CD4+CD25+ T regulatory cells control anti-islet CD8+ T cells through TGF-beta-TGF-beta receptor interactions in type 1 diabetes

Defining Human Regulatory T Cells beyond FOXP3: The Need to Combine Phenotype with Function

Regulatory T cells (Tregs) are essential to maintain immune homeostasis by promoting self-tolerance. Reduced Treg numbers or functionality can lead to a loss of tolerance, increasing the risk of developing autoimmune diseases. An overwhelming variety of human Tregs has been described, based on either specific phenotype, tissue compartment, or pathological condition, yet the bulk of the literature only addresses CD25-positive and CD127-negative cells, coined by naturally occurring Tregs (nTregs), most of which express the transcription factor Forkhead box protein 3 (FOXP3). While the discovery of FOXP3 was seminal to understanding the origin and biology of nTregs, there is evidence in humans that not all T cells expressing FOXP3 are regulatory, and that not all Tregs express FOXP3. Namely, the activation of human T cells induces the transient expression of FOXP3, irrespective of whether they are regulatory or inflammatory effectors, while some induced T cells that may be broadly defined as Tregs (e.g., Tr1 cells) typically lack demethylation and do not express FOXP3. Furthermore, it is unknown whether and how many nTregs exist without FOXP3 expression. Several other candidate regulatory molecules, such as GITR, Lag-3, GARP, GPA33, Helios, and Neuropilin, have been identified but subsequently discarded as Treg-specific markers. Multiparametric analyses have uncovered a plethora of Treg phenotypes, and neither single markers nor combinations thereof can define all and only Tregs. To date, only the functional capacity to inhibit immune responses defines a Treg and distinguishes Tregs from inflammatory T cells (Teffs) in humans. This review revisits current knowledge of the Treg universe with respect to their heterogeneity in phenotype and function. We propose that it is unavoidable to characterize human Tregs by their phenotype in combination with their function, since phenotype alone does not unambiguously define Tregs. There is an unmet need to align the expression of specific markers or combinations thereof with a particular suppressive function to coin functional Treg entities and categorize Treg diversity.

Artemisinin and its derivatives as promising therapies for autoimmune diseases

Artemisinin, a traditional Chinese medicine with remarkable antimalarial activity. In recent years, studies demonstrated that artemisinin and its derivatives (ARTs) showed anti-inflammatory and immunoregulatory effects. ARTs have been developed and gradually applied to treat autoimmune and inflammatory diseases. However, their role in the treament of patients with autoimmune and inflammatory diseases in particular is less well recognized. This review will briefly describe the history of ARTs use in patients with autoimmune and inflammatory diseases, the theorized mechanisms of action of the agents ARTs, their efficacy in patients with autoinmmune and inflammatory diseases. Overall, ARTs have numerous beneficial effects in patients with autoimmune and inflammatory diseases, and have a good safety profile.

Immunomodulation of streptozotocin induced Type 1 diabetes mellitus in mouse model by Macrophage migration inhibitory factor-2 (MIF-2) homologue of human lymphatic filarial parasite, Wuchereria bancrofti

Helminth parasites modulate the host immune system to ensure a long-lasting asymptomatic form of infection generally, mediated by the secretion of immunomodulatory molecules and one such molecule is a homologue of human host cytokine, Macrophage migratory Inhibitory Factor (hMIF). In this study, we sought to understand the role of homologue of hMIF from the lymphatic filarial parasite, Wuchereria bancrofti (Wba-MIF2), in the immunomodulation of the Streptozotocin (STZ)-induced Type1 Diabetes Mellitus (T1DM) animal model. Full-length recombinant Wba-MIF2 was expressed and found to have both oxidoreductase and tautomerase activities. Wba-MIF2 recombinant protein was treated to STZ induced T1DM animals, and after 5 weeks pro-inflammatory (IL-1, IL-2, IL-6, TNF-α, IFN-γ) and anti-inflammatory (IL-4, IL-10) cytokines and gene expressions were determined in sera samples and spleen respectively. Pro-inflammatory and anti-inflammatory cytokine levels were significantly (p<0.05) up-regulated and down-regulated respectively, in the STZ-T1DM animals, as compared to treated groups. Histopathology showed macrophage infiltration and greater damage of islets of beta cells in the pancreatic tissue of STZ-T1DM animals, than Wba-MIF2 treated STZ-T1DM animals. The present study clearly showed the potential of Wba-MIF2 as an immunomodulatory molecule, which could modulate the host immune system in the STZ-T1DM mice model from a pro-inflammatory to anti-inflammatory milieu.

Umbilical cord blood and peripheral blood-derived regulatory T cells therapy: Progress in type 1 diabetes

Regulatory T cells (Tregs) are key regulators for the inflammatory response and play a role in maintaining the immune tolerance. Type 1 diabetes (T1D) is a relatively common autoimmune disease that results from the loss of immune tolerance to β-cell-associated antigens. Preclinical models have demonstrated the safety and efficacy of Tregs given in transplant rejection and autoimmune diseases such as T1D. Adoptive transfer of Tregs has been utilized in clinical trials for over a decade. However, the achievement of the adoptive transfer of Tregs therapy in clinical application remains challenging. In this review, we highlight the characterization of Tregs and compare the differences between umbilical cord blood and adult peripheral blood-derived Tregs. Additionally, we summarize conditional modifications in the expansion of Tregs in clinical trials, especially for the treatment of T1D. Finally, we discuss the existing technical challenges for Tregs in clinical trials for the treatment of T1D.

Intricacies of TGF-β signaling in Treg and Th17 cell biology

Balanced immunity is pivotal for health and homeostasis. CD4+ helper T (Th) cells are central to the balance between immune tolerance and immune rejection. Th cells adopt distinct functions to maintain tolerance and clear pathogens. Dysregulation of Th cell function often leads to maladies, including autoimmunity, inflammatory disease, cancer, and infection. Regulatory T (Treg) and Th17 cells are critical Th cell types involved in immune tolerance, homeostasis, pathogenicity, and pathogen clearance. It is therefore critical to understand how Treg and Th17 cells are regulated in health and disease. Cytokines are instrumental in directing Treg and Th17 cell function. The evolutionarily conserved TGF-β (transforming growth factor-β) cytokine superfamily is of particular interest because it is central to the biology of both Treg cells that are predominantly immunosuppressive and Th17 cells that can be proinflammatory, pathogenic, and immune regulatory. How TGF-β superfamily members and their intricate signaling pathways regulate Treg and Th17 cell function is a question that has been intensely investigated for two decades. Here, we introduce the fundamental biology of TGF-β superfamily signaling, Treg cells, and Th17 cells and discuss in detail how the TGF-β superfamily contributes to Treg and Th17 cell biology through complex yet ordered and cooperative signaling networks.

Pancreatic draining lymph nodes (PLNs) serve as a pathogenic hub contributing to the development of type 1 diabetes

Type 1 diabetes (T1D) is a chronic, progressive autoinflammatory disorder resulting from the breakdown of self-tolerance and unrestrained β cell-reactive immune response. Activation of immune cells is initiated in islet and amplified in lymphoid tissues, especially those pancreatic draining lymph nodes (PLNs). The knowledge of PLNs as the hub of aberrant immune response is continuously being replenished and renewed. Here we provide a PLN-centered view of T1D pathogenesis and emphasize that PLNs integrate signal inputs from the pancreas, gut, viral infection or peripheral circulation, undergo immune remodeling within the local microenvironment and export effector cell components into pancreas to affect T1D progression. In accordance, we suggest that T1D intervention can be implemented by three major ways: cutting off the signal inputs into PLNs (reduce inflammatory β cell damage, enhance gut integrity and control pathogenic viral infections), modulating the immune activation status of PLNs and blocking the outputs of PLNs towards pancreatic islets. Given the dynamic and complex nature of T1D etiology, the corresponding intervention strategy is thus required to be comprehensive to ensure optimal therapeutic efficacy.

