Opportunities for Treg cell therapy for the treatment of human disease

Cell Therapy and the Skin: Great Potential but in Need of Optimization

Cell therapy is rapidly growing owing to its therapeutic potential for diseases with currently poor outcomes. Cell therapy encompasses both nonengineered and engineered cells and possesses unique abilities such as sense-and-respond functions and long-term engraftment for persistent curative potential. Cell therapy capabilities have expanded to address a wide spectrum of diseases, and our review is focused on dermatological applications. The use of fibroblasts and keratinocytes as cell therapy has shown promise in skin disorders such as epidermolysis bullosa. Future efforts include testing the ability of fibroblasts to reprogram nonvolar to volar skin to reduce stump dermatoses in patients with limb loss using prosthetics.

Emerging role of regulatory T cells in the immunopathogenesis of vitiligo and implications for treatment

Vitiligo is an autoimmune skin disease that targets pigment-producing melanocytes and results in depigmentation. This disfiguring condition frequently affects visible areas of the body and therefore causes a heavy psychological burden and a decreased quality of life. Although it remains intractable, the ever-growing understanding of its immunopathogenesis has dramatically shaped the treatment paradigm for vitiligo. With the impact of autoreactive cytotoxic T cells explained extensively, accumulating evidence suggests the unique role of regulatory T cells (Tregs) in the immune microenvironment of vitiligo. We systematically reviewed Treg deficiency, instability, reduced vitality and dysfunction in people with vitiligo, combined with novel findings regarding Treg function modulation in autoimmune backgrounds, including metabolic alteration, post-translational modifications and interaction with other immune cells. We further summarized classic and advanced Treg-targeted therapeutics in vitiligo practice and research. Herein, we share up-to-date knowledge of Tregs in vitiligo, providing insights into novel Treg-based therapeutic strategies.

Transfer of bone marrow niche-residential regulatory T cells ameliorates experimental colitis

BACKGROUND

Adoptive transfer of regulatory T cells (Tregs) has been proposed as a next-generation treatment approach for the treatment of various inflammatory or autoimmune disorders(Amini et al., 2022; Bluestone et al., 2023, 2015; Dall'Era et al., 2019; Chandran et al., 2017; Laukova and Glatman Zaretsky, 2023; Voskens et al., 2023; Canavan et al., 20161-8), inclusive of inflammatory bowel diseases (IBD). Identification of the appropriate Treg populations as donor sources for effective cell therapy is of great importance. We have recently identified specialized Tregs that localize within the hematopoietic stem cell (HSC) microenvironments(Fujisaki et al., 2011; Hirata et al., 2018, 2019, 2015; Kakiuchi et al., 2021a, 2021b; Furuhashi et al., 20259-16) of bone marrow (BM), termed HSC niches. These BM niche Tregs exhibit robust anti-inflammatory and pro-regenerative effects and render HSCs immune privileged. The transfer of BM niche Tregs exhibits high therapeutic effects against BM transplantation and injury(Hirata et al., 2018; Kakiuchi et al., 2021b10, 14). Yet, the treatment effects of transferred BM niche Tregs in non-BM disease settings remain unknown.

OBJECTIVES

We investigated the therapeutic effects of transfer of BM niche Tregs for IBD using mouse models of experimental colitis. To identify the key effector molecule of niche Tregs, we further examined the roles of cell-surface ectoenzyme CD39 expressed at high levels by BM niche Tregs.

STUDY DESIGN

Mouse colitis was induced by administering dextran sulfate sodium salt. Subsequently, the mice received intravenous injections of BM niche Tregs, BM non-niche Tregs, lymph node Tregs, or vehicle alone. We compared these treatment effects on clinical scores, histopathological features and profiles of immune cells. We also tested how targeted deletion of CD39 in the adoptively transferred Tregs impacted experimental outcomes.

RESULTS

The transfer of as few as 1.5 × 104 BM niche Tregs per mouse ameliorated clinical and histopathological features of the mouse colitis far better than the transfer of other Tregs. The transfer of BM niche Tregs inhibited the generation of Th17 cells and promoted the regeneration and recovery of the colon tissue. Targeted deletion of CD39 in Tregs abrogated therapeutic effects of transferred BM niche Tregs.

CONCLUSION

We show robust therapeutic effects of the transfer of BM niche Tregs in the experimental model of colitis. Donor niche Tregs mediate anti-inflammatory and pro-regenerative effects via Treg CD39. Our work suggests the transfer of BM niche Tregs is a promising approach to treat colitic disorders and boost tissue regeneration.

Role of regulatory immune cells in pathogenesis and therapy of periodontitis

Periodontitis disease (PD) is a serious gum infection that progresses from gingivitis. PD is defined by gingival recession and bone loss and can lead to tooth loss. Bacterial infections are the main cause, as they induce inflammation and the development of periodontal pockets. Traditional therapies such as scaling and root planning aim to remove the subgingival biofilm via mechanical debridement but fail to address the fundamental inflammatory imbalance within the periodontium. The immune homeostasis linked to periodontal health necessitates a regulated immuno-inflammatory response, within which the presence of regulatory cells is critical to guarantee a managed response that reduces unintended tissue damage. Given that regulatory cells influence both innate and adaptive immunity, pathological conditions that might be alleviated through the establishment of immuno-tolerance, such as PD, could potentially gain from the application of regulatory cell immunotherapy. This review will reveal regulatory cell types, how they change phenotypes, and how they can be targets for new immunotherapies. As our understanding of regulatory cell biology advances, we can create novel therapeutics to improve their stability and function in PD.

Enumeration and gentle sorting of immune cells on chip, key to next generation advanced therapies in outpatient setting

BACKGROUND

A thorough understanding of immune-oncology and molecular medicine has been vital in the development of cell therapeutics. At the basis of this translational research and its future implementation into a medicinal product, lies the availability of pure and viable cell populations. Currently, FACS and magnetic bead isolation are successfully used but suffer to fulfill all requirements. FACS is costly and difficult to upscale due to the limitation of shear stress, especially fragile, cells can handle. Therefore, magnetic bead isolation is often used as it is gentler, but it lacks the multiparametric aspect to isolate more complex cellular profiles.

AIMS

We aim to develop a versatile technology able of multi marker detection and isolation of complex cell types with high purity, viability and throughput.

METHODS

We have developed a gentle sorting mechanism based on a jet flow created by micro vapor bubbles, enabling a closed microfluidic cell isolation platform capable of multiparametric sorting with high viability, purity and throughput. In this work we compared the purity, recovery and viability of sorted CD4+ CD14- cells to magnetic isolation, most often used for other cell manufacturing approaches. Futhermore, we cultured the sorted cells of both isolation strategies and compared their growth curve and expression of activation-induced IL2 and IFN-γ.

