The architecture of the interleukin-2 promoter: a reflection of T lymphocyte activation

摘要

The secretion of the T cell growth factor Interleukin 2 (IL-2) is a key event in the activation of T lymphocytes. IL-2 triggers peripheral T lymphocytes to enter the S phase of the cell cycle and to divide. This is probably due to the suppressive effect of IL-2 on cell cycle inhibitors which interfere with the activity of cyclin dependent kinases (cdks) at checkpoints of the cell cycle [1,2]. However, this is not the only effect IL-2 exerts on the regulation of the immune response and the differentiation of the immune system. Apart from the influence of IL-2 on the expression of molecules involved in the control of the cell cycle, there is a large amount of experimental data indicating that IL-2 might take part in the differentiation of thymocytes, peripheral T and B lymphocytes and numerous other cells of hematopoietic origin [3,4]. The normal development of lymphocytes and other hematopoietic cells in IL-2 deficient mice [5,6] seems to contradict these findings on the functional importance of IL-2. However, in these IL-2 knock-out mice the lack of IL-2 might be compensated by other lymphokines. Such lymphokines could use the common y-chain of the IL-2 receptor which is part of the IL-2, IL-4, IL-7, IL-9 and IL-15 receptors, and the IL-2 /3 chain which is also part of the IL-15 receptor (see [7] for a review). These lymphokines could induce signalling path-ways similar to IL-2. Cytokine-specific JAK/STAT path-ways (see [8] for a review) that are not induced through TCR mediated signals [9] could then be activated by these lymphokines.