Tolerogenic dendritic cells for autoimmune disease and transplantation

Impact of immune cell metabolism on membranous nephropathy and prospective therapy

Membranous nephropathy (MN) is a primary glomerular disease commonly causing adult nephrotic syndrome. Characterized by thickened glomerular capillary walls due to immune complex deposition, MN is a complex autoimmune disorder. Its pathogenesis involves immune deposit formation, complement activation, and a heightened risk of renal failure. Central to MN is immune system dysfunction, particularly the dysregulation of B and T cell responses. B cells contribute to renal injury through the production of autoantibodies, particularly IgG targeting the phospholipase A2 receptor (PLA2R) on podocytes, while T cells modulate immune responses that influence disease progression. Metabolic reprogramming alters lymphocyte survival, differentiation, proliferation, and function, potentially triggering autoimmune processes. Although the link between immune cell metabolism and MN remains underexplored, this review highlights recent advances in understanding immune metabolism and its role in MN. These insights may provide novel biomarkers and therapeutic strategies for MN treatment.

Arginine vasopressin (AVP) treatment increases the expression of inhibitory immune checkpoint molecules in monocyte-derived dendritic cells

Arginine vasopressin (AVP) has disparate impacts on immune responses by divergent receptors on cells including DCs. This study was conducted with the aim of investigating the impact of AVP on the maturation and expression of the inhibitory immune checkpoint molecules in tolerogenic monocyte-derived DCs. CD14 marker was used to separate monocytes from peripheral blood mononuclear cells (PBMCs) by MACS method. To differentiate monocytes from DCs, we utilized GM-CSF and IL-4 cytokines. Tolerogenic DCs were generated using vitamin D3 and dexamethasone. We added LPS and AVP to the culture medium on day 6 after incubation of DCs at 37 °C. Finally, we assessed the surface molecules by flow cytometry and used real-time PCR to evaluate the expression of genes related to the inhibitory immune checkpoints. Based on the obtained data, AVP increased the expression of CD11c (P ≤ 0.0001), HLA-DR (P ≤ 0.01), and CD86 (P ≤ 0.01) in AVP-mDCs. Also, the expression of all the immune checkpoint genes including CTLA-4 (P ≤ 0.001), BTLA (P ≤ 0.001), PDL-1 (P ≤ 0.05), B7H7 (P ≤ 0.001), LAG3 (P ≤ 0.01), and VISTA (P ≤ 0.001) in AVP-mDCs was increased in comparison to the control group. Vasopressin caused the generation of mature and tolerogenic DCs. Our data may help to consider AVP-mDCs to take part in autoimmune disease therapy, transplanted tissue rejection impedance, and allergies.

Evolving understanding of autoimmune mechanisms and new therapeutic strategies of autoimmune disorders

Autoimmune disorders are characterized by aberrant T cell and B cell reactivity to the body's own components, resulting in tissue destruction and organ dysfunction. Autoimmune diseases affect a wide range of people in many parts of the world and have become one of the major concerns in public health. In recent years, there have been substantial progress in our understanding of the epidemiology, risk factors, pathogenesis and mechanisms of autoimmune diseases. Current approved therapeutic interventions for autoimmune diseases are mainly non-specific immunomodulators and may cause broad immunosuppression that leads to serious adverse effects. To overcome the limitations of immunosuppressive drugs in treating autoimmune diseases, precise and target-specific strategies are urgently needed. To date, significant advances have been made in our understanding of the mechanisms of immune tolerance, offering a new avenue for developing antigen-specific immunotherapies for autoimmune diseases. These antigen-specific approaches have shown great potential in various preclinical animal models and recently been evaluated in clinical trials. This review describes the common epidemiology, clinical manifestation and mechanisms of autoimmune diseases, with a focus on typical autoimmune diseases including multiple sclerosis, type 1 diabetes, rheumatoid arthritis, systemic lupus erythematosus, and sjögren's syndrome. We discuss the current therapeutics developed in this field, highlight the recent advances in the use of nanomaterials and mRNA vaccine techniques to induce antigen-specific immune tolerance.

