Induction of interleukin‐2 receptor α‐chain gene expression by cytochalasin B and 12‐O‐tetradecanoylphorbol‐13‐acetate in T lymphocytes

Abstract. The high affinity form of interleukin‐2 receptor (IL‐2R) is composed of two subunits; the α (p55) and β (p75). The α chain, unlike the β, is expressed only on activated T lymphocytes. Therefore, high affinity binding of interleukin‐2 (IL‐2) is controlled by the expression of the IL‐2R α‐chain. In this study, we examined the effect of cytochalasin B (CB) plus 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA) on expression of IL‐2 and IL‐2R. Northern blot and flow cytometric analysis showed that the IL‐2R α‐chain was expressed both at mRNA and protein levels. However, IL‐2 gene expression was not induced by this treatment. Unlike the cells treated individually with CB or TPA, cells treated with CB plus TPA accumulated IL‐2R mRNA at all the times examined. In order to determine the percentage of cells that incorporated tritiated thymidine ([³H]dT) in the presence of IL‐2 after treatment with CB plus TPA, autoradiography was carried out. We found that about 11% of the cells were labelled. Because the percentage of labelled cells and cells expressing IL‐2R α‐chain was relatively low (11% and 9% respectively), perhaps CB plus TPA caused IL‐2R expression in only a subset of T cells.