bims-imseme Biomed News
on Immunosenescence and T cell metabolism
Issue of 2020‒09‒27
nineteen papers selected by
Pierpaolo Ginefra
Ludwig Institute for Cancer Research


  1. Nat Metab. 2020 Sep 21.
    Franco F, Jaccard A, Romero P, Yu YR, Ho PC.
      Current immunotherapies yield remarkable clinical outcomes by boosting the power of host immunity in cancer cell elimination and viral clearance. However, after prolonged antigen exposure, CD8+ T cells differentiate into a special differentiation state known as T-cell exhaustion, which poses one of the major hurdles to antiviral and antitumor immunity during chronic viral infection and tumour development. Growing evidence indicates that exhausted T cells undergo metabolic insufficiency with altered signalling cascades and epigenetic landscapes, which dampen effector immunity and cause poor responsiveness to immune-checkpoint-blockade therapies. How metabolic stress affects T-cell exhaustion remains unclear; therefore, in this Review, we summarize current knowledge of how T-cell exhaustion occurs, and discuss how metabolic insufficiency and prolonged stress responses may affect signalling cascades and epigenetic reprogramming, thus locking T cells into an exhausted state via specialized differentiation programming.
    DOI:  https://doi.org/10.1038/s42255-020-00280-9
  2. Nat Commun. 2020 09 21. 11(1): 4767
    Penkava F, Velasco-Herrera MDC, Young MD, Yager N, Nwosu LN, Pratt AG, Lara AL, Guzzo C, Maroof A, Mamanova L, Cole S, Efremova M, Simone D, Filer A, Brown CC, Croxford AL, Isaacs JD, Teichmann S, Bowness P, Behjati S, Hussein Al-Mossawi M.
      Psoriatic arthritis (PsA) is a debilitating immune-mediated inflammatory arthritis of unknown pathogenesis commonly affecting patients with skin psoriasis. Here we use complementary single-cell approaches to study leukocytes from PsA joints. Mass cytometry demonstrates a 3-fold expansion of memory CD8 T cells in the joints of PsA patients compared to peripheral blood. Meanwhile, droplet-based and plate-based single-cell RNA sequencing of paired T cell receptor alpha and beta chain sequences show pronounced CD8 T cell clonal expansions within the joints. Transcriptome analyses find these expanded synovial CD8 T cells to express cycling, activation, tissue-homing and tissue residency markers. T cell receptor sequence comparison between patients identifies clonal convergence. Finally, chemokine receptor CXCR3 is upregulated in the expanded synovial CD8 T cells, while two CXCR3 ligands, CXCL9 and CXCL10, are elevated in PsA synovial fluid. Our data thus provide a quantitative molecular insight into the cellular immune landscape of psoriatic arthritis.
    DOI:  https://doi.org/10.1038/s41467-020-18513-6
  3. Trends Cell Biol. 2020 Sep 23. pii: S0962-8924(20)30170-7. [Epub ahead of print]
    Nakao M, Tanaka H, Koga T.
      Cellular senescence is a state of permanent cell cycle arrest accompanied by unique secretory actions, which influences tissue formation, tumor suppression and aging in vivo. Recent evidences suggest that metabolic and epigenomic reprogram cooperatively creates phenotypic differences of senescent cells, which may provide new clues to control aging processes.
    Keywords:  cellular senescence; epigenome; gene regulation; metabolism; senescence-associated secretory phenotype
    DOI:  https://doi.org/10.1016/j.tcb.2020.08.009
  4. Front Immunol. 2020 ;11 1953
    Majdoubi A, Lee JS, Kishta OA, Balood M, Moulefera MA, Ishido S, Talbot S, Cheong C, Alquier T, Thibodeau J.
