Transcriptional control of the IL-5 gene by human helper T cells: IL-5 synthesis is regulated independently from IL-2 or IL-4 synthesis. 
BACKGROUND: IL-5 is fundamentally involved in eosinophilic inflammation. Control of IL-5 production may be effective for the management of allergic diseases. OBJECTIVE: We aimed to find the transcriptional mechanisms that regulate the IL-5 gene to selectively control IL-5 synthesis. METHODS: Allergen-specific T-cell clones and T-cell hybridomas were established from the peripheral blood lymphocytes of patients with asthma, and the transcriptional regulation of the IL-5 gene was investigated with transient transfection and electrophoretic mobility shift analysis. RESULTS: A human IL-5 promoter/enhancer-luciferase gene construct, pIL-5(-511)Luc, was transcribed on activation of IL-5-producing T-cell clones, but not IL-5-nonproducing clones. pIL-5(-511)Luc was transcribed by T-cell hybridomas derived from fusion between IL-5-producing T-cell clones and an IL-5 gene-nonexpressing T-cell line, but not by hybridomas derived from IL-5-nonproducing T-cell clones. IL-5 synthesis was not only induced by T-cell receptor stimulation but also by IL-2 receptor stimulation. Binding of NF-AT, NF-kappaB, and AP-1 was induced by T-cell receptor (TcR) stimulation, although there was no significant upregulation of binding by IL-2 stimulation. CONCLUSION: IL-5 synthesis by human helper T cells is regulated at the transcriptional level. A unique transcriptional mechanism distinct from those regulating the IL-2 or IL-4 genes seems to control the IL-5 gene. Selective regulation of IL-5 gene transcription may be useful for treating eosinophlic inflammation.