eosinophil-activating cytokines (IL-5, IL-3, GM-CSF, IFN-gamma) with and without TGF-beta 1 for 3 days. Eosinophil viability was determined by staining the cells with fluorescein diacetate and propidium iodide. Without cytokine, most eosinophils died by day 3 in culture, but human recombinant IL-5, IL-3, GM-CSF, and IFN-gamma enhanced eosinophil survival in a dose-dependent manner. To test the effect of TGF-beta 1 on enhanced eosinophil survival, eosinophils were cultured with activating cytokine and TGF-beta 1. TGF-beta 1 inhibited eosinophil survival in a dose-dependent manner. The inhibitory effects of TGF-beta 1 on IL-5 enhanced survival was partially reversed by high concentrations of IL-5 and was completely neutralized with anti-TGF-beta antibody. Moreover, the apoptosis of eosinophils induced by TGF-beta 1 was determined with the assay of DNA fragmentation on agarose gel electrophoresis. It is possible that TGF-beta 1 activates the pathway of apoptosis. The results suggest that TGF-beta 1 may play a crucial role in the regulation of allergic inflammation.