      Obesity is a major risk factor for the development of insulin resistance and type 2 diabetes. However, the mechanisms that trigger the underlying adipose tissues inflammation are not completely understood. Here, we show that the E3 ubiquitin ligase March1 controls the phenotypic and functional properties of CD8+ T cells in mice white adipose tissue. In a diet-induced obesity model, mice lacking March1 [March1 knockout (KO)] show increased insulin resistance compared to their WT counterparts. Also, in obese March1 KO mice, the proportions of effector/memory (Tem) and resident/memory (Trm) CD8+ T cells were higher in the visceral adipose tissue, but not in the spleen. The effect of March1 on insulin resistance and on the phenotype of adipose tissue CD8+ T cells was independent of major histocompatibility complex class II ubiquitination. Interestingly, we adoptively transferred either WT or March1 KO splenic CD8+ T cells into obese WT chimeras that had been reconstituted with Rag1-deficient bone marrow. We observed an enrichment of Tem and Trm cells and exacerbated insulin resistance in mice that received March1 KO CD8 T cells. Mechanistically, we found that March1 deficiency alters the metabolic activity of CD8+ T cells. Our results provide additional evidence of the involvement of CD8+ T cells in adipose tissue inflammation and suggest that March1 controls the metabolic reprogramming of these cells.
    Keywords:  March1; T cell metabolism; memory CD8 T cell; obesity
    DOI:  https://doi.org/10.3389/fimmu.2020.01953
  5. EMBO Rep. 2020 Sep 23. e50635
    Altea-Manzano P, Cuadros AM, Broadfield LA, Fendt SM.
      Nutrients are indispensable resources that provide the macromolecular building blocks and energy requirements for sustaining cell growth and survival. Cancer cells require several key nutrients to fulfill their changing metabolic needs as they progress through stages of development. Moreover, both cell-intrinsic and microenvironment-influenced factors determine nutrient dependencies throughout cancer progression-for which a comprehensive characterization remains incomplete. In addition to the widely studied role of genetic alterations driving cancer metabolism, nutrient use in cancer tissue may be affected by several factors including the following: (i) diet, the primary source of bodily nutrients which influences circulating metabolite levels; (ii) tissue of origin, which can influence the tumor's reliance on specific nutrients to support cell metabolism and growth; (iii) local microenvironment, which dictates the accessibility of nutrients to tumor cells; (iv) tumor heterogeneity, which promotes metabolic plasticity and adaptation to nutrient demands; and (v) functional demand, which intensifies metabolic reprogramming to fuel the phenotypic changes required for invasion, growth, or survival. Here, we discuss the influence of these factors on nutrient metabolism and dependence during various steps of tumor development and progression.
    Keywords:  cancer metabolism; diet; microenvironment; nutrients; tumor heterogeneity
    DOI:  https://doi.org/10.15252/embr.202050635
  6. Int J Mol Sci. 2020 Sep 22. pii: E6966. [Epub ahead of print]21(18):
    Ren HM, Lukacher AE.
      CD4 T cells guide the development of CD8 T cells into memory by elaborating mitogenic and differentiation factors and by licensing professional antigen-presenting cells. CD4 T cells also act to stave off CD8 T cell dysfunction during repetitive antigen stimulation in persistent infection and cancer by mitigating generation of exhausted T cells (TEX). CD4 T cell help is also required for establishing and maintaining tissue-resident memory T cells (TRM), the nonrecirculating memory T cell subset parked in nonlymphoid tissues to provide frontline defense against reinvading pathogens. Interleukin (IL)-21 is the signature cytokine secreted by follicular helper CD4 T cells (TFH) to drive B cell expansion and differentiation in germinal centers to mount high-affinity, isotype class-switched antibodies. In several infection models, IL-21 has been identified as the CD4 T help needed for formation and survival of TRM and TEX. In this review, we will explore the different memory subsets of CD8 T cells in persistent infections, the metabolic profiles associated with each, and evidence documenting the importance of CD4 T cell-derived IL-21 in regulating CD8 TRM and TEX development, homeostasis, and function.