Dendritic cells in Parkinson's disease: Regulatory role and therapeutic potential

Parkinson's Disease (PD) is a debilitating neurodegenerative disorder characterized by the progressive loss of dopaminergic neurons and the presence of Lewy bodies. While the traditional focus has been on neuronal and glial cell dysfunction, recent research has shifted towards understanding the role of the immune system, particularly dendritic cells (DCs), in PD pathogenesis. As pivotal antigen-presenting cells, DCs are traditionally recognized for initiating and regulating immune responses. In PD, DCs contribute to disease progression through the presentation of α-synuclein to T cells, leading to an adaptive immune response against neuronal elements. This review explores the emerging role of DCs in PD, highlighting their potential involvement in antigen presentation and T cell immune response modulation. Understanding the multifaceted functions of DCs could reveal novel insights into PD pathogenesis and open new avenues for therapeutic strategies, potentially altering the course of this devastating disease.

Amniotic fluid stem cell-derived extracellular vesicles educate type 2 conventional dendritic cells to rescue autoimmune disorders in a multiple sclerosis mouse model

Dendritic cells (DCs) are essential orchestrators of immune responses and represent potential targets for immunomodulation in autoimmune diseases. Human amniotic fluid secretome is abundant in immunoregulatory factors, with extracellular vesicles (EVs) being a significant component. However, the impact of these EVs on dendritic cells subsets remain unexplored. In this study, we investigated the interaction between highly purified dendritic cell subsets and EVs derived from amniotic fluid stem cell lines (HAFSC-EVs). Our results suggest that HAFSC-EVs are preferentially taken up by conventional dendritic cell type 2 (cDC2) through CD29 receptor-mediated internalization, resulting in a tolerogenic DC phenotype characterized by reduced expression and production of pro-inflammatory mediators. Furthermore, treatment of cDC2 cells with HAFSC-EVs in coculture systems resulted in a higher proportion of T cells expressing the regulatory T cell marker Foxp3 compared to vehicle-treated control cells. Moreover, transfer of HAFSC-EV-treated cDC2s into an EAE mouse model resulted in the suppression of autoimmune responses and clinical improvement. These results suggest that HAFSC-EVs may serve as a promising tool for reprogramming inflammatory cDC2s towards a tolerogenic phenotype and for controlling autoimmune responses in the central nervous system, representing a potential platform for the study of the effects of EVs in DC subsets.

Roles and application of exosomes in the development, diagnosis and treatment of gastric cancer

As important messengers of intercellular communication, exosomes can regulate local and distant cellular communication by transporting specific exosomal contents and can also promote or suppress the development and progression of gastric cancer (GC) by regulating the growth and proliferation of tumor cells, the tumor-related immune response and tumor angiogenesis. Exosomes transport bioactive molecules including DNA, proteins, and RNA (coding and noncoding) from donor cells to recipient cells, causing reprogramming of the target cells. In this review, we will describe how exosomes regulate the cellular immune response, tumor angiogenesis, proliferation and metastasis of GC cells, and the role and mechanism of exosome-based therapy in human cancer. We will also discuss the potential application value of exosomes as biomarkers in the diagnosis and treatment of GC and their relationship with drug resistance.

Signaling pathways involved in the biological functions of dendritic cells and their implications for disease treatment

The ability of dendritic cells (DCs) to initiate and regulate adaptive immune responses is fundamental for maintaining immune homeostasis upon exposure to self or foreign antigens. The immune regulatory function of DCs is strictly controlled by their distribution as well as by cytokines, chemokines, and transcriptional programming. These factors work in conjunction to determine whether DCs exert an immunosuppressive or immune-activating function. Therefore, understanding the molecular signals involved in DC-dependent immunoregulation is crucial in providing insight into the generation of organismal immunity and revealing potential clinical applications of DCs. Considering the many breakthroughs in DC research in recent years, in this review we focused on three basic lines of research directly related to the biological functions of DCs and summarized new immunotherapeutic strategies involving DCs. First, we reviewed recent findings on DC subsets and identified lineage-restricted transcription factors that guide the development of different DC subsets. Second, we discussed the recognition and processing of antigens by DCs through pattern recognition receptors, endogenous/exogenous pathways, and the presentation of antigens through peptide/major histocompatibility complexes. Third, we reviewed how interactions between DCs and T cells coordinate immune homeostasis in vivo via multiple pathways. Finally, we summarized the application of DC-based immunotherapy for autoimmune diseases and tumors and highlighted potential research prospects for immunotherapy that targets DCs. This review provides a useful resource to better understand the immunomodulatory signals involved in different subsets of DCs and the manipulation of these immune signals can facilitate DC-based immunotherapy.

