Blimp-1 transcription factor is required for the differentiation of effector CD8(+) T cells and memory responses

Genetic disruption of Blimp-1 drastically augments the antitumor efficacy of BCMA-targeting CAR T cells

ABSTRACT

Chimeric antigen receptor (CAR) T cells directed against B-cell maturation antigen (BCMA) are an effective treatment for multiple myeloma (MM), but short persistence and frequent relapses are challenges for this immunotherapy. This lack of durability has been attributed to the premature terminal differentiation of CAR T cells, which prevents the formation of long-lived memory cells that maintain antitumor responses. To improve long-term efficacy, we used CRISPR/CRISPR-associated protein 9-mediated gene editing to ablate the expression of the transcription factor Blimp-1. Blimp-1 knockout (KO) CAR T cells displayed a memory-like phenotype compared with control (Mock) CAR T cells, but had reduced effector function, with a striking loss of granzyme B. However, in a murine model of advanced MM, Blimp-1 KO CAR T cells effectively slowed or even prevented disease progression, significantly outperforming Mock CAR T cells in improving survival (P = .006). To understand this enhanced in vivo effectiveness, Blimp-1 KO CAR T cells were characterized after being repeatedly challenged with tumor cells in vitro. In this setting, Blimp-1 KO CAR T cells maintained a highly active state with high expression of memory markers, but, crucially, demonstrated enhanced effector function and increased energetic capacity. RNA-sequencing analysis of tumor-exposed Blimp-1 KO CAR T cells confirmed the presence of a memory-like transcriptomic signature and, additionally, revealed enhanced ribosome biogenesis and repressed CAR T-cell dysfunction as mechanisms that could contribute to improved antitumor activity. Put together, our findings show that dampening Blimp-1 expression altered the phenotype and function of anti-BCMA CAR T cells, leading to augmented therapeutic efficacy in MM.

Tissue-resident immune cells: from defining characteristics to roles in diseases

Tissue-resident immune cells (TRICs) are a highly heterogeneous and plastic subpopulation of immune cells that reside in lymphoid or peripheral tissues without recirculation. These cells are endowed with notably distinct capabilities, setting them apart from their circulating leukocyte counterparts. Many studies demonstrate their complex roles in both health and disease, involving the regulation of homeostasis, protection, and destruction. The advancement of tissue-resolution technologies, such as single-cell sequencing and spatiotemporal omics, provides deeper insights into the cell morphology, characteristic markers, and dynamic transcriptional profiles of TRICs. Currently, the reported TRIC population includes tissue-resident T cells, tissue-resident memory B (BRM) cells, tissue-resident innate lymphocytes, tissue-resident macrophages, tissue-resident neutrophils (TRNs), and tissue-resident mast cells, but unignorably the existence of TRNs is controversial. Previous studies focus on one of them in specific tissues or diseases, however, the origins, developmental trajectories, and intercellular cross-talks of every TRIC type are not fully summarized. In addition, a systemic overview of TRICs in disease progression and the development of parallel therapeutic strategies is lacking. Here, we describe the development and function characteristics of all TRIC types and their major roles in health and diseases. We shed light on how to harness TRICs to offer new therapeutic targets and present burning questions in this field.

In Vivo CRISPR Screening Reveals CHD7 as a Positive Regulator of Short-lived Effector Cells

CD8+ T cells differentiate into two subpopulations in response to acute viral infection: memory precursor effector cells (MPECs) and short-lived effector cells (SLECs). MPECs and SLECs are epigenetically distinct; however, the epigenetic regulators required for formation of these subpopulations are mostly unknown. In this study, we performed an in vivo CRISPR screen in murine naive CD8+ T cells to identify the epigenetic regulators required for MPEC and SLEC formation, using the acute lymphocytic choriomeningitis virus Armstrong infection model. We identified the ATP-dependent chromatin remodeler CHD7 (chromodomain-helicase DNA-binding protein 7) as a positive regulator of SLEC formation, as knockout (KO) of Chd7 reduced SLECs numerically. In contrast, KO of Chd7 increased the formation of central memory T cells following pathogen clearance yet attenuated memory cell expansion following a rechallenge. These findings establish CHD7 as a novel positive regulator of SLEC and a negative regulator of central memory T cell formation.

Immunoediting in acute myeloid leukemia: Reappraising T cell exhaustion and the aberrant antigen processing machinery in leukemogenesis

Acute myeloid leukemia (AML) establishes an immunosuppressive microenvironment that favors leukemic proliferation. The immune-suppressive cytokines altered antigen processing, and presentation collectively assist AML cells in escaping cytotoxic T-cell surveillance. These CD8+ T cell dysfunction features are emerging therapeutic targets in relapsed/refractory AML patients. Besides, CD8+ T cell exhaustion is a hotspot in recent clinical oncology studies, but its pathophysiology has yet to be elucidated in AML. In this review, we summarize high-quality original studies encompassing the phenotypic and genomic characteristics of T cell exhaustion events in the leukemia progression, emphasize the surface immuno-peptidome that dynamically tunes the fate of T cells to function or dysfunction states, and revisit the biochemical and biophysical properties of type 1 MHC antigen processing mechanism (APM) that pivots in the phenomenon of leukemia antigen dampening.

Viral imitation is the sincerest form of epigenetic flattery

Viruses use multiple strategies to successfully generate progeny and overcome host defenses. In recent years, it has become increasingly evident that epigenetic mechanisms of host gene regulation are vulnerable to viral manipulation. In the form of histone mimicry, viral invasion of host chromatin is a striking example of how viruses have evolved to invade every aspect of cellular function for viral benefit. In this perspective, we will review how three viruses-influenza A, SARS-CoV-2, and Cotesia plutellae bracovirus-use histone mimicry to promote viral success through immune evasion. These examples highlight the importance of this burgeoning field and point toward the wealth of knowledge we have yet to uncover.

NaCl enhances CD8+ T cell effector functions in cancer immunotherapy

CD8+ T cells control tumors but inevitably become dysfunctional in the tumor microenvironment. Here, we show that sodium chloride (NaCl) counteracts T cell dysfunction to promote cancer regression. NaCl supplementation during CD8+ T cell culture induced effector differentiation, IFN-γ production and cytotoxicity while maintaining the gene networks responsible for stem-like plasticity. Accordingly, adoptive transfer of tumor-specific T cells resulted in superior anti-tumor immunity in a humanized mouse model. In mice, a high-salt diet reduced the growth of experimental tumors in a CD8+ T cell-dependent manner by inhibiting terminal differentiation and enhancing the effector potency of CD8+ T cells. Mechanistically, NaCl enhanced glutamine consumption, which was critical for transcriptional, epigenetic and functional reprogramming. In humans, CD8+ T cells undergoing antigen recognition in tumors and predicting favorable responses to checkpoint blockade immunotherapy resembled those induced by NaCl. Thus, NaCl metabolism is a regulator of CD8+ T cell effector function, with potential implications for cancer immunotherapy.

Transcriptional rewiring in CD8+ T cells: implications for CAR-T cell therapy against solid tumours

T cells engineered to express chimeric-antigen receptors (CAR-T cells) can effectively control relapsed and refractory haematological malignancies in the clinic. However, the successes of CAR-T cell therapy have not been recapitulated in solid tumours due to a range of barriers such as immunosuppression, poor infiltration, and tumour heterogeneity. Numerous strategies are being developed to overcome these barriers, which include improving culture conditions and manufacturing protocols, implementing novel CAR designs, and novel approaches to engineering the T cell phenotype. In this review, we describe the various emerging strategies to improve CAR T cell therapy for solid tumours. We specifically focus on new strategies to modulate cell function and fate that have precipitated from the growing knowledge of transcriptional circuits driving T cell differentiation, with the ultimate goal of driving more productive anti-tumour T cell immunity. Evidence shows that enrichment of particular phenotypic subsets of T cells in the initial cell product correlates to improved therapeutic responses and clinical outcomes. Furthermore, T cell exhaustion and poor persistence are major factors limiting therapeutic efficacy. The latest preclinical work shows that targeting specific master regulators and transcription factors can overcome these key barriers, resulting in superior T cell therapeutic products. This can be achieved by targeting key transcriptional circuits promoting memory-like phenotypes or sustaining key effector functions within the hostile tumour microenvironment. Additional discussion points include emerging considerations for the field such as (i) targeting permutations of transcription factors, (ii) transient expression systems, (iii) tissue specificity, and (iv) expanding this strategy beyond CAR-T cell therapy and cancer.