    Keywords:  CD4 T cells; CD8 T cells; exhaustion; interleukin (IL)-21; persistent infection; resident memory
    DOI:  https://doi.org/10.3390/ijms21186966
  7. Ageing Res Rev. 2020 Sep 21. pii: S1568-1637(20)30310-X. [Epub ahead of print] 101175
    Hamrick MW, Stranahan AM.
      Inquiry into relationships between energy metabolism and brain function requires a uniquely interdisciplinary mindset, and implementation of anti-aging lifestyle strategies based on this work also involves consistent mental and physical discipline. Dr. Mark P. Mattson embodies both of these qualities, based on the breadth and depth of his work on neurobiological responses to energetic stress, and on his own diligent practice of regular exercise and caloric restriction. Dr. Mattson created a neurotrophic niche in his own laboratory, allowing trainees to grow their skills, form new connections, and eventually migrate, forming their own labs while remaining part of the extended lab family. In this historical review, we highlight Dr. Mattson's many contributions to understanding neurobiological responses to physical exercise and dietary restriction, with an emphasis on the mechanisms that may underlie neuroprotection in ageing and age-related disease. On the occasion of Dr. Mattson's retirement from the National Institute on Aging, we highlight his foundational work on metabolism and neuroplasticity by reviewing the context for these findings and considering their impact on future research on the neuroscience of aging.
    Keywords:  Aging; Caloric restriction; Exercise; Hippocampus; Intermittent fasting; Mitochondria
    DOI:  https://doi.org/10.1016/j.arr.2020.101175
  8. J Am Chem Soc. 2020 Sep 25.
    Parasar B, Chang PV.
      T helper 17 (Th17) cells, an important subset of CD4+ T cells, help to eliminate extracellular infectious pathogens that have invaded our tissues. Despite the critical roles of Th17 cells in immunity, how the immune system regulates the production and maintenance of this cell type remains poorly understood. In particular, the plasticity of these cells, or their dynamic ability to trans-differentiate into other CD4+ T cell subsets, remains mostly uncharacterized. Here, we report a synthetic immunology approach using a photo-activatable immune modulator (PIM) to increase Th17 cell differentiation on demand with spatial and temporal precision to help elucidate this important and dynamic process. In this chemical strategy, we developed a latent agonist that, upon photochemical activation, releases a small-molecule ligand that targets the aryl hydrocarbon receptor (AhR) and ultimately induces Th17 cell differentiation. We used this chemical tool to control AhR activation with spatiotemporal precision within cells and to modulate Th17 cell differentiation on demand by using UV light illumination. We envision that this approach will enable an understanding of the dynamic functions and behaviors of Th17 cells in vivo during immune responses and in mouse models of inflammatory disease.
    DOI:  https://doi.org/10.1021/jacs.0c07485
  9. J Clin Invest. 2020 Sep 21. pii: 134091. [Epub ahead of print]
    Faust HJ, Zhang H, Han J, Wolf MT, Jeon OH, Sadtler K, Peña AN, Chung L, Maestas DR, Tam AJ, Pardoll DM, Campisi J, Housseau F, Zhou D, Bingham CO, Elisseeff JH.
      Senescent cells (SnCs) are implicated in the pathogenesis of age-related diseases including osteoarthritis (OA), in part via expression of a senescence-associated secretory phenotype (SASP) that includes immunologically relevant factors and cytokines. In a model of posttraumatic OA (PTOA), anterior cruciate ligament transection (ACLT) induced a type 17 immune response in the articular compartment and draining inguinal lymph nodes (LNs) that paralleled expression of the senescence marker p16INK4a (Cdkn2a) and p21 (Cdkn1a). Innate lymphoid cells, γδ+ T cells, and CD4+ T cells contributed to IL-17 expression. Intra-articular injection of IL-17-neutralizing antibody reduced joint degeneration and decreased expression of the senescence marker Cdkn1a. Local and systemic senolysis was required to attenuate tissue damage in aged animals and was associated with decreased IL-17 and increased IL-4 expression in the articular joint and draining LNs. In vitro, we found that Th17 cells induced senescence in fibroblasts and that SnCs skewed naive T cells toward Th17 or Th1, depending on the presence of TGF-β. The SASP profile of the inflammation-induced SnCs included altered Wnt signaling, tissue remodeling, and cell-cycle pathways not previously implicated in senescence. These findings provide molecular targets and mechanisms for senescence induction and therapeutic strategies to support tissue healing in an aged environment.
