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Int. J. Mol. Sci. 2012, 13(9), 10863-10879; doi:10.3390/ijms130910863

Indoleamine 2,3-Dioxygenase (IDO) Downregulates the Cell Surface Expression of the CD4 Molecule

1,2,†,* , 2,†
1 Reproductive Medicine Center, Affiliated Hospital of Guiyang Medical College, Guiyang 550004, China 2 Institute of Tissue Transplantation and Immunology, Jinan University, Guangzhou 510632, China 3 Peking University Shenzhen Graduate School, Shenzhen 518000, China 4 Department of Gastroenterology, Second Affiliated Hospital, Shantou University Medical College, Shantou 515041, China These authors contributed equally to this work.
* Author to whom correspondence should be addressed.
Received: 4 July 2012 / Revised: 20 August 2012 / Accepted: 21 August 2012 / Published: 30 August 2012
(This article belongs to the Section Biochemistry, Molecular Biology and Biophysics)
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Indoleamine 2,3-dioxygenase (IDO) has been implicated in preventing the fetus from undergoing maternal T cell-mediated immune responses, yet the mechanism underlying these kinds of IDO-mediated immune responses has not been fully elucidated. Since the CD4 molecule plays a central role in the onset and regulation of antigen-specific immune responses, and T cell is sensitive in the absence of tryptophan, we hypothesize that IDO may reduce cell surface CD4 expression. To test this hypothesis, an adenoviral vector-based construct IDO-EGFP was generated and the effect of IDO-EGFP on CD4 expression was determined on recombinant adenoviral infected C8166 and MT-2 cells, by flow cytometry and/or Western blot analysis. The results revealed a significant downregulation of cell membrane CD4 in pAd-IDOEGFP infected cells when compared to that of mock-infected cells or infection with empty vector pAd-EGFP. Further experiments disclosed that either an addition of tryptophan or IDO inhibitor could partly restore CD4 expression in pAd-IDOEGFP infected C8166 cells. Our findings suggest that downregulation of CD4 by IDO might be one of the mechanisms through which IDO regulates T cell-mediated immune responses.
Keywords: human IDO; CD4; T cell; immune tolerance; immune response human IDO; CD4; T cell; immune tolerance; immune response
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).

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Huang, G.; Zeng, Y.; Liang, P.; Zhou, C.; Zhao, S.; Huang, X.; Wu, L.; He, X. Indoleamine 2,3-Dioxygenase (IDO) Downregulates the Cell Surface Expression of the CD4 Molecule. Int. J. Mol. Sci. 2012, 13, 10863-10879.

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