Regulatory T cells targeting a pathogenic MHC class II: Insulin peptide epitope postpone spontaneous autoimmune diabetes

Introduction

In spontaneous type 1 diabetes (T1D) non-obese diabetic (NOD) mice, the insulin B chain peptide 9-23 (B:9-23) can bind to the MHC class II molecule (IAg7) in register 3 (R3), creating a bimolecular IAg7/InsulinB:9-23 register 3 conformational epitope (InsB:R3). Previously, we showed that the InsB:R3-specific chimeric antigen receptor (CAR), constructed using an InsB:R3-monoclonal antibody, could guide CAR-expressing CD8 T cells to migrate to the islets and pancreatic lymph nodes. Regulatory T cells (Tregs) specific for an islet antigen can broadly suppress various pathogenic immune cells in the islets and effectively halt the progression of islet destruction. Therefore, we hypothesized that InsB:R3 specific Tregs would suppress autoimmune reactivity in islets and efficiently protect against T1D.

Methods

To test our hypothesis, we produced InsB:R3-Tregs and tested their disease-protective effects in spontaneous T1D NOD.CD28-/- mice.

Results

InsB:R3-CAR expressing Tregs secrete IL-10 dominated cytokines upon engagement with InsB:R3 antigens. A single infusion of InsB:R3 Tregs delayed the onset of T1D in 95% of treated mice, with 35% maintaining euglycemia for two healthy lifespans, readily home to the relevant target whereas control Tregs did not. Our data demonstrate that Tregs specific for MHC class II: Insulin peptide epitope (MHCII/Insulin) protect mice against T1D more efficiently than polyclonal Tregs lacking islet antigen specificity, suggesting that the MHC II/insulin-specific Treg approach is a promising immune therapy for safely preventing T1D.

TCR repertoire landscape reveals macrophage-mediated clone deletion in endotoxin tolerance

BACKGROUND

Endotoxin tolerance (ET) is a protective mechanism in the process of sepsis, septic shock, and their sequelae including uncontrolled inflammation. Accumulating evidence has shown that peripheral T cells contribute to the induction of ET. However, what and how T-cell development contributes to ET inductions remain unclear.

METHODS

Mice were intraperitoneally injected with LPS at a concentration of 5 mg/kg to establish an LPS tolerance model and were divided into two groups: a group examined 72 h after LPS injection (72-h group) and a group examined 8 days after LPS injection (8-day group). Injection of PBS was used as a control. We performed high-throughput sequencing to analyze the characteristics and changes of CD4⁺SP TCRβ CDR3 repertoires with respect to V direct to J rearrangement during the ET induction. Moreover, the proportion and proliferation, as well as surface molecules such as CD80 and CD86, of F4/80⁺ macrophages were analyzed using FCM. Furthermore, ACT assay was designed and administered by the tail vein into murine LPS-induced mouse model to evaluate the role of F4/80⁺ macrophages on the development of CD4⁺SP thymocytes in ET condition.

RESULTS

We found that the frequency and characteristics of the TCRβ chain CDR3 changed obviously under condition of ET, indicating the occurrence of TCR rearrangement and thymocyte diversification. Moreover, the absolute numbers of F4/80⁺ macrophages, but not other APCs, were increased in thymic medulla at 72-h group, accompanied by the elevated function-related molecules of F4/80⁺ macrophages. Furthermore, adoptively transferred OVA_332-339 peptide-loaded macrophages into Rag-1^-/- mice induced the clone deletion of OVA-specific CD4⁺SP, thereby ameliorating the pathology in lung tissue in LPS challenge.

CONCLUSIONS

These data reveal that the frequency and characteristics of the TCRβ chain CDR3 undergo dynamic programming under conditions of LPS tolerance. Furthermore, the peripheral macrophages may be a key factor which carry peripheral antigen to thymic medulla and affect the negative selection of T-cell population, thereby contributing to the formation of ET. These results suggest that the clone selection in thymus in ET may confer protection against microbial sepsis.

Regulatory T cells suppress the formation of potent KLRK1 and IL-7R expressing effector CD8 T cells by limiting IL-2

Regulatory T cells (Tregs) are indispensable for maintaining self-tolerance by suppressing conventional T cells. On the other hand, Tregs promote tumor growth by inhibiting anticancer immunity. In this study, we identified that Tregs increase the quorum of self-reactive CD8⁺ T cells required for the induction of experimental autoimmune diabetes in mice. Their major suppression mechanism is limiting available IL-2, an essential T-cell cytokine. Specifically, Tregs inhibit the formation of a previously uncharacterized subset of antigen-stimulated KLRK1⁺ IL-7R⁺ (KILR) CD8⁺ effector T cells, which are distinct from conventional effector CD8⁺ T cells. KILR CD8⁺ T cells show superior cell-killing abilities in vivo. The administration of agonistic IL-2 immunocomplexes phenocopies the absence of Tregs, i.e., it induces KILR CD8⁺ T cells, promotes autoimmunity, and enhances antitumor responses in mice. Counterparts of KILR CD8⁺ T cells were found in the human blood, revealing them as a potential target for immunotherapy.

Regulatory T-cell-derived interleukin-15 shapes cytotoxic T cell memory

It is well known that regulatory T-cells (Tregs) are required to prevent autoimmunity, but they may also have some less-well understood immune-stimulatory effects. In particular, in CD8⁺ T-cell responses Tregs select high-affinity clones upon priming and promote memory by inhibiting inflammation-dependent generation of short-lived effector cells. In the current issue of the European Journal of Immunology [Eur. J. Immunol. 2023. 53: 2149400], Madi et al. report the surprising finding that human and murine FOXP3⁺ Tregs are a physiologically relevant source of IL-15, a homeostatic cytokine that promotes antigen-independent maintenance of CD8⁺ memory T-cells. In mice that lack IL-15 selectively in FOXP3⁺ Tregs the authors show that the composition of the CD8⁺ T-cell memory pool is altered in the absence of Treg-derived IL-15, since a subset of terminally effector memory cells is drastically reduced. Otherwise Treg-derived IL-15 is dispensable for antiviral immune responses and the generation of anti-viral CD8⁺ memory T-cells. These findings add to our understanding of the multifaceted role of Tregs in immune responses, and how IL-15 derived from different cellular sources maintains anti-viral T-cell memory.

Development of Adaptive Immunity and Its Role in Lung Remodeling

Asthma is characterized by airflow limitations resulting from bronchial closure, which can be either reversible or fixed due to changes in airway tissue composition and structure, also known as remodeling. Airway remodeling is defined as increased presence of mucins-producing epithelial cells, increased thickness of airway smooth muscle cells, angiogenesis, increased number and activation state of fibroblasts, and extracellular matrix (ECM) deposition. Airway inflammation is believed to be the main cause of the development of airway remodeling in asthma. In this chapter, we will review the development of the adaptive immune response and the impact of its mediators and cells on the elements defining airway remodeling in asthma.