    Keywords:  Aging; Arthritis; Cellular immune response; Cellular senescence; Immunology
    DOI:  https://doi.org/10.1172/JCI134091
  10. Front Immunol. 2020 ;11 1915
    Mondino A, Manzo T.
      The generation of immunological memory is a hallmark of adaptive immunity by which the immune system "remembers" a previous encounter with an antigen expressed by pathogens, tumors, or normal tissues; and, upon secondary encounters, mounts faster and more effective recall responses. The establishment of T cell memory is influenced by both cell-intrinsic and cell-extrinsic factors, including genetic, epigenetic and environmental triggers. Our current knowledge of the mechanisms involved in memory T cell differentiation has instructed new opportunities to engineer T cells with enhanced anti-tumor activity. The development of adoptive T cell therapy has emerged as a powerful approach to cure a subset of patients with advanced cancers. Efficacy of this approach often requires long-term persistence of transferred T cell products, which can vary according to their origin and manufacturing conditions. Host preconditioning and post-transfer supporting strategies have shown to promote their engraftment and survival by limiting the competition with a hostile tumor microenvironment and between pre-existing immune cell subsets. Although in the general view pre-existing memory can confer a selective advantage to adoptive T cell therapy, here we propose that also "bad memories"-in the form of antigen-experienced T cell subsets-co-evolve with consequences on newly transferred lymphocytes. In this review, we will first provide an overview of selected features of memory T cell subsets and, then, discuss their putative implications for adoptive T cell therapy.
    Keywords:  T cell; adoptive T cell immunotherapy of cancer; competition; memory; tumor immunity
    DOI:  https://doi.org/10.3389/fimmu.2020.01915
  11. Front Immunol. 2020 ;11 1787
    You L, Han Q, Zhu L, Zhu Y, Bao C, Yang C, Lei W, Qian W.
      Chimeric antigen receptor (CAR) T cells represent a potentially curative therapy for patients with advanced hematological cancers; however, uncertainties surround the cell-intrinsic fitness as well as the exhaustion that restrict the capacity of CAR-T. Decitabine (DAC), a DNA demethylating agent, has been demonstrated to reverse exhaustion-associated DNA-methylation programs and to improve T cell responses against tumors. Here we show that DAC significantly enhances antileukemia functions of CD123 CAR-T cells in vitro and in vivo. Additionally, it inhibits the expression of DMNT3a and DNMT1. Using the Illumina Methylation EPIC BeadChip (850 K), we identified differentially methylated regions, most of which undergo hypomethylated changes. Transcriptomic profiling revealed that CD123 CAR-T cells treated with DAC were enriched in genes associated with naive, early memory T cells, as well as non-exhausted T cells. DAC treatment also results in upregulation of immune synapse-related genes. Finally, our data further suggest that DAC works through the regulation of cellular differentiation characterized by naive and memory phenotypes. Taken together, these findings demonstrate that DAC improves the anti-leukemia properties of CD123-directed CAR-T cells, and provides a basis for rational combinatorial CAR-T-based immunotherapy for patients with acute myeloid leukemia (AML).
