Plasmacytoid dendritic cells from mouse tumor-draining lymph nodes directly activate mature Tregs via indoleamine 2,3-dioxygenase
Madhav D. Sharma, … , Andrew L. Mellor, David H. Munn
Madhav D. Sharma, … , Andrew L. Mellor, David H. Munn
Published September 4, 2007
Citation Information: J Clin Invest. 2007;117(9):2570-2582. https://doi.org/10.1172/JCI31911.
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Research Article Oncology

Plasmacytoid dendritic cells from mouse tumor-draining lymph nodes directly activate mature Tregs via indoleamine 2,3-dioxygenase

Abstract

A small population of plasmacytoid DCs (pDCs) in mouse tumor-draining LNs can express the immunoregulatory enzyme indoleamine 2,3-dioxygenase (IDO). We show that these IDO+ pDCs directly activate resting CD4+CD25+Foxp3+ Tregs for potent suppressor activity. In vivo, Tregs isolated from tumor-draining LNs were constitutively activated and suppressed antigen-specific T cells immediately ex vivo. In vitro, IDO+ pDCs from tumor-draining LNs rapidly activated resting Tregs from non–tumor-bearing hosts without the need for mitogen or exogenous anti-CD3 crosslinking. Treg activation by IDO+ pDCs was MHC restricted, required an intact amino acid–responsive GCN2 pathway in the Tregs, and was prevented by CTLA4 blockade. Tregs activated by IDO markedly upregulated programmed cell death 1 ligand 1 (PD-L1) and PD-L2 expression on target DCs, and the ability of Tregs to suppress target T cell proliferation was abrogated by antibodies against the programmed cell death 1/PD-L (PD-1/PD-L) pathway. In contrast, Tregs activated by anti-CD3 crosslinking did not cause upregulation of PD-Ls, and suppression by these cells was unaffected by blocking the PD-1/PD-L pathway. Tregs isolated from tumor-draining LNs in vivo showed potent PD-1/PD-L–mediated suppression, which was selectively lost when tumors were grown in IDO-deficient hosts. We hypothesize that IDO+ pDCs create a profoundly suppressive microenvironment within tumor-draining LNs via constitutive activation of Tregs.

Authors

Madhav D. Sharma, Babak Baban, Phillip Chandler, De-Yan Hou, Nagendra Singh, Hideo Yagita, Miyuki Azuma, Bruce R. Blazar, Andrew L. Mellor, David H. Munn

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Figure 7

IDO-activated Tregs in TDLNs.

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IDO-activated Tregs in TDLNs. (A) Tumors were grown in wild-type or IDO-...
(A) Tumors were grown in wild-type or IDO-KO hosts. Tregs from day 7 TDLNs were sorted and added to readout assays (A1 T cells + CBA DCs) with and without PD-1/PD-L blocking antibodies. Mean ± SD of 4 pooled experiments with B78H1–GM-CSF, 4 experiments with B16-OVA, and 3 experiments with IDO-KO hosts (2 with B78H1–GM-CSF and 1 with B16-OVA). (B) Wild-type mice were treated throughout tumor growth with vehicle control or sustained-release 1MT. Tregs from day 7 tumors were tested in readout assays as described above with added isotype, PD-1/PD-L–blocking antibodies, or a combination of anti–PD-1/PD-L plus IL-2 plus anti–IL-10/TGF-β antibodies. One of 3 experiments using B78H1–GM-CSF and B16-OVA. (C) Upper panels: CFSE-labeled OT-I were injected into mice with B16-OVA tumors (days 7–8) with and without oral 1MT administration after transfer. After 4 days, TDLNs and contralateral LNs (CLN) were stained for the 1B11 activation marker. Percentages show the CFSE+ OT-I in total LN cells. Histogram shows 1B11 on OT-I in TDLNs. Representative of 4 transfers each. Lower panels: Similar experiments as described above using OT-IGCN2-KO cells transferred into WT or GCN2-KO hosts bearing B16-OVA tumors. One of 3 similar experiments. (D) B78H1–GM-CSF tumors were treated on day 11 with vehicle (control), cyclophosphamide (CY; 150 mg/kg), or cyclophosphamide plus 1MT pellets. Seven days later cells from TDLNs were harvested and added to readout assays (allospecific BM3 T cells plus B6 splenocytes, as described in ref. 1). One group in each readout assay also received 1MT added during the assay, as shown on the last bar of each graph. One of 3 experiments.