Versatility of mesenchymal stem cell-derived extracellular vesicles in tissue repair and regenerative applications

Mesenchymal stem/stromal cells (MSCs) are multipotent somatic cells that have been widely explored in the field of regenerative medicine. MSCs possess the ability to secrete soluble factors as well as lipid bound extracellular vesicles (EVs). MSCs have gained increased interest and attention as a result of their therapeutic properties, which are thought to be attributed to their secretome. However, while the use of MSCs as whole cells pose heterogeneity concerns and survival issues post-transplantation, such limitations are absent in cell-free EV-based treatments. EVs derived from MSCs are promising therapeutic agents for a range of clinical conditions and disorders owing to their immunomodulatory, pro-regenerative, anti-inflammatory, and antifibrotic activity. Recent successes with preclinical studies using EVs for repair and regeneration of damaged tissues such as cardiac tissue, lung, liver, pancreas, bone, skin, cornea, and blood diseases are discussed in this review. We also discuss delivery strategies of EVs using biomaterials as delivery vehicles through systemic or local administration. Despite its effectiveness in preclinical investigations, the application of MSC-EV in clinical settings will necessitate careful consideration surrounding issues such as: i) scalability and isolation, ii) biodistribution, iii) targeting specific tissues, iv) quantification and characterization, and v) safety and efficacy of dosage. The future of EVs in regenerative medicine is promising yet still needs further investigation on enhancing the efficacy, scalability, and potency for clinical applications.

Manufacturing and validation of Good Manufacturing Practice-compliant regulatory dendritic cells for infusion into organ transplant recipients

BACKGROUND AIMS

Regulatory (or "tolerogenic") dendritic cells (DCregs) are a highly promising, innovative cell therapy for the induction or restoration of antigen-specific tolerance in immune-mediated inflammatory disorders. These conditions include organ allograft rejection, graft-versus-host disease following bone marrow transplantation and various autoimmune disorders. DCregs generated for adoptive transfer have potential to reduce patients' dependence on non-specific immunosuppressive drugs that can induce serious side effects and enhance the risk of infection and certain types of cancer. Here, our aim was to provide a detailed account of our experience manufacturing and validating comparatively large numbers of Good Manufacturing Practice-grade DCregs for systemic (intravenous) infusion into 28 organ (liver) transplant recipients and to discuss factors that influence the satisfaction of release criteria and attainment of target cell numbers.

RESULTS

DCregs were generated in granulocyte-macrophage colony stimulating factor and interleukin (IL)-4 from elutriated monocyte fractions isolated from non-mobilized leukapheresis products of consenting healthy adult prospective liver transplant donors. Vitamin D3 was added on day 0 and 4 and IL-10 on day 4 during the 7-day culture period. Release and post-release criteria included cell viability, purity, phenotype, sterility and functional assessment. The overall conversion rate of monocytes to DCregs was 28 ± 8.2%, with 94 ± 5.1% product viability. The mean cell surface T-cell co-inhibitory to co-stimulatory molecule (programmed death ligand-1:CD86) mean fluorescence intensity ratio was 3.9 ± 2.2, and the mean ratio of anti-inflammatory:pro-inflammatory cytokine product (IL-10:IL-12p70) secreted upon CD40 ligation was 60 ± 63 (median = 40). The mean total number of DCregs generated from a single leukapheresis product (n = 25 donors) and from two leukapheresis products (n = 3 donors) was 489 ± 223 × 10⁶ (n = 28). The mean total number of DCregs infused was 5.9 ± 2.8 × 10⁶ per kg body weight. DCreg numbers within a target cell range of 2.5-10 × 10⁶/kg were achieved for 25 of 27 (92.6%) of products generated.

CONCLUSIONS

High-purity DCregs meeting a range of quality criteria were readily generated from circulating blood monocytes under Good Manufacturing Practice conditions to meet target cell numbers for infusion into prospective organ transplant recipients.

