Regulatory T cells mediate specific suppression by depleting peptide-MHC class II from dendritic cells

Nanoneedle Array-Electroporation Facilitates Intranuclear Ribonucleoprotein Delivery and High Throughput Gene Editing

Dendritic cells (DCs) are critical regulators of T cell immunity, with immense therapeutic potential against tumors and autoimmune diseases. Efficient gene editing in DCs is crucial for understanding their regulatory mechanisms and maximizing their therapeutic efficacy. However, DCs are notoriously difficult to transfect, posing a major bottleneck for conventional DNA and RNA-based editing approaches. Microneedle-mediated injection of Cas9/sgRNA ribonucleoprotein (RNP) directly into the nucleus, akin to gene editing in reproductive cells, offers promise but suffers from limitations in scalability. Here, an intranuclear delivery system using a hollow nanoneedle array (HNA) combined with nano-electroporation is developed. The 2 µm-high HNA physically reaches the nucleus, positioning the nuclear envelope and plasma membrane in close proximity at the tip. Transient electronic pulses then induce simultaneous perforations across all 3 membranes, enabling direct RNP delivery into the nucleus. This HNA-based system achieves efficient knockout of genes like PD-L1 in primary DCs, demonstrating its potential as a powerful tool for gene editing in DCs and other hard-to-transfect cells.

Indirect suppression of CD4 T cell activation through LAG-3-mediated trans-endocytosis of MHC class II

Blockade of immune checkpoint receptors has shown outstanding efficacy for tumor immunotherapy. Promising treatment with anti-lymphocyte-activation gene-3 (LAG-3) has already been recognized as the next efficacious treatment, but there is still limited understanding of the mechanism of LAG-3-mediated immune suppression. Here, utilizing high-resolution molecular imaging, we find a mechanism of CD4 T cell suppression via LAG-3, in which LAG-3-bound major histocompatibility complex (MHC) class II molecules on antigen-presenting cells (APCs) gather at the central region of an immunological synapse and are trans-endocytosed by T cell receptor-driven internalization motility toward CD4 and CD8 T cells expressing LAG-3. Downregulation of MHC class II molecules on APCs thus results in the attenuation of their antigen-presentation function and impairment of CD4 T cell activation. From these data, anti-LAG-3 treatment is suggested to have potency to directly block the inhibitory signaling via LAG-3 and simultaneously reduce MHC class II expression on APCs by LAG-3-mediated trans-endocytosis for recovery from T cell exhaustion.

Excess generation and activation of naturally arising memory-phenotype CD4+ T lymphocytes are inhibited by regulatory T cells in steady state

Conventional CD4+ T lymphocytes consist of naïve, foreign antigen-specific memory, and self-antigen-driven memory-phenotype (MP) cell compartments at homeostasis. We recently showed that MP cells tonically proliferate in response to self-antigens and differentiate into the T-bet+ subset in steady state. How excess proliferation and differentiation of MP cells are inhibited remains unclear. Given immunosuppressive function of regulatory T cells (Tregs), it is possible that they are also involved in inhibition of spontaneous MP cell activation. Here we show using Foxp3-diphtheria toxin receptor-transgenic mice that both MP and naïve CD4+ T cells spontaneously proliferate and differentiate into Th1 cells upon acute Treg depletion. At an early time point post Treg depletion, MP as compared to naïve CD4+ T cells are preferentially activated while at a later stage, the response is dominated by activated cells originated from the naïve pool. Moreover, we argue that MP cell proliferation is driven by TCR and CD28 signaling whereas Th1 differentiation mediated by IL-2. Furthermore, our data indicate that such activation of MP and naïve CD4+ T lymphocytes contribute to development of multi-organ inflammation at early and later time points, respectively, after Treg ablation. Together our findings reveal that Tregs tonically inhibit early, spontaneous proliferation and Th1 differentiation of MP CD4+ T lymphocytes as well as late activation of naïve cells, thereby contributing to maintenance of T cell homeostasis.

Fragile Treg cells: Traitors in immune homeostasis?

Regulatory T (Treg) cells play a key role in maintaining immune tolerance and tissue homeostasis. However, in some disease microenvironments, Treg cells exhibit fragility, which manifests as preserved FoxP3 expression accompanied by inflammation and loss of immunosuppression. Fragile Treg cells are formatively, phenotypically and functionally diverse in various diseases, further complicating the role of Treg cells in the immunotherapeutic response and offering novel targets for disease treatment by modulating specific Treg subsets. In this review, we summarize findings on fragile Treg cells to provide a framework for characterizing the formation and role of fragile Treg cells in different diseases, and we discuss how this information may guide the development of more specific Treg-targeted immunotherapies.

Regulatory T cells in the context: deciphering the dynamic interplay with the tissue environment

The delicate balance between protective immunity against pathogens and the prevention of autoimmunity requires finely tuned generation and function of regulatory CD4+ T (Treg) cells. Here, we review recent progress in the understanding of a complex set of cues, which converge on Treg cells in lymphoid and nonlymphoid organs and in tumors and how these cues modulate Treg functions. We highlight the versatility of Treg cells underlying their ability to dynamically adapt to local microenvironments and perform a wide range of functions that extend beyond the archetypal role of Treg cells in moderating adverse effects of immune response-associated inflammation and in suppressing autoimmunity.

PARP11 inhibition inactivates tumor-infiltrating regulatory T cells and improves the efficacy of immunotherapies

Tumor-infiltrating regulatory T cells (TI-Tregs) elicit immunosuppressive effects in the tumor microenvironment (TME) leading to accelerated tumor growth and resistance to immunotherapies against solid tumors. Here, we demonstrate that poly-(ADP-ribose)-polymerase-11 (PARP11) is an essential regulator of immunosuppressive activities of TI-Tregs. Expression of PARP11 correlates with TI-Treg cell numbers and poor responses to immune checkpoint blockade (ICB) in human patients with cancer. Tumor-derived factors including adenosine and prostaglandin E2 induce PARP11 in TI-Tregs. Knockout of PARP11 in the cells of the TME or treatment of tumor-bearing mice with selective PARP11 inhibitor ITK7 inactivates TI-Tregs and reinvigorates anti-tumor immune responses. Accordingly, ITK7 decelerates tumor growth and significantly increases the efficacy of anti-tumor immunotherapies including ICB and adoptive transfer of chimeric antigen receptor (CAR) T cells. These results characterize PARP11 as a key driver of TI-Treg activities and a major regulator of immunosuppressive TME and argue for targeting PARP11 to augment anti-cancer immunotherapies.

Low-dose Interleukin-2 Therapy: Fine-tuning Treg in Solid Organ Transplantation?

