Abstract: 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
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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.
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. International Journal of Molecular Sciences. 2012; 13(9):10863-10879.
Huang, Guanyou; Zeng, Yaoying; Liang, Peiyan; Zhou, Congrong; Zhao, Shuyun; Huang, Xiuyan; Wu, Lingfei; He, Xianhui. 2012. "Indoleamine 2,3-Dioxygenase (IDO) Downregulates the Cell Surface Expression of the CD4 Molecule." Int. J. Mol. Sci. 13, no. 9: 10863-10879.