Leverage biomaterials to modulate immunity for type 1 diabetes

The pathogeny of type 1 diabetes (T1D) is mainly provoked by the β-cell loss due to the autoimmune attack. Critically, autoreactive T cells firsthand attack β-cell in islet, that results in the deficiency of insulin in bloodstream and ultimately leads to hyperglycemia. Hence, modulating immunity to conserve residual β-cell is a desirable way to treat new-onset T1D. However, systemic immunosuppression makes patients at risk of organ damage, infection, even cancers. Biomaterials can be leveraged to achieve targeted immunomodulation, which can reduce the toxic side effects of immunosuppressants. In this review, we discuss the recent advances in harness of biomaterials to immunomodulate immunity for T1D. We investigate nanotechnology in targeting delivery of immunosuppressant, biological macromolecule for β-cell specific autoreactive T cell regulation. We also explore the biomaterials for developing vaccines and facilitate immunosuppressive cells to restore immune tolerance in pancreas.

Rebooting Regulatory T Cell and Dendritic Cell Function in Immune-Mediated Inflammatory Diseases: Biomarker and Therapy Discovery under a Multi-Omics Lens

Immune-mediated inflammatory diseases (IMIDs) are a group of autoimmune and chronic inflammatory disorders with constantly increasing prevalence in the modern world. The vast majority of IMIDs develop as a consequence of complex mechanisms dependent on genetic, epigenetic, molecular, cellular, and environmental elements, that lead to defects in immune regulatory guardians of tolerance, such as dendritic (DCs) and regulatory T (Tregs) cells. As a result of this dysfunction, immune tolerance collapses and pathogenesis emerges. Deeper understanding of such disease driving mechanisms remains a major challenge for the prevention of inflammatory disorders. The recent renaissance in high throughput technologies has enabled the increase in the amount of data collected through multiple omics layers, while additionally narrowing the resolution down to the single cell level. In light of the aforementioned, this review focuses on DCs and Tregs and discusses how multi-omics approaches can be harnessed to create robust cell-based IMID biomarkers in hope of leading to more efficient and patient-tailored therapeutic interventions.

Endothelial Cell TGF-β (Transforming Growth Factor-Beta) Signaling Regulates Venous Adaptive Remodeling to Improve Arteriovenous Fistula Patency

BACKGROUND

Arteriovenous fistulae (AVF) are the gold standard for vascular access for hemodialysis. Although the vein must thicken and dilate for successful hemodialysis, excessive wall thickness leads to stenosis causing AVF failure. Since TGF-β (transforming growth factor-beta) regulates ECM (extracellular matrix) deposition and smooth muscle cell (SMC) proliferation-critical components of wall thickness-we hypothesized that disruption of TGF-β signaling prevents excessive wall thickening during venous remodeling.

METHODS

A mouse aortocaval fistula model was used. SB431542-an inhibitor of TGF-β receptor I-was encapsulated in nanoparticles and applied to the AVF adventitia in C57BL/6J mice. Alternatively, AVFs were created in mice with conditional disruption of TGF-β receptors in either SMCs or endothelial cells. Doppler ultrasound was performed serially to confirm patency and to measure vessel diameters. AVFs were harvested at predetermined time points for histological and immunofluorescence analyses.

RESULTS

Inhibition of TGF-β signaling with SB431542-containing nanoparticles significantly reduced p-Smad2-positive cells in the AVF wall during the early maturation phase (days 7-21) and was associated with decreased AVF wall thickness that showed both decreased collagen density and decreased SMC proliferation. SMC-specific TGF-β signaling disruption decreased collagen density but not SMC proliferation or wall thickness. Endothelial cell-specific TGF-β signaling disruption decreased both collagen density and SMC proliferation in the AVF wall and was associated with reduced wall thickness, increased outward remodeling, and improved AVF patency.

CONCLUSIONS

Endothelial cell-targeted TGF-β inhibition may be a translational strategy to improve AVF patency.

Gut mucosa alterations and loss of segmented filamentous bacteria in type 1 diabetes are associated with inflammation rather than hyperglycaemia

OBJECTIVE

Type 1 diabetes (T1D) is an autoimmune disease caused by the destruction of pancreatic β-cells producing insulin. Both T1D patients and animal models exhibit gut microbiota and mucosa alterations, although the exact cause for these remains poorly understood. We investigated the production of key cytokines controlling gut integrity, the abundance of segmented filamentous bacteria (SFB) involved in the production of these cytokines, and the respective role of autoimmune inflammation and hyperglycaemia.

DESIGN

We used several mouse models of autoimmune T1D as well as mice rendered hyperglycaemic without inflammation to study gut mucosa and microbiota dysbiosis. We analysed cytokine expression in immune cells, epithelial cell function, SFB abundance and microbiota composition by 16S sequencing. We assessed the role of anti-tumour necrosis factor α on gut mucosa inflammation and T1D onset.

RESULTS

We show in models of autoimmune T1D a conserved loss of interleukin (IL)-17A, IL-22 and IL-23A in gut mucosa. Intestinal epithelial cell function was altered and gut integrity was impaired. These defects were associated with dysbiosis including progressive loss of SFB. Transfer of diabetogenic T-cells recapitulated these gut alterations, whereas induction of hyperglycaemia with no inflammation failed to do so. Moreover, anti-inflammatory treatment restored gut mucosa and immune cell function and dampened diabetes incidence.

CONCLUSION

Our results demonstrate that gut mucosa alterations and dysbiosis in T1D are primarily linked to inflammation rather than hyperglycaemia. Anti-inflammatory treatment preserves gut homeostasis and protective commensal flora reducing T1D incidence.

Synergistic and additive interactions between receptor signaling networks drive the regulatory T cell versus T helper 17 cell fate choice

CD4+ T cells differentiate into subsets that promote immunity or minimize damage to the host. T helper 17 cells (Th17) are effector cells that function in inflammatory responses. T regulatory cells (Tregs) maintain tolerance and prevent autoimmunity by secreting immunosuppressive cytokines and expressing check point receptors. While the functions of Th17 and Treg cells are different, both cell fate trajectories require T cell receptor (TCR) and TGF-β receptor (TGF-βR) signals, and Th17 polarization requires an additional IL-6 receptor (IL-6R) signal. Utilizing high-resolution phosphoproteomics, we identified that both synergistic and additive interactions between TCR, TGF-βR, and IL-6R shape kinase signaling networks to differentially regulate key pathways during the early phase of Treg versus Th17 induction. Quantitative biochemical analysis revealed that CD4+ T cells integrate receptor signals via SMAD3, which is a mediator of TGF-βR signaling. Treg induction potentiates the formation of the canonical SMAD3/4 trimer to activate a negative feedback loop through kinases PKA and CSK to suppress TCR signaling, phosphatidylinositol metabolism, and mTOR signaling. IL-6R signaling activates STAT3 to bind SMAD3 and block formation of the SMAD3/4 trimer during the early phase of Th17 induction, which leads to elevated TCR and PI3K signaling. These data provide a biochemical mechanism by which CD4+ T cells integrate TCR, TGF-β, and IL-6 signals via generation of alternate SMAD3 complexes that control the development of early signaling networks to potentiate the choice of Treg versus Th17 cell fate.

