Department of Medical Microbiology and Immunobiology, University of Szeged, Dóm tér 10, 6720, Szeged, Hungary.
J Neural Transm (Vienna). 2012 Feb;119(2):197-209. doi: 10.1007/s00702-011-0681-y. Epub 2011 Jul 9.
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.
人们对犬尿氨酸在免疫功能中的作用越来越感兴趣。关于犬尿氨酸途径、细胞因子和神经系统之间的相互作用，已经积累了相当多的证据。吲哚胺 2,3-双加氧酶（IDO）在连接免疫系统和犬尿氨酸途径方面占据关键位置。有证据表明 IDO 具有免疫抑制作用。在干扰素（IFN）介导的抗原呈递细胞激活后，IDO 和犬尿氨酸系统的诱导会产生反向调节作用，维持体内平衡。抑制 T 细胞功能、激活调节性 T 细胞以及抑制自然杀伤细胞是 IDO 和犬尿氨酸的免疫抑制作用的重要因素。细胞因子（IFN-α、IFN-γ、TNF-α、TGF-β、IL-4 和 IL-23）与犬尿氨酸系统之间存在密切联系，TH1/TH2 细胞因子谱的失衡可能导致神经或精神疾病。由于促炎刺激会激活色氨酸代谢途径，犬尿氨酸酸的抗炎作用为调节免疫反应提供了进一步的反馈机制。