Innate immune cellular therapeutics in transplantation

Successful organ transplantation provides an opportunity to extend the lives of patients with end-stage organ failure. Selectively suppressing the donor-specific alloimmune response, however, remains challenging without the continuous use of non-specific immunosuppressive medications, which have multiple adverse effects including elevated risks of infection, chronic kidney injury, cardiovascular disease, and cancer. Efforts to promote allograft tolerance have focused on manipulating the adaptive immune response, but long-term allograft survival rates remain disappointing. In recent years, the innate immune system has become an attractive therapeutic target for the prevention and treatment of transplant organ rejection. Indeed, contemporary studies demonstrate that innate immune cells participate in both the initial alloimmune response and chronic allograft rejection and undergo non-permanent functional reprogramming in a phenomenon termed "trained immunity." Several types of innate immune cells are currently under investigation as potential therapeutics in transplantation, including myeloid-derived suppressor cells, dendritic cells, regulatory macrophages, natural killer cells, and innate lymphoid cells. In this review, we discuss the features and functions of these cell types, with a focus on their role in the alloimmune response. We examine their potential application as therapeutics to prevent or treat allograft rejection, as well as challenges in their clinical translation and future directions for investigation.

Deinococcus radiodurans R1 Lysate Induces Tolerogenic Maturation in Lipopolysaccharide-Stimulated Dendritic Cells and Protects Dextran Sulfate Sodium-Induced Colitis in Mice

Deinococcus radiodurans is an extremophilic bacterium that can thrive in harsh environments. This property can be attributed to its unique metabolites that possess strong antioxidants and other pharmacological properties. To determine the potential of D. radiodurans R1 lysate (DeinoLys) as a pharmacological candidate for inflammatory bowel disease (IBD), we investigated the anti-inflammatory activity of DeinoLys in bone marrow-derived dendritic cells (BMDCs) and a colitis mice model. Lipopolysaccharide (LPS)-stimulated BMDCs treated with DeinoLys exhibited alterations in their phenotypic and functional properties by changing into tolerogenic DCs, including strongly inhibited proinflammatory cytokines (TNF-α and IL-12p70) and surface molecule expression and activated DC-induced T cell proliferation/activation with high IL-10 production. These phenotypic and functional changes in BMDCs induced by DeinoLys in the presence of LPS were abrogated by IL-10 neutralization. Furthermore, oral administration of DeinoLys significantly reduced clinical symptoms against dextran sulfate sodium-induced colitis, including body weight loss, disease activity index, histological severity in colon tissue, and lower myeloperoxidase level in mice. Our results establish DeinoLys as a potential anti-inflammatory candidate for IBD therapy.

COVID-19 immunopathology with emphasis on Th17 response and cell-based immunomodulation therapy: Potential targets and challenges

The role of the immune system against coronavirus disease 2019 (COVID-19) is unknown in many aspects, and the protective or pathologic mechanisms of the immune response are poorly understood. Pro-inflammatory cytokine release and a consequent cytokine storm can lead to acute respiratory distress syndrome (ARDS) and result in multi-organ failure. There are many T cell subsets during anti-viral immunity. The Th17-associated response, as a pro-inflammatory pathway, and its consequent outcomes in many autoimmune disorders play a fundamental role in progression of systemic hyper-inflammation during COVID-19. Therapeutic strategies based on immunomodulation therapy could be helpful for targeting hyper-inflammatory immune responses in COVID-19, especially Th17-related inflammation and hyper-cytokinemia. Cell-based immunotherapeutic approaches including mesenchymal stem cells (MSCs), tolerogenic dendritic cells (tolDCs) and regulatory T cells (Tregs) seem to be promising strategies as orchestrators of the immune response against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In this review, we highlight Th17-related immunopathology of SARS-CoV-2 infection and discuss cell-based immunomodulatory strategies and their mechanisms for regulation of the hyper-inflammation during COVID-19.