Regulatory T cells (Treg), a subset of CD4 + T cells, are potent regulators of immune reactions, which have been shown to be a promising therapeutic alternative to toxic immunosuppressive drugs. Data support the utility of Treg in managing immunopathologies, including solid organ transplant rejection, graft-versus-host disease, and autoimmune disorders. Notably, reports suggest that interleukin-2 (IL-2) is critical to survival of Treg, which constitutively express high levels of CD25, that is, the IL-2 receptor α-chain, and are exquisitely sensitive to IL-2, even at very low concentrations in contrast to effector T cells, which only upregulate IL-2 receptor α-chain on activation. This has led to the notion of using low doses of exogenous IL-2 therapeutically to modulate the immune system, specifically Treg numbers and function. Here, we summarize developments of clinical experience with low-dose IL-2 (LD-IL-2) as a therapeutic agent. So far, no clinical data are available to support the therapeutic use of LD-IL-2 therapy in the solid organ transplant setting. For the latter, fine-tuning by biotechnological approaches may be needed because of the narrow therapeutic window and off-target effects of LD-IL-2 therapy and so to realize the therapeutic potential of this molecule.

Regulatory T Cell Dysfunction in Autoimmune Diseases

Regulatory T cells (Tregs), a suppressive subpopulation of T cells, are potent mediators of peripheral tolerance, responsible for immune homeostasis. Many autoimmune diseases exhibit disruptions in Treg function or quantity, resulting in an imbalance between protective and pathogenic immune cells. Selective expansion or manipulation of Tregs is a promising therapeutic approach for autoimmune diseases. However, the extensive diversity of Treg subpopulations and the multiple approaches used for Treg identification leads to high complexity, making it difficult to develop a successful treatment capable of modulating Tregs. In this review, we describe the suppressive mechanisms, subpopulations, classification, and identification methodology for Tregs, and their role in the pathogenesis of autoimmune diseases.

Polyclonally Derived Alloantigen-Specific T Regulatory Cells Exhibit Target-Specific Suppression and Capture MHC Class II from Dendritic Cells

Foxp3+ T regulatory (Treg) cells prevent allograft rejection and graft-versus-host disease. Although polyclonal Tregs have been used both in animal models and in humans, the fine specificity of their suppressive function is poorly defined. We have generated mouse recipient-derived alloantigen-specific Tregs in vitro and explored the fine specificity of their suppressive function and their mechanism of action in vitro and in vivo. In vitro, when alloantigen and peptide Ag were both presented on the same dendritic cell, both responses were suppressed by iTregs specific either for the alloantigen or for the peptide Ag. In vivo, iTreg suppression was limited to the cognate Ag, and no bystander suppression was observed when both allo-antigen and peptide Ag were present on the same dendritic cell. In vitro, alloantigen-specific Tregs captured cognate MHC but failed to capture noncognate MHC. Our results demonstrate that a polyclonal population of iTregs generated from naive T cells can mediate highly specific function in vivo and support the view that Treg therapy, even with unselected polyclonal populations, is likely to be target antigen-specific and that bystander responses to self-antigens or to infectious agents are unlikely.

Tumor-Associated Myeloid Cells Selective Delivery of a Therapeutic Tumor Nano-Vaccine for Overcoming Immune Barriers for Effective and Long-Term Cancer Immunotherapy

Therapeutic cancer vaccines have the potential to induce regression of established tumors, eradicate microscopic residual lesions, and prevent metastasis and recurrence, but their efficacy is limited by the low antigenicity of soluble antigens and the immunosuppressive tumor-associated macrophages (TAMs) that promote tumor growth. In this study, a novel strategy is reported for overcoming these defenses: a dual-targeting nano-vaccine (NV) based on hepatitis B core antigen (HBcAg) derived virus-like particles (VLPs), N-M2T-gp100 HBc NV, equipped with both SIGNR+ dendritic cells (DCs)/TAMs-targeting ability and high-density display of tumor-associated antigen (TAA). N-M2T-gp100 HBc NVs-based immunotherapy has demonstrated an optimal interaction between tumor-associated antigens (TAAs) and the immune composition of the tumor microenvironment. In a melanoma model, N-M2T-gp100 HBc VLPs significantly reducing in situ and abscopal tumor growth, and provide long-term immune protection. This remarkable anti-tumor effect is achieved by efficiently boosting of T cells and repolarizing of M2-like TAMs. This work opens exciting avenues for the development of personalized tumor vaccines targeting not just melanoma but potentially a broad range of cancer types based on functionalized VLPs.

Dendritic Cell Immune Modulation via Polyphenol Membrane Coatings

Cellular hitchhiking is an emerging strategy for the in vivo control of adoptively transferred immune cells. Hitchhiking approaches are primarily mediated by adhesion of nano and microparticles to the cell membrane, which conveys an ability to modulate transferred cells via local drug delivery. Although T cell therapies employing this strategy have progressed into the clinic, phagocytic cells including dendritic cells (DCs) are much more challenging to engineer. DC vaccines hold great potential for a spectrum of diseases, and the combination drug delivery is an attractive strategy to manipulate their function and overcome in vivo plasticity. However, DCs are not compatible with current hitchhiking approaches due to their broad phagocytic capacity. In this work, we developed and validated META (membrane engineering using tannic acid) to enable DC cellular hitchhiking for the first time. META employs the polyphenol tannic acid (TA) to facilitate supramolecular assembly of protein drug cargoes on the cell membrane, enabling the creation of cell surface-bound formulations for local drug delivery to carrier DCs. We optimized META formulations to incorporate and release protein cargoes with varying physical properties alone and in combination and to preserve DC viability and critical functions such as migration. We further show that META loaded with either a pro- or anti-inflammatory cargo can influence the carrier cell phenotype, thus demonstrating the flexibility of the approach for applications from cancer to autoimmune disease. Overall, this approach illustrates a new platform for the local control of phagocytic immune cells as a next step to advance DC therapies in the clinic.

A model of dysregulated crosstalk between dendritic, natural killer, and regulatory T cells in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is characterized by infiltration of the airways and lung parenchyma by inflammatory cells. Lung pathology results from the cumulative effect of complex and aberrant interactions between multiple cell types. However, three cell types, natural killer cells (NK), dendritic cells (DCs), and regulatory T cells (Tregs), are understudied and underappreciated. We propose that their mutual interactions significantly contribute to the development of COPD. Here, we highlight recent advances in NK, DC, and Treg biology with relevance to COPD, discuss their pairwise bidirectional interactions, and identify knowledge gaps that must be bridged to develop novel therapies. Understanding their interactions will be crucial for therapeutic use of autologous Treg, an approach proving effective in other diseases with immune components.

