The indoleamine 2,3-dioxygenase pathway is essential for human plasmacytoid dendritic cell-induced adaptive T regulatory cell generation

Wei Chen, Xueqing Liang, Amanda J. Peterson, David H Munn, Bruce R. Blazar

Research output: Contribution to journalArticle

291 Scopus citations


Human plasmacytoid dendritic cells (PDCs) can drive naive, allogeneic CD4+CD25+ T cells to differentiate into CD4 +CD25+. Foxp3+ regulatory T cells (Tregs). However, the intracellular mechanism or mechanisms underlying PDC-induced Treg generation are unknown. In this study, we show that human PDCs express high levels of IDO, an intracellular enzyme that catabolizes tryptophan degradation. Triggering of TLR 9 with CpG oligodeoxynucleotides activates PDCs to up-regulate surface expression of B7 ligands and HLA-DR Ag, but also significantly increases the expression of IDO and results in the generation of inducible Tregs from CD4+CD25+ T cells with potent suppressor cell function. Blocking IDO activity with the pharmacologic inhibitor 1-methyl-D-tryptophan significantly abrogates PDC-driven inducible Treg generation and suppressor cell function. Adding kynurenine, the immediate downstream metabolite of tryptophan, bypasses the 1-methyl-D-tryptophan effect and restores PDC-driven Treg generation. Our results demonstrate that the IDO pathway is essential for PDC-driven Treg generation from CD4+ CD25- T cells and implicate the generation of kynurenine pathway metabolites as the critical mediator of this process.

Original languageEnglish (US)
Pages (from-to)5396-5404
Number of pages9
JournalJournal of Immunology
Issue number8
StatePublished - Jan 1 2008


ASJC Scopus subject areas

  • Immunology

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