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

The high affinity form of interleukin-2 receptor (IL-2R) is composed of two subunits; the alpha (p55) and beta (p75). The alpha chain, unlike the beta, 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 alpha-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 alpha-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 alpha-chain was relatively low (11% and 9% respectively), perhaps CB plus TPA caused IL-2R expression in only a subset of T cells.