Chronic viral infection alters PD-1 locus subnuclear localization in cytotoxic CD8+ T cells

During chronic infection, virus-specific CD8+ cytotoxic T lymphocytes (CTLs) progressively lose their ability to mount effective antiviral responses. This "exhaustion" is coupled to persistent upregulation of inhibitory receptor programmed death-1 (PD-1) (Pdcd1)-key in suppressing antiviral CTL responses. Here, we investigate allelic Pdcd1 subnuclear localization and transcription during acute and chronic lymphocytic choriomeningitis virus (LCMV) infection in mice. Pdcd1 alleles dissociate from transcriptionally repressive chromatin domains (lamin B) in virus-specific exhausted CTLs but not in naive or effector CTLs. Relative to naive CTLs, nuclear positioning and Pdcd1-lamina dissociation in exhausted CTLs reflect loss of Pdcd1 promoter methylation and greater PD-1 upregulation, although a direct correlation is not observed in effector cells, 8 days post-infection. Genetic deletion of B lymphocyte-induced maturation protein 1 (Blimp-1) enhances Pdcd1-lamina dissociation in effector CTLs, suggesting that Blimp-1 contributes to maintaining Pdcd1 localization to repressive lamina. Our results identify mechanisms governing Pdcd1 subnuclear localization and the broader role of chromatin dynamics in T cell exhaustion.

Blockade of LAG-3 and PD-1 leads to co-expression of cytotoxic and exhaustion gene modules in CD8+ T cells to promote antitumor immunity

Relatlimab (rela; anti-LAG-3) plus nivolumab (nivo; anti-PD-1) is safe and effective for treatment of advanced melanoma. We designed a trial (NCT03743766) where advanced melanoma patients received rela, nivo, or rela+nivo to interrogate the immunologic mechanisms of rela+nivo. Analysis of biospecimens from this ongoing trial demonstrated that rela+nivo led to enhanced capacity for CD8+ T cell receptor signaling and altered CD8+ T cell differentiation, leading to heightened cytotoxicity despite the retention of an exhaustion profile. Co-expression of cytotoxic and exhaustion signatures was driven by PRDM1, BATF, ETV7, and TOX. Effector function was upregulated in clonally expanded CD8+ T cells that emerged after rela+nivo. A rela+nivo intratumoral CD8+ T cell signature was associated with a favorable prognosis. This intratumoral rela+nivo signature was validated in peripheral blood as an elevated frequency of CD38+TIM3+CD8+ T cells. Overall, we demonstrated that cytotoxicity can be enhanced despite the retention of exhaustion signatures, which will inform future therapeutic strategies.

IL-2 based cancer immunotherapies: an evolving paradigm

Discovered over 4 decades ago in the supernatants of activated T cells, interleukin-2 (IL-2) is a potent pleiotropic cytokine involved in the regulation of immune responses. It is required for effector T cell expansion and differentiation as well as for peripheral tolerance induced by regulatory T cells. High-dose IL-2 treatment was the first FDA-approved immunotherapy for renal cell carcinoma and melanoma, achieving single agent complete and durable responses, albeit only in a small proportion of patients. The therapeutic potential of wild type IL-2 is clinically limited by its short half-life and severe vascular toxicity. Moreover, the activation of regulatory T cells and the terminal differentiation of effector T cells on IL-2 pose additional restrictions. To overcome the toxicity of IL-2 in order to realize its full potential for patients, several novel engineering strategies are being developed and IL-2 based immunotherapy for cancer has emerged as a burgeoning field of clinical and experimental research. In addition, combination of IL-2 with PD-1/L1 pathway blockade shows vastly improved anti-tumor efficacy over either monotherapy in preclinical tumor models. In this review we discuss the biological characteristics of IL-2 and its receptors, as well as its efficacy and treatment limiting toxicities in cancer patients. We also explore the efforts aimed at developing novel and safer IL-2 therapies to harness the full therapeutic potential of this cytokine.

BRD7 as key factor in PBAF complex assembly and CD8+ T cell differentiation

Upon infection, naive CD8+ T cells differentiate into cytotoxic effector cells to eliminate the pathogen-infected cells. Although many mechanisms underlying this process have been demonstrated, the regulatory role of chromatin remodeling system in this process remains largely unknown. Here we show that BRD7, a component of the polybromo-associated BAF complex (PBAF), was required for naive CD8+ T cells to differentiate into functional short-lived effector cells (SLECs) in response to acute infections caused by influenza virus or lymphocytic choriomeningitis virus (LCMV). BRD7 deficiency in CD8+ T cells resulted in profound defects in effector population and functions, thereby impairing viral clearance and host recovery. Further mechanical studies indicate that the expression of BRD7 significantly turned to high from naive CD8+ T cells to effector cells, which bridged BRG1 and PBRM1 to the core module of PBAF complex, consequently facilitating the assembly of PBAF complex rather than BAF complex in the effector cells. The PBAF complex changed the chromatin accessibility at the loci of Tbx21 gene and upregulated its expression, leading to the maturation of effector T cells. Our research demonstrates that BRD7 and the PBAF complex are key in CD8+ T cell development and present a significant target for advancing immune therapies.

Transcriptional and hormonal control of adipose Treg heterogeneity and function

Adipose tissue stores excess energy and produces a broad range of factors that regulate multiple physiological processes including systemic energy homeostasis. Visceral adipose tissue (VAT) plays a particularly important role in glucose metabolism as its endocrine function underpins food uptake and energy expenditure. Caloric excess triggers VAT inflammation which can impair insulin sensitivity and cause metabolic deregulation. Regulatory T cells (Tregs) that reside in the VAT suppress inflammation and protect from metabolic disease. The cellular components of VAT and its secretory products play a vital role in fostering the differentiation and maintenance of VAT Tregs. Critically, the physiology and inflammatory tone of VAT exhibit sex-specific disparities, resulting in substantial VAT Treg heterogeneity. Indeed, cytokines and sex hormones promote the differentiation of distinct populations of mature VAT Tregs, each characterized by unique phenotypes, homeostatic requirements, and functions. This review focuses on key findings that have significantly advanced our understanding of VAT Treg biology and the current state of the field, while also discussing open questions that require further exploration.

The role of KLRG1: a novel biomarker and new therapeutic target

Killer cell lectin-like receptor G1 (KLRG1) is an immune checkpoint receptor expressed predominantly in NK and T-cell subsets that downregulates the activation and proliferation of immune cells and participates in cell-mediated immune responses. Accumulating evidence has demonstrated the importance of KLRG1 as a noteworthy disease marker and therapeutic target that can influence disease onset, progression, and prognosis. Blocking KLRG1 has been shown to effectively mitigate the effects of downregulation in various mouse tumor models, including solid tumors and hematologic malignancies. However, KLRG1 inhibitors have not yet been approved for human use, and the understanding of KLRG1 expression and its mechanism of action in various diseases remains incomplete. In this review, we explore alterations in the distribution, structure, and signaling pathways of KLRG1 in immune cells and summarize its expression patterns and roles in the development and progression of autoimmune diseases, infectious diseases, and cancers. Additionally, we discuss the potential applications of KLRG1 as a tool for tumor immunotherapy.

