Regulation of follicular T-helper cell positioning and function by PD-1
Ontology highlight
ABSTRACT: Follicular T-helper (TFH) cells highly express the programmed cell death-1 (PD-1) molecule. Whereas inhibition of T cell receptor (TCR) signaling and CD28 co-stimulation is thought to be the primary mode of PD-1 functions, how PD-1 regulates TFH development and function remains unclear. Here we show that, when engaged by the ensemble of bystander B cells constitutively expressing PD-1 ligand 1 (PD-L1), PD-1 inhibits T-cell recruitment into follicles. This inhibition involves suppression of PI3K activities downstream of follicle-guidance receptor CXCR5, is independent from co-signaling with the TCR, and necessitates ICOS signaling to overcome. PD-1 further restricts CXCR3 upregulation on TFH cells, serving to concentrate these cells toward the GC territory, where PD-L1-PD-1 interactions between individual TFH and B cells optimize B-cell competition and affinity maturation. Therefore, operating in both costimulation-independent and -dependent manners, PD-1 plays an integral role in orchestrating tissue positioning and function of TFH cells.
Project description:PD-1 ligation delimits immunogenic responses in T cells. However, the consequences of PD-L1 ligation in T cells are uncertain. We found that T cell expression of PD-L1 in cancer was regulated by tumor-antigen, microbial signals, and sterile inflammatory cues. PD-L1+ T cells exerted tumor-promoting tolerance via three distinct mechanisms: (i) Binding of PD-L1 induced STAT3-dependent back-signaling in CD4+ T cells preventing activation, reducing Th1-polarization, and directing Th17-differentiation. PD-L1 signaling also induced an anergic Tbet-IFNg- phenotype in CD8+ T cells and was equally suppressive compared to PD-1 signaling. (ii) PD-L1+ T cells restrained effector T cells via the canonical PD-L1-PD-1 axis and were sufficient to accelerate tumorigenesis even in the absence of endogenous PD-L1. (iii) PD-L1+ T cells engaged PD-1+ macrophages inducing an alternative M2-like program, which had crippling effects on adaptive anti-tumor immunity. Collectively, we demonstrate that PD-L1+ T cells have diverse tolerogenic effects on tumor immunity.
Project description:Response to immune checkpoint inhibitors may be improved through combinations with each other and other therapies, raising questions about non-redundancy and resistance. We report results from parallel studies of melanoma patients and mice treated with anti-CTLA4 and radiation (RT). Although combined treatment improved responses, resistance was common. Computational analyses of immune and transcriptomic profiles (provided here) revealed that resistance in mice was due to upregulation of tumor PD-L1 that drives T cell exhaustion. Accordingly, optimal response requires RT, anti-CTLA4, and anti-PD-L1. Anti-CTLA4 inhibits Tregs, RT diversifies and shapes the TCR repertoire, and anti-PD-L1 reinvigorates exhausted T cells. Together, all three therapies promote the expansion of clonotypes with distinct TCR traits. Similar to mice, patients with melanoma showing high PD-L1 did not respond to RT + anti-CTLA4, demonstrated persistent T cell exhaustion, and rapidly progressed. Thus, the combination of RT, anti-CTLA4, and anti-PD-L1 promotes response through distinct mechanisms.
Project description:T follicular helper CD4 T cells (Tfh) provide requisite help to B cells in the germinal centers (GC) of lymphoid tissue. GC Tfh are identified by high expression of the chemokine receptor CXCR5 and the inhibitory molecule PD-1. Although more accessible, blood contains lower frequencies of CXCR5+ and PD-1+ cells that have been termed circulating Tfh (cTfh). However, it remains unclear whether GC Tfh exit lymphoid tissues and populate this cTfh pool. To examine exiting cells, we assessed the phenotype of Tfh present within the major conduit of efferent lymph from lymphoid tissues into blood, the human thoracic duct. Unlike blood, we consistently identified a CXCR5-Bright PD-1-Bright (CXCR5BrPD-1Br) Tfh population in thoracic duct lymph (TDL). These CXCR5BrPD-1Br TDL Tfh shared phenotypic and transcriptional similarities with GC Tfh. Moreover, components of the epigenetic profile of GC Tfh could be detected in CXCR5BrPD-1Br TDL Tfh, and the transcriptional imprint of this epigenetic signature was enriched in an activated cTfh subset known to contain vaccine-responding cells. Together with data showing shared TCR sequences between the CXCR5BrPD-1Br TDL Tfh and cTfh, these studies identify a population in TDL as a circulatory intermediate connecting the biology of Tfh in blood to Tfh in lymphoid tissue.
Project description:T follicular helper CD4 T cells (Tfh) provide requisite help to B cells in the germinal centers (GC) of lymphoid tissue. GC Tfh are identified by high expression of the chemokine receptor CXCR5 and the inhibitory molecule PD-1. Although more accessible, blood contains lower frequencies of CXCR5+ and PD-1+ cells that have been termed circulating Tfh (cTfh). However, it remains unclear whether GC Tfh exit lymphoid tissues and populate this cTfh pool. To examine exiting cells, we assessed the phenotype of Tfh present within the major conduit of efferent lymph from lymphoid tissues into blood, the human thoracic duct. Unlike blood, we consistently identified a CXCR5-Bright PD-1-Bright (CXCR5BrPD-1Br) Tfh population in thoracic duct lymph (TDL). These CXCR5BrPD-1Br TDL Tfh shared phenotypic and transcriptional similarities with GC Tfh. Moreover, components of the epigenetic profile of GC Tfh could be detected in CXCR5BrPD-1Br TDL Tfh, and the transcriptional imprint of this epigenetic signature was enriched in an activated cTfh subset known to contain vaccine-responding cells. Together with data showing shared TCR sequences between the CXCR5BrPD-1Br TDL Tfh and cTfh, these studies identify a population in TDL as a circulatory intermediate connecting the biology of Tfh in blood to Tfh in lymphoid tissue.
