INTERLEUKIN-4 MESSENGER-RNA AND PROTEIN IN ACTIVATED HUMAN T-CELLS ARE ENHANCED BY INTERLEUKIN-7

We studied the effect of the stroma-derived cytokine interleukin-7 (IL-7) on the expression of IL-4 in human T cells at mRNA and protein level. The results demonstrate that IL-7 did not induce IL-4 mRNA in resting T cells. However, concanavalin A (con A)-induced IL-4 mRNA. expression was enhanced by costimulation with con A plus IL-7. Nuclear run-on analysis revealed that IL-7 did not affect the transcription rate of the IL-4 gene. The half-life of con A-induced IL-4 transcripts, however, was increased upon con A plus IL-7 treatment, indicating that the effect of IL-7 is mediated at posttranscriptional level. In accordance with the mRNA results, IL-4 protein was not detected in supernatants of unstimulated T cells or T cells exposed to IL-7. In contrast, IL-7 augmented the con A-induced secretion of IL-4 protein significantly. In addition, it was noticed that anti-IL-1 beta and anti-tumor necrosis factor-a (anti-TNF-alpha) did not abolish the effect of IL-7 on the con A-induced IL-4 secretion, indicating that the IL-7 effect is not mediated by the release of these cytokines. These results indicate that a stroma-derived factor can affect IL-4 expression in activated human T cells.