Original Article

Journal of Molecular Medicine

, Volume 86, Issue 4, pp 443-455

TLR-mediated induction of negative regulatory ligands on dendritic cells

  • Stefan GröschelAffiliated withKathleen B. and Mason I. Lowance Center for Human Immunology, Department of Medicine, Emory University School of Medicine
  • , Kisha D. PiggottAffiliated withKathleen B. and Mason I. Lowance Center for Human Immunology, Department of Medicine, Emory University School of Medicine
  • , Augusto VaglioAffiliated withKathleen B. and Mason I. Lowance Center for Human Immunology, Department of Medicine, Emory University School of MedicineClinical Medicine and Nephrology, University of Parma
  • , Wei Ma-KrupaAffiliated withKathleen B. and Mason I. Lowance Center for Human Immunology, Department of Medicine, Emory University School of Medicine
  • , Karnail SinghAffiliated withKathleen B. and Mason I. Lowance Center for Human Immunology, Department of Medicine, Emory University School of Medicine
  • , Jörg J. GoronzyAffiliated withKathleen B. and Mason I. Lowance Center for Human Immunology, Department of Medicine, Emory University School of Medicine
  • , Cornelia M. WeyandAffiliated withKathleen B. and Mason I. Lowance Center for Human Immunology, Department of Medicine, Emory University School of Medicine Email author 

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Abstract

Dendritic cells (DCs) shape T-cell response patterns and determine early, intermediate, and late outcomes of immune recognition events. They either facilitate immunostimulation or induce tolerance, possibly determined by initial DC activation signals, such as binding Toll-like receptor (TLR) ligands. Here, we report that DC stimulation through the TLR3 ligand dsRNA [poly(I:C)] limits CD4 T-cell proliferation, curtailing adaptive immune responses. CD4+ T cells instructed by either lipopolysaccharide (LPS) or poly(I:C)-conditioned DCs promptly upregulated the activation marker CD69. Whereas LPS-pretreated DCs subsequently sustained T-cell clonal expansion, proliferation of CD4+ T cells exposed to poly(I:C)-pretreated DCs was markedly suppressed. This proliferative defect required DC–T cell contact, was independent of IFN-α, and was overcome by exogenous IL-2, indicating T-cell anergy. Coinciding with the downregulation, CD4+ T cells expressed the inhibitory receptor PD-1. Antibodies blocking the PD-1 ligand PD-L1 restored proliferation. dsRNA-stimulated DCs preferentially induced PD-L1, whereas poly(I:C) and LPS both upregulated the costimulatory molecule CD86 to a comparable extent. Poly(dA-dT), a ligand targeting the cytoplasmic RNA helicase pattern-recognition pathway, failed to selectively induce PD-L1 upregulation, assigning this effect to the TLR3 pathway. Poly(I:C)-conditioned DCs promoted accumulation of phosphorylated SHP-2, the intracellular phosphatase mediating PD-1 inhibitory effects. The ability of dsRNA to bias DC differentiation toward providing inhibitory signals to interacting CD4+ T cells may be instrumental in viral immune evasion. Conversely, TLR3 ligands may have therapeutic value in silencing pathogenic immune responses.

Keywords

Dendritic cell T cell Toll-like receptor 3 PD-L1