Depletion of follicular B cell-derived antibody secreting cells does not attenuate angiotensin II-induced hypertension or vascular compliance

Introduction

Marginal zone and follicular B cells are known to contribute to the development of angiotensin II-induced hypertension in mice, but the effector function(s) mediating this effect (e.g., antigen presentation, antibody secretion and/or cytokine production) are unknown. B cell differentiation into antibody secreting cells (ASCs) requires the transcription factor Blimp-1. Here, we studied mice with a Blimp-1 deficiency in follicular B cells to evaluate whether antibody secretion underlies the pro-hypertensive action of B cells.

Methods

10- to 14-week-old male follicular B cell Blimp-1 knockout (FoB-Blimp-1-KO) and floxed control mice were subcutaneously infused with angiotensin II (0.7 mg/kg/d) or vehicle (0.1% acetic acid in saline) for 28 days. BP was measured by tail-cuff plethysmography or radiotelemetry. Pulse wave velocity was measured by ultrasound. Aortic collagen was quantified by Masson's trichrome staining. Cell types and serum antibodies were quantified by flow cytometry and a bead-based multiplex assay, respectively.

Results

In control mice, angiotensin II modestly increased serum IgG3 levels and markedly increased BP, cardiac hypertrophy, aortic stiffening and fibrosis. FoB-Blimp-1-KO mice exhibited impaired IgG1, IgG2a and IgG3 production despite having comparable numbers of B cells and ASCs to control mice. Nevertheless, FoB-Blimp-1-KO mice still developed hypertension, cardiac hypertrophy, aortic stiffening and fibrosis following angiotensin II infusion.

Conclusions

Inhibition of follicular B cell differentiation into ASCs did not protect against angiotensin II-induced hypertension or vascular compliance. Follicular B cell functions independent of their differentiation into ASCs and ability to produce high-affinity antibodies, or other B cell subtypes, are likely to be involved in angiotensin II-induced hypertension.

Immunocytes interact directly with cancer cells in the tumor microenvironment: one coin with two sides and future perspectives

The tumor microenvironment is closely linked to the initiation, promotion, and progression of solid tumors. Among its constitutions, immunologic cells emerge as critical players, facilitating immune evasion and tumor progression. Apart from their indirect impact on anti-tumor immunity, immunocytes directly influence neoplastic cells, either bolstering or impeding tumor advancement. However, current therapeutic modalities aimed at alleviating immunosuppression from regulatory cells on effector immune cell populations may not consistently yield satisfactory results in various solid tumors, such as breast carcinoma, colorectal cancer, etc. Therefore, this review outlines and summarizes the direct, dualistic effects of immunocytes such as T cells, innate lymphoid cells, B cells, eosinophils, and tumor-associated macrophages on tumor cells within the tumor microenvironment. The review also delves into the underlying mechanisms involved and presents the outcomes of clinical trials based on these direct effects, aiming to propose innovative and efficacious therapeutic strategies for addressing solid tumors.

Tuberculosis Vaccines and T Cell Immune Memory

Tuberculosis (TB) remains a major infectious disease partly due to the lack of an effective vaccine. Therefore, developing new and more effective TB vaccines is crucial for controlling TB. Mycobacterium tuberculosis (M. tuberculosis) usually parasitizes in macrophages; therefore, cell-mediated immunity plays an important role. The maintenance of memory T cells following M. tuberculosis infection or vaccination is a hallmark of immune protection. This review analyzes the development of memory T cells during M. tuberculosis infection and vaccine immunization, especially on immune memory induced by BCG and subunit vaccines. Furthermore, the factors affecting the development of memory T cells are discussed in detail. The understanding of the development of memory T cells should contribute to designing more effective TB vaccines and optimizing vaccination strategies.

PD-1 regulation in immune homeostasis and immunotherapy

Harnessing the programmed cell death protein 1 (PD-1)/programmed death-ligand 1 (PD-L1) axis is pivotal in autoimmunity and cancer immunotherapy. PD-1 receptors on immune cells engage with one of its ligands, PD-L1 or PD-L2, expressed on antigen-presenting cells or tumor cells, driving T-cell dysfunction and tumor immune escape. Thus, targeting PD-1/PD-L1 revitalizes cytotoxic T cells for cancer elimination. However, a majority of cancer patients don't respond to PD-1/PD-L1 blockade, and the underlying mechanisms remain partially understood. Recent studies have revealed that PD-1 expression levels or modifications impact the effectiveness of anti-PD-1/PD-L1 treatments. Therefore, understanding the molecular mechanisms governing PD-1 expression and modifications is crucial for innovating therapeutic strategies to enhance the efficacy of PD-1/PD-L1 inhibition. This article presents a comprehensive overview of advancements in PD-1 regulation and highlights their potential in modulating immune homeostasis and cancer immunotherapy, aiming to refine clinical outcomes.

Functional CRISPR screens in T cells reveal new opportunities for cancer immunotherapies

T cells are fundamental components in tumour immunity and cancer immunotherapies, which have made immense strides and revolutionized cancer treatment paradigm. However, recent studies delineate the predicament of T cell dysregulation in tumour microenvironment and the compromised efficacy of cancer immunotherapies. CRISPR screens enable unbiased interrogation of gene function in T cells and have revealed functional determinators, genetic regulatory networks, and intercellular interactions in T cell life cycle, thereby providing opportunities to revamp cancer immunotherapies. In this review, we briefly described the central roles of T cells in successful cancer immunotherapies, comprehensively summarised the studies of CRISPR screens in T cells, elaborated resultant master genes that control T cell activation, proliferation, fate determination, effector function, and exhaustion, and highlighted genes (BATF, PRDM1, and TOX) and signalling cascades (JAK-STAT and NF-κB pathways) that extensively engage in multiple branches of T cell responses. In conclusion, this review bridged the gap between discovering element genes to a specific process of T cell activities and apprehending these genes in the global T cell life cycle, deepened the understanding of T cell biology in tumour immunity, and outlined CRISPR screens resources that might facilitate the development and implementation of cancer immunotherapies in the clinic.

The mitochondrial fission protein DRP1 influences memory CD8+ T cell formation and function

Pharmacological methods for promoting mitochondrial elongation suggest that effector T cells can be altered to support a memory T cell-like metabolic state. Such mitochondrial elongation approaches may enhance the development of immunological memory. Therefore, we hypothesized that deletion of the mitochondrial fission protein dynamin-related protein 1 (DRP1) would lead to mitochondrial elongation and generate a large memory T cell population, an approach that could be exploited to enhance vaccination protocols. We find that, as expected, while deletion of DRP1 from T cells in dLckCre × Drp1flfl does compromise the magnitude and functionality of primary effector CD8+ T cells, a disproportionately large pool of memory CD8+ T cells does form. In contrast to primary effector CD8+ T cells, DRP1-deficient memory dLckCre × Drp1flfl CD8+ T cells mount a secondary response comparable to control memory T cells with respect to kinetics, magnitude, and effector capabilities. Interestingly, the relative propensity to form memory cells in the absence of DRP1 was associated with neither differentiation toward more memory precursor CD8+ T cells nor decreased cellular death of effector T cells. Instead, the tendency to form memory CD8+ T cells in the absence of DRP1 is associated with decreased T cell receptor expression. Remarkably, in a competitive environment with DRP1-replete CD8+ T cells, the absence of DRP1 from CD8+ T cells compromised the generation of primary, memory, and secondary responses, indicating that approaches targeting DRP1 need to be carefully tailored.