Regulatory T Cells in Chronic Heart Failure

Heart failure is a global problem with high hospitalization and mortality rates. Inflammation and immune dysfunction are involved in this disease. Owing to their unique function, regulatory T cells (Tregs) have reacquired attention recently. They participate in immunoregulation and tissue repair in the pathophysiology of heart failure. Tregs are beneficial in heart by suppressing excessive inflammatory responses and promoting stable scar formation in the early stage of heart injury. However, in chronic heart failure, the phenotypes and functions of Tregs changed. They transformed into an antiangiogenic and profibrotic cell type. In this review, we summarized the functions of Tregs in the development of chronic heart failure first. Then, we focused on the interactions between Tregs and their target cells. The target cells of Tregs include immune cells (such as monocytes/macrophages, dendritic cells, T cells, and B cells) and parenchymal cells (such as cardiomyocytes, fibroblasts, and endothelial cells). Next-generation sequencing and gene editing technology make immunotherapy of heart failure possible. So, prospective therapeutic approaches based on Tregs in chronic heart failure had also been evaluated.

CD8+ T regulatory cells in lupus

T regulatory cells (T_regs) have a key role in the maintenance of immune homeostasis and the regulation of immune tolerance by preventing the inflammation and suppressing the autoimmune responses. Numerical and functional deficits of these cells have been reported in systemic lupus erythematosus (SLE) patients and mouse models of SLE, where their imbalance and dysregulated activities have been reported to significantly influence the disease pathogenesis, progression and outcomes. Most studies in SLE have focused on CD4⁺ T_regs and it has become clear that a critical role in the control of immune tolerance after the breakdown of self-tolerance is provided by CD8⁺ T_regs. Here we review the role, cellular and molecular phenotypes, and mechanisms of action of CD8⁺ T_regs in SLE, including ways to induce these cells for immunotherapeutic modulation in SLE.

Adoptive Transfer of Regulatory Immune Cells in Organ Transplantation

Chronic graft rejection remains a significant barrier to solid organ transplantation as a treatment for end-organ failure. Patients receiving organ transplants typically require systemic immunosuppression in the form of pharmacological immunosuppressants for the duration of their lives, leaving these patients vulnerable to opportunistic infections, malignancies, and other use-restricting side-effects. In recent years, a substantial amount of research has focused on the use of cell-based therapies for the induction of graft tolerance. Inducing or adoptively transferring regulatory cell types, including regulatory T cells, myeloid-derived suppressor cells, and IL-10 secreting B cells, has the potential to produce graft-specific tolerance in transplant recipients. Significant progress has been made in the optimization of these cell-based therapeutic strategies as our understanding of their underlying mechanisms increases and new immunoengineering technologies become more widely available. Still, many questions remain to be answered regarding optimal cell types to use, appropriate dosage and timing, and adjuvant therapies. In this review, we summarize what is known about the cellular mechanisms that underly the current cell-based therapies being developed for the prevention of allograft rejection, the different strategies being explored to optimize these therapies, and all of the completed and ongoing clinical trials involving these therapies.

Inhibition of T-Cells by Cyclosporine A Reduces Macrophage Accumulation to Regulate Venous Adaptive Remodeling and Increase Arteriovenous Fistula Maturation

OBJECTIVE

Arteriovenous fistulae (AVF) are the preferred vascular access for hemodialysis, but the primary success rate of AVF remains poor. Successful AVF maturation requires vascular wall thickening and outward remodeling. A key factor determining successful AVF maturation is inflammation that is characterized by accumulation of both T-cells and macrophages. We have previously shown that anti-inflammatory (M2) macrophages are critically important for vascular wall thickening during venous remodeling; therefore, regulation of macrophage accumulation may be an important mechanism promoting AVF maturation. Since CD4+ T-cells such as T-helper type 1 cells, T-helper type 2 cells, and regulatory T-cells can induce macrophage migration, proliferation, and polarization, we hypothesized that CD4+ T-cells regulate macrophage accumulation to promote AVF maturation. Approach and Results: In a mouse aortocaval fistula model, T-cells temporally precede macrophages in the remodeling AVF wall. CsA (cyclosporine A; 5 mg/kg, sq, daily) or vehicle (5% dimethyl sulfoxide) was administered to inhibit T-cell function during venous remodeling. CsA reduced the numbers of T-helper type 1 cells, T-helper type 2, and regulatory T-cells, as well as M1- and M2-macrophage accumulation in the wall of the remodeling fistula; these effects were associated with reduced vascular wall thickening and increased outward remodeling in wild-type mice. However, these effects were eliminated in nude mice, showing that the effects of CsA on macrophage accumulation and adaptive venous remodeling are T-cell-dependent.

CONCLUSIONS

T-cells regulate macrophage accumulation in the maturing venous wall to control adaptive remodeling. Regulation of T-cells during AVF maturation may be a strategy that can improve AVF maturation. Graphic Abstract: A graphic abstract is available for this article.

Single-cell RNA sequencing of murine islets shows high cellular complexity at all stages of autoimmune diabetes

Tissue-specific autoimmune diseases are driven by activation of diverse immune cells in the target organs. However, the molecular signatures of immune cell populations over time in an autoimmune process remain poorly defined. Using single-cell RNA sequencing, we performed an unbiased examination of diverse islet-infiltrating cells during autoimmune diabetes in the nonobese diabetic mouse. The data revealed a landscape of transcriptional heterogeneity across the lymphoid and myeloid compartments. Memory CD4 and cytotoxic CD8 T cells appeared early in islets, accompanied by regulatory cells with distinct phenotypes. Surprisingly, we observed a dramatic remodeling in the islet microenvironment, in which the resident macrophages underwent a stepwise activation program. This process resulted in polarization of the macrophage subpopulations into a terminal proinflammatory state. This study provides a single-cell atlas defining the staging of autoimmune diabetes and reveals that diabetic autoimmunity is driven by transcriptionally distinct cell populations specialized in divergent biological functions.

Induced regulatory T cells suppress Tc1 cells through TGF-β signaling to ameliorate STZ-induced type 1 diabetes mellitus

Type 1 diabetes mellitus (T1D) is a chronic autoimmune condition in which the immune system destroys insulin-producing pancreatic β cells. In addition to well-established pathogenic effector T cells, regulatory T cells (Tregs) have also been shown to be defective in T1D. Thus, an increasing number of therapeutic approaches are being developed to target Tregs. However, the role and mechanisms of TGF-β-induced Tregs (iTregs) in T1D remain poorly understood. Here, using a streptozotocin (STZ)-induced preclinical T1D mouse model, we found that iTregs could ameliorate the development of T1D and preserve β cell function. The preventive effect was associated with the inhibition of type 1 cytotoxic T (Tc1) cell function and rebalancing the Treg/Tc1 cell ratio in recipients. Furthermore, we showed that the underlying mechanisms were due to the TGF-β-mediated combinatorial actions of mTOR and TCF1. In addition to the preventive role, the therapeutic effects of iTregs on the established STZ-T1D and nonobese diabetic (NOD) mouse models were tested, which revealed improved β cell function. Our findings therefore provide key new insights into the basic mechanisms involved in the therapeutic role of iTregs in T1D.