    Keywords:  CAR-T immunotherapy; DNA-methylation; T cell subsets; acute myeloid leukemia; decitabine; immune synapse
    DOI:  https://doi.org/10.3389/fimmu.2020.01787
  12. Proc Natl Acad Sci U S A. 2020 Sep 21. pii: 202001966. [Epub ahead of print]
    Fernandez Lahore G, Raposo B, Lagerquist M, Ohlsson C, Sabatier P, Xu B, Aoun M, James J, Cai X, Zubarev RA, Nandakumar KS, Holmdahl R.
      It has proven difficult to identify the underlying genes in complex autoimmune diseases. Here, we use forward genetics to identify polymorphisms in the vitamin D receptor gene (Vdr) promoter, controlling Vdr expression and T cell activation. We isolated these polymorphisms in a congenic mouse line, allowing us to study the immunomodulatory properties of VDR in a physiological context. Congenic mice overexpressed VDR selectively in T cells, and thus did not suffer from calcemic effects. VDR overexpression resulted in an enhanced antigen-specific T cell response and more severe autoimmune phenotypes. In contrast, vitamin D3-deficiency inhibited T cell responses and protected mice from developing autoimmune arthritis. Our observations are likely translatable to humans, as Vdr is overexpressed in rheumatic joints. Genetic control of VDR availability codetermines the proinflammatory behavior of T cells, suggesting that increased presence of VDR at the site of inflammation might limit the antiinflammatory properties of its ligand.
    Keywords:  T cells; genetics; inflammation; vitamin D; vitamin D receptor
    DOI:  https://doi.org/10.1073/pnas.2001966117
  13. Front Immunol. 2020 ;11 1906
    Liu YN, Yang JF, Huang DJ, Ni HH, Zhang CX, Zhang L, He J, Gu JM, Chen HX, Mai HQ, Chen QY, Zhang XS, Gao S, Li J.
      T cell exhaustion is an obstacle to immunotherapy for solid tumors. An understanding of the mechanism by which T cells develop this phenotype in solid tumors is needed. Here, hypoxia, a feature of the tumor microenvironment, causes T cell exhaustion (TExh) by inducing a mitochondrial defect. Upon exposure to hypoxia, activated T cells with a TExh phenotype are characterized by mitochondrial fragmentation, decreased ATP production, and decreased mitochondrial oxidative phosphorylation activity. The TExh phenotype is correlated with the downregulation of the mitochondrial fusion protein mitofusin 1 (MFN1) and upregulation of miR-24. Overexpression of miR-24 alters the transcription of many metabolism-related genes including its target genes MYC and fibroblast growth factor 11 (FGF11). Downregulation of MYC and FGF11 induces TExh differentiation, reduced ATP production and a loss of the mitochondrial mass in T cell receptor (TCR)-stimulated T cells. In addition, we determined that MYC regulates the transcription of FGF11 and MFN1. In nasopharyngeal carcinoma (NPC) tissues, the T cells exhibit an increased frequency of exhaustion and loss of mitochondrial mass. In addition, inhibition of miR-24 signaling decreases NPC xenograft growth in nude mice. Our findings reveal a mechanism for T cell exhaustion in the tumor environment and provide potential strategies that target mitochondrial metabolism for cancer immunotherapy.
    Keywords:  MYC; T cell exhaustion; miR-24; mitochondrial dynamics; nasopharyngeal carcinoma
    DOI:  https://doi.org/10.3389/fimmu.2020.01906
  14. J Clin Hypertens (Greenwich). 2020 Sep 22.
    Wenstedt EFE, Remmerswaal EBM, van der Bom-Baylon ND, Schrooten EM, Bemelman FJ, Vogt L.
      Animal studies show that high-salt diet affects T-cell subpopulations, but evidence in humans is scarce and contradictory. This pilot study investigated the effect of a 2-week high-salt diet on T-cell subpopulations (ie, γδ T cells, Th17 cells, and regulatory T cells) in five healthy males. The mean (SD) age of the participants was 33 (2) years, with normal body mass index, kidney function, and baseline blood pressure. In terms of phenotype, there was an isolated increase of CD69 expression in Vδ1 T cells (P = .04), which is an early activation marker. There were no statistically significant changes or trends in any of the other tested markers or in the Th17 or regulatory T-cell subsets. The increase in CD69 was strongly correlated to increases in 24-hour urinary sodium excretion (r = .93, P = .02). These results of this pilot may motivate the use of longer dietary salt interventions in future studies on salt and adaptive immune cells.