Spatial and functional targeting of intratumoral Tregs reverses CD8+ T cell exhaustion and promotes cancer immunotherapy

Intratumoral Tregs are key mediators of cancer immunotherapy resistance, including anti-programmed cell death (ligand) 1 [anti-PD-(L)1] immune checkpoint blockade (ICB). The mechanisms driving Treg infiltration into the tumor microenvironment (TME) and the consequence on CD8+ T cell exhaustion remain elusive. Here, we report that heat shock protein gp96 (also known as GRP94) was indispensable for Treg tumor infiltration, primarily through the roles of gp96 in chaperoning integrins. Among various gp96-dependent integrins, we found that only LFA-1 (αL integrin), and not αV, CD103 (αE), or β7 integrin, was required for Treg tumor homing. Loss of Treg infiltration into the TME by genetic deletion of gp96/LFA-1 potently induced rejection of tumors in multiple ICB-resistant murine cancer models in a CD8+ T cell-dependent manner, without loss of self-tolerance. Moreover, gp96 deletion impeded Treg activation primarily by suppressing IL-2/STAT5 signaling, which also contributed to tumor regression. By competing for intratumoral IL-2, Tregs prevented the activation of CD8+ tumor-infiltrating lymphocytes, drove thymocyte selection-associated high mobility group box protein (TOX) induction, and induced bona fide CD8+ T cell exhaustion. By contrast, Treg ablation led to striking CD8+ T cell activation without TOX induction, demonstrating clear uncoupling of the 2 processes. Our study reveals that the gp96/LFA-1 axis plays a fundamental role in Treg biology and suggests that Treg-specific gp96/LFA-1 targeting represents a valuable strategy for cancer immunotherapy without inflicting autoinflammatory conditions.

Combining Treg Therapy With Donor Bone Marrow Transplantation: Experimental Progress and Clinical Perspective

Donor-specific tolerance remains a goal in transplantation because it could improve graft survival and reduce morbidity. Cotransplantation of donor hematopoietic cells to achieve chimerism is a promising approach for tolerance induction, which was successfully tested in clinical trials. However, current protocols are associated with side effects related to the myelosuppressive recipient conditioning, which makes it difficult to introduce them as standard therapy. More recently, adoptive cell therapy with polyclonal or donor-specific regulatory T cells (Treg) proved safe and feasible in several transplant trials, but it is unclear whether it can induce tolerance on its own. The combination of both approaches-Treg therapy and hematopoietic cell transplantation-leads to chimerism and tolerance without myelosuppressive treatment in murine models. Treg therapy promotes engraftment of allogeneic hematopoietic cells, reducing conditioning requirements and enhancing regulatory mechanisms maintaining tolerance. This review discusses possible modes of action of transferred Treg in experimental chimerism models and describes translational efforts investigating the potent synergy of Treg and chimerism.

Exploring the therapeutic potential of regulatory T cell in rheumatoid arthritis: Insights into subsets, markers, and signaling pathways

Rheumatoid arthritis (RA) is a complex autoimmune inflammatory rheumatic disease characterized by an imbalance between immunological reactivity and immune tolerance. Regulatory T cells (Tregs), which play a crucial role in controlling ongoing autoimmunity and maintaining peripheral tolerance, have shown great potential for the treatment of autoimmune inflammatory rheumatic diseases such as RA. This review aims to provide an updated summary of the latest insights into Treg-targeting techniques in RA. We focus on current therapeutic strategies for targeting Tregs based on discussing their subsets, surface markers, suppressive function, and signaling pathways in RA.

Immunosuppressive tumor microenvironment and immunotherapy of hepatocellular carcinoma: current status and prospectives

Hepatocellular carcinoma (HCC) is a major health concern worldwide, with limited therapeutic options and poor prognosis. In recent years, immunotherapies such as immune checkpoint inhibitors (ICIs) have made great progress in the systemic treatment of HCC. The combination treatments based on ICIs have been the major trend in this area. Recently, dual immune checkpoint blockade with durvalumab plus tremelimumab has also emerged as an effective treatment for advanced HCC. However, the majority of HCC patients obtain limited benefits. Understanding the immunological rationale and exploring novel ways to improve the efficacy of immunotherapy has drawn much attention. In this review, we summarize the latest progress in this area, the ongoing clinical trials of immune-based combination therapies, as well as novel immunotherapy strategies such as chimeric antigen receptor T cells, personalized neoantigen vaccines, oncolytic viruses, and bispecific antibodies.

Short Report: CAR Tregs mediate linked suppression and infectious tolerance in islet transplantation

Regulatory T cells (Tregs) have potential as a cell-based therapy to prevent or treat transplant rejection and autoimmunity. Using an HLA-A2-specific chimeric antigen receptor (A2-CAR), we previously showed that adoptive transfer of A2-CAR Tregs limited anti-HLA-A2 alloimmunity. However, it was unknown if A2-CAR Tregs could also limit immunity to autoantigens. Using a model of HLA-A2+ islet transplantation into immunodeficient non-obese diabetic mice, we investigated if A2-CAR Tregs could control diabetes induced by islet-autoreactive (BDC2.5) T cells. In mice transplanted with HLA-A2+ islets, A2-CAR Tregs reduced BDC2.5 T cell engraftment, proliferation and cytokine production, and protected mice from diabetes. Tolerance to islets was systemic, including protection of the HLA-A2negative endogenous pancreas. In tolerant mice, a significant proportion of BDC2.5 T cells gained FOXP3 expression suggesting that long-term tolerance is maintained by de novo Treg generation. Thus, A2-CAR Tregs mediate linked suppression and infectious tolerance and have potential therapeutic use to simultaneously control both allo- and autoimmunity in islet transplantation.

IL-23 stabilizes an effector Treg cell program in the tumor microenvironment

Interleukin-23 (IL-23) is a proinflammatory cytokine mainly produced by myeloid cells that promotes tumor growth in various preclinical cancer models and correlates with adverse outcomes. However, as to how IL-23 fuels tumor growth is unclear. Here, we found tumor-associated macrophages to be the main source of IL-23 in mouse and human tumor microenvironments. Among IL-23-sensing cells, we identified a subset of tumor-infiltrating regulatory T (Treg) cells that display a highly suppressive phenotype across mouse and human tumors. The use of three preclinical models of solid cancer in combination with genetic ablation of Il23r in Treg cells revealed that they are responsible for the tumor-promoting effect of IL-23. Mechanistically, we found that IL-23 sensing represents a crucial signal driving the maintenance and stabilization of effector Treg cells involving the transcription factor Foxp3. Our data support that targeting the IL-23/IL-23R axis in cancer may represent a means of eliciting antitumor immunity.

The Role of Regulatory T Cells in Allergic Diseases: Collegium Internationale Allergologicum (CIA) Update 2024

BACKGROUND

Allergy represents a major health problem of increasing prevalence worldwide with a high socioeconomic impact. Our knowledge on the molecular mechanisms underlying allergic diseases and their treatments has significantly improved over the last years. The generation of allergen-specific regulatory T cells (Tregs) is crucial in the induction of healthy immune responses to allergens, preventing the development and worsening of allergic diseases.

SUMMARY

In the last decades, intensive research has focused on the study of the molecular mechanisms involved in Treg development and Treg-mediated suppression. These mechanisms are essential for the induction of sustained tolerance by allergen-specific immunotherapy (AIT) after treatment discontinuation. Compelling experimental evidence demonstrated altered suppressive capacity of Tregs in patients suffering from allergic rhinitis, allergic asthma, food allergy, or atopic dermatitis, as well as the restoration of their numbers and functionality after successful AIT.

KEY MESSAGE

The better understanding of the molecular mechanisms involved in Treg generation during allergen tolerance induction might well contribute to the development of novel strategies for the prevention and treatment of allergic diseases.