OCA-B/Pou2af1 is sufficient to promote CD4+ T cell memory and prospectively identifies memory precursors

The molecular mechanisms leading to the establishment of immunological memory are inadequately understood, limiting the development of effective vaccines and durable antitumor immune therapies. Here, we show that ectopic OCA-B expression is sufficient to improve antiviral memory recall responses, while having minimal effects on primary effector responses. At peak viral response, short-lived effector T cell populations are expanded but show increased Gadd45b and Socs2 expression, while memory precursor effector cells show increased expression of Bcl2, Il7r, and Tcf7 on a per-cell basis. Using an OCA-B mCherry reporter mouse line, we observe high OCA-B expression in CD4+ central memory T cells. We show that early in viral infection, endogenously elevated OCA-B expression prospectively identifies memory precursor cells with increased survival capability and memory recall potential. Cumulatively, the results demonstrate that OCA-B is both necessary and sufficient to promote CD4 T cell memory in vivo and can be used to prospectively identify memory precursor cells.

The transcriptional cofactor Tle3 reciprocally controls effector and central memory CD8+ T cell fates

Antigen-experienced CD8+ T cells form effector and central memory T cells (TEM and TCM cells, respectively); however, the mechanism(s) controlling their lineage plasticity remains incompletely understood. Here we show that the transcription cofactor Tle3 critically regulates TEM and TCM cell fates and lineage stability through dynamic redistribution in antigen-responding CD8+ T cell genome. Genetic ablation of Tle3 promoted CD8+ TCM cell formation at the expense of CD8+ TEM cells. Lineage tracing showed that Tle3-deficient CD8+ TEM cells underwent accelerated conversion into CD8+ TCM cells while retaining robust recall capacity. Tle3 acted as a coactivator for Tbet to increase chromatin opening at CD8+ TEM cell-characteristic sites and to activate CD8+ TEM cell signature gene transcription, while engaging Runx3 and Tcf1 to limit CD8+ TCM cell-characteristic molecular features. Thus, Tle3 integrated functions of multiple transcription factors to guard lineage fidelity of CD8+ TEM cells, and manipulation of Tle3 activity could favor CD8+ TCM cell production.

Circulating NK cells establish tissue residency upon acute infection of skin and mediate accelerated effector responses to secondary infection

Natural killer (NK) cells are present in the circulation and can also be found residing in tissues, and these populations exhibit distinct developmental requirements and are thought to differ in terms of ontogeny. Here, we investigate whether circulating conventional NK (cNK) cells can develop into long-lived tissue-resident NK (trNK) cells following acute infections. We found that viral and bacterial infections of the skin triggered the recruitment of cNK cells and their differentiation into Tcf1hiCD69hi trNK cells that share transcriptional similarity with CD56brightTCF1hi NK cells in human tissues. Skin trNK cells arose from interferon (IFN)-γ-producing effector cells and required restricted expression of the transcriptional regulator Blimp1 to optimize Tcf1-dependent trNK cell formation. Upon secondary infection, trNK cells rapidly gained effector function and mediated an accelerated NK cell response. Thus, cNK cells redistribute and permanently position at sites of previous infection via a mechanism promoting tissue residency that is distinct from Hobit-dependent developmental paths of NK cells and ILC1 seeding tissues during ontogeny.

Pharmacogenomic and epigenomic approaches to untangle the enigma of IL-10 blockade in oncology

The host immune system status remains an unresolved mystery among several malignancies. An immune-compromised state or smart immune-surveillance tactics orchestrated by cancer cells are the primary cause of cancer invasion and metastasis. Taking a closer look at the tumour-immune microenvironment, a complex network and crosstalk between infiltrating immune cells and cancer cells mediated by cytokines, chemokines, exosomal mediators and shed ligands are present. Cytokines such as interleukins can influence all components of the tumour microenvironment (TME), consequently promoting or suppressing tumour invasion based on their secreting source. Interleukin-10 (IL-10) is an interlocked cytokine that has been associated with several types of malignancies and proved to have paradoxical effects. IL-10 has multiple functions on cellular and non-cellular components within the TME. In this review, the authors shed the light on the regulatory role of IL-10 in the TME of several malignant contexts. Moreover, detailed epigenomic and pharmacogenomic approaches for the regulation of IL-10 were presented and discussed.

Blimp-1 and c-Maf regulate Il10 and negatively regulate common and unique proinflammatory gene networks in IL-12 plus IL-27-driven T helper-1 cells

Background

CD4 + Th1 cells producing IFN-γ are required to eradicate intracellular pathogens, however if uncontrolled these cells can cause immunopathology. The cytokine IL-10 is produced by multiple immune cells including Th1 cells during infection and regulates the immune response to minimise collateral host damage. In this study we aimed to elucidate the transcriptional network of genes controlling the expression of Il10 and proinflammatory cytokines, including Ifng in Th1 cells differentiated from mouse naive CD4 + T cells.

Methods

We applied computational analysis of gene regulation derived from temporal profiling of gene expression clusters obtained from bulk RNA sequencing (RNA-seq) of flow cytometry sorted naïve CD4 + T cells from mouse spleens differentiated in vitro into Th1 effector cells with IL-12 and IL-27 to produce Ifng and Il10, compared to IL-27 alone which express Il10 only , or IL-12 alone which express Ifng and no Il10, or medium control driven-CD4 + T cells which do not express effector cytokines . Data were integrated with analysis of active genomic regions from these T cells using an assay for transposase-accessible chromatin with sequencing (ATAC)-seq, integrated with literature derived-Chromatin-immunoprecipitation (ChIP)-seq data and the RNA-seq data, to elucidate the transcriptional network of genes controlling expression of Il10 and pro-inflammatory effector genes in Th1 cells. The co-dominant role for the transcription factors, Prdm1 (encoding Blimp-1) and Maf (encoding c-Maf) , in cytokine gene regulation in Th1 cells, was confirmed using T cells obtained from mice with T-cell specific deletion of these transcription factors.

Results

We show that the transcription factors Blimp-1 and c-Maf each have unique and common effects on cytokine gene regulation and not only co-operate to induce Il10 gene expression in IL-12 plus IL-27 differentiated mouse Th1 cells, but additionally directly negatively regulate key proinflammatory cytokines including Ifng, thus providing mechanisms for reinforcement of regulated Th1 cell responses.

Conclusions

These data show that Blimp-1 and c-Maf positively and negatively regulate a network of both unique and common anti-inflammatory and pro-inflammatory genes to reinforce a Th1 response in mice that will eradicate pathogens with minimum immunopathology.

Egress of resident memory T cells from tissue with neoadjuvant immunotherapy: Implications for systemic anti-tumor immunity

INTRODUCTION

Resident memory T (TRM) cells are embedded in peripheral tissue and capable of acting as sentinels that can respond quickly to repeat pathogen exposure as part of an endogenous anti-microbial immune response. Recent evidence suggests that chronic antigen exposure and other microenvironment cues may promote the development of TRM cells within solid tumors as well, and that this TRM phenotype can sequester tumor-specific T cells into tumors and out of circulation resulting in limited systemic antitumor immunity. Here, we perform a review of the published English literature and describe tissue-specific mediators of TRM cell differentiation in states of infection and malignancy with special focus on the role of TGF-β and how targeting TGF-β signaling could be used as a therapeutical approach to promote tumor systemic immunity.

DISCUSSION

The presence of TRM cells with antigen specificity to neoepitopes in tumors associates with positive clinical prognosis and greater responsiveness to immunotherapy. Recent evidence indicates that solid tumors may act as reservoirs for tumor specific TRM cells and limit their circulation - possibly resulting in impaired systemic antitumor immunity. TRM cells utilize specific mechanisms to egress from peripheral tissues into circulation and other peripheral sites, and emerging evidence indicates that immunotherapeutic approaches may initiate these processes and increase systemic antitumor immunity.