    Keywords:  T cells; Th17 cells; blood pressure; gamma delta T cells; regulatory T cells; salt; sodium
    DOI:  https://doi.org/10.1111/jch.14049
  15. Trends Mol Med. 2020 Sep 17. pii: S1471-4914(20)30190-8. [Epub ahead of print]
    Saeb-Parsy K, Martin JL, Summers DM, Watson CJE, Krieg T, Murphy MP.
      Advances in surgical procedures, technology, and immune suppression have transformed organ transplantation. However, the metabolic changes that occur during organ retrieval, storage, and implantation have been relatively neglected since the developments many decades ago of cold storage organ preservation solutions. In this review we discuss how the metabolic changes that occur within the organ during transplantation, particularly those associated with mitochondria, may contribute to the outcome. We show how a better understanding of these processes can lead to changes in surgical practice and the development of new drug classes to improve the function and longevity of transplanted grafts, while increasing the pool of organs available for transplantation.
    Keywords:  ischemia–reperfusion injury; metabolism.; mitochondria; transplantation
    DOI:  https://doi.org/10.1016/j.molmed.2020.08.001
  16. Sci Rep. 2020 Sep 25. 10(1): 15786
    Tran HTT, Herz C, Lamy E.
      Exposure to the endocrine disruptor bisphenol A (BPA) has been linked with immune disorders and increased tumour risk. Our previous work in activated human peripheral blood mononuclear cells demonstrated that exposure to "low-dose" BPA diminished telomerase activity via an ER/GPR30-ERK signalling pathway. Leukocyte telomerase activity and telomere maintenance are crucial for normal immune function and homeostasis. We thus here further studied the effects of BPA on human T cell subpopulations. Exposure to 0.3-3 nM BPA, i. e. at doses in the realm of human exposure, notably reduced telomerase activity in activated CD8 + T but not CD4 + T cells in a non-monotonic response pattern as determined by the TRAP-ELISA assay. Under long-term BPA exposure, significant telomere length shortening, reduction in mitochondrial DNA copy number, cell proliferation and IFN-γ as well as hTERT protein suppression could be observed in CD8 + lymphocytes, as analysed by qRT-PCR, flow cytometry and western blot analysis. This study extends our previous in vitro findings that "low-dose" BPA has potential negative effects on healthy human cytotoxic T cell response. These results might merit some special attention to further investigate chronic BPA exposure in the context of adaptive immune response dysfunction and early onset of cancer in man.
    DOI:  https://doi.org/10.1038/s41598-020-72546-x
  17. Nat Commun. 2020 09 21. 11(1): 4766
    Chakravarti D, Hu B, Mao X, Rashid A, Li J, Li J, Liao WT, Whitley EM, Dey P, Hou P, LaBella KA, Chang A, Wang G, Spring DJ, Deng P, Zhao D, Liang X, Lan Z, Lin Y, Sarkar S, Terranova C, Deribe YL, Blutt SE, Okhuysen P, Zhang J, Vilar E, Nielsen OH, Dupont A, Younes M, Patel KR, Shroyer NF, Rai K, Estes MK, Wang YA, Bertuch AA, DePinho RA.
