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 o f two subunits; the alpha (p55) and beta (p75). The a chain, unlike th e beta, is expressed only on activated T lymphocytes. Therefore, high affinity binding of interleukin-2 (IL-2) is controlled by the expressi on of the IL-2R alpha-chain. In this study, we examined the effect of cytochalasin B (CB) plus 12-0-tetradecanoylphorbol-13-acetate (TPA) on expression of IL-2 and IL-2R. Northern blot and flow cytometric analy sis showed that the IL-2R alpha-chain was expressed both at mRNA and p rotein levels. However, IL-2 gene expression was not induced by this t reatment. Unlike the cells treated individually with CB or TPA, cells treated with CB plus TPA accumulated IL-2R mRNA at all the times exami ned. In order to determine the percentage of cells that incorporated t ritiated thymidine ([H-3]dT) in the presence of IL-2 after treatment w ith CB plus TPA, autoradiography was carried out. We found that about 11% of the cells were labelled. Because the percentage of labelled cel ls 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.