The Role of Lymphangiogenesis in Coronary Atherosclerosis

Lymphatic circulation, a one-way channel system independent of blood circulation, collects interstitial fluid in a blind-end way. Existing widely in various organs and tissues, lymphatic vessels play important roles in maintaining tissue fluid homeostasis, regulating immune function, and promoting lipid transport. Recent studies have shown clear evidence that lymphangiogenesis has a strong mutual effect on coronary atherosclerosis (AS). In this study, we focus on this topic, especially in the aspects of relevant ligand/receptor, inflammation, and adipose metabolism. For the moment, however, the role of lymphangiogenesis and remodeling in coronary AS still remains controversial. The studies of our group and accumulating published evidence show that the pathological remodeling of lymphatic vessels in coronary AS may have a negative effect, but normal functional lymphangiogenesis is probably beneficial to the regression of coronary AS. Thus, the conclusion of this review is that lymphatic vessel function rather than its quantity determines its influence in AS, which needs more evidence to support.

Activation of Aryl Hydrocarbon Receptor by ITE Improves Cardiac Function in Mice After Myocardial Infarction

Background The immune and inflammatory responses play a considerable role in left ventricular remodeling after myocardial infarction (MI). Binding of AhR (aryl hydrocarbon receptor) to its ligands modulates immune and inflammatory responses; however, the effects of AhR in the context of MI are unknown. Therefore, we evaluated the potential association between AhR and MI by treating mice with a nontoxic endogenous AhR ligand, ITE (2-[1'H-indole-3'-carbonyl]-thiazole-4-carboxylic acid methyl ester). We hypothesized that activation of AhR by ITE in MI mice would boost regulatory T-cell differentiation, modulate macrophage activity, and facilitate infarct healing. Methods and Results Acute MI was induced in C57BL/6 mice by ligation of the left anterior descending coronary artery. Then, the mice were randomized to daily intraperitoneal injection of ITE (200 µg/mouse, n=19) or vehicle (n=16) to examine the therapeutic effects of ITE during the postinfarct healing process. Echocardiographic and histopathological analyses revealed that ITE-treated mice exhibited significantly improved systolic function (P<0.001) and reduced infarct size compared with control mice (P<0.001). In addition, we found that ITE increased regulatory T cells in the mediastinal lymph node, spleen, and infarcted myocardium, and shifted the M1/M2 macrophage balance toward the M2 phenotype in vivo, which plays vital roles in the induction and resolution of inflammation after acute MI. In vitro, ITE expanded the Foxp3+ (forkhead box protein P3-positive) regulatory T cells and tolerogenic dendritic cell populations. Conclusions Activation of AhR by a nontoxic endogenous ligand, ITE, improves cardiac function after MI. Post-MI mice treated with ITE have a significantly lower risk of developing advanced left ventricular systolic dysfunction than nontreated mice. Thus, the results imply that ITE has a potential as a stimulator of cardiac repair after MI to prevent heart failure.

Dendritic Cells: Versatile Players in Renal Transplantation

Dendritic cells (DCs) induce and regulate adaptive immunity through migrating and maturing in the kidney. In this procedure, they can adopt different phenotypes—rejection-associated DCs promote acute or chronic injury renal grafts while tolerogenic DCs suppress the overwhelmed inflammation preventing damage to renal functionality. All the subsets interact with effector T cells and regulatory T cells (Tregs) stimulated by the ischemia–reperfusion procedure, although the classification corresponding to different effects remains controversial. Thus, in this review, we discuss the origin, maturation, and pathological effects of DCs in the kidney. Then we summarize the roles of divergent DCs in renal transplantation: taking both positive and negative stages in ischemia–reperfusion injury (IRI), switching phenotypes to induce acute or chronic rejection, and orchestrating surface markers for allograft tolerance via alterations in metabolism. In conclusion, we prospect that multidimensional transcriptomic analysis will revolute researches on renal transplantation by addressing the elusive mononuclear phagocyte classification and providing a holistic view of DC ontogeny and subpopulations.

Synergistic therapeutic effect of mesenchymal stem cells and tolerogenic dendritic cells in an acute colitis mouse model