CONCLUSIONS

Reversing tumor sequestration of tumor-specific T cells prior to surgical removal or radiation of tumor may increase systemic antitumor immunity. This finding may underlie the improved recurrence free survival observed with neoadjuvant immunotherapy in clinical trials.

Active maintenance of CD8+ T cell naivety through regulation of global genome architecture

The differentiation of naive CD8+ T lymphocytes into cytotoxic effector and memory CTL results in large-scale changes in transcriptional and phenotypic profiles. Little is known about how large-scale changes in genome organization underpin these transcriptional programs. We use Hi-C to map changes in the spatial organization of long-range genome contacts within naive, effector, and memory virus-specific CD8+ T cells. We observe that the architecture of the naive CD8+ T cell genome is distinct from effector and memory genome configurations, with extensive changes within discrete functional chromatin domains associated with effector/memory differentiation. Deletion of BACH2, or to a lesser extent, reducing SATB1 DNA binding, within naive CD8+ T cells results in a chromatin architecture more reminiscent of effector/memory states. This suggests that key transcription factors within naive CD8+ T cells act to restrain T cell differentiation by actively enforcing a unique naive chromatin state.

Blimp-1 signaling pathways in T lymphocytes is essential to control the Trypanosoma cruzi infection-induced inflammation

In many infectious diseases, the pathogen-induced inflammatory response could result in protective immunity that should be regulated to prevent tissue damage and death. In fact, in Trypanosoma cruzi infection, the innate immune and the inflammatory response should be perfectly controlled to avoid significant lesions and death. Here, we investigate the role of Blimp-1 expression in T cells in resistance to T. cruzi infection. Therefore, using mice with Blimp-1 deficiency in T cells (CKO) we determined its role in the controlling parasites growth and lesions during the acute phase of infection. Infection of mice with Blimp-1 ablation in T cells resulted failure the cytotoxic CD8+ T cells and in marked Th1-mediated inflammation, high IFN-γ and TNF production, and activation of inflammatory monocyte. Interestingly, despite high nitric-oxide synthase activation (NOS-2), parasitemia and mortality in CKO mice were increased compared with infected WT mice. Furthermore, infected-CKO mice exhibited hepatic lesions characteristic of steatosis, with significant AST and ALT activity. Mechanistically, Blimp-1 signaling in T cells induces cytotoxic CD8+ T cell activation and restricts parasite replication. In contrast, Blimp-1 represses the Th1 response, leading to a decreased monocyte activation, less NOS-2 activation, and, consequently preventing hepatic damage and dysfunction. These data demonstrate that T. cruzi-induced disease is multifactorial and that the increased IFN-γ, NO production, and dysfunction of CD8+ T cells contribute to host death. These findings have important implications for the design of potential vaccines against Chagas disease.

Stem-like CD4+ T cells in perivascular tertiary lymphoid structures sustain autoimmune vasculitis

Autoimmune vasculitis of the medium and large elastic arteries can cause blindness, stroke, aortic arch syndrome, and aortic aneurysm. The disease is often refractory to immunosuppressive therapy and progresses over decades as smoldering aortitis. How the granulomatous infiltrates in the vessel wall are maintained and how tissue-infiltrating T cells and macrophages are replenished are unknown. Single-cell and whole-tissue transcriptomic studies of immune cell populations in vasculitic arteries identified a CD4+ T cell population with stem cell-like features. CD4+ T cells supplying the tissue-infiltrating and tissue-damaging effector T cells survived in tertiary lymphoid structures around adventitial vasa vasora, expressed the transcription factor T cell factor 1 (TCF1), had high proliferative potential, and gave rise to two effector populations, Eomesodermin (EOMES)+ cytotoxic T cells and B cell lymphoma 6 (BCL6)+ T follicular helper-like cells. TCF1hiCD4+ T cells expressing the interleukin 7 receptor (IL-7R) sustained vasculitis in serial transplantation experiments. Thus, TCF1hiCD4+ T cells function as disease stem cells and promote chronicity and autonomy of autoimmune tissue inflammation. Remission-inducing therapies will require targeting stem-like CD4+ T cells instead of only effector T cells.

Challenges and new technologies in adoptive cell therapy

Adoptive cell therapies (ACTs) have existed for decades. From the initial infusion of tumor-infiltrating lymphocytes to the subsequent specific enhanced T cell receptor (TCR)-T and chimeric antigen receptor (CAR)-T cell therapies, many novel strategies for cancer treatment have been developed. Owing to its promising outcomes, CAR-T cell therapy has revolutionized the field of ACTs, particularly for hematologic malignancies. Despite these advances, CAR-T cell therapy still has limitations in both autologous and allogeneic settings, including practicality and toxicity issues. To overcome these challenges, researchers have focused on the application of CAR engineering technology to other types of immune cell engineering. Consequently, several new cell therapies based on CAR technology have been developed, including CAR-NK, CAR-macrophage, CAR-γδT, and CAR-NKT. In this review, we describe the development, advantages, and possible challenges of the aforementioned ACTs and discuss current strategies aimed at maximizing the therapeutic potential of ACTs. We also provide an overview of the various gene transduction strategies employed in immunotherapy given their importance in immune cell engineering. Furthermore, we discuss the possibility that strategies capable of creating a positive feedback immune circuit, as healthy immune systems do, could address the flaw of a single type of ACT, and thus serve as key players in future cancer immunotherapy.

Graded expression of the chemokine receptor CX3CR1 marks differentiation states of human and murine T cells and enables cross-species interpretation

T cells differentiate into functionally distinct states upon antigen encounter. These states are delineated by different cell surface markers for murine and human T cells, which hamper cross-species translation of T cell properties. We aimed to identify surface markers that reflect the graded nature of CD8+ T cell differentiation and delineate functionally comparable states in mice and humans. CITEseq analyses revealed that graded expression of CX3CR1, encoding the chemokine receptor CX3CR1, correlated with the CD8+ T cell differentiation gradient. CX3CR1 expression distinguished human and murine CD8+ and CD4+ T cell states, as defined by migratory and functional properties. Graded CX3CR1 expression, refined with CD62L, accurately captured the high-dimensional T cell differentiation continuum. Furthermore, the CX3CR1 expression gradient delineated states with comparable properties in humans and mice in steady state and on longitudinally tracked virus-specific CD8+ T cells in both species. Thus, graded CX3CR1 expression provides a strategy to translate the behavior of distinct T cell differentiation states across species.

T cells in health and disease

T cells are crucial for immune functions to maintain health and prevent disease. T cell development occurs in a stepwise process in the thymus and mainly generates CD4+ and CD8+ T cell subsets. Upon antigen stimulation, naïve T cells differentiate into CD4+ helper and CD8+ cytotoxic effector and memory cells, mediating direct killing, diverse immune regulatory function, and long-term protection. In response to acute and chronic infections and tumors, T cells adopt distinct differentiation trajectories and develop into a range of heterogeneous populations with various phenotype, differentiation potential, and functionality under precise and elaborate regulations of transcriptional and epigenetic programs. Abnormal T-cell immunity can initiate and promote the pathogenesis of autoimmune diseases. In this review, we summarize the current understanding of T cell development, CD4+ and CD8+ T cell classification, and differentiation in physiological settings. We further elaborate the heterogeneity, differentiation, functionality, and regulation network of CD4+ and CD8+ T cells in infectious disease, chronic infection and tumor, and autoimmune disease, highlighting the exhausted CD8+ T cell differentiation trajectory, CD4+ T cell helper function, T cell contributions to immunotherapy and autoimmune pathogenesis. We also discuss the development and function of γδ T cells in tissue surveillance, infection, and tumor immunity. Finally, we summarized current T-cell-based immunotherapies in both cancer and autoimmune diseases, with an emphasis on their clinical applications. A better understanding of T cell immunity provides insight into developing novel prophylactic and therapeutic strategies in human diseases.