      Germline telomere maintenance defects are associated with an increased incidence of inflammatory diseases in humans, yet whether and how telomere dysfunction causes inflammation are not known. Here, we show that telomere dysfunction drives pATM/c-ABL-mediated activation of the YAP1 transcription factor, up-regulating the major pro-inflammatory factor, pro-IL-18. The colonic microbiome stimulates cytosolic receptors activating caspase-1 which cleaves pro-IL-18 into mature IL-18, leading to recruitment of interferon (IFN)-γ-secreting T cells and intestinal inflammation. Correspondingly, patients with germline telomere maintenance defects exhibit DNA damage (γH2AX) signaling together with elevated YAP1 and IL-18 expression. In mice with telomere dysfunction, telomerase reactivation in the intestinal epithelium or pharmacological inhibition of ATM, YAP1, or caspase-1 as well as antibiotic treatment, dramatically reduces IL-18 and intestinal inflammation. Thus, telomere dysfunction-induced activation of the ATM-YAP1-pro-IL-18 pathway in epithelium is a key instigator of tissue inflammation.
    DOI:  https://doi.org/10.1038/s41467-020-18420-w
  18. Proc Natl Acad Sci U S A. 2020 Sep 25. pii: 202008571. [Epub ahead of print]
    Milner JJ, Nguyen H, Omilusik K, Reina-Campos M, Tsai M, Toma C, Delpoux A, Boland BS, Hedrick SM, Chang JT, Goldrath AW.
      Memory CD8 T cells provide durable protection against diverse intracellular pathogens and can be broadly segregated into distinct circulating and tissue-resident populations. Paradigmatic studies have demonstrated that circulating memory cells can be further divided into effector memory (Tem) and central memory (Tcm) populations based on discrete functional characteristics. Following resolution of infection, we identified a persisting antigen-specific CD8 T cell population that was terminally fated with potent effector function but maintained memory T cell qualities and conferred robust protection against reinfection. Notably, this terminally differentiated effector memory CD8 T cell population (terminal-Tem) was conflated within the conventional Tem population, prompting redefinition of the classical characteristics of Tem cells. Murine terminal-Tem were transcriptionally, functionally, and developmentally unique compared to Tem cells. Through mass cytometry and single-cell RNA sequencing (RNA-seq) analyses of human peripheral blood from healthy individuals, we also identified an analogous terminal-Tem population of CD8 T cells that was transcriptionally distinct from Tem and Tcm Key findings from this study show that parsing of terminal-Tem from conventionally defined Tem challenge the reported characteristics of Tem biology, including enhanced presence in lymphoid tissues, robust IL-2 production, and recall potential, greater than expected homeostatic fitness, refined transcription factor dependencies, and a distinct molecular phenotype. Classification of terminal-Tem and clarification of Tem biology hold broad implications for understanding the molecular regulation of memory cell states and harnessing immunological memory to improve immunotherapies.
    Keywords:  T cells; immunology; infection; memory T cells
    DOI:  https://doi.org/10.1073/pnas.2008571117
  19. Nat Commun. 2020 09 24. 11(1): 4835
    Peng Q, Qiu X, Zhang Z, Zhang S, Zhang Y, Liang Y, Guo J, Peng H, Chen M, Fu YX, Tang H.
      Immune checkpoint blockade therapies have shown clinical promise in a variety of cancers, but how tumor-infiltrating T cells are activated remains unclear. In this study, we explore the functions of PD-L1 on dendritic cells (DCs), which highly express PD-L1. We observe that PD-L1 on DC plays a critical role in limiting T cell responses. Type 1 conventional DCs are essential for PD-L1 blockade and they upregulate PD-L1 upon antigen uptake. Upregulation of PD-L1 on DC is mediated by type II interferon. While DCs are the major antigen presenting cells for cross-presenting tumor antigens to T cells, subsequent PD-L1 upregulation protects them from killing by cytotoxic T lymphocytes, yet dampens the antitumor responses. Blocking PD-L1 in established tumors promotes re-activation of tumor-infiltrating T cells for tumor control. Our study identifies a critical and dynamic role of PD-L1 on DC, which needs to be harnessed for better invigoration of antitumor immune responses.
    DOI:  https://doi.org/10.1038/s41467-020-18570-x