The TGF-β superfamily cytokine Activin-A is induced during autoimmune neuroinflammation and drives pathogenic Th17 cell differentiation

Th17 cells are known to exert pathogenic and non-pathogenic functions. Although the cytokine transforming growth factor β1 (TGF-β1) is instrumental for Th17 cell differentiation, it is dispensable for generation of pathogenic Th17 cells. Here, we examined the T cell-intrinsic role of Activin-A, a TGF-β superfamily member closely related to TGF-β1, in pathogenic Th17 cell differentiation. Activin-A expression was increased in individuals with relapsing-remitting multiple sclerosis and in mice with experimental autoimmune encephalomyelitis. Stimulation with interleukin-6 and Activin-A induced a molecular program that mirrored that of pathogenic Th17 cells and was inhibited by blocking Activin-A signaling. Genetic disruption of Activin-A and its receptor ALK4 in T cells impaired pathogenic Th17 cell differentiation in vitro and in vivo. Mechanistically, extracellular-signal-regulated kinase (ERK) phosphorylation, which was essential for pathogenic Th17 cell differentiation, was suppressed by TGF-β1-ALK5 but not Activin-A-ALK4 signaling. Thus, Activin-A drives pathogenic Th17 cell differentiation, implicating the Activin-A-ALK4-ERK axis as a therapeutic target for Th17 cell-related diseases.

The Cardiac Injury Immune Response as a Target for Regenerative and Cellular Therapies

PURPOSE

Despite modern reperfusion and pharmacologic therapies, myocardial infarction (MI) remains a leading cause of morbidity and mortality worldwide. Therefore, the development of further therapeutics affecting post-MI recovery poses significant benefits. This review focuses on the post-MI immune response and immunomodulatory therapeutics that could improve the wound-healing response.

METHODS

This narrative review used OVID versions of MEDLINE and EMBASE searching for clinical therapeutics targeting the immune system during MI. Preclinical models and clinical trials were included. Additional studies were sourced from the reference lists of relevant articles and other personal files.

FINDINGS

After MI, cardiomyocytes are starved of oxygen and undergo cell death via coagulative necrosis. This process activates the immune system and a multifaceted wound-healing response, comprising a number of complex and overlapping phases. Overactivation or persistence of one or more of these phases can have potentially lethal implications. This review describes the immune response post-MI and any adverse events that can occur during these different phases. Second, we describe immunomodulatory therapies that attempt to target these immune cell aberrations by mitigating or diminishing their effects on the wound-healing response. Also discussed are adult stem/progenitor cell therapies, exosomes, and regulatory T cells, and their immunomodulatory effects in the post-MI setting.

IMPLICATIONS

An updated understanding into the importance of various inflammatory cell phenotypes, coupled with new technologies, may hold promise for a new era of immunomodulatory therapeutics. The implications of such therapies could dramatically improve patients' quality of life post-MI and reduce the incidence of progressive heart failure.

Regulatory T cell therapy: Current and future design perspectives

Regulatory T cells (Tregs) maintain immune equilibrium by suppressing immune responses through various multistep contact dependent and independent mechanisms. Cellular therapy using polyclonal Tregs in transplantation and autoimmune diseases has shown promise in preclinical models and clinical trials. Although novel approaches have been developed to improve specificity and efficacy of antigen specific Treg based therapies, widespread application is currently restricted. To date, design-based approaches to improve the potency and persistence of engineered chimeric antigen receptor (CAR) Tregs are limited. Here, we describe currently available Treg based therapies, their advantages and limitations for implementation in clinical studies. We also examine various strategies for improving CAR T cell design that can potentially be applied to CAR Tregs, such as identifying co-stimulatory signalling domains that enhance suppressive ability, determining optimal scFv affinity/avidity, and co-expression of accessory molecules. Finally, we discuss the importance of tailoring CAR Treg design to suit the individual disease.

Identification of a Multi-Long Noncoding RNA Signature for the Diagnosis of Type 1 Diabetes Mellitus

Due to the increasing prevalence of type 1 diabetes mellitus (T1DM) and its complications, there is an urgent need to identify novel methods for predicting the occurrence and understanding the pathogenetic mechanisms of the disease. Accumulated data have demonstrated the potential of long noncoding RNAs (lncRNAs), as biomarkers in establishing diagnosis and predicting prognosis of numerous diseases. Yet, little is known about the expression patterns and regulatory roles of lncRNAs in the pathogenesis of T1DM and whether they can be used as diagnostic biomarkers for the disease. To further explore these questions, in the present study, we conducted a comparative analysis of the expression patterns of lncRNAs between 20 T1DM patients and 42 health controls by retrospectively analyzing a published microarray data set. Our results indicate that, compared with healthy controls, diabetic patients had altered levels of lncRNAs. Then, we used three time cross-validation strategy and support vector machine to propose a specific 26-lncRNA signature (termed 26LncSigT1DM). This 26LncSigT1DM signature can be used to effectively distinguish between healthy and diabetic individuals (area under the curve = 0.825) of a validation cohort. After the 26LncSigT1DM was prospectively validated, we used Pearson correlation to identify 915 mRNAs, whose expression levels were positively correlated with those of the 26 lncRNAs. According to their Gene Ontology annotations, these mRNAs participate in processes including cellular response to stimulus, cell communication, multicellular organismal process, and cell motility. Kyoto Encyclopedia of Genes and Genomes analysis demonstrated that the genes encoding the 915 mRNAs may be associated with the NOD-like receptor signaling pathway, transforming growth factor β signaling pathway, and mineral absorption, suggesting that the deregulation of these lncRNAs may mediate inflammatory abnormalities and immune dysfunctions, which jointly promote the pathogenesis of T1DM. Thus, our study identifies a novel diagnostic tool and may shed more light on the molecular mechanisms underlying the pathogenesis of T1DM.

T regulatory cells-derived extracellular vesicles and their contribution to the generation of immune tolerance

T regulatory (Treg) cells have a major role in the maintenance of immune tolerance against self and foreign antigens through the control of harmful inflammation. Treg cells exert immunosuppressive function by several mechanisms, which can be distinguished as contact dependent or independent. Recently, the secretion of extracellular vesicles (EVs) by Treg cells has been reported as a novel suppressive mechanism capable of modulating immunity in a cell-contact independent and targeted manner, which has been identified in different pathologic scenarios. EVs are cell-derived membranous structures involved in physiologic and pathologic processes through protein, lipid, and genetic material exchange, which allow intercellular communication. In this review, we revise and discuss current knowledge on Treg cells-mediated immune tolerance giving special attention to the production and release of EVs. Multiple studies support that Treg cells-derived EVs represent a refined intercellular exchange device with the capacity of modulating immune responses, thus creating a tolerogenic microenvironment in a cell-free manner. The mechanisms proposed encompass miRNAs-induced gene silencing, the action of surface proteins and the transmission of enzymes. These observations gain relevance by the fact that Treg cells are susceptible to converting into effector T cells after exposition to inflammatory environments. Yet, in contrast to their cells of origin, EVs are unlikely to be modified under inflammatory conditions, highlighting the advantage of their use. Moreover, we speculate in the possibility that Treg cells may contribute to infectious tolerance via vesicle secretion, intervening with CD4⁺ T cells differentiation and/or stability.

