Indoleamine 2,3-dioxygenase controls conversion of Foxp3+ Tregs to TH17-like cells in tumor-draining lymph nodes.
The immunoregulatory enzyme indoleamine 2,3-dioxygenase (IDO) is expressed by a subset of murine plasmacytoid DCs (pDCs) in tumor-draining lymph nodes (TDLNs), where it can potently activate Foxp3+ regulatory T cells (Tregs). We now show that IDO functions as a molecular switch in TDLNs, maintaining Tregs in their normal suppressive phenotype when IDO was active, but allowing inflammation-induced conversion of Tregs to a polyfunctional T-helper phenotype similar to proinflammatory T-helper-17 (TH17) cells when IDO was blocked. In vitro, conversion of Tregs to the TH17-like phenotype was driven by antigen-activated effector T cells and required interleukin-6 (IL-6) produced by activated pDCs. IDO regulated this conversion by dominantly suppressing production of IL-6 in pDCs, in a GCN2-kinase dependent fashion. In vivo, using a model of established B16 melanoma, the combination of an IDO-inhibitor drug plus antitumor vaccine caused up-regulation of IL-6 in pDCs and in situ conversion of a majority of Tregs to the TH17 phenotype, with marked enhancement of CD8+ T-cell activation and antitumor efficacy. Thus, Tregs in TDLNs can be actively reprogrammed in situ into T-helper cells, without the need for physical depletion, and IDO serves as a key regulator of this critical conversion.
Sharma
Madhav D
MD
Department of Pediatrics, Medical College of Georgia, Augusta, GA 30912, USA.
Hou
De-Yan
DY
Liu
Yanjun
Y
Koni
Pandelakis A
PA
Metz
Richard
R
Chandler
Phillip
P
Mellor
Andrew L
AL
He
Yukai
Y
Munn
David H
DH
D019264:Adoptive Transfer; D000818:Animals; D015153:Blotting, Western; D019496:Cancer Vaccines / Q000627:therapeutic use; D002645:Chickens; D003713:Dendritic Cells / Q000276:immunology; D051858:Forkhead Transcription Factors / Q000378:metabolism*; D016130:Immunophenotyping; D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase / Q000502:physiology*; D020381:Interleukin-17 / Q000378:metabolism; D015850:Interleukin-6 / Q000378:metabolism; D008198:Lymph Nodes / Q000201:enzymology / Q000276:immunology*; D008213:Lymphocyte Activation; D008546:Melanoma, Experimental / Q000201:enzymology / Q000276:immunology* / Q000473:pathology; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D010047:Ovalbumin / Q000502:physiology; D011948:Receptors, Antigen, T-Cell / Q000502:physiology; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology* / Q000473:pathology; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*
D019496:Cancer Vaccines; D051858:Forkhead Transcription Factors; C498833:Foxp3 protein, mouse; D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase; D020381:Interleukin-17; D015850:Interleukin-6; D011948:Receptors, Antigen, T-Cell; D010047:Ovalbumin