Project description:To test the hypothesis that the activation and regulatory signaling in γ-TCRγ-T cells could be dissimilar from the conventional TCR-T, we stimulated anti-PD-L1 δ-TCRγδ- and γ-TCRγ-T cells engineered from three different donors, and then compared the genome-wide transcriptome profiles by RNA sequencing (RNA-Seq).
Project description:TC-510 is a novel cell therapy that consists of autologous genetically engineered T cells expressing two synthetic constructs: first, a single-domain antibody that recognizes human Mesothelin, fused to the CD3-epsilon subunit which, upon expression, is incorporated into the endogenous T cell receptor (TCR) complex and second, a PD-1:CD28 switch receptor, which is expressed on the surface of the T cell, independently from the TCR. The PD-1:CD28 switch receptor comprises the PD-1 extracellular domain fused to the CD28 intracellular domain via a transmembrane domain. Thus, the switch is designed to produce a costimulatory signal upon engagement with PD-L1 on cancer cells.
Project description:TGFb signaling is a major pathway associated with poor clinical outcome in patients with
advanced metastatic cancers and non-response to immune checkpoint blockade, particularly in the immune-excluded tumor phenotype. While previous pre-clinical studies demonstrated that converting tumors from an excluded to an inflamed phenotype and curative anti-tumor immunity require attenuation of both PD-L1 and TGFb signaling, the underlying cellular mechanisms remain unclear. Recent studies suggest that stem cell-like CD8 T cells (TSCL) can differentiate into non-exhausted CD8 T effector cells that drive durable anti-tumor immunity. Here, we show that TGFb and PD-L1 restrain TSCL expansion as well as replacement of progenitor exhausted and dysfunctional CD8 T cells with non-exhausted IFNghi CD8 T effector cells in the tumor microenvironment (TME). Blockade of TGFb and PD-L1 generated IFNghi CD8 T effector cells with enhanced motility, enabling both their accumulation in the TME and increased interaction with other cell types. Ensuing IFNg signaling markedly transformed myeloid, stromal, and tumor niches to yield a broadly immune-supportive ecosystem. Blocking IFNg completely abolished the effect of anti-PD-L1/ TGFb combination therapy. Our data suggest that TGFb works in concert with PD-L1 to prevent TSCL expansion and replacement of exhausted CD8 T cells with fresh CD8
T effector cells, thereby maintaining the CD8 T cell compartment in a dysfunctional state.
Project description:Dendritic cells (DCs) express high levels of PD-L1 in the tumor microenvironment. However, the physiological functions of PD-L1 on DCs remain incompletely understood. Here, we explored the roles of PD-L1 signaling in dendritic cells. PD-L1 was knocked out in DC2.4 cells and transcriptional profiles were analyzed.
Project description:Tight control of follicular helper T(Tfh) cells is required for optimal maturation of the germinal center (GC) response. The molecular mechansims controlling Tfh cell differentiation remain incompletely understood. Here we sought to to identfiy miRNAs that might regulate Tfh cell development and/or function. To identfiy miRNAs that are differentially expressed in Tfh cells, we performed Agilent microRNA microarray analysis comparing Tfh cells with the other main T cell subsets (naive T cells, non-Tfh effector or non-Tfh memory T cells, CD57+ Tfh cells and CD57- Tfh cells). RNA was extracted from 4 separate human tonsils (biological replicates) using mirVANA RNA isolation kit (Ambion) according to the manufacturerM-bM-^@M-^Ys protocol. Each biological sample was analysed individually. Live lymphocytes were sorted based on negative 7AAD staining, and thefollowing four subsets were purified: Naive T cells (CD4+ CD45RO-); CD57+ Tfh cells (CD4+ CD45RO+ PD-1_high CXCR5_high CD57+); CD57- Tfh cells (CD4+ CD45RO+ PD-1_high CXCR5_high CD57-) and non-Tfh effector or memory T cells (CD4+ CD45RO+ PD-1_neg CXCR5_neg). RNA quantity and quality was determined using a Nanodrop 1000 and an Agilent 2100 Bioanalyzer respectively. Hybridization on Agilent Human miRNA Microarray (V1) Kit, 8x15K and was performed at The Ramaciotti Center for Genomics (University of New South Wales, Australia). The mean of 3-4 biological replicates from each population of each population were calculated and values were plotted using Prism.
Project description:Therapeutic checkpoint antibodies blocking PD1/PD-L1 signaling have radically improved clinical outcomes in cancer. However, the regulation of PD-L1 expression on tumor cells is still poorly understood. Here we show that intra-tumoral copper levels influence PD-L1 expression in cancer cells. Copper supplementation enhanced PD-L1 expression at mRNA and protein levels in cancer cells and RNAseq revealed that copper regulates key signaling pathways mediating PD-L1-driven cancer immune evasion. Conversely, copper chelators inhibited phosphorylation of STAT3 and EGFR and promoted ubiquitin-mediated degradation of PD-L1. Overall, this study reveals an important role for copper in regulating PD-L1 and suggests that anti-cancer immunotherapy might be enhanced by pharmacologically reducing intra-tumor copper levels.