Old age-associated enrichment of peripheral T regulatory cells and altered redox status in pulmonary tuberculosis patients

Aging influences the susceptibility and prognosis to various infectious diseases including tuberculosis (TB). Despite the impairment of T-cell function and immunity in older individuals, the mechanism for the higher incidence of TB in the elderly remains largely unknown. Here, we evaluated the age-associated immune alterations, particularly in effector and Treg responses in pulmonary TB patients. We also evaluated the impact of redox status and its modulation with N-acetyl-cysteine (NAC) in elderly TB. Higher frequency of Treg cells and reduced IFN-γ positive T cells were observed among older TB patients. The elevated number of Treg cells correlated tightly with bacillary load (i.e. disease severity); which declined significantly in response to successful anti-tubercular treatment. We could rescue Myobacterium tuberculosis-specific effector T cell (Th1) responses through various in vitro approaches, for example, Treg cell depletion and co-culture experiments, blocking experiments using antibodies against IL-10, TGF-β, and programmed death-1 (PD-1) as well as NAC supplementation. We report old age-associated enrichment of Treg cells and suppression of M. tuberculosis-specific effector T (Th1) cell immune responses. Monitoring these immune imbalances in older patients may assist in immune potentiation through selectively targeting Treg cells and/or optimizing redox status by NAC supplementation.

Cytokines in type 1 diabetes: mechanisms of action and immunotherapeutic targets

Cytokines play crucial roles in orchestrating complex multicellular interactions between pancreatic β cells and immune cells in the development of type 1 diabetes (T1D) and are thus potential immunotherapeutic targets for this disorder. Cytokines that can induce regulatory functions-for example, IL-10, TGF-β and IL-33-are thought to restore immune tolerance and prevent β-cell damage. By contrast, cytokines such as IL-6, IL-17, IL-21 and TNF, which promote the differentiation and function of diabetogenic immune cells, are thought to lead to T1D onset and progression. However, targeting these dysregulated cytokine networks does not always result in consistent effects because anti-inflammatory or proinflammatory functions of cytokines, responsible for β-cell destruction, are context dependent. In this review, we summarise the current knowledge on the involvement of well-known cytokines in both the initiation and destruction phases of T1D and discuss advances in recently discovered roles of cytokines. Additionally, we emphasise the complexity and implications of cytokine modulation therapy and discuss the ways in which this strategy has been translated into clinical trials.

Fucoidan prevent murine autoimmune diabetes via suppression TLR4-signaling pathways, regulation DC/Treg induced immune tolerance and improving gut microecology

Background

This study was to investigate the effect and its possible mechanism of fucoidan on the development of spontaneous autoimmune diabetes in non-obese diabetic (NOD) mice.

Methods

7-week-old NOD mice were randomly divided into three groups: control group, low-dose (300 mg/kg) and high-dose (600 mg/kg) fucoidan-treatment groups. After 5 weeks of treatment, 10 mice per group were randomly selected to be sacrificed after feces collection. The remaining 12 mice per group were fed until 26 weeks of age to assess the incidence of diabetes.

Results

Treatment with fucoidan increased serum insulin level, delayed the onset and decreased the development of diabetes in NOD mice. Fucoidan reduced the levels of strong Th1 proinflammatory cytokines, but induced Th2-bias ed. cytokine response. And dentridic cells (DCs) in fucoidan treatment group were characterized as low expression of MHC class II and CD86 molecules. TLR4 expressions and the downstream molecules in pancreas were down-regulated in fucoidan-treated groups. There were significant differences in the composition of gut flora between NOD control group and fucoidan group. Lactobacillus and Akkermansia were significantly enriched in fucoidan group.

Conclusions

Fucoidan could prevent the development of autoimmune diabetes in NOD mice via regulating DC/Treg induced immune tolerance, improving gut microecology, down-regulating TLR4 signaling pathway, and maintaining pancreatic internal environment.

From bench to bedside: evolving therapeutic targets in autoimmune blistering disease

Autoimmune blistering diseases comprise a group of heterogenous conditions characterized by the loss of tolerance and subsequent development of autoantibodies targeting epidermal and subepidermal adhesion proteins. Blisters and erosions form on the skin and mucous membranes leading to significant morbidity and mortality. Traditional therapies rely on systemic immunosuppression. Advancements in our understanding of the pathophysiology of pemphigus and pemphigoid have led to the development of molecules which target specific pathways involved in induction and perpetuation of disease. In this review, we outline the novel therapeutic strategies including B-cell depletion, T-regulatory cell repletion, cell signalling inhibitors and small molecular inhibitors, inhibitory monoclonal antibodies, as well as complement inhibition. We additionally review their current level of clinical evidence. We lastly review therapeutics targets gleaned from the experimental epidermolysis bullosa acquisita mouse model. These emerging treatments offer an exciting progression from basic science discoveries that have the potential to transform the treatment paradigm in autoimmune blistering diseases.

The Pungent and Hot Chinese Herbs Cause Heat Syndrome in Rats by Affecting the Regulatory T Cells

Heat syndrome is a folk saying in China, which is used to describe people with symptoms such as aphtha, oral ulcer, glossitis, swelling and aching of gingiva, and dry eye. Aconitum carmichaelii Debx. (A), Zingiber officinale Rosc. (Z), and Cinnamomum cassia Presl (C) are the representatives of pungent and hot Chinese herbs which may cause heat syndrome. In order to explore the mechanism of pungent herbs-induced heat syndrome, rats were treated with AZC extracts at different concentrations and at different time periods. A series of cytokines were determined using the cytokine antibody array; some immunosuppressive cytokines, including TGF-β, IL-10, and IL-35, significantly increased in AZC group as compared with control group. Higher mRNA expressions of Foxp3, TGF-β, IL-10, and IL-35 were found in the spleen and thymus of rats after treatment for 18 days based on RT-PCR. Flow cytometry result revealed that the percentage of CD4⁺CD25⁺ Treg cells and Foxp3⁺CD4⁺CD25⁺ Treg cells in spleen lymphocytes showed an increasing trend from the 3^rd day to the 18^th day after treatment with middle dose of AZC extracts. It is speculated that extracts of AZC herbs may affect the development of heat syndrome by influencing Treg cells and immunosuppressive cytokines.

Regulatory T cells as therapeutic targets and mediators

With the advent of the concept of dominant tolerance and the subsequent discovery of CD4⁺ regulatory T cells expressing the transcription factor FOXP3 (Tregs), almost all productive as well as nonproductive immune responses can be compartmentalized to a binary of immune effector T cells and immune regulatory Treg populations. A beneficial immune response warrants the timely regulation by Tregs, whereas a nonproductive immune response indicates insufficient effector functions or an outright failure of tolerance. There are ample reports supporting role of Tregs in suppressing spontaneous auto-immune diseases as well as promoting immune evasion by cancers. To top up their importance, several non-immune functions like tissue homeostasis and regeneration are also being attributed to Tregs. Hence, after being in the center stage of basic and translational immunological research, Tregs are making the next jump towards clinical studies. Therefore, newer small molecules, biologics as well as adoptive cell therapy (ACT) approaches are being tested to augment or undermine Treg responses in the context of autoimmunity and cancer. In this brief review, we present the strategies to modulate Tregs towards a favorable clinical outcome.