RESULTS

We demonstrate that this tool can achieve a pure population of CD4+ CD14- cells with high viability after sorting without compromising the recovery. On top of the viability also the growth and activation potential of sorted cells is unhampered by comparison to the benchmark gentle magnetic isolation.

CONCLUSIONS

Our technology allows for the development of a compact system which sets it apart from other efforts intended to create automated cell therapeutic solutions.

Biomaterial-Based Therapeutic Delivery of Immune Cells

Immune cell therapy (ICT) is a transformative approach used to treat a wide range of diseases including type 1 diabetes, sickle cell disease, disorders of the hematopoietic system, and certain forms of cancers. Despite excellent clinical successes, the scope of adoptively transferred immune cells is limited because of toxicities like cytokine release syndrome and immune effector cell-associated neurotoxicity in patients. Furthermore, reports suggest that such treatment can impact major organ systems including cardiac, renal, pulmonary, and hepatic systems in the long term. Additionally, adoptively transferred immune cells cannot achieve significant penetration into solid tissues, thus limiting their therapeutic potential. Recent studies suggest that biomaterial-assisted delivery of immune cells can address these challenges by reducing toxicity, improving localization, and maintaining desired phenotypes to eventually regain tissue function. In this review, recent efforts in the field of biomaterial-based immune cell delivery for the treatment of diseases, their pros and cons, and where these approaches stand in terms of clinical treatment are highlighted.

Antigen-specific immunotherapies for autoimmune disease

Antigen-specific therapies have a long history in the treatment of allergy but have not been successful in autoimmunity. However, in the past 20 years, advances in the definition of the self-antigens that promote autoimmunity and the growing understanding of the mechanisms that maintain tolerance in health but fail in autoimmunity have led to antigen-specific approaches being considered for the treatment of autoimmune diseases. The core goal of each antigen-specific treatment approach is to remove the immune response that promotes autoimmunity whilst sparing protective responses. Approaches to antigen-specific therapy range from targeted deletion of autoreactive lymphocytes to tolerization of autoreactive T cells and active inhibition of autoimmune responses. Technologies such as vaccines, nanoparticles, cell-based therapies and gene editing are being harnessed to achieve these goals. Remaining challenges include the selection of the best antigen to target, modality and timing of administration of these therapies and the disease in which the therapies are used; overcoming these challenges will be vital to move antigen-specific therapies forward. Once established, antigen-specific therapy has the potential to be applied broadly in the area of autoimmunity.

Immune mechanisms and shared immune targets in neurodegenerative diseases

The immune system plays a major part in neurodegenerative diseases. In some, such as multiple sclerosis, it is the primary driver of the disease. In others, such as Alzheimer disease, amyotrophic lateral sclerosis and Parkinson disease, it has an amplifying role. Immunotherapeutic approaches that target the adaptive and innate immune systems are being explored for the treatment of almost all neurological diseases, and the targets and approaches are often common across diseases. Microglia are the primary immune cells in the brain that contribute to disease pathogenesis, and are consequently a common immune target for therapy. Other therapeutic approaches target components of the peripheral immune system, such as regulatory T cells and monocytes, which in turn act within the CNS. This Review considers in detail how microglia, monocytes and T cells contribute to the pathogenesis of multiple sclerosis, Alzheimer disease, amyotrophic lateral sclerosis and Parkinson disease, and their potential as shared therapeutic targets across these diseases. The microbiome is also highlighted as an emerging therapeutic target that indirectly modulates the immune system. Therapeutic approaches being developed to target immune function in neurodegenerative diseases are discussed, highlighting how immune-based approaches developed to treat one disease could be applicable to multiple other neurological diseases.

The Efficiency of Brain-Derived Neurotrophic Factor Secretion by mRNA-Electroporated Regulatory T Cells Is Highly Impacted by Their Activation Status

Genetic engineering of regulatory T cells (Tregs) presents a promising avenue for advancing immunotherapeutic strategies, particularly in autoimmune diseases and transplantation. This study explores the modification of Tregs via mRNA electroporation, investigating the influence of T-cell activation status on transfection efficiency, phenotype, and functionality. For this CD45RA+ Tregs were isolated, expanded, and modified to overexpress brain-derived neurotrophic factor (BDNF). Kinetics of BDNF expression and secretion were explored. Treg activation state was assessed by checking the expression of activation markers CD69, CD71, and CD137. Our findings show that only activated Tregs secrete BDNF post-genetic engineering, even though both activated and resting Tregs express BDNF intracellularly. Notably, the mTOR pathway and CD137 are implicated in the regulation of protein secretion in activated Tregs, indicating a complex interplay of signalling pathways. This study contributes to understanding the mechanisms governing protein expression and secretion in engineered Tregs, offering insights for optimizing cell-based therapies and advancing immune regulation strategies.

Harnessing the biology of regulatory T cells to treat disease

Regulatory T (Treg) cells are a suppressive subset of CD4+ T cells that maintain immune homeostasis and restrain inflammation. Three decades after their discovery, the promise of strategies to harness Treg cells for therapy has never been stronger. Multiple clinical trials seeking to enhance endogenous Treg cells or deliver them as a cell-based therapy have been performed and hint at signs of success, as well as to important limitations and unanswered questions. Strategies to deplete Treg cells in cancer are also in active clinical testing. Furthermore, multi-dimensional methods to interrogate the biology of Treg cells are leading to a refined understanding of Treg cell biology and new approaches to harness tissue-specific functions for therapy. A new generation of Treg cell clinical trials is now being fuelled by advances in nanomedicine and synthetic biology, seeking more precise ways to tailor Treg cell function. This Review will discuss recent advances in our understanding of human Treg cell biology, with a focus on mechanisms of action and strategies to assess outcomes of Treg cell-targeted therapies. It highlights results from recent clinical trials aiming to enhance or inhibit Treg cell activity in a variety of diseases, including allergy, transplantation, autoimmunity and cancer, and discusses ongoing strategies to refine these approaches.

