title: The kynurenine system and immunoregulation.
abstract: There is developing interest in the role of the kynurenines in the immune function. A considerable amount of evidence has accumulated as concerns interactions between the kynurenine pathway, cytokines and the nervous system. Indoleamine 2,3-dioxygenase (IDO) occupies a key position connecting the immune system and the kynurenine pathway. There are evidences of the immunosuppressive effect of IDO. Following the interferon (IFN)-mediated activation of antigen presenting cells, the induction of IDO and the kynurenine system exerts a counter-regulating effect, maintaining the homeostasis. Inhibition of T cell functions, activation of the regulatory T cells, and the inhibition of Natural Killer cells are among the important factors in the immunosuppressive effects of IDO and kynurenines. There is a close connection between cytokines (IFN-α, IFN-γ, TNF-α, TGF-β, IL-4 and IL-23) and the kynurenine system, and an imbalance in the TH1/TH2 cytokine profile may possibly lead to neurologic or psychiatric disorders. As the tryptophan metabolic pathway is activated by pro-inflammatory stimuli, the anti-inflammatory effect of kynurenic acid provides a further feedback mechanism in modulating the immune responses.
authors: Department of Medical Microbiology and Immunobiology, University of Szeged, Dóm tér 10, 6720, Szeged, Hungary. yvette@comser.szote.u-szeged.hu
authors: Yvette
authors: Y
authors: Mándi
authors: László
authors: L
authors: Vécsei
mesh_terms: D000818:Animals; D006801:Humans; D007108:Immune Tolerance / Q000276:immunology*; D056747:Immunomodulation / Q000502:physiology*; D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase / Q000502:physiology; D007249:Inflammation / Q000201:enzymology / Q000276:immunology / Q000517:prevention & control; D007737:Kynurenine / Q000378:metabolism / Q000502:physiology* / Q000627:therapeutic use*; D009434:Neural Pathways / Q000201:enzymology / Q000276:immunology / Q000473:pathology; D050378:T-Lymphocytes, Regulatory / Q000201:enzymology / Q000276:immunology / Q000473:pathology
chemical_list: D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase; D007737:Kynurenine