Regulatory T cells demonstrate significantly increased functions following stimulation with IL-2 in a Tim-3-dependent manner in intracranial aneurysms

The formation of intracranial aneurysm (IA) is associated with the destruction of various cellular and structural components, which induces pathogenic inflammatory responses that further propagate tissue damage. The regulatory immune system can suppress exacerbated inflammation and offer tissue protection; however, previous studies by others and us have demonstrated that the regulatory T (Treg) cells were functionally impaired in IA patients. Hence, strategies that can improve Treg function in IA patients should be investigated. Based on our previous finding that IL-2 strongly elevated the expression of the checkpoint molecule Tim-3 in Treg cells, we examined the effect of IL-2 in the function of Treg cells from IA patients. External IL-2 significantly improved the proliferation of Treg cells, increased the expression of CTLA-4 and LAG-3, and enhanced Treg-mediated suppression of conventional T cell (Tconv) proliferation. Importantly, compared to the Tim-3^- Treg cells, the Tim-3⁺ Treg cells presented comparable proliferation capacity, but significantly greater expressions of CTLA-4 and LAG-3 and significantly higher capacity to suppress Tconv proliferation. In addition, blocking Tim-3 abrogated IL-2-mediated enhancement of Tim-3⁺ Treg cells. We then investigated the IL-2 level in IA patients, and found that although IA patients and healthy controls presented similar serum IL-2 concentration, the concentrations of IL-1β and TNF-α were significantly higher in IA patients than in healthy controls, signaling a relative reduction in IL-2 abundance. Together, we found that IL-2 could significantly enhance the function of Treg cells from IA patients in a Tim-3-dependent manner.

Regulatory T Cells Suppress Effector T Cell Proliferation by Limiting Division Destiny

Understanding how the strength of an effector T cell response is regulated is a fundamental problem in immunology with implications for immunity to pathogens, autoimmunity, and immunotherapy. The initial magnitude of the T cell response is determined by the sum of independent signals from antigen, co-stimulation and cytokines. By applying quantitative methods, the contribution of each signal to the number of divisions T cells undergo (division destiny) can be measured, and the resultant exponential increase in response magnitude accurately calculated. CD4⁺CD25⁺Foxp3⁺ regulatory T cells suppress self-reactive T cell responses and limit pathogen-directed immune responses before bystander damage occurs. Using a quantitative modeling framework to measure T cell signal integration and response, we show that Tregs modulate division destiny, rather than directly increasing the rate of death or delaying interdivision times. The quantitative effect of Tregs could be mimicked by modulating the availability of stimulatory co-stimuli and cytokines or through the addition of inhibitory signals. Thus, our analysis illustrates the primary effect of Tregs on the magnitude of effector T cell responses is mediated by modifying division destiny of responding cell populations.

Cell-Based Therapies with T Regulatory Cells

CD4⁺CD25^highFoxP3⁺ T regulatory cells (Tregs) are immunodominant suppressors in the immune system. Tregs use various mechanisms to control immune responses. Preclinical data from animal models have confirmed the huge therapeutic potential of Tregs in many immune-mediated diseases. Hence, these cells are now on the road to translation to cell therapy in the clinic as the first clinical trials are accomplished. To date, clinical research has involved mainly hematopoietic stem cell transplantations, solid organ transplantations, and autoimmunity. Despite difficulties with legislation and technical issues, treatment is constantly evolving and may soon represent a valid alternative for patients with diseases that are currently incurable. This review focuses on the basic and clinical experience with Tregs with adoptive transfer of these cells, primarily from clinical trials, as well as on perspectives on clinical use and technical problems with implementing the therapy.

Functional Defects of Treg Cells: New Targets in Rheumatic Diseases, Including Ankylosing Spondylitis

PURPOSE OF REVIEW

This study aims to review the advances of Treg cell biology, the functional defects of Treg cells, and the potential strategies for the experimental, preclinical or clinical application of Treg cell therapy in the context of autoimmune/immune-mediated rheumatic diseases.

RECENT FINDINGS

CD4⁺CD25⁺ regulatory T (Treg) cells are a phenotypically and functionally heterogeneous subset of lymphocytes that prevent a variety of autoimmune diseases. As in many autoimmune diseases, the functional defects of Treg cells are supposed to play relevant roles in the pathogenesis and development of systemic lupus erythematosus, rheumatoid arthritis, ankylosing spondylitis, and other autoimmune/immune-mediated rheumatic diseases. Consequently, manipulation and modulation of Treg cells represent a potent strategy for therapeutic benefit in many such diseases. A further understanding of the functional defects of Treg cells in rheumatic diseases will contribute to find new targets and therapies in rheumatic diseases, including ankylosing spondylitis.

Intestinal Immunomodulatory Cells (T Lymphocytes): A Bridge between Gut Microbiota and Diabetes

Diabetes mellitus (DM) is one of the most familiar chronic diseases threatening human health. Recent studies have shown that the development of diabetes is closely related to an imbalance of the gut microbiota. Accordingly, there is increasing interest in how changes in the gut microbiota affect diabetes and its underlying mechanisms. Immunomodulatory cells play important roles in maintaining the normal functioning of the human immune system and in maintaining homeostasis. Intestinal immunomodulatory cells (IICs) are located in the intestinal mucosa and are regarded as an intermediary by which the gut microbiota affects physiological and pathological properties. Diabetes can be regulated by IICs, which act as a bridge linking the gut microbiota and DM. Understanding this bridge role of IICs may clarify the mechanisms by which the gut microbiota contributes to DM. Based on recent research, we summarize this process, thereby providing a basis for further studies of diabetes and other similar immune-related diseases.

Cytokine Signaling in the Development and Homeostasis of Regulatory T cells

Cytokine signaling is indispensable for regulatory T-cell (Treg) development in the thymus, and also influences the homeostasis, phenotypic diversity, and function of Tregs in the periphery. Because Tregs are required for establishment and maintenance of immunological self-tolerance, investigating the role of cytokines in Treg biology carries therapeutic potential in the context of autoimmune disease. This review discusses the potent and diverse influences of interleukin (IL)-2 signaling on the Treg compartment, an area of knowledge that has led to the use of low-dose IL-2 as a therapy to reregulate autoaggressive immune responses. Evidence suggesting Treg-specific impacts of the cytokines transforming growth factor β (TGF-β), IL-7, thymic stromal lymphopoietin (TSLP), IL-15, and IL-33 is also presented. Finally, we consider the technical challenges and knowledge limitations that must be overcome to bring other cytokine-based, Treg-targeted therapies into clinical use.

Neutralization Versus Reinforcement of Proinflammatory Cytokines to Arrest Autoimmunity in Type 1 Diabetes

As physiological pathways of intercellular communication produced by all cells, cytokines are involved in the pathogenesis of inflammatory insulitis as well as pivotal mediators of immune homeostasis. Proinflammatory cytokines including interleukins, interferons, transforming growth factor-β, tumor necrosis factor-α, and nitric oxide promote destructive insulitis in type 1 diabetes through amplification of the autoimmune reaction, direct toxicity to β-cells, and sensitization of islets to apoptosis. The concept that neutralization of cytokines may be of therapeutic benefit has been tested in few clinical studies, which fell short of inducing sustained remission or achieving disease arrest. Therapeutic failure is explained by the redundant activities of individual cytokines and their combinations, which are rather dispensable in the process of destructive insulitis because other cytolytic pathways efficiently compensate their deficiency. Proinflammatory cytokines are less redundant in regulation of the inflammatory reaction, displaying protective effects through restriction of effector cell activity, reinforcement of suppressor cell function, and participation in islet recovery from injury. Our analysis suggests that the role of cytokines in immune homeostasis overrides their contribution to β-cell death and may be used as potent immunomodulatory agents for therapeutic purposes rather than neutralized.

Interactions Between the Neuroendocrine System and T Lymphocytes in Diabetes

It is well established that there is a fine-tuned bidirectional communication between the immune and neuroendocrine tissues in maintaining homeostasis. Several types of immune cells, hormones, and neurotransmitters of different chemical nature are involved as communicators between organs. Apart of being key players of the adaptive arm of the immune system, it has been recently described that T lymphocytes are involved in the modulation of metabolism of several tissues in health and disease. Diabetes may result mainly from lack of insulin production (type 1 diabetes) or insufficient insulin and insulin resistance (type 2 diabetes), both influenced by genetic and environmental components. Herein, we discuss accumulating data regarding the role of the adaptive arm of the immune system in the pathogenesis of diabetes; including the action of several hormones and neurotransmitters influencing on central and peripheral T lymphocytes development and maturation, particularly under the metabolic burden triggered by diabetes. In addition, we comment on the role of T-effector lymphocytes in adipose and liver tissues during diabetes, which together enhances pancreatic β-cell stress aggravating the disease.

Unique Features of Pancreatic-Resident Regulatory T Cells in Autoimmune Type 1 Diabetes

Recent progress in regulatory T cells (Tregs) biology emphasizes the importance of understanding tissue-resident Tregs in response to tissue-specific environment. Now, emerging evidence suggests that pancreatic-resident forkhead box P3⁺ Tregs have distinguishable effects on the suppression of over-exuberant immune responses in autoimmune type 1 diabetes (T1D). Thus, there is growing interest in elucidating the role of pancreatic-resident Tregs that function and evolve in the local environment. In this review, we discuss the phenotype and function of Tregs residing in pancreatic tissues and pancreatic lymph nodes, with emphasis on the unique subpopulations of Tregs that control the disease progression in the context of T1D. Specifically, we discuss known and possible modulators that influence the survival, migration, and maintenance of pancreatic Tregs.

The regulation of regulation: interleukin-10 increases CD4+ CD25+ regulatory T cells but impairs their immunosuppressive activity in murine models with schistosomiasis japonica or asthma

CD4⁺ CD25⁺ Foxp3⁺ regulatory T (Treg) cells play an important role in maintaining immune homeostasis. Interleukin-10 (IL-10), a cytokine with anti-inflammatory capacities, also has a critical role in controlling immune responses. In addition, it is well known that production of IL-10 is one of the suppression mechanisms of Treg cells. However, the action of IL-10 on Treg cells themselves remains insufficiently understood. In this study, by using a Schistosoma japonicum-infected murine model, we show that the elevated IL-10 contributed to Treg cell induction but impaired their immunosuppressive function. Our investigations further suggest that this may relate to the up-regulation of serum transforming growth factor (TGF-β) level but the decrease in membrane-bound TGF-β of Treg cells by IL-10 during S. japonicum infection. In addition, similar IL-10-mediated regulation on Treg cells was also confirmed in the murine model of asthma. In general, our findings identify a previously unrecognized opposing regulation of IL-10 on Treg cells and provide a deep insight into the precise regulation in immune responses.

Expression of Transforming Growth Factor-β by Human Islets: Impact on Islet Viability and Function

Transforming growth factor-β1 (TGF-β1) is a pleotropic cytokine that promotes angiogenesis and extracellular matrix protein synthesis in addition to its immunosuppressive effects. The purpose of this study is to identify optimal conditions for in vivo expression of TGF-β1 by human islets to exploit the possible beneficial effects and minimize undesirable side effects. We transduced human islets with adenoviral vectors encoding the active form of Ad-TGF-β1 or Ad-LacZ to test the effects of TGF-β1 gene expression on islet in vivo function following their transplantation into a NOD-SCID mouse model. Islets were transduced with multiplicity of infection (MOI) of 20, 10, 5, and 2.5 per islet cell. At a MOI ranging from 2.5 to 20, expression of TGF-β1 in islet supernatant persisted for 1–2 months and ranged from 153 ± 5 to 2574 ± 1299 pg/ml, respectively. Transduction with the lowest MOI (2.5) did not compromise the in vivo production of human C-peptide. We conclude that TGF-β1 expression in transplanted islets does not compromise viability and that adenoviral transduction with the TGF-β1 gene has a dose-dependent effect, with larger MOIs being deleterious. The data also indicate that in vitro culture system and the in vivo NOD-SCID model could be used successfully to evaluate the nonimmune effects of gene transduction.

Interleukin-37 Enhances the Suppressive Activity of Naturally Occurring CD4+CD25+ Regulatory T Cells

Naturally occurring CD4⁺CD25⁺ regulatory T cells (Tregs) are essential for the suppression of autoimmunity and can control the immune-mediated pathology during the early phase of sepsis. Our previous data showed that silencing interleukin-37 (IL-37) in human CD4⁺CD25⁺ Tregs obviously reduced the suppressive activity of CD4⁺CD25⁺ Tregs. Here, we found that rhIL-37 stimulation markedly enhanced the suppressive activity of CD4⁺CD25⁺ Tregs isolated from naive C57BL/6 J mice in the absence or presence of lipopolysaccharide (LPS). Treatment with rhIL-37 could significantly upregulate the expression of cytotoxic T-lymphocyte-associated antigen (CTLA)-4 and forkhead/winged helix transcription factor p3 (Foxp3) on CD4⁺CD25⁺ Tregs. Also, rhIL-37 stimulation promoted the production of transforming growth factor-β1 (TGF-β1) but not IL-10 in the supernatants of cultured CD4⁺CD25⁺ Tregs. Pretreated CD4⁺CD25⁺ Tregs with rhIL-37 in the presence or absence of LPS were cocultured with CD4⁺CD25⁻ T cells, ratio of IL-4/interferon-γ in the supernatants obviously increased in IL-37-stimulated groups. In addition, early administration of IL-37 significantly improved the survival rate of septic mice induced by cecal ligation and puncture. Taken together, we concluded that rhIL-37 enhances the suppressive activity of CD4⁺CD25⁺ Tregs and might be a potential immunomodulator for the treatment of septic complications.

Inflammation-induced CD69+ Kupffer cell feedback inhibits T cell proliferation via membrane-bound TGF-β1

Kupffer cells, tissue-resident macrophage lineage cell, are enriched in vertebrate liver. The mouse F4/80⁺ Kupffer cells have been subclassified into two subpopulations according to their phenotype and function: CD68⁺ subpopulation with potent reactive oxygen species (ROS) production and phagocytic capacities, and CD11b⁺ subpopulation with a potent capacity to produce T helper 1 cytokines. In addition, CD11b⁺ Kupffer cells/macrophages may be migrated from the bone marrow or spleen, especially in inflammatory conditions of the liver. For analyzing diverse Kupffer cell subsets, we infected mice with Listeria monocytogenes and analyzed the phenotype variations of hepatic Kupffer cells. During L. monocytogenes infection, hepatic CD69⁺ Kupffer cells were significantly induced and expanded, and CD69⁺ Kupffer cells expressed higher level of CD11b, and particularly high level of membrane-bound TGF-β1 (mTGF-β1) but lower level of F4/80. We also found that clodronate liposome administration did not eliminate hepatic CD69⁺ Kupffer cell subset. We consider the hepatic CD69⁺ Kupffer cell population corresponds to CD11b⁺ Kupffer cells, the bone marrow-derived population. Hepatic CD69⁺ Kupffer cells suppressed Ag-nonspecific and OVA-specific CD4 T cell proliferation through mTGF-β1 both in vitro and in vivo, meanwhile, they did not interfere with activation of CD4 T cells. Thus, we have identified a new subset of inflammation-induced CD69⁺ Kupffer cells which can feedback inhibit CD4 T cell response via cell surface TGF-β1 at the late stage of immune response against infection. CD69⁺ Kupffer cells may contribute to protect host from pathological injure by preventing overactivation of immune response.