Cell-based therapy with tolerizing cells has been applied for the treatment of inflammatory bowel disease (IBD) in previous experimental and clinical studies with promising results. In the current study, we utilized the dextran sulfate sodium (DSS)-induced colitis model, to investigate if tolerogenic dendritic cell-mesenchymal stem cell (tDC-MSC) combination therapy can augment the therapeutic effects of single transplantation of each cell type. The effect of MSC and tDC co-transplantation on the severity of colitis was assessed by daily monitoring of body weight, stool consistency, and rectal bleeding, and compared with control groups. Moreover, the colon length, colon weight, myeloperoxidase (MPO) activity were measured and evaluated with histological analysis of colon tissues. The Treg cell percentage and cytokine levels in spleens and mesenteric lymph nodes (MLNs) were measured by flow cytometry and ELISA, respectively. The results showed co-transplantation of MSCs and tDCs was more effective in alleviating the clinical and histological manifestations of colitis than monotherapy, especially when compared with MSC alone. The protective effects of tDC-MSC were accompanied by the induction of Treg cells and increased the production of anti-inflammatory cytokines in spleens and mesenteric lymph nodes. Together, co-transplantation of MSCs and tDCs could be a promising and effective therapeutic approach in the treatment of IBD.

Progress in Liver Transplant Tolerance and Tolerance-Inducing Cellular Therapies

Liver transplantation is currently the most effective method for treating end-stage liver disease. However, recipients still need long-term immunosuppressive drug treatment to control allogeneic immune rejection, which may cause various complications and affect the long-term survival of the recipient. Many liver transplant researchers constantly pursue the induction of immune tolerance in liver transplant recipients, immunosuppression withdrawal, and the maintenance of good and stable graft function. Although allogeneic liver transplantation is more tolerated than transplantation of other solid organs, and it shows a certain incidence of spontaneous tolerance, there is still great risk for general recipients. With the gradual progress in our understanding of immune regulatory mechanisms, a variety of immune regulatory cells have been discovered, and good results have been obtained in rodent and non-human primate transplant models. As immune cell therapies can induce long-term stable tolerance, they provide a good prospect for the induction of tolerance in clinical liver transplantation. At present, many transplant centers have carried out tolerance-inducing clinical trials in liver transplant recipients, and some have achieved gratifying results. This article will review the current status of liver transplant tolerance and the research progress of different cellular immunotherapies to induce this tolerance, which can provide more support for future clinical applications.

Bone marrow dendritic cells deficient for CD40 and IL-23p19 are tolerogenic in vitro

Objective(s):

In addition to pro-inflammatory role, dendritic cells (DCs) can also be anti-inflammatory when they acquire tolerogenic phenotype. In this study we tested the role of CD40 and IL-23p19 in antigen presenting function of bone marrow-derived DCs (BMDCs) by comparing BMDCs derived from CD40 knockout (CD40KO-DCs) and IL-23p19 (IL-23p19KO-DCs) knockout mice with those from C57BL/6 mice (Cont-DCs). We have focused on CD40 and IL-23, as these molecules have well established pro-inflammatory roles in a number of autoimmune and inflammatory diseases.

Materials and Methods:

The expression of maturation markers MHC II and co-stimulatory molecules CD40, CD80, and CD86 was analyzed by flow cytometry, while the expression of CD40 and IL-23p19 was measured by RT-PCR. The capacity of BMDCs to activate CD4+ T cells was evaluated by 3H-thymidine incorporation, and the capacity of BMDCs to uptake antigen was evaluated using fluorescent OVA and flow cytometry.

Results:

The lack of CD40 or IL-23p19 had no effect on uptake of FITC-OVA by the DCs, confirming their immature phenotype. Moreover, CD40KO-DCs had significantly reduced capacity to stimulate proliferation of CD4+ T cells. CD4+ T cells activated by CD40KO-DCs and IL-23p19KO-DCs produced significantly less IFN-γ (P-value ≤0.05), while CD4+ T cells stimulated by IL-23p19KO-DCs produced less GM-CSF and more IL-10 than Cont-DCs.

Conclusion:

This study shows that CD40KO-DCs and IL-23p19KO-DCs have a marked tolerogenic potency in vitro. Future in vivo studies should determine if and to what extent DCs lacking CD40 or IL-23 have a potential to be useful in therapy of autoimmune inflammation.

Effect of mesenchymal stem cell-derived exosomes on the induction of mouse tolerogenic dendritic cells

Dendritic cells (DCs) orchestrate innate inflammatory responses and adaptive immunity through T‐cell activation via direct cell–cell interactions and/or cytokine production. Tolerogenic DCs (tolDCs) help maintain immunological tolerance through the induction of T‐cell unresponsiveness or apoptosis, and generation of regulatory T cells. Mesenchymal stromal cells (MSCs) are adult multipotