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.
View: Text | PDF
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

×

Figure 3

Suppression by IDO-activated Tregs requires the PD-1/PD-L pathway.

Options: View larger image (or click on image) Download as PowerPoint
Suppression by IDO-activated Tregs requires the PD-1/PD-L pathway. (A) T...
(A) Tregs were activated with IDO+ pDCs as described in Figure 2, then 1 × 104 sorted Tregs were added to readout assays (A1 T cells + CBA DCs). After 24 hours, cultures were harvested and stained for PD-L1 and PD-L2 relative to CD11c. Percentages indicate the proportion of cells that are dual-positive (right-upper quadrant). One of 3 experiments. (B) IDO-activated Tregs (5,000/well) were added to readout assays (A1 T cells plus either wild-type CBA DCs or IDO-KO DCs on the CBA background). Readout assays received either no additive, 1MT, or a cocktail of blocking antibodies against PD-1, PD-L1, and PD-L2 (50 μg/ml each). Control Tregs received 1MT during the activation step. One of 3 experiments; *P < 0.01 by ANOVA. (C) Tregs were activated with IDO+ pDCs or in identical cultures containing 1MT to block IDO and αCD3 plus IL-2 to activate the Tregs. After sorting, Tregs were added to readout assays (A1 T cells + CBA DCs) with or without PD-1/PD-L–blocking antibodies as shown. Graphs show the mean ± SD of 10 independent experiments with IDO-activated Tregs and 3 experiments with αCD3-activated Tregs, using TDLN pDCs from B78H1–GM-CSF and B16-OVA tumors. (D) IDO-activated Tregs (1 × 104/well) and αCD3/IL-2–activated Tregs (2 × 104/well) were prepared as described in the previous panel and added to readout assays with or without recombinant IL-2, anti–IL-10 plus anti–TGF-β blocking antibodies (100 μg/ml each), PD-1/PD-L–blocking antibodies, or no additive (-0-). Error bars show SD for replicate wells in 1 of 4 similar experiments. *P < 0.01 by ANOVA.