IDO: a double-edged sword for T(H)1/T(H)2 regulation.
Indoleamine 2,3-dioxygenase (IDO) has been well defined as one of the important immunosuppressive properties for T(H)1 cell-mediated immune responses, but its function in T(H)2 dominant system is poorly understood. Recently, an appreciable number of publications suggest that the role of IDO in T(H)2 cell regulation may be different from that of T(H)1 immune responses. Here we review the evidence on the regulatory function of IDO and tryptophan metabolites in T(H)1/T(H)2 differentiation. We propose that IDO-kynurenine pathway can serve as a negative feedback loop for T(H)1 cells but it may play a distinct role in up-regulating T(H)2 dominant immune responses.
Xu
Hui
H
Department of Neurology, Thomas Jefferson University, 900 Walnut Street, Philadelphia, PA 19107, USA. hui.xu@jefferson.edu
Zhang
Guang-Xian
GX
Ciric
Bogoljub
B
Rostami
Abdolmohamad
A
D000818:Animals; D002454:Cell Differentiation; D003713:Dendritic Cells / Q000276:immunology / Q000378:metabolism; D006801:Humans; D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase / Q000172:deficiency / Q000276:immunology* / Q000378:metabolism; D007371:Interferon-gamma / Q000276:immunology / Q000378:metabolism*; D007737:Kynurenine / Q000276:immunology / Q000378:metabolism; D018417:Th1 Cells / Q000201:enzymology / Q000276:immunology*; D018418:Th2 Cells / Q000201:enzymology / Q000276:immunology*; D051193:Toll-Like Receptors / Q000276:immunology / Q000378:metabolism; D014364:Tryptophan / Q000276:immunology / Q000378:metabolism; D015854:Up-Regulation
D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase; D051193:Toll-Like Receptors; D007737:Kynurenine; D007371:Interferon-gamma; D014364:Tryptophan