Cytokine Mediated Regulation of Interferon-Gamma-Induced Ido Activation

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Abstract
Stimulation of human monocyte-derived-macrophages (MDM) with interferon gamma induces the l-tryptophan degrading enzyme indoleamine 2,3-dioxygenase (IDO). It has been well documented that the growth of some intra-cellular parasites such as Chlamydia and Toxoplasma in human fibroblasts and glioblastoma cells is inhibited by IDO mediated L-tryptophan depletion. We have recently shown that IDO induction in cord blood MDM is also responsible for the growth inhibition of extra-cellular group B streptococci and thus for the first time shown an anti-bacterial effect of IDO activation. In view of this immunological function we sought to investigate the regulation, and in particular the downregula-tion of IDO by the immune system. We describe here the effect of cytokines on IDO activation and in particular the inhibitory function of IL-10, TGFβ and IL-4.