Mechanisms underlying immunosuppression by regulatory cells

Regulatory cells, such as regulatory T cells (Tregs), regulatory B cells (Bregs), and myeloid-derived suppressor cells (MDSCs), play a crucial role in preserving immune tolerance and controlling immune responses during infections to prevent excessive immune activation. However, pathogens have developed strategies to hijack these regulatory cells to decrease the overall effectiveness of the immune response and persist within the host. Consequently, therapeutic targeting of these immunosuppressive mechanisms during infection can reinvigorate the immune response and improve the infection outcome. The suppressive mechanisms of regulatory cells are not only numerous but also redundant, reflecting the complexity of the regulatory network in modulating the immune responses. The context of the immune response, such as the type of pathogen or tissue involved, further influences the regulatory mechanisms involved. Examples of these immunosuppressive mechanisms include the production of inhibitory cytokines such as interleukin 10 (IL-10) and transforming growth factor beta (TGF-β) that inhibit the production of pro-inflammatory cytokines and dampen the activation and proliferation of effector T cells. In addition, regulatory cells utilize inhibitory receptors like cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and programmed cell death protein 1 (PD-1) to engage with their respective effector cells, thereby suppressing their function. An alternative approach involves the modulation of metabolic reprogramming in effector immune cells to limit their activation and proliferation. In this review, we provide an overview of the major mechanisms mediating the immunosuppressive effect of the different regulatory cell subsets in the context of infection.

Illuminating T cell-dendritic cell interactions in vivo by FlAsHing antigens

Delineating the complex network of interactions between antigen-specific T cells and antigen presenting cells (APCs) is crucial for effective precision therapies against cancer, chronic infections, and autoimmunity. However, the existing arsenal for examining antigen-specific T cell interactions is restricted to a select few antigen-T cell receptor pairs, with limited in situ utility. This lack of versatility is largely due to the disruptive effects of reagents on the immune synapse, which hinder real-time monitoring of antigen-specific interactions. To address this limitation, we have developed a novel and versatile immune monitoring strategy by adding a short cysteine-rich tag to antigenic peptides that emits fluorescence upon binding to thiol-reactive biarsenical hairpin compounds. Our findings demonstrate the specificity and durability of the novel antigen-targeting probes during dynamic immune monitoring in vitro and in vivo. This strategy opens new avenues for biological validation of T-cell receptors with newly identified epitopes by revealing the behavior of previously unrecognized antigen-receptor pairs, expanding our understanding of T cell responses.

The Biological Significance of Trogocytosis

Trogocytosis is the intercellular transfer of membrane and membrane-associated proteins between cells. Trogocytosis is an underappreciated phenomenon that has historically routinely been dismissed as an artefact. With a greater understanding of the process and the implications it has on biological systems, trogocytosis has the potential to become a paradigm changer. The presence on a cell of molecules they don't endogenously express can alter the biological activity of the cell and could also lead to the acquisition of new functions. To better appreciate this phenomenon, it is important to understand how these intercellular membrane exchanges influence the function and activity of the donor and the recipient cells. In this chapter, we will examine how the molecules acquired by trogocytosis influence the biology of a variety of systems including mammalian fertilization, treatment of hemolytic disease of the newborn, viral and parasitic infections, cancer immunotherapy, and immune modulation.

Intercellular Transfer of Immune Regulatory Molecules Via Trogocytosis

Trogocytosis, an active cellular process involving the transfer of plasma membrane and attached cytosol during cell-to-cell contact, has been observed prominently in CD4 T cells interacting with antigen-presenting cells carrying antigen-loaded major histocompatibility complex (MHC) class II molecules. Despite the inherent absence of MHC class II molecules in CD4 T cells, they actively acquire these molecules from encountered antigen-presenting cells, leading to the formation of antigen-loaded MHC class II molecules-dressed CD4 T cells. Subsequently, these dressed CD4 T cells engage in antigen presentation to other CD4 T cells, revealing a dynamic mechanism of immune communication. The transferred membrane proteins through trogocytosis retain their surface localization, thereby altering cellular functions. Concurrently, the donor cells experience a loss of membrane proteins, resulting in functional changes due to the altered membrane properties. This chapter provides a focused exploration into trogocytosis-mediated transfer of immune regulatory molecules and its consequential impact on diverse immune responses.

T Cell Subsets and Immune Homeostasis

T cells are a heterogeneous group of cells that can be classified into different subtypes according to different classification methods. The body's immune system has a highly complex and effective regulatory network that allows for the relative stability of immune system function. Maintaining proper T cell homeostasis is essential for promoting protective immunity and limiting autoimmunity and tumor formation. Among the T cell family members, more and more T cell subsets have gradually been characterized. In this chapter, we summarize the functions of some key T cell subsets and their impact on immune homeostasis.

Illuminating T cell-dendritic cell interactions in vivo by FlAsHing antigens

Delineating the complex network of interactions between antigen-specific T cells and antigen presenting cells (APCs) is crucial for effective precision therapies against cancer, chronic infections, and autoimmunity. However, the existing arsenal for examining antigen-specific T cell interactions is restricted to a select few antigen-T cell receptor pairs, with limited in situ utility. This lack of versatility is largely due to the disruptive effects of reagents on the immune synapse, which hinder real-time monitoring of antigen-specific interactions. To address this limitation, we have developed a novel and versatile immune monitoring strategy by adding a short cysteine-rich tag to antigenic peptides that emits fluorescence upon binding to thiol-reactive biarsenical hairpin compounds. Our findings demonstrate the specificity and durability of the novel antigen-targeting probes during dynamic immune monitoring in vitro and in vivo. This strategy opens new avenues for biological validation of T-cell receptors with newly identified epitopes by revealing the behavior of previously unrecognized antigen-receptor pairs, expanding our understanding of T cell responses.

Illuminating T cell-dendritic cell interactions in vivo by FlAsHing antigens

Delineating the complex network of interactions between antigen-specific T cells and antigen presenting cells (APCs) is crucial for effective precision therapies against cancer, chronic infections, and autoimmunity. However, the existing arsenal for examining antigen-specific T cell interactions is restricted to a select few antigen-T cell receptor pairs, with limited in situ utility. This lack of versatility is largely due to the disruptive effects of reagents on the immune synapse, which hinder real-time monitoring of antigen-specific interactions. To address this limitation, we have developed a novel and versatile immune monitoring strategy by adding a short cysteine-rich tag to antigenic peptides that emits fluorescence upon binding to thiol-reactive biarsenical hairpin compounds. Our findings demonstrate the specificity and durability of the novel antigen-targeting probes during dynamic immune monitoring in vitro and in vivo. This strategy opens new avenues for biological validation of T-cell receptors with newly identified epitopes by revealing the behavior of previously unrecognized antigen-receptor pairs, expanding our understanding of T cell responses.

Antigen recognition reinforces regulatory T cell mediated Leishmania major persistence

Cutaneous Leishmania major infection elicits a rapid T cell response that is insufficient to clear residually infected cells, possibly due to the accumulation of regulatory T cells in healed skin. Here, we used Leishmania-specific TCR transgenic mice as a sensitive tool to characterize parasite-specific effector and immunosuppressive responses in vivo using two-photon microscopy. We show that Leishmania-specific Tregs displayed higher suppressive activity compared to polyclonal Tregs, that was mediated through IL-10 and not through disrupting cell-cell contacts or antigen presentation. In vivo expansion of endogenous Leishmania-specific Tregs resulted in disease reactivation that was also IL-10 dependent. Interestingly, lack of Treg expansion that recognized the immunodominant Leishmania peptide PEPCK was sufficient to restore robust effector Th1 responses and resulted in parasite control exclusively in male hosts. Our data suggest a stochastic model of Leishmania major persistence in skin, where cellular factors that control parasite numbers are counterbalanced by Leishmania-specific Tregs that facilitate parasite persistence.

Foxp3-mediated blockage of ryanodine receptor 2 underlies contact-based suppression by regulatory T cells

The suppression mechanism of Tregs remains an intensely investigated topic. As our focus has shifted toward a model centered on indirect inhibition of DCs, a universally applicable effector mechanism controlled by the transcription factor forkhead box P3 (Foxp3) expression has not been found. Here, we report that Foxp3 blocked the transcription of ER Ca2+-release channel ryanodine receptor 2 (RyR2). Reduced RyR2 shut down basal Ca2+ oscillation in Tregs, which reduced m-calpain activities that are needed for T cells to disengage from DCs, suggesting a persistent blockage of DC antigen presentation. RyR2 deficiency rendered the CD4+ T cell pool immune suppressive and caused it to behave in the same manner as Foxp3+ Tregs in viral infection, asthma, hypersensitivity, colitis, and tumor development. In the absence of Foxp3, Ryr2-deficient CD4+ T cells rescued the systemic autoimmunity associated with scurfy mice. Therefore, Foxp3-mediated Ca2+ signaling inhibition may be a central effector mechanism of Treg immune suppression.

The role of transcription factors in shaping regulatory T cell identity

Forkhead box protein 3-expressing (FOXP3+) regulatory T cells (Treg cells) suppress conventional T cells and are essential for immunological tolerance. FOXP3, the master transcription factor of Treg cells, controls the expression of multiples genes to guide Treg cell differentiation and function. However, only a small fraction (<10%) of Treg cell-associated genes are directly bound by FOXP3, and FOXP3 alone is insufficient to fully specify the Treg cell programme, indicating a role for other accessory transcription factors operating upstream, downstream and/or concurrently with FOXP3 to direct Treg cell specification and specialized functions. Indeed, the heterogeneity of Treg cells can be at least partially attributed to differential expression of transcription factors that fine-tune their trafficking, survival and functional properties, some of which are niche-specific. In this Review, we discuss the emerging roles of accessory transcription factors in controlling Treg cell identity. We specifically focus on members of the basic helix-loop-helix family (AHR), basic leucine zipper family (BACH2, NFIL3 and BATF), CUT homeobox family (SATB1), zinc-finger domain family (BLIMP1, Ikaros and BCL-11B) and interferon regulatory factor family (IRF4), as well as lineage-defining transcription factors (T-bet, GATA3, RORγt and BCL-6). Understanding the imprinting of Treg cell identity and specialized function will be key to unravelling basic mechanisms of autoimmunity and identifying novel targets for drug development.

Emerging approaches to induce immune tolerance to therapeutic proteins

Immunogenicity affects the safety and efficacy of therapeutic proteins. This review is focused on approaches for inducing immunological tolerance to circumvent the immunogenicity of therapeutic proteins in the clinic. The few immune tolerance strategies that are used in the clinic tend to be inefficient and expensive and typically involve global immunosuppression, putting patients at risk of infections. The hallmark of a desirable immune tolerance regimen is the specific alleviation of immune responses to the therapeutic protein. In the past decade, proof-of-principle studies have demonstrated that emerging technologies, including nanoparticle-based delivery of immunomodulators, cellular targeting and depletion, cellular engineering, gene therapy, and gene editing, can be leveraged to promote tolerance to therapeutic proteins. We discuss the potential of these novel approaches and the barriers that need to be overcome for translation into the clinic.

Resident regulatory T cells reflect the immune history of individual lymph nodes

Regulatory T cells (Tregs) are present in lymphoid and nonlymphoid tissues where they restrict immune activation, prevent autoimmunity, and regulate inflammation. Tregs in nonlymphoid tissues are typically resident, whereas those in lymph nodes (LNs) are considered to recirculate. However, Tregs in LNs are not a homogenous population, and circulation kinetics of different Treg subsets are poorly characterized. Furthermore, whether Tregs can acquire memory T cell properties and persist for extended periods after their activation in LNs is unclear. Here, we used in situ labeling with a stabilized photoconvertible protein to uncover turnover rates of Tregs in LNs in vivo. We found that, whereas most Tregs in LNs recirculate, 10 to 20% are memory-like resident cells that remain in their respective LNs for weeks to months. Single-cell RNA sequencing revealed that LN-resident cells are a functionally and ontogenetically heterogeneous population and share the same core residency gene signature with conventional CD4+ and CD8+ T cells. Resident cells in LNs did not actively proliferate and did not require continuous T cell receptor (TCR) signaling for their residency. However, resident and circulating Tregs had distinct TCR repertoires, and each LN contained exclusive clonal subpopulations of resident Tregs. Our results demonstrate that, similar to conventional T cells, Tregs can form resident memory-like populations in LNs after adaptive immune responses. Specific and local suppression of immune responses by resident Tregs in draining LNs might provide previously unidentified therapeutic opportunities for the treatment of local chronic inflammatory conditions.

MHC cross-dressing in antigen presentation

Dendritic cells (DCs) orchestrate T cell responses by presenting antigenic peptides on major histocompatibility complex (MHC) and providing costimulation and other instructive signals. Professional antigen presenting cells (APCs), including DCs, are uniquely capable of generating and presenting peptide antigens derived from exogenous proteins. In addition to these canonical cross-presentation and MHC-II presentation pathways, APCs can also display exogenous peptide/MHC (p/MHC) acquired from neighboring cells and extracellular vesicles (EVs). This process, known as MHC cross-dressing, has been implicated in the regulation of T cell responses in a variety of in vivo contexts, including allogeneic solid organ transplantation, tumors, and viral infection. Although the occurrence of MHC cross-dressing has been clearly demonstrated, the importance of this antigen presentation mechanism continues to be elucidated. The contribution of MHC cross-dressing to overall antigen presentation has been obfuscated by the fact that DCs express the same MHC alleles as all other cells in the host, making it difficult to distinguish p/MHC generated within the DC from p/MHC acquired from another cell. As a result, much of what is known about MHC cross-dressing comes from studies using allogeneic organ transplantation and bone marrow chimeric mice, though recent development of mice bearing conditional knockout MHC and β2-microglobulin alleles should facilitate substantial progress in the coming years. In this review, we highlight recent advances in our understanding of MHC cross-dressing and its role in activating T cell responses in various contexts, as well as the experimental insights into the mechanism by which it occurs.

Rapamycin nanoparticles increase the therapeutic window of engineered interleukin-2 and drive expansion of antigen-specific regulatory T cells for protection against autoimmune disease

Interleukin-2 (IL-2) therapies targeting the high affinity IL-2 receptor expressed on regulatory T cells (Tregs) have shown promising therapeutic benefit in autoimmune diseases through nonselective expansion of pre-existing Treg populations, but are potentially limited by the inability to induce antigen-specific Tregs, as well as by dose-limiting activation of effector immune cells in settings of inflammation. We recently developed biodegradable nanoparticles encapsulating rapamycin, called ImmTOR, which induce selective immune tolerance to co-administered antigens but do not increase total Treg numbers. Here we demonstrate that the combination of ImmTOR and an engineered Treg-selective IL-2 variant (termed IL-2 mutein) increases the number and durability of total Tregs, as well as inducing a profound synergistic increase in antigen-specific Tregs when combined with a target antigen. We demonstrate that the combination of ImmTOR and an IL-2 mutein leads to durable inhibition of antibody responses to co-administered AAV gene therapy capsid, even at sub-optimal doses of ImmTOR, and provides protection in autoimmune models of type 1 diabetes and primary biliary cholangitis. Importantly, ImmTOR also increases the therapeutic window of engineered IL-2 molecules by mitigating effector immune cell expansion and preventing exacerbation of disease in a model of graft-versus-host-disease. At the same time, IL-2 mutein shows potential for dose-sparing of ImmTOR. Overall, these results establish that the combination of ImmTOR and an IL-2 mutein show synergistic benefit on both safety and efficacy to provide durable antigen-specific immune tolerance to mitigate drug immunogenicity and to treat autoimmune diseases.

Revisiting regulatory T cells as modulators of innate immune response and inflammatory diseases

Regulatory T cells (Treg) are known to be critical for the maintenance of immune homeostasis by suppressing the activation of auto- or allo-reactive effector T cells through a diverse repertoire of molecular mechanisms. Accordingly, therapeutic strategies aimed at enhancing Treg numbers or potency in the setting of autoimmunity and allogeneic transplants have been energetically pursued and are beginning to yield some encouraging outcomes in early phase clinical trials. Less well recognized from a translational perspective, however, has been the mounting body of evidence that Treg directly modulate most aspects of innate immune response under a range of different acute and chronic disease conditions. Recognizing this aspect of Treg immune modulatory function provides a bridge for the application of Treg-based therapies to common medical conditions in which organ and tissue damage is mediated primarily by inflammation involving myeloid cells (mononuclear phagocytes, granulocytes) and innate lymphocytes (NK cells, NKT cells, γδ T cells and ILCs). In this review, we comprehensively summarize pre-clinical and human research that has revealed diverse modulatory effects of Treg and specific Treg subpopulations on the range of innate immune cell types. In each case, we emphasize the key mechanistic insights and the evidence that Treg interactions with innate immune effectors can have significant impacts on disease severity or treatment. Finally, we discuss the opportunities and challenges that exist for the application of Treg-based therapeutic interventions to three globally impactful, inflammatory conditions: type 2 diabetes and its end-organ complications, ischemia reperfusion injury and atherosclerosis.

Tregs integrate native and CAR-mediated costimulatory signals for control of allograft rejection

Tregs expressing chimeric antigen receptors (CAR-Tregs) are a promising tool to promote transplant tolerance. The relationship between CAR structure and Treg function was studied in xenogeneic, immunodeficient mice, revealing advantages of CD28-encoding CARs. However, these models could underrepresent interactions between CAR-Tregs, antigen-presenting cells (APCs), and donor-specific Abs. We generated Tregs expressing HLA-A2-specific CARs with different costimulatory domains and compared their function in vitro and in vivo using an immunocompetent model of transplantation. In vitro, the CD28-encoding CAR had superior antigen-specific suppression, proliferation, and cytokine production. In contrast, in vivo, Tregs expressing CARs encoding CD28, ICOS, programmed cell death 1, and GITR, but not 4-1BB or OX40, all extended skin allograft survival. To reconcile in vitro and in vivo data, we analyzed effects of a CAR encoding CD3ζ but no costimulatory domain. These data revealed that exogenous costimulation from APCs can compensate for the lack of a CAR-encoded CD28 domain. Thus, Tregs expressing a CAR with or without CD28 are functionally equivalent in vivo, mediating similar extension of skin allograft survival and controlling the generation of anti-HLA-A2 alloantibodies. This study reveals a dimension of CAR-Treg biology and has important implications for the design of CARs for clinical use in Tregs.

CD4+CD25+FOXP3+ regulatory T cells: a potential "armor" to shield "transplanted allografts" in the war against ischemia reperfusion injury

Despite the advances in therapeutic interventions, solid organ transplantation (SOT) remains the "gold standard" treatment for patients with end-stage organ failure. Recently, vascularized composite allotransplantation (VCA) has reemerged as a feasible treatment option for patients with complex composite tissue defects. In both SOT and VCA, ischemia reperfusion injury (IRI) is inevitable and is a predominant factor that can adversely affect transplant outcome by potentiating early graft dysfunction and/or graft rejection. Restoration of oxygenated blood supply to an organ which was previously hypoxic or ischemic for a period of time triggers cellular oxidative stress, production of both, pro-inflammatory cytokines and chemokines, infiltration of innate immune cells and amplifies adaptive alloimmune responses in the affected allograft. Currently, Food and Drug Administration (FDA) approved drugs for the treatment of IRI are unavailable, therefore an efficacious therapeutic modality to prevent, reduce and/or alleviate allograft damages caused by IRI induced inflammation is warranted to achieve the best-possible transplant outcome among recipients. The tolerogenic capacity of CD4+CD25+FOXP3+ regulatory T cells (Tregs), have been extensively studied in the context of transplant rejection, autoimmunity, and cancer. It was not until recently that Tregs have been recognized as a potential cell therapeutic candidate to be exploited for the prevention and/or treatment of IRI, owing to their immunomodulatory potential. Tregs can mitigate cellular oxidative stress, produce anti-inflammatory cytokines, promote wound healing, and tissue repair and prevent the infiltration of pro-inflammatory immune cells in injured tissues. By using strategic approaches to increase the number of Tregs and to promote targeted delivery, the outcome of SOT and VCA can be improved. This review focuses on two sections: (a) the therapeutic potential of Tregs in preventing and mitigating IRI in the context of SOT and VCA and (b) novel strategies on how Tregs could be utilized for the prevention and/or treatment of IRI.

Systems immunology of regulatory T cells: can one circuit explain it all?

Regulatory T (Treg) cells play vital roles in immune homeostasis and response, including discrimination between self- and non-self-antigens, containment of immunopathology, and inflammation resolution. These diverse functions are orchestrated by cellular circuits involving Tregs and other cell types across space and time. Despite dramatic progress in our understanding of Treg biology, a quantitative framework capturing how Treg-containing circuits give rise to these diverse functions is lacking. Here, we propose that different facets of Treg function can be interpreted as distinct operating regimes of the same underlying circuit. We discuss how a systems immunology approach, involving quantitative experiments, computational modeling, and machine learning, can advance our understanding of Treg function, and help identify general operating and design principles underlying immune regulation.

Tregs with an MHC class II peptide-specific chimeric antigen receptor prevent autoimmune diabetes in mice

Adoptive immunotherapy with Tregs is a promising approach for preventing or treating type 1 diabetes. Islet antigen-specific Tregs have more potent therapeutic effects than polyclonal cells, but their low frequency is a barrier for clinical application. To generate Tregs that recognize islet antigens, we engineered a chimeric antigen receptor (CAR) derived from a monoclonal antibody with specificity for the insulin B chain 10-23 peptide presented in the context of the IAg7 MHC class II allele present in NOD mice. Peptide specificity of the resulting InsB-g7 CAR was confirmed by tetramer staining and T cell proliferation in response to recombinant or islet-derived peptide. The InsB-g7 CAR redirected NOD Treg specificity such that insulin B 10-23-peptide stimulation enhanced suppressive function, measured via reduction of proliferation and IL-2 production by BDC2.5 T cells and CD80 and CD86 expression on dendritic cells. Cotransfer of InsB-g7 CAR Tregs prevented adoptive transfer diabetes by BDC2.5 T cells in immunodeficient NOD mice. In WT NOD mice, InsB-g7 CAR Tregs prevented spontaneous diabetes. These results show that engineering Treg specificity for islet antigens using a T cell receptor-like CAR is a promising therapeutic approach for the prevention of autoimmune diabetes.

Low-dose interleukin-2 therapy in systemic lupus erythematosus

In systemic lupus erythematosus (SLE), T regulatory cells (Tregs) contribute to the inhibition of autoimmune responses by suppressing self-reactive immune cells. Interleukin (IL)-2 plays an essential role in the generation, function and homeostasis of the Tregs and is reduced in SLE. Several clinical studies, including randomized trials, have shown that low-dose IL-2 therapy in SLE patients is safe and effective and can reduce disease manifestations. This review discusses the rationale for the use of low-dose IL-2 therapy in SLE, the clinical responses in patients, and the effects of this therapy on different types of T cells. Considerations are made on the current and future directions of use of low-dose IL-2 regimens in SLE.

The functional adaptation of effector Foxp3+ regulatory T cells to pulmonary inflammation

During infections, the timings of effector differentiation of pulmonary immune responses are of paramount importance, as pathogen persistence and unsuppressed inflammation can rapidly lead to a loss of function, increased frailty, and death. Thus, both an efficient clearance of the danger and a rapid resolution of inflammation are critical to host survival. We now know that tissue-localized FoxP3+ regulatory T cells, a subset of CD4+ T cells, are highly attuned to the type of immune response, acquiring unique phenotypic characteristics that allow them to adapt their suppressive functions with the nature of inflammatory cells. To achieve this, activated effector TREG cells acquire specialized TH 1, TH 2, and TH 17-like characteristics that allow them to migrate, survive, and time their function(s) through refined mechanisms. Herein, we describe how this process requires a unique developmental path that includes the acquisition of master transcription factors and the expression of receptors adapted to sense local danger signals that are found during pulmonary inflammation. In turn, we offer an overview of how these characteristics promote the capacity of local effector TREG cells to proliferate, survive, and display suppressive strategies to resolve lung injury.

Targeting sphingosine 1-phosphate receptor 3 inhibits T-cell exhaustion and regulates recruitment of proinflammatory macrophages to improve antitumor efficacy of CAR-T cells against solid tumor

BACKGROUNDS

Chimeric antigen receptor (CAR)-modified T cells (CAR-T) are limited in solid tumors due to the hostile tumor microenvironment (TME). Combination therapy could be a promising approach to overcome this obstacle. Recent studies have shown that sphingosine 1-phosphate receptor (S1PR)3 has tremendous potential in regulating the immune environment. However, the functional significance of S1PR3 in T-cell-based immunotherapies and the molecular mechanisms have not been fully understood.

METHODS

Here, we studied the combination of EpCAM-specific CAR T-cell therapy with pharmacological blockade of S1PR3 against solid tumor. We have applied RNA sequencing, flow cytometry, ELISA, cellular/molecular immunological technology, and mouse models of solid cancers.

RESULTS

Our study provided evidence that S1PR3 high expression is positively associated with resistance to programmed cell death protein-1 (PD-1)-based immunotherapy and increased T-cell exhaustion. In addition, pharmacological inhibition of S1PR3 improves the efficacy of anti-PD-1 therapy. Next, we explored the possible combination of S1PR3 antagonist with murine EpCAM-targeted CAR-T cells in immunocompetent mouse models of breast cancer and colon cancer. The results indicated that the S1PR3 antagonist could significantly enhance the efficacy of murine EpCAM CAR-T cells in vitro and in vivo. Mechanistically, the S1PR3 antagonist improved CAR-T cell activation, regulated the central memory phenotype, and reduced CAR-T cell exhaustion in vitro. Targeting S1PR3 was shown to remodel the TME through the recruitment of proinflammatory macrophages by promoting macrophage activation and proinflammatory phenotype polarization, resulting in improved CAR-T cell infiltration and amplified recruitment of CD8+T cells.

CONCLUSIONS

This work demonstrated targeting S1PR3 could increase the antitumor activities of CAR-T cell therapy at least partially by inhibiting T-cell exhaustion and remodeling the TME through the recruitment of proinflammatory macrophages. These findings provided additional rationale for combining S1PR3 inhibitor with CAR-T cells for the treatment of solid tumor.

The unique expression pattern of human leukocyte antigen in trophoblasts potentially explains the key mechanism of maternal-fetal tolerance and successful pregnancy

The success of pregnancy mainly depends on immune tolerance of the mother for the semi-allogeneic fetus. The placenta carrying paternal antigens develops in the maternal uterus without suffering immune attack, making the underlying mechanism of maternal tolerance an enduring mystery. As we all know, human leukocyte antigen (HLA) plays an important role in antigen processing and presentation, thus inducing specific immune responses. Therefore, it is reasonable to speculate that the absence of classical HLA class-I（HLA-I) and HLA class-II (HLA-II) molecules in trophoblasts may account for the maternal-fetal tolerance. Here, we review the HLA-involved interactions between trophoblast cells and decidual immune cells, which contribute to the immunotolerance in the development of normal pregnancy. We also compare the similarity between the maternal-fetal interface and tumor-immune microenvironment because the important role of HLA molecules in tumor immune invasion can provide some references to studies of maternal-fetal immune tolerance. Besides, the abnormal HLA expression is likely to be associated with unexplained miscarriage, making HLA molecules potential therapeutic targets. The advances reported by these studies may exert profound influences on other research areas, including tumor immunity, organ transplantation and autoimmune disease in the future.

T Cell Development and Function

T cells play critical roles in the immune system, including in responses to cancer, autoimmunity, and tissue regeneration. T cells arise from common lymphoid progenitors (CLPs) that differentiate from hematopoietic stem cells in the bone marrow. CLPs then traffic to the thymus, where they undergo thymopoiesis through a number of selection steps, resulting in mature single positive naive CD4 helper or CD8 cytotoxic T cells. Naive T cells are home to secondary lymphoid organs like lymph nodes and are primed by antigen-presenting cells, which scavenge for both foreign and self-antigens. Effector T cell function is multifaceted, including direct target cell lysis and secretion of cytokines, which regulate the functions of other immune cells (refer to "Graphical Abstract"). This review will discuss T cell development and function, from the development of lymphoid progenitors in the bone marrow to principles that govern T cell effector function and dysfunction, specifically within the context of cancer.

Pro-Tumorigenic and Thrombotic Activities of Platelets in Lung Cancer

Aside from their key protective roles in hemostasis and innate immunity, platelets are now recognized as having multifaceted, adverse roles in the pathogenesis, progression and outcome of many types of human malignancy. The most consistent and compelling evidence in this context has been derived from the notable association of elevated circulating platelet counts with the onset and prognosis of various human malignancies, particularly lung cancer, which represents the primary focus of the current review. Key topics include an overview of the association of lung cancer with the circulating platelet count, as well as the mechanisms of platelet-mediated, pro-tumorigenic immunosuppression, particularly the role of transforming growth factor beta 1. These issues are followed by a discussion regarding the pro-tumorigenic role of platelet-derived microparticles (PMPs), the most abundant type of microparticles (MPs) in human blood. In this context, the presence of increased levels of PMPs in the blood of lung cancer patients has been associated with tumor growth, invasion, angiogenesis and metastasis, which correlate with disease progression and decreased survival times. The final section of the review addresses, firstly, the role of cancer-related platelet activation and thrombosis in the pathogenesis of secondary cardiovascular disorders and the associated mortality, particularly in lung cancer, which is second only to disease progression; secondly, the review addresses the potential role of antiplatelet agents in the adjunctive therapy of cancer.

CTLA4 depletes T cell endogenous and trogocytosed B7 ligands via cis-endocytosis

CD28 and CTLA4 are T cell coreceptors that competitively engage B7 ligands CD80 and CD86 to control adaptive immune responses. While the role of CTLA4 in restraining CD28 costimulatory signaling is well-established, the mechanism has remained unclear. Here, we report that human T cells acquire antigen-presenting-cell (APC)-derived B7 ligands and major histocompatibility complex (MHC) via trogocytosis through CD28:B7 binding. Acquired MHC and B7 enabled T cells to autostimulate, and this process was limited cell-intrinsically by CTLA4, which depletes B7 ligands trogocytosed or endogenously expressed by T cells through cis-endocytosis. Extending this model to the previously proposed extrinsic function of CTLA4 in human regulatory T cells (Treg), we show that blockade of either CD28 or CTLA4 attenuates Treg-mediated depletion of APC B7, indicating that trogocytosis and CTLA4-mediated cis-endocytosis work together to deplete B7 from APCs. Our study establishes CTLA4 as a cell-intrinsic molecular sink that limits B7 availability on the surface of T cells, with implications for CTLA4-targeted therapy.

Reprogramming the immunosuppressive tumor microenvironment: exploiting angiogenesis and thrombosis to enhance immunotherapy

This review focuses on the immunosuppressive effects of tumor angiogenesis and coagulation on the tumor microenvironment (TME). We summarize previous research efforts leveraging these observations and targeting these processes to enhance immunotherapy outcomes. Clinical trials have documented improved outcomes when combining anti-angiogenic agents and immunotherapy. However, their overall survival benefit over conventional therapy remains limited and certain tumors exhibit poor response to anti-angiogenic therapy. Additionally, whilst preclinical studies have shown several components of the tumor coagulome to curb effective anti-tumor immune responses, the clinical studies reporting combinations of anticoagulants with immunotherapies have demonstrated variable treatment outcomes. By reviewing the current state of the literature on this topic, we address the key questions and future directions in the field, the answers of which are crucial for developing effective strategies to reprogram the TME in order to further the field of cancer immunotherapy.

RORing toward immunoregulation in glomerulonephritis?

CD4+ T cells that express forkhead box protein 3 are important in maintaining tolerance and restraining effector responses. Herrnstadt et al. use a model of rapidly progressive glomerulonephritis to examine the nature and role of forkhead box protein 3-positive and retinoid acid-related orphan receptor γt-positive regulatory T cells. These cells are prominent in experimental glomerulonephritis, both locally and systemically, and are present in kidneys of people with anti-neutrophil cytoplasmic antibody-associated vasculitis. Functionally, despite their expression of retinoid acid-related orphan receptor γt, associated with T-helper cell 17 cells, they regulate cellular immunity, both systemically and within the kidney.

Aceclofenac and methotrexate combination therapy could influence Th1/Th17 axis to modulate rheumatoid-arthritis-induced inflammation

Rheumatoid arthritis (RA) is an inflammatory, autoimmune and connective-tissue arthropathy. The methotrexate (MTX) and aceclofenac (ACL) combination drug regimen is known to regulate the immunological pathways. Also, RA-elicited inflammation is decreased by the combination drug treatment. ACL and MTX combination treatment has been shown to regulate the signaling pathway controlled by NF-κB and FOXO1. The present manuscript reviews the importance of the combination drug regimen to treat and/or manage RA. The combination drug regimen could affect the Th1/Th17 axis to switch the balance toward the immunoregulatory (Th1) phenotype for establishing immune homeostasis. In conclusion, we propose the study of the immunological signaling pathways in experimental humanized RA mice.

Research Progress of Dendritic Cell Surface Receptors and Targeting

Dendritic cells are the only antigen-presenting cells capable of activating naive T cells in humans and mammals and are the most effective antigen-presenting cells. With deepening research, it has been found that dendritic cells have many subsets, and the surface receptors of each subset are different. Specific receptors targeting different subsets of DCs will cause different immune responses. At present, DC-targeted research plays an important role in the treatment and prevention of dozens of related diseases in the clinic. This article focuses on the current status of DC surface receptors and targeted applications.

Immunomodulation for Tissue Repair and Regeneration

Various immune cells participate in repair and regeneration following tissue injury or damage, orchestrating tissue inflammation and regeneration processes. A deeper understanding of the immune system's involvement in tissue repair and regeneration is critical for the development of successful reparatory and regenerative strategies. Here we review recent technologies that facilitate cell-based and biomaterial-based modulation of the immune systems for tissue repair and regeneration. First, we summarize the roles of various types of immune cells in tissue repair. Second, we review the principle, examples, and limitations of regulatory T (Treg) cell-based therapy, a representative cell-based immunotherapy. Finally, we discuss biomaterial-based immunotherapy strategies that aim to modulate immune cells using various biomaterials for tissue repair and regeneration.