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 6

Direct activation of mature Tregs is more potent than de novo differentiation of new Tregs.

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Direct activation of mature Tregs is more potent than de novo differenti...
(A) Activation cocultures were set up as described in Figure 2 using Thy1.1-congenic B6 Tregs. To these were added CD4+CD25– (naive, nonregulatory) T cells from A1 mice plus CBA spleen DCs. Parallel groups received either no H-Y antigen for the A1 cells, H-Y, or H-Y plus 1MT. (All cultures received OVA peptide for the OT-I). After 2 days, cocultures were stained for CD4, Foxp3, and Thy1.1. The smaller dot plots show similar cultures in which the A1 cells and OT-I were labeled with CFSE prior to addition, then analyzed for cell division at the end of the assay. CFSE histograms for the A1 cells (CD4+CFSE+) are superimposed. One of 4 experiments. (B) Assays were set up as described in the previous panel, using Thy1.1 congenic Tregs plus nonregulatory CD4+CD25– cells from wild-type B6 mice, activated with αCD3 mAb. Dot plots show upregulation of Foxp3 in this model using CD4+CD25– cells prelabeled with CFSE. After 2 days the Treg and non-Treg populations were sorted separately based on Thy1.1 expression and tested in readout assays (A1 T cells + CBA DCs). One of 3 similar experiments; error bars show SD.