Pretransplant targeting of TNFRSF25 and CD25 stimulates recipient Tregs in target tissues ameliorating GVHD post-HSCT

The current approach to minimize transplant-associated complications, including graft-versus-host disease (GVHD) includes long-term pharmacological immune suppression frequently accompanied by unwanted side effects. Advances in targeted immunotherapies regulating alloantigen responses in the recipient continue to reduce the need for pan-immunosuppression. Here, in vivo targeting of the TNF superfamily receptor 25 (TNFRSF25) and the high affinity IL-2 receptor with a TL1A-Ig fusion protein and low dose IL-2, respectively, was used to pretreat recipient mice prior to allogeneic-HSCT (aHSCT). Pretreatment induced Treg expansion persisting early post-aHSCT leading to diminished GVHD and improved transplant outcomes. Expansion was accompanied by an increase in frequency of stable and functionally active Tregs as evidenced by in vitro assays using cells from major GVHD target tissues including colon, liver, and eye. Importantly, pretreatment supported epithelial cell function/integrity, a diverse microbiome including reduction of pathologic bacteria overgrowth and promotion of butyrate producing bacteria, while maintaining physiologic levels of obligate/facultative anaerobes. Notably, using a sphingosine 1-phosphate receptor agonist to sequester T cells in lymphoid tissues, we found that the increased tissue Treg frequency included resident CD69 + CD103 + FoxP3 + hepatic Tregs. In contrast to infusion of donor Treg cells, the strategy developed here resulted in the presence of immunosuppressive target tissue environments in the recipient prior to the receipt of donor allo-reactive T cells and successful perseveration of GVL responses. We posit strategies that circumvent the need of producing large numbers of ex-vivo manipulated Tregs, may be accomplished through in vivo recipient Treg expansion, providing translational approaches to improve aHSCT outcomes.

CXCR5-targeted chimeric antigen receptor T regulatory cells for the selective inhibition of follicular helper T cell and B cell interaction

BACKGROUND

The dysregulation of follicular helper T (Tfh) cell function, followed by the proliferation of self-reactive B cells, can lead to the development of autoimmune diseases. Recently, adaptive T regulatory cell (Treg) transfer therapy has attracted considerable attention for inducing effective immune tolerance owing to Tregs' diverse immune-inhibitory activities. However, preclinical studies and recent clinical trials of polyclonal Treg therapy have suggested further improving the efficacy of Treg therapy through targeted tissue specificity and local persistence by gene engineering. In this study, we reported a novel approach to specifically inhibit Tfh cells by CXC motif chemokine receptor 5-targeted chimeric antigen receptor (CXCR5-CAR) Tregs.

METHODS

Tregs expressing CAR against CXCR5 were generated from human peripheral blood mononuclear cells-derived Tregs. The phenotype and suppressive capacity of the engineered Tregs were evaluated using coculture assays with naïve T cells, circulating Tfh (cTfh) cells, or a combination of cTfh cells and naïve B cells through flow cytometry analysis.

RESULT

CXCR5-CAR Tregs induced more potent inhibition of circulating cTfh cell proliferation while maintaining similar suppressive properties on CXCR5-negative responder cells compared with non-selective polyclonal Tregs. The antigen-dependent activation of CXCR5-CAR Tregs was confirmed by latency-associated peptide (LAP) expression in the coculture with cTfh cells. In the coculture condition with both cTfh and naïve B cells, the activation of naïve B cells induced by cTfh cells was more effectively inhibited by CXCR5-CAR Tregs than by polyclonal Tregs.

CONCLUSION

The results demonstrate the potential of CXCR5-CAR Tregs to effectively inhibit the Tfh-B cell response in autoimmune diseases, paving the way for further research to confirm their functional superiority in vivo. This novel approach offers promise for achieving local, long-term immune tolerance compared with existing approaches such as nonspecific immunosuppression and polyclonal Treg therapy.

Multifunctional ICG-SB@Lip-ZA Nanosystem Focuses on Remodeling the Inflammatory-Immunosuppressive Microenvironment After Photothermal Therapy to Potentiate Cancer Photothermal Immunotherapy

Achieving full eradication of residual tumors post photothermal therapy (PTT) hinges on the immune system's activation and response. Nevertheless, the resultant local inflammation attracts a significant influx of aberrant immune cells and fibroblasts, such as tumor-associated macrophages (TAMs) and cancer-associated fibroblasts (CAFs), following tumor PTT. This phenomenon exacerbates immune evasion and the persistence of residual tumor cells, culminating in tumor recurrence and advancement. To tackle this challenge, a combined therapeutic approach utilizing multifunctional ICG-SB@Lip-ZA nanosystem has been introduced. Indocyanine green (ICG) as a photothermal-transducer ablated tumor cells, zoledronic acid (ZA) depletes TAMs recruited by the inflammatory tumor microenvironment (mostly M2-like phenotype), SB-505124 affects CAFs proliferation in the tumor microenvironment (TME) by inhibiting the transforming growth factor-β （TGF-β） pathway, thereby removing physical barriers to T cell infiltration. In a breast cancer model, these immunomodulatory nanoliposomes markedly decrease the population of M2-like TAMs in the TME, eliminate physical barriers hindering T cell infiltration, reshape the inflammatory immune-suppressive tumor microenvironment, eventually leading to a rate of tumor eradication of 94%. This multifunctional ICG-SB@Lip-ZA nanosystem (including photothermal conversion, TAM depletion, and TGF-β pathway blockade) offers a promising strategy for mitigating the deteriorating tumor microenvironment following PTT and presents a more efficient approach for clinical photothermal-immune combination therapy.

CXC chemokine receptor 4 - mediated immune modulation and tumor microenvironment heterogeneity in gastric cancer: Utilizing multi-omics approaches to identify potential therapeutic targets

G-protein-coupled receptors (GPRs) are critical regulators of various biological behaviors, and their role in gastric cancer (GC) progression is gaining increasing attention. Among them, the immune regulatory mechanisms mediated by chemokine receptor 4 (CXCR4) remain insufficiently understood. This study aims to explore the immune regulatory functions of CXCR4 and the heterogeneity of the tumor microenvironment (TME) by examining GPR-related gene expression in GC. Through multi-omics approaches, including spatial transcriptomics and single-cell RNA sequencing, we investigated the oncogenic mechanisms of CXCR4, particularly its role in T cell immune exhaustion. In vitro experiments, including ELISA, PCR, CCK8 assays, cell scratch assays, and colony formation assays, were used to validate the role of CXCR4 in the migration and invasion of AGS and SNU-1 cell lines. CXCR4 silencing using siRNA further demonstrated its regulatory effects on these cellular processes. Our results revealed a strong correlation between elevated CXCR4 expression and increased exhaustion of regulatory T cells (Tregs) in the TME. Furthermore, heightened CXCR4 expression was linked to increased TME heterogeneity, driven by oxidative stress and activation of the NF-κB pathway, promoting immune evasion and tumor progression. Silencing CXCR4 significantly inhibited the invasive and proliferative abilities of AGS and SNU-1 cells, while also reducing the expression of pro-inflammatory cytokines IL-1β and interleukin-6, thus alleviating chronic inflammation and improving TME conditions. In conclusion, our comprehensive investigation highlights CXCR4 as a key mediator of TME dynamics and immune modulation in GC. Targeting CXCR4 presents a promising therapeutic strategy to slow tumor progression by reducing Tregs-mediated immune exhaustion and TME heterogeneity, positioning it as a novel therapeutic target in GC treatment.

The 'Treg paradox' in inflammatory arthritis

Classic regulatory T (Treg) cells expressing CD4 and the hallmark transcription factor FOXP3 are integral to the prevention of multi-system autoimmunity. However, immune-mediated arthritis is often associated with increased numbers of Treg cells in the inflamed joints. To understand these seemingly conflicting observations, which we collectively describe as 'the Treg paradox', we provide an overview of Treg cell biology with a focus on Treg cell heterogeneity, function and dysfunction in arthritis. We discuss how the inflamed environment constrains the immunosuppressive activity of Treg cells while also promoting the differentiation of TH17-like Treg cell, exTreg cell (effector T cells that were formerly Treg cells), and osteoclastogenic Treg cell subsets that mediate tissue injury. We present a new framework to understand Treg cells in joint inflammation and define potential strategies for Treg cell-directed interventions in human inflammatory arthritis.

Regulatory T cell-associated gene signature correlates with prognostic risk and immune infiltration in patients with breast cancer

Background

Regulatory T cells (Tregs) play a pivotal role in the development, prognosis, and treatment of breast cancer. This study aimed to develop a Treg-associated gene signature that contributes to predict prognosis and therapy benefits in breast cancer.

Methods

Treg-associated genes were screened based on single-cell RNA-sequencing (RNA-seq) in TISCH2 database and the bulk RNA-seq in The Cancer Genome Atlas (TCGA) database. Treg-associated gene signature was identified via survival analysis, univariate cox, least absolute shrinkage and selection operator (LASSO) and multivariable Cox regression analyses. Immune status was assessed using single-sample gene set enrichment analysis (ssGSEA) and Estimation of STromal and Immune cells in MAlignant Tumor tissues using Expression data (ESTIMATE) algorithms. Drug sensitivity was estimated using pRRophetic. Gene set enrichment analysis (GSEA) was conducted to explore the changed pathways.

Results

A total of 169 genes were identified as Treg-associated genes, and close interactions existed among these genes. Kaplan-Meier (KM) survival and univariate cox revealed 29 prognostic genes (all P<0.05), and finally a six-gene prognostic signature including TBC1D4, PMAIP1, IFNG, LEF1, MZB1 and EZR was identified by LASSO and multivariable Cox. Based on this signature, patients in high-risk group exhibited a worse survival probability than those in low-risk group in the TCGA training dataset (P<0.001). Additionally, this signature showed a moderate predictive power for 1-, 3- and 5-year survival for breast cancer patients in both training dataset [area under the curve (AUC) =0.705, 0.678 and 0.668, respectively]. Similar predictive power for 1-, 3- and 5-year survival was also observed in validation datasets. Risk scores significantly differed between subgroups divided by clinicopathologic features, especially by molecular subtypes. Patients in high- and low-risk groups showed significant differences on infiltration abundance of multiple types of immune cells (such as, activated B cells/CD8+ T cells/CD4+ T cells), immune and stromal scores (all P<0.05). Moreover, sensitivity to 83 chemotherapeutic drugs such as lapatinib, methotrexate, and gefitinib were significantly differed between the two risk groups (all P<0.001).

Conclusions

This is the first to develop a Treg-associated gene signature for breast cancer, which could predict prognosis of patients and help to identify patients who might be benefit from immunotherapy and/or chemotherapy.

Engineering synthetic suppressor T cells that execute locally targeted immunoprotective programs

Immune homeostasis requires a balance of inflammatory and suppressive activities. To design cells potentially useful for local immune suppression, we engineered conventional CD4+ T cells with synthetic Notch (synNotch) receptors driving antigen-triggered production of anti-inflammatory payloads. Screening a diverse library of suppression programs, we observed the strongest suppression of cytotoxic T cell attack by the production of both anti-inflammatory factors (interleukin-10, transforming growth factor-β1, programmed death ligand 1) and sinks for proinflammatory cytokines (interleukin-2 receptor subunit CD25). Engineered cells with bespoke regulatory programs protected tissues from immune attack without systemic suppression. Synthetic suppressor T cells protected transplanted beta cell organoids from cytotoxic T cells. They also protected specific tissues from unwanted chimeric antigen receptor (CAR) T cell cross-reaction. Synthetic suppressor T cells are a customizable platform to potentially treat autoimmune diseases, organ rejection, and CAR T cell toxicities with spatial precision.

From promise to practice: CAR T and Treg cell therapies in autoimmunity and other immune-mediated diseases

Autoimmune diseases, characterized by the immune system's attack on the body's own tissues, affect millions of people worldwide. Current treatments, which primarily rely on broad immunosuppression and symptom management, are often associated with significant adverse effects and necessitate lifelong therapy. This review explores the next generation of therapies for immune-mediated diseases, including chimeric antigen receptor (CAR) T cell and regulatory T cell (Treg)-based approaches, which offer the prospect of targeted, durable disease remission. Notably, we highlight the emergence of CD19-targeted CAR T cell therapies, and their ability to drive sustained remission in B cell-mediated autoimmune diseases, suggesting a possible paradigm shift. Further, we discuss the therapeutic potential of Type 1 and FOXP3+ Treg and CAR-Treg cells, which aim to achieve localized immune modulation by targeting their activity to specific tissues or cell types, thereby minimizing the risk of generalized immunosuppression. By examining the latest advances in this rapidly evolving field, we underscore the potential of these innovative cell therapies to address the unmet need for long-term remission and potential tolerance induction in individuals with autoimmune and immune-mediated diseases.

Immune safety challenges facing the preclinical assessment and clinical progression of cell therapies

The promise of curative outcomes for life-limiting diseases using cell therapies is starting to become a reality, not only for patients with end-stage cancer, but also increasingly for regenerative therapies, including dentistry, ocular, neurodegenerative, and cardiac diseases. The introduction of often genetically modified cells into a patient can come with an extensive range of safety considerations. From an immune perspective, cell-based therapies carry inherent consequences and consideration of factors, such as the cell source (donor-derived autologous cells versus allogeneic cells), the intrinsic cellular nature of the therapy, and engineering/manufacturing methods, all of which influence the likelihood of inducing unwanted immune responses. Here, we provide an overview of the potential immune safety risks associated with cell therapies and explore possible mitigation approaches.

Identification of a novel PDC-E2 epitope in primary biliary cholangitis: Application for engineered Treg therapy

Primary biliary cholangitis (PBC) is a chronic autoimmune liver disease, characterized by progressive destruction of small intrahepatic bile ducts and portal inflammation. Treatment options are limited, with reliance on liver transplantation in advanced cases. The adaptive immune response is implicated in disease pathogenesis by the presence of anti-mitochondrial antibodies targeting the E2 subunit of the pyruvate dehydrogenase complex (PDC-E2) in 90-95 % of patients and T cells infiltrating the portal tracts. Here, we examined T cell responses to peptides derived from PDC-E2, with a focus on CD4 T cell responses restricted to HLA Class II DRB4∗01:01, an allele found in 62 % of PBC patients, to uncover PDC-E2 epitopes that could be used for engineered regulatory T cell (Treg; EngTreg) therapy. Using an activation-induced marker assay and single cell RNA-sequencing, we found clonal expansion of CD4 T cells reactive to PDC-E2 epitopes among both T conventional (Tconv) and Tregs. Those T cell receptor (TCR) repertoires were non-overlapping and private and included TCRs specific for a novel PDC-E2 epitope restricted to DRB4∗01:01. CD4 Tconv cells reactive to the PDC-E2 novel epitope showed phenotypic heterogeneity skewed towards T follicular helper cells. Using a TCR specific for this novel PDC-E2 epitope, we created an EngTreg that suppressed PDC-E2-specific polyclonal CD4 Tconv cells from PBC patients. This study advances knowledge of PDC-E2-specific T cell responses and introduces a novel PDC-E2 epitope recognized by both Tconv and Tregs. Generation of EngTreg specific for this epitope provides therapeutic potential for PBC.

A preclinical and phase I clinical study of ex vivo-expanded amyloid beta-specific human regulatory T cells in Alzheimer's disease

INTRODUCTION

Despite advancements in adoptive regulatory T cell (Treg) therapy, its application in Alzheimer's disease (AD) remains constrained by challenges in ex vivo Treg selection and expansion with antigen specificity. Our previous findings demonstrated the bystander suppressive immunomodulatory mechanism of ex vivo expanded amyloid β-specific mouse Tregs in AD models, prompting inquiry into the efficacy of ex vivo expanded human Tregs in AD.

METHODS

We developed an effective ex vivo expansion method for manufacturing amyloid β-specific human Tregs (Aβ-hTreg) and evaluated their safety and efficacy in 3xTg mouse models of AD and a phase 1 clinical trial with six AD patients. The phenotype of Aβ-hTreg was analyzed using single-cell transcriptomics. The clinical trial involved intravenous administration of Aβ-hTreg, with three patients receiving a low dose and three receiving a high dose. Exploratory assessments of effectiveness, including cognitive tasks and functional evaluations, were conducted ninety days post-treatment.

RESULTS

Behavioral spatial learning and memory impairment, neuroinflammatory and amyloid pathology were dramatically ameliorated by single intrathecal administration of ex vivo expanded Aβ-hTreg to 3xTg AD mice. Single cell transcriptomics analysis revealed alterations in five key genes within a cluster of Tregs under antigen-specific manufacturing conditions. In the clinical trial with six AD patients, dose-limiting toxicity was experienced by none of the participants within five days of receiving GMP-grade Aβ-hTreg (VT301), indicating its good tolerability. Although exploratory assessments of effectiveness did not reach statistically significant values among the groups, these findings offer valuable insights for AD treatment and management, guiding the planning of the next phase of clinical trials.

DISCUSSION

This study suggests that hTregs may modulate Alzheimer's disease pathology by suppressing neuroinflammation, while VT301 shows promise as a safe treatment option. However, further research is necessary to confirm its clinical efficacy and optimize treatment strategies.

TRIAL REGISTRATION

Title: A Study of Possibility of Using Regulatory T Cells (VT301) for Treatment of Alzheimer's Disease, ClinicalTrials.gov NCT05016427, Study approval date: Ministry of Food and Drug Safety of the Republic of Korea (MFDS) - August 31st, 2020, Institutional Review Board (IRB) of Seoul National University Hospital, Republic of Korea - September 29th, 2020, The date of first patient enrollment: December 7th, 2020. https://clinicaltrials.gov/study/NCT05016427.

Chimeric antigen receptor T-cell therapy in autoimmune diseases

The administration of T cells that have been modified to carry chimeric antigen receptors (CARs) aimed at B cells has been an effective strategy in treating B cell malignancies. This breakthrough has spurred the creation of CAR T cells intended to specifically reduce or alter the faulty immune responses associated with autoimmune disorders. Early positive outcomes from clinical trials involving CAR T cells that target the B cell protein CD19 in patients suffering from autoimmune diseases driven by B cells have been reported. Additional strategies are being developed to broaden the use of CAR T cell therapy and enhance its safety in autoimmune conditions. These include employing chimeric autoantireceptors (CAAR) to specifically eliminate B cells that are reactive to autoantigens, and using regulatory T cells (Tregs) engineered to carry antigen-specific CARs for precise immune modulation. This discussion emphasizes key factors such as choosing the right target cell groups, designing CAR constructs, defining tolerable side effects, and achieving a lasting immune modification, all of which are critical for safely integrating CAR T cell therapy in treating autoimmune diseases.

Regulatory T-cells: The Face-off of the Immune Balance

Regulatory T-cells (Tregs) play a crucial role in maintaining immune homeostasis, ensuring a balanced immune response. Tregs primarily operate in an antigen-specific fashion, facilitated by their distinct distribution within discrete niches. Tregs have been studied extensively, from their point of origin in the thymus origin to their fate in the periphery or organs. Signals received from antigen-presenting cells (APCs) stimulate Tregs to dampen inflammation. Almost all tumors are characterized by a pathological abundance of immune suppression in their microenvironment. Conversely, the lack thereof proves detrimental to immunological disorders. Achieving a balanced expression of Tregs in relation to other immune compartments is important in establishing an effective and adaptable immune tolerance towards cancer cells and autoantigens. In the context of cancer, it is essential to decrease the frequency of Tregs to overcome tumor suppression. A lower survival rate is associated with the presence of excessive exhausted effector immune cells and an increased frequency of regulatory cells. However, when it comes to treating graft rejection and autoimmune diseases, the focus lies on immune tolerance and the transfer of Tregs. Here, we explore the complex mechanisms that Tregs use in human disease to balance effector immune cells.

Chimeric antigen receptor T cell therapy for autoimmune disease

Infusion of T cells engineered to express chimeric antigen receptors (CARs) that target B cells has proven to be a successful treatment for B cell malignancies. This success inspired the development of CAR T cells to selectively deplete or modulate the aberrant immune responses that underlie autoimmune disease. Promising results are emerging from clinical trials of CAR T cells targeting the B cell protein CD19 in patients with B cell-driven autoimmune diseases. Further approaches are being designed to extend the application and improve safety of CAR T cell therapy in the setting of autoimmunity, including the use of chimeric autoantibody receptors to selectively deplete autoantigen-specific B cells and the use of regulatory T cells engineered to express antigen-specific CARs for targeted immune modulation. Here, we highlight important considerations, such as optimal target cell populations, CAR construct design, acceptable toxicities and potential for lasting immune reset, that will inform the eventual safe adoption of CAR T cell therapy for the treatment of autoimmune diseases.

Human OX40L-CAR-Tregs target activated antigen-presenting cells and control T cell alloreactivity

Regulatory T cells (Tregs) make major contributions to immune homeostasis. Because Treg dysfunction can lead to both allo- and autoimmunity, there is interest in correcting these disorders through Treg adoptive transfer. Two of the central challenges in clinically deploying Treg cellular therapies are ensuring phenotypic stability and maximizing potency. Here, we describe an approach to address both issues through the creation of OX40 ligand (OX40L)-specific chimeric antigen receptor (CAR)-Tregs under the control of a synthetic forkhead box P3 (FOXP3) promoter. The creation of these CAR-Tregs enabled selective Treg stimulation by engagement of OX40L, a key activation antigen in alloimmunity, including both graft-versus-host disease and solid organ transplant rejection, and autoimmunity, including rheumatoid arthritis, systemic sclerosis, and systemic lupus erythematosus. We demonstrated that OX40L-CAR-Tregs were robustly activated in the presence of OX40L-expressing cells, leading to up-regulation of Treg suppressive proteins without induction of proinflammatory cytokine production. Compared with control Tregs, OX40L-CAR-Tregs more potently suppressed alloreactive T cell proliferation in vitro and were directly inhibitory toward activated monocyte-derived dendritic cells (DCs). We identified trogocytosis as one of the central mechanisms by which these CAR-Tregs effectively decrease extracellular display of OX40L, resulting in decreased DC stimulatory capacity. OX40L-CAR-Tregs demonstrated an enhanced ability to control xenogeneic graft-versus-host disease compared with control Tregs without abolishing the graft-versus-leukemia effect. These results suggest that OX40L-CAR-Tregs may have wide applicability as a potent cellular therapy to control both allo- and autoimmune diseases.

Regulatory T Cells in Acute Respiratory Distress Syndrome: Current Status and Potential for Future Immunotherapies

This Clinical Focus Review aims to comprehensively assess current knowledge regarding the biology of Tregs and their role in COVID-19–associated and nonassociated ARDS, focusing on their involvement during the acute and resolution phases of the disease. The authors discuss the potential of Treg-based cell therapies and drugs targeting Tregs as therapeutic strategies in ARDS.

Regulatory T cells administration reduces anxiety-like behavior in mice submitted to chronic restraint stress

Background

Major depression disorder (MDD) and anxiety are common mental disorders that significantly affect the quality of life of those who suffer from them, altering the person's normal functioning. From the biological perspective, the most classical hypothesis explaining their occurrence relies on neurotransmission and hippocampal excitability alterations. However, around 30% of MDD patients do not respond to medication targeting these processes. Over the last decade, the involvement of inflammatory responses in depression and anxiety pathogenesis has been strongly acknowledged, opening the possibility of tackling these disorders from an immunological point of view. In this context, regulatory T cells (Treg cells), which naturally maintain immune homeostasis by suppressing inflammation could be promising candidates for their therapeutic use in mental disorders.

Methods

To test this hypothesis, C57BL/6 adult male mice were submitted to classical stress protocols to induce depressive and anxiety-like behavior; chronic restriction stress (CRS), and chronic unpredictable stress (CUS). Some of the stressed mice received a single adoptive transfer of Treg cells during stress protocols. Mouse behavior was analyzed through the open field (OFT) and forced swim test (FST). Blood and spleen samples were collected for T cell analysis using cell cytometry, while brains were collected to study changes in microglia by immunohistochemistry.

Results

Mice submitted to CRS and CUS develop anxiety and depressive-like behavior, and only CRS mice exhibit lower frequencies of circulating Treg cells. Adoptive transfer of Treg cells decreased anxiety-like behavior in the OFT only in CRS model, but not depressive behavior in FST in neither of the two models. In CRS mice, Treg cells administration lowered the number of microglia in the hippocampus, which increased due this stress paradigm, and restored its arborization. However, in CUS mice, Treg cells administration increased microglia number with no significant effect on their arborization.

Conclusion

Our results for effector CD4+ T cells in the spleen and microglia number and morphology in the hippocampus add new evidence in favor of the participation of inflammatory responses in the development of depressive and anxiety-like behavior and suggest that the modulation of key immune cells such as Treg cells, could have beneficial effects on these disorders.

Advancing mouse models for transplantation research

Mouse models have been instrumental in understanding mechanisms of transplant rejection and tolerance, but cross-study reproducibility and translation of experimental findings into effective clinical therapies are issues of concern. The Mouse Models in Transplantation symposium gathered scientists and physician-scientists involved in basic and clinical research in transplantation to discuss the strengths and limitations of mouse transplant models and strategies to enhance their utility. Participants recognized that increased procedure standardization, including the use of prespecified, defined endpoints, and statistical power analyses, would benefit the field. They also discussed the generation of new models that incorporate environmental and genetic variables affecting clinical outcomes as potentially important. If implemented, these strategies are expected to improve the reproducibility of mouse studies and increase their translation to clinical trials and, ideally, new Food and Drug Administration-approved drugs.

Past, present, and future of cell replacement therapy for parkinson's disease: a novel emphasis on host immune responses

Parkinson's disease (PD) stands as the second most common neurodegenerative disorder after Alzheimer's disease, and its prevalence continues to rise with the aging global population. Central to the pathophysiology of PD is the specific degeneration of midbrain dopamine neurons (mDANs) in the substantia nigra. Consequently, cell replacement therapy (CRT) has emerged as a promising treatment approach, initially supported by various open-label clinical studies employing fetal ventral mesencephalic (fVM) cells. Despite the initial favorable results, fVM cell therapy has intrinsic and logistical limitations that hinder its transition to a standard treatment for PD. Recent efforts in the field of cell therapy have shifted its focus towards the utilization of human pluripotent stem cells, including human embryonic stem cells and induced pluripotent stem cells, to surmount existing challenges. However, regardless of the transplantable cell sources (e.g., xenogeneic, allogeneic, or autologous), the poor and variable survival of implanted dopamine cells remains a major obstacle. Emerging evidence highlights the pivotal role of host immune responses following transplantation in influencing the survival of implanted mDANs, underscoring an important area for further research. In this comprehensive review, building upon insights derived from previous fVM transplantation studies, we delve into the functional ramifications of host immune responses on the survival and efficacy of grafted dopamine cells. Furthermore, we explore potential strategic approaches to modulate the host immune response, ultimately aiming for optimal outcomes in future clinical applications of CRT for PD.

Role of FoxP3+ Regulatory T Cells in Modulating Immune Responses to Adeno-Associated Virus Gene Therapy

Adeno-associated virus (AAV) gene therapy is making rapid strides owing to its wide range of therapeutic applications. However, development of serious immune responses to the capsid antigen or the therapeutic transgene product hinders its full clinical impact. Immune suppressive (IS) drug treatments have been used in various clinical trials to prevent the deleterious effects of cytotoxic T cells to the viral vector or transgene, although there is no consensus on the best treatment regimen, dosage, or schedule. Regulatory T cells (Tregs) are crucial for maintaining tolerance against self or nonself antigens. Of importance, Tregs also play an important role in dampening immune responses to AAV gene therapy, including tolerance induction to the transgene product. Approaches to harness the tolerogenic effect of Tregs include the use of selective IS drugs that expand existing Tregs, and skew activated conventional T cells into antigen-specific peripherally induced Tregs. In addition, Tregs can be expanded ex vivo and delivered as cellular therapy. Furthermore, receptor engineering can be used to increase the potency and specificity of Tregs allowing for suppression at lower doses and reducing the risk of disrupting protective immunity. Because immune-mediated toxicities to AAV vectors are a concern in the clinic, strategies that can enhance or preserve Treg function should be considered to improve both the safety and efficacy of AAV gene therapy.

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.

From stem cells to regulatory T cells: A tale of plasticity

In this issue, Yano et al.1 present a method to obtain suppressive regulatory T (Treg) cells from human induced pluripotent stem cells (hiPSCs). This approach has the potential to address the low Treg cell yields of current ex vivo Treg cell expansion and induction protocols, an unmet challenge for autologous Treg cell treatments.

Many Faces of Regulatory T Cells: Heterogeneity or Plasticity?

Regulatory T cells (Tregs) are essential for maintaining the immune balance in normal and pathological conditions. In autoimmune diseases and transplantation, they restrain the loss of self-tolerance and promote engraftment, whereas in cancer, an increase in Treg numbers is mostly associated with tumor growth and poor prognosis. Numerous markers and their combinations have been used to identify Treg subsets, demonstrating the phenotypic diversity of Tregs. The complexity of Treg identification can be hampered by the unstable expression of some markers, the decrease in the expression of a specific marker over time or the emergence of a new marker. It remains unclear whether such phenotypic shifts are due to new conditions or whether the observed changes are due to initially different populations. In the first case, cellular plasticity is observed, whereas in the second, cellular heterogeneity is observed. The difference between these terms in relation to Tregs is rather blurred. Considering the promising perspectives of Tregs in regenerative cell-based therapy, the existing confusing data on Treg phenotypes require further investigation and analysis. In our review, we introduce criteria that allow us to distinguish between the heterogeneity and plasticity of Tregs normally and pathologically, taking a closer look at their diversity and drawing the line between two terms.

A phase 2 randomized trial with autologous polyclonal expanded regulatory T cells in children with new-onset type 1 diabetes

CD4+CD25hiCD127lo/-FOXP3+ regulatory T cells (Tregs) play a key role in preventing autoimmunity. In autoimmune type 1 diabetes (T1D), adoptive transfer of autologous polyclonal Tregs has been shown to be safe in adults in phase 1 clinical trials. We explored factors contributing to efficacy of autologous polyclonal expanded Tregs (expTregs) in a randomized phase 2 multi-center, double-blind, clinical trial (Sanford/Lisata Therapeutics T-Rex phase 2 trial, ClinicalTrials.gov NCT02691247). One hundred ten treated children and adolescents with new-onset T1D were randomized 1:1:1 to high-dose (20 × 106 cells/kilogram) or low-dose (1 × 106 cells/kilogram) treatments or to matching placebo. Cytometry as well as bulk and single-cell RNA sequencing were performed on selected expTregs and peripheral blood samples from participants. The single doses of expTregs were safe but did not prevent decline in residual β cell function over 1 year compared to placebo (P = 0.94 low dose, P = 0.21 high dose), regardless of age or baseline C-peptide. ExpTregs were highly activated and suppressive in vitro. A transient increase of activated memory Tregs was detectable 1 week after infusion in the high-dose cohort, suggesting effective transfer of expTregs. However, the in vitro fold expansion of expTregs varied across participants, even when accounting for age, and lower fold expansion and its associated gene signature were linked with better C-peptide preservation regardless of Treg dose. These results suggest that a single dose of polyclonal expTregs does not alter progression in T1D; instead, Treg quality may be an important factor.

Regulatory T cells: Supporting lung homeostasis and promoting resolution and repair after lung injury

Regulatory T cells, characterized by their expression of the transcription factor Forkhead box P3, are indispensable in maintaining immune homeostasis. The respiratory system is constantly exposed to many environmental challenges, making it susceptible to various insults and infections. Regulatory T cells play essential roles in maintaining homeostasis in the lung and promoting repair after injury. Regulatory T cell function dysregulation can lead to inflammation, tissue damage, or aberrant repair. Research on regulatory T cell mechanisms in the lung has unveiled their influence on lung inflammation and repair mechanisms. In this review, our goal is to highlight the advances in regulatory T cell biology with respect to lung injury and resolution. We further provide a perspective that a deeper understanding of regulatory T cell interactions in the lung microenvironment in health and disease states offers opportunities for therapeutic interventions as treatments to promote lung health.

Therapeutic induction of antigen-specific immune tolerance

The development of therapeutic approaches for the induction of robust, long-lasting and antigen-specific immune tolerance remains an important unmet clinical need for the management of autoimmunity, allergy, organ transplantation and gene therapy. Recent breakthroughs in our understanding of immune tolerance mechanisms have opened new research avenues and therapeutic opportunities in this area. Here, we review mechanisms of immune tolerance and novel methods for its therapeutic induction.

Research progress of autoimmune diseases based on induced pluripotent stem cells

Autoimmune diseases can damage specific or multiple organs and tissues, influence the quality of life, and even cause disability and death. A 'disease in a dish' can be developed based on patients-derived induced pluripotent stem cells (iPSCs) and iPSCs-derived disease-relevant cell types to provide a platform for pathogenesis research, phenotypical assays, cell therapy, and drug discovery. With rapid progress in molecular biology research methods including genome-sequencing technology, epigenetic analysis, '-omics' analysis and organoid technology, large amount of data represents an opportunity to help in gaining an in-depth understanding of pathological mechanisms and developing novel therapeutic strategies for these diseases. This paper aimed to review the iPSCs-based research on phenotype confirmation, mechanism exploration, drug discovery, and cell therapy for autoimmune diseases, especially multiple sclerosis, inflammatory bowel disease, and type 1 diabetes using iPSCs and iPSCs-derived cells.

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.

IPEX syndrome from diagnosis to cure, learning along the way

In the past 2 decades, a significant number of studies have been published describing the molecular and clinical aspects of immune dysregulation polyendocrinopathy enteropathy X-linked (IPEX) syndrome. These studies have refined our knowledge of this rare yet prototypic genetic autoimmune disease, advancing the diagnosis, broadening the clinical spectrum, and improving our understanding of the underlying immunologic mechanisms. Despite these advances, Forkhead box P3 mutations have devastating consequences, and treating patients with IPEX syndrome remains a challenge, even with safer strategies for hematopoietic stem cell transplantation and gene therapy becoming a promising reality. The aim of this review was to highlight novel features of the disease to further advance awareness and improve the diagnosis and treatment of patients with IPEX syndrome.

Enhancing Human Treg Cell Induction through Engineered Dendritic Cells and Zinc Supplementation

Regulatory T (Treg) cells hold promise for the ultimate cure of immune-mediated diseases. However, how to effectively restore Treg function in patients remains unknown. Previous reports suggest that activated dendritic cells (DCs) de novo synthesize locally high concentrations of 1,25-dihydroxy vitamin D, i.e., the active vitamin D or 1,25(OH)2D by upregulating the expression of 25-hydroxy vitamin D 1α-hydroxylase. Although 1,25(OH)2D has been shown to induce Treg cells, DC-derived 1,25(OH)2D only serves as a checkpoint to ensure well-balanced immune responses. Our animal studies have shown that 1,25(OH)2D requires high concentrations to generate Treg cells, which can cause severe side effects. In addition, our animal studies have also demonstrated that dendritic cells (DCs) overexpressing the 1α-hydroxylase de novo synthesize the effective Treg-inducing 1,25(OH)2D concentrations without causing the primary side effect of hypercalcemia (i.e., high blood calcium levels). This study furthers our previous animal studies and explores the efficacy of the la-hydroxylase-overexpressing DCs in inducing human CD4+FOXP3+regulatory T (Treg) cells. We discovered that the effective Treg-inducing doses of 1,25(OH)2D were within a range. Additionally, our data corroborated that the 1α-hydroxylase-overexpressing DCs synthesized 1,25(OH)2D within this concentration range in vivo, thus facilitating effective Treg cell induction. Moreover, this study demonstrated that 1α-hydroxylase expression levels were pivotal for DCs to induce Treg cells because physiological 25(OH)D levels were sufficient for the engineered but not parental DCs to enhance Treg cell induction. Interestingly, adding non-toxic zinc concentrations significantly augmented the Treg-inducing capacity of the engineered DCs. Our new findings offer a novel therapeutic avenue for immune-mediated human diseases, such as inflammatory bowel disease, type 1 diabetes, and multiple sclerosis, by integrating zinc with the 1α-hydroxylase-overexpressing DCs.

The Role of Gut Microbiota-Derived Lithocholic Acid, Deoxycholic Acid and Their Derivatives on the Function and Differentiation of Immune Cells

A wide variety and large number of bacterial species live in the gut, forming the gut microbiota. Gut microbiota not only coexist harmoniously with their hosts, but they also induce significant effects on each other. The composition of the gut microbiota can be changed due to environmental factors such as diet and antibiotic intake. In contrast, alterations in the composition of the gut microbiota have been reported in a variety of diseases, including intestinal, allergic, and autoimmune diseases and cancer. The gut microbiota metabolize exogenous dietary components ingested from outside the body to produce short-chain fatty acids (SCFAs) and amino acid metabolites. Unlike SCFAs and amino acid metabolites, the source of bile acids (BAs) produced by the gut microbiota is endogenous BAs from the liver. The gut microbiota metabolize BAs to generate secondary bile acids, such as lithocholic acid (LCA), deoxycholic acid (DCA), and their derivatives, which have recently been shown to play important roles in immune cells. This review focuses on current knowledge of the role of LCA, DCA, and their derivatives on immune cells.

Treg Cells in Ischemic Stroke: A Small Key to a Great Orchestrion

Ischemic stroke is a global medical problem and one of the leading causes of death or disability worldwide. The main approach of ischemic stroke therapy in the most acute period, which can prevent or minimize the development of a neurological deficit, is the restoration of the blood flow in the ischemic brain tissue using enzymatic thrombolysis or endovascular thromboextraction. When the therapeutic window is missed, the modulation of the acute inflammatory response may play an important role in determining the fate of neurons in the penumbra. The key players in this process are T-regulatory cells (Tregs) an immunosuppressive population of CD4+ T-cells with the CD4+, CD25+ CD127low, FoxP3+ phenotype. Despite the existing reports that Tregs (or certain Treg subpopulations) can exacerbate microcirculatory disorders in the ischemic tissue, many stadies convincingly suggest the positive role of Tregs in ischemic stroke. Resident CD69+ Tregs found in the normal mammalian brain have neuroprotective activity, produce IL-10 and other anti-inflammatory cytokines, control astrogliosis, and downregulate cytotoxic subpopulations of T cells and microglia. Systemic administration of Treg in stroke is accompained by a decrease in the volume of cerebral infarction and decreased levels of secondary neuronal death. Thus, the methods allowing Treg activation and expansion ex vivo open up several new avenues for the immunocorrection not only in systemic and autoimmune diseases, but, potentially, in the neuroprotective therapy for ischemic stroke. The relationship between Treg, inflammation, and cerebrovascular pathology is of particular interest in the case of ischemic stroke and COVID-19 as a comorbidity. It has been demonstrated that systemic inflammation caused by SARS-CoV-2 infection leads to a significant suppression of Treg, which is accompanied by an increased risk for the development of ischemic stroke and other neurological complications. Overall, the information summarized herein about the possible therapeutic potential of Treg in cerebrovascular pathology may be of practical interest not only for researchers, but also for clinicians.