The SWI/SNF chromatin remodeling complexes BAF and PBAF differentially regulate epigenetic transitions in exhausted CD8+ T cells

CD8⁺ T cell exhaustion (Tex) limits disease control during chronic viral infections and cancer. Here, we investigated the epigenetic factors mediating major chromatin-remodeling events in Tex-cell development. A protein-domain-focused in vivo CRISPR screen identified distinct functions for two versions of the SWI/SNF chromatin-remodeling complex in Tex-cell differentiation. Depletion of the canonical SWI/SNF form, BAF, impaired initial CD8⁺ T cell responses in acute and chronic infection. In contrast, disruption of PBAF enhanced Tex-cell proliferation and survival. Mechanistically, PBAF regulated the epigenetic and transcriptional transition from TCF-1⁺ progenitor Tex cells to more differentiated TCF-1^- Tex subsets. Whereas PBAF acted to preserve Tex progenitor biology, BAF was required to generate effector-like Tex cells, suggesting that the balance of these factors coordinates Tex-cell subset differentiation. Targeting PBAF improved tumor control both alone and in combination with anti-PD-L1 immunotherapy. Thus, PBAF may present a therapeutic target in cancer immunotherapy.

Cumulative effects of weakly repressive regulatory regions in the 3' UTR maintain PD-1 expression homeostasis in mammals

PD-1 has become a common target for cancer treatment. However, the molecular regulation of PD-1 expression homeostasis remains unclear. Here we report the PD-1 3' UTR can dramatically repress gene expression via promoting mRNA decay. Deletion of the PD-1 3' UTR inhibits T cell activity and promotes T-ALL cell proliferation. Interestingly, the robust repression is attributable to cumulative effects of many weak regulatory regions, which we show together are better able to maintain PD-1 expression homeostasis. We further identify several RNA binding proteins (RBPs) that modulate PD-1 expression via the 3' UTR, including IGF2BP2, RBM38, SRSF7, and SRSF4. Moreover, despite rapid evolution, PD-1 3' UTRs are functionally conserved and strongly repress gene expression through many common RBP binding sites. These findings reveal a previously unrecognized mechanism of maintaining PD-1 expression homeostasis and might represent a general model for how small regulatory effects play big roles in regulation of gene expression and biology.

Intrinsically determined turnover underlies broad heterogeneity in plasma-cell lifespan

Antibodies produced by antibody-secreting plasma cells (ASCs) underlie multiple forms of long-lasting immunity. Here we examined the mechanisms regulating ASC turnover and persistence using a genetic reporter to time-stamp ASCs. This approach revealed ASC lifespans as heterogeneous and falling on a continuum, with only a small fraction surviving for >60 days. ASC longevity past 60 days was independent of isotype but correlated with a phenotype that developed progressively and ultimately associated with an underlying "long-lived" ASC (LL ASC)-enriched transcriptional program. While some of the differences between LL ASCs and other ASCs appeared to be acquired with age, other features were shared with some younger ASCs, such as high CD138 and CD93. Turnover was unaffected by altered ASC production, arguing against competition for niches as a major driver of turnover. Thus, ASC turnover is set by intrinsic lifespan limits, with steady-state population dynamics governed by niche vacancy rather than displacement.

Bcl11b sustains multipotency and restricts effector programs of intestinal-resident memory CD8+ T cells

The networks of transcription factors (TFs) that control intestinal-resident memory CD8⁺ T (T_RM) cells, including multipotency and effector programs, are poorly understood. In this work, we investigated the role of the TF Bcl11b in T_RM cells during infection with Listeria monocytogenes using mice with post-activation, conditional deletion of Bcl11b in CD8⁺ T cells. Conditional deletion of Bcl11b resulted in increased numbers of intestinal T_RM cells and their precursors as well as decreased splenic effector and circulating memory cells and precursors. Loss of circulating memory cells was in part due to increased intestinal homing of Bcl11b^-/- circulating precursors, with no major alterations in their programs. Bcl11b^-/- T_RM cells had altered transcriptional programs, with diminished expression of multipotent/multifunctional (MP/MF) program genes, including Tcf7, and up-regulation of the effector program genes, including Prdm1. Bcl11b also limits the expression of Ahr, another TF with a role in intestinal CD8⁺ T_RM cell differentiation. Deregulation of T_RM programs translated into a poor recall response despite T_RM cell accumulation in the intestine. Reduced expression of MP/MF program genes in Bcl11b^-/- T_RM cells was linked to decreased chromatin accessibility and a reduction in activating histone marks at these loci. In contrast, the effector program genes displayed increased activating epigenetic status. These findings demonstrate that Bcl11b is a frontrunner in the tissue residency program of intestinal memory cells upstream of Tcf1 and Blimp1, promoting multipotency and restricting the effector program.

Dietary tryptophan metabolite released by intratumoral Lactobacillus reuteri facilitates immune checkpoint inhibitor treatment

The use of probiotics by cancer patients is increasing, including among those undergoing immune checkpoint inhibitor (ICI) treatment. Here, we elucidate a critical microbial-host crosstalk between probiotic-released aryl hydrocarbon receptor (AhR) agonist indole-3-aldehyde (I3A) and CD8 T cells within the tumor microenvironment that potently enhances antitumor immunity and facilitates ICI in preclinical melanoma. Our study reveals that probiotic Lactobacillus reuteri (Lr) translocates to, colonizes, and persists within melanoma, where via its released dietary tryptophan catabolite I3A, it locally promotes interferon-γ-producing CD8 T cells, thereby bolstering ICI. Moreover, Lr-secreted I3A was both necessary and sufficient to drive antitumor immunity, and loss of AhR signaling within CD8 T cells abrogated Lr's antitumor effects. Further, a tryptophan-enriched diet potentiated both Lr- and ICI-induced antitumor immunity, dependent on CD8 T cell AhR signaling. Finally, we provide evidence for a potential role of I3A in promoting ICI efficacy and survival in advanced melanoma patients.

CTCF mediates CD8+ effector differentiation through dynamic redistribution and genomic reorganization

Differentiation of effector CD8+ T cells is instructed by stably and dynamically expressed transcription regulators. Here we show that naive-to-effector differentiation was accompanied by dynamic CTCF redistribution and extensive chromatin architectural changes. Upon CD8+ T cell activation, CTCF acquired de novo binding sites and anchored novel chromatin interactions, and these changes were associated with increased chromatin accessibility and elevated expression of cytotoxic program genes including Tbx21, Ifng, and Klrg1. CTCF was also evicted from its ex-binding sites in naive state, with concomitantly reduced chromatin interactions in effector cells, as observed at memory precursor-associated genes including Il7r, Sell, and Tcf7. Genetic ablation of CTCF indeed diminished cytotoxic gene expression, but paradoxically elevated expression of memory precursor genes. Comparative Hi-C analysis revealed that key memory precursor genes were harbored within insulated neighborhoods demarcated by constitutive CTCF binding, and their induction was likely due to disrupted CTCF-dependent insulation. CTCF thus promotes cytotoxic effector differentiation by integrating local chromatin accessibility control and higher-order genomic reorganization.

Transcriptional regulation of innate lymphoid cells and T cells by aryl hydrocarbon receptor

The aryl hydrocarbon receptor (Ahr) is a ligand-dependent transcription factor and facilitates immune cell environmental sensing through its activation by cellular, dietary, and microbial metabolites, as well as environmental toxins. Although expressed in various cell types, Ahr in innate lymphoid cells (ILCs) and their adaptive T cell counterparts regulates essential aspects of their development and function. As opposed to T cells, ILCs exclusively rely on germ-line encoded receptors for activation, but often share expression of core transcription factors and produce shared effector molecules with their T cell counterparts. As such, core modules of transcriptional regulation are both shared and diverge between ILCs and T cells. In this review, we highlight the most recent findings regarding Ahr’s transcriptional regulation of both ILCs and T cells. Furthermore, we focus on insights elucidating the shared and distinct mechanisms by which Ahr regulates both innate and adaptive lymphocytes.

Exploring the putative role of PRDM1 and PRDM2 transcripts as mediators of T lymphocyte activation

BACKGROUND

T cell activation and programming from their naïve/resting state, characterized by widespread modifications in chromatin accessibility triggering extensive changes in transcriptional programs, is orchestrated by several cytokines and transcription regulators. PRDM1 and PRDM2 encode for proteins with PR/SET and zinc finger domains that control several biological processes, including cell differentiation, through epigenetic regulation of gene expression. Different transcripts leading to main protein isoforms with (PR +) or without (PR-) the PR/SET domain have been described. Although many studies have established the critical PRDM1 role in hematopoietic cell differentiation, maintenance and/or function, the single transcript contribution has not been investigated before. Otherwise, very few evidence is currently available on PRDM2. Here, we aimed to analyze the role of PRDM1 and PRDM2 different transcripts as mediators of T lymphocyte activation.

METHODS

We analyzed the transcription signature of the main variants from PRDM1 (BLIMP1a and BLIMP1b) and PRDM2 (RIZ1 and RIZ2) genes, in human T lymphocytes and Jurkat cells overexpressing PRDM2 cDNAs following activation through different signals.

RESULTS

T lymphocyte activation induced an early increase of RIZ2 and RIZ1 followed by BLIMP1b increase and finally by BLIMP1a increase. The "first" and the "second" signals shifted the balance towards the PR- forms for both genes. Interestingly, the PI3K signaling pathway modulated the RIZ1/RIZ2 ratio in favor of RIZ1 while the balance versus RIZ2 was promoted by MAPK pathway. Cytokines mediating different Jak/Stat signaling pathways (third signal) early modulated the expression of PRDM1 and PRDM2 and the relationship of their different transcripts confirming the early increase of the PR- transcripts. Different responses of T cell subpopulations were also observed. Jurkat cells showed that the acute transient RIZ2 increase promoted the balancing of PRDM1 forms towards BLIMP1b. The stable forced expression of RIZ1 or RIZ2 induced a significant variation in the expression of key transcription factors involved in T lymphocyte differentiation. The BLIMP1a/b balance shifted in favor of BLIMP1a in RIZ1-overexpressing cells and of BLIMP1b in RIZ2-overexpressing cells.

CONCLUSIONS

This study provides the first characterization of PRDM2 in T-lymphocyte activation/differentiation and novel insights on PRDM1 and PRDM2 transcription regulation during initial activation phases.

Linoleic acid potentiates CD8+ T cell metabolic fitness and antitumor immunity

The metabolic state represents a major hurdle for an effective adoptive T cell therapy (ACT). Indeed, specific lipids can harm CD8⁺ T cell (CTL) mitochondrial integrity, leading to defective antitumor responses. However, the extent to which lipids can affect the CTL functions and fate remains unexplored. Here, we show that linoleic acid (LA) is a major positive regulator of CTL activity by improving metabolic fitness, preventing exhaustion, and stimulating a memory-like phenotype with superior effector functions. We report that LA treatment enhances the formation of ER-mitochondria contacts (MERC), which in turn promotes calcium (Ca²⁺) signaling, mitochondrial energetics, and CTL effector functions. As a direct consequence, the antitumor potency of LA-instructed CD8 T cells is superior in vitro and in vivo. We thus propose LA treatment as an ACT potentiator in tumor therapy.

Pyrimidine de novo synthesis inhibition selectively blocks effector but not memory T cell development

Blocking pyrimidine de novo synthesis by inhibiting dihydroorotate dehydrogenase is used to treat autoimmunity and prevent expansion of rapidly dividing cell populations including activated T cells. Here we show memory T cell precursors are resistant to pyrimidine starvation. Although the treatment effectively blocked effector T cells, the number, function and transcriptional profile of memory T cells and their precursors were unaffected. This effect occurred in a narrow time window in the early T cell expansion phase when developing effector, but not memory precursor, T cells are vulnerable to pyrimidine starvation. This vulnerability stems from a higher proliferative rate of early effector T cells as well as lower pyrimidine synthesis capacity when compared with memory precursors. This differential sensitivity is a drug-targetable checkpoint that efficiently diminishes effector T cells without affecting the memory compartment. This cell fate checkpoint might therefore lead to new methods to safely manipulate effector T cell responses.

Active maintenance of CD8+ T cell naïvety through regulation of global genome architecture

The differentiation of naïve CD8+ cytotoxic T lymphocytes (CTLs) into effector and memory states results in large scale changes in transcriptional and phenotypic profiles. Little is known about how large-scale changes in genome organisation reflect or underpin these transcriptional programs. We utilised Hi-C to map changes in the spatial organisation of long-range genome contacts within naïve, effector and memory virus-specific CD8+ T cells. We observed that the architecture of the naive CD8+ T cell genome was distinct from effector and memory genome configurations with extensive changes within discrete functional chromatin domains. However, deletion of the BACH2 or SATB1 transcription factors was sufficient to remodel the naïve chromatin architecture and engage transcriptional programs characteristic of differentiated cells. This suggests that the chromatin architecture within naïve CD8+ T cells is preconfigured to undergo autonomous remodelling upon activation, with key transcription factors restraining differentiation by actively enforcing the unique naïve chromatin state.

Identification of circRNAs and circRNA-miRNA-mRNA regulatory network in radiation-induced heart disease

OBJECTIVE

Radiation-induced heart disease (RIHD) is one of the most common and serious long-term adverse effect after thoracic radiotherapy. Our aim was to investigate the potential molecular mechanism underlying RIHD using RNA-sequencing (RNA-seq) and bioinformatics methods.

MATERIALS AND METHODS

An RIHD rat model was established and transcription profiles were identified using RNA-seq. Differentially expressed circRNAs, miRNAs and mRNAs were identified. Enrichment of functions and signaling pathways analysis were performed based on GO and the KEGG database. Potential circRNA-miRNA-mRNA regulatory network underlying RIHD was established. qRT-PCR was used to validate the associated genes.

RESULTS

In total, 21 circRNAs, 26 miRNAs, and 178 mRNA transcripts were differentially expressed in RIHD. GO and KEGG pathway analyses identified that differentially expressed mRNAs were most enriched in pathways referring to endothelial function and vascular pathological processes. Nine circRNAs, 10 miRNAs, and 6 mRNA transcripts were most likely involved in vascular function and a candidate competitive endogenous RNA (ceRNA) network of circRNA-miRNA-mRNA was established, which were further validated by qRT-PCR.

CONCLUSIONS

Our study revealed that vascular pathology plays an important role in the early stage of RIHD. Furthermore, a circRNA-miRNA-mRNA ceRNA network was found that may be involved in the regulation of vascular function and RIHD.

The Function of Memory CD8+ T Cells in Immunotherapy for Human Diseases

Memory T (Tm) cells protect against Ags that they have previously contacted with a fast and robust response. Therefore, developing long-lived Tm cells is a prime goal for many vaccines and therapies to treat human diseases. The remarkable characteristics of Tm cells have led scientists and clinicians to devise methods to make Tm cells more useful. Recently, Tm cells have been highlighted for their role in coronavirus disease 2019 vaccines during the ongoing global pandemic. The importance of Tm cells in cancer has been emerging. However, the precise characteristics and functions of Tm cells in these diseases are not completely understood. In this review, we summarize the known characteristics of Tm cells and their implications in the development of vaccines and immunotherapies for human diseases. In addition, we propose to exploit the beneficial characteristics of Tm cells to develop strategies for effective vaccines and overcome the obstacles of immunotherapy.

Regulation of CD8 T cell by B-cells: A narrative review

Activation of CD4 T cells by B cells has been extensively studied, but B cell-regulated priming, proliferation, and survival of CD8 T cells remains controversial. B cells express high levels of MHC class I molecules and can potentially act as antigen-presenting cells (APCs) for CD8 T cells. Several in vivo studies in mice and humans demonstrate the role of B cells as modulators of CD8 T cell function in the context of viral infections, autoimmune diseases, cancer and allograft rejection. In addition, B-cell depletion therapies can lead to impaired CD8 T-cell responses. In this review, we attempt to answer 2 important questions: 1. the role of B cell antigen presentation and cytokine production in the regulation of CD8 T cell survival and cell fate determination, and 2. The role of B cells in the formation and maintenance of CD8 T cell memory.

Beyond target cell death - Granzyme serine proteases in health and disease

Granzymes are a family of small (∼32 kDa) serine proteases with a range of substrate specificities that are stored in, and released from, the cytoplasmic secretory vesicles ('granules') of cytotoxic T lymphocytes and natural killer cells. Granzymes are not digestive proteases but finely tuned processing enzymes that target their substrates in specific ways to activate various signalling pathways, or to inactivate viral proteins and other targets. Great emphasis has been placed on studying the pro-apoptotic functions of granzymes, which largely depend on their synergy with the pore-forming protein perforin, on which they rely for penetration into the target cell cytosol to access their substrates. While a critical role for granzyme B in target cell apoptosis is undisputed, both it and the remaining granzymes also influence a variety of other biological processes (including important immunoregulatory functions), which are discussed in this review. This includes the targeting of many extracellular as well as intracellular substrates, and can also lead to deleterious outcomes for the host if granzyme expression or function are dysregulated or abrogated. A final important consideration is that granzyme repertoire, biochemistry and function vary considerably across species, probably resulting from the pressures applied by viruses and other pathogens across evolutionary time. This has implications for the interpretation of granzyme function in preclinical models of disease.

Next-generation immunotherapy for solid tumors: combination immunotherapy with crosstalk blockade of TGFβ and PD-1/PD-L1

INTRODUCTION

In solid tumor immunotherapy, less than 20% of patients respond to anti-programmed cell death 1 (PD-1)/programmed cell death 1 ligand 1 (PD-L1) agents. The role of transforming growth factor β (TGFβ) in diverse immunity is well-established; however, systemic blockade of TGFβ is associated with toxicity. Accumulating evidence suggests the role of crosstalk between TGFβ and PD-1/PD-L1 pathways.

AREAS COVERED

We focus on TGFβ and PD-1/PD-L1 signaling pathway crosstalk and the determinant role of TGFβ in the resistance of immune checkpoint blockade. We provide the rationale for combination anti-TGFβ and anti-PD-1/PD-L1 therapies for solid tumors and discuss the current status of dual blockade therapy in preclinical and clinical studies.

EXPERT OPINION

The heterogeneity of tumor microenvironment across solid tumors complicates patient selection, treatment regimens, and response and toxicity assessment for investigation of dual blockade agents. However, clinical knowledge from single-agent studies provides infrastructure to translate dual blockade therapies. Dual TGFβ and PD-1/PD-L1 blockade results in enhanced T-cell infiltration into tumors, a primary requisite for successful immunotherapy. A bifunctional fusion protein specifically targets TGFβ in the tumor microenvironment, avoiding systemic toxicity, and prevents interaction of PD-1+ cytotoxic cells with PD-L1+ tumor cells.

Long-lived plasma cells accumulate in the bone marrow at a constant rate from early in an immune response

Vaccines work largely by generating long-lived plasma cells (LLPCs), but knowledge of how such cells are recruited is sparse. Although it is clear that LLPCs preferentially originate in germinal centers (GCs) and relocate to survival niches in bone marrow where they can persist for decades, the issues of the timing of LLPC recruitment and the basis of their retention remain uncertain. Here, using a genetic timestamping system in mice, we show that persistent PCs accrue in bone marrow at an approximately constant rate of one cell per hour over a period spanning several weeks after a single immunization with a model antigen. Affinity-based selection was evident in persisting PCs, reflecting a relative and dynamic rather than absolute affinity threshold as evidenced by the changing pattern of V H gene somatic mutations conveying increased affinity for antigen. We conclude that the life span of persistent, antigen-specific PCs is in part intrinsic, preprogrammed, and varied and that their final number is related to the duration of the response in a predictable way. This implies that modulating vaccines to extend the duration of the GC reaction will enhance antibody-mediated protective immunity.

Recent advances in CAR-T cells therapy for colorectal cancer

Colorectal cancer (CRC) is the third most common cancer, with a high mortality rate and a serious impact on people’s life and health. In recent years, adoptive chimeric antigen receptor T (CAR-T) cells therapy has shown well efficacy in the treatment of hematological malignancies, but there are still many problems and challenges in solid tumors such as CRC. For example, the tumor immunosuppressive microenvironment, the low targeting of CAR-T cells, the short time of CAR-T cells in vivo, and the limited proliferation capacity of CAR-T cells, CAR-T cells can not effectively infiltrate into the tumor and so on. New approaches have been proposed to address these challenges in CRC, and this review provides a comprehensive overview of the current state of CAR-T cells therapy in CRC.

OncomiRs as noncoding RNAs having functions in cancer: Their role in immune suppression and clinical implications

Currently, microRNAs have been established as central players in tumorigenesis, but above all, they have opened an important door for our understanding of immune and tumor cell communication. This dialog is largely due to onco-miR transfer from tumor cells to cells of the tumor microenvironment by exosome. This review outlines recent advances regarding the role of oncomiRs in enhancing cancer and how they modulate the cancer-related immune response in the tumor immune microenvironment.

MicroRNAs (miRNAs) are a type of noncoding RNA that are important posttranscriptional regulators of messenger RNA (mRNA) translation into proteins. By regulating gene expression, miRNAs enhance or inhibit cancer development and participate in several cancer biological processes, including proliferation, invasion metastasis, angiogenesis, chemoresistance and immune escape. Consistent with their widespread effects, miRNAs have been categorized as oncogenes (oncomiRs) or tumor suppressor (TS) miRNAs. MiRNAs that promote tumor growth, called oncomiRs, inhibit messenger RNAs of TS genes and are therefore overexpressed in cancer. In contrast, TS miRNAs inhibit oncogene messenger RNAs and are therefore underexpressed in cancer. Endogenous miRNAs regulate different cellular pathways in all cell types. Therefore, they are not only key modulators in cancer cells but also in the cells constituting their microenvironments. Recently, it was shown that miRNAs are also involved in intercellular communication. Indeed, miRNAs can be transferred from one cell type to another where they regulate targeted gene expression. The primary carriers for the transfer of miRNAs from one cell to another are exosomes. Exosomes are currently considered the primary carriers for communication between the tumor and its surrounding stromal cells to support cancer progression and drive immune suppression. Exosome and miRNAs are seen by many as a hope for developing a new class of targeted therapy. This review outlines recent advances in understanding the role of oncomiRs in enhancing cancer and how they promote its aggressive characteristics and deeply discusses the role of oncomiRs in suppressing the anticancer immune response in its microenvironment. Additionally, further understanding the mechanism of oncomiR-related immune suppression will facilitate the use of miRNAs as biomarkers for impaired antitumor immune function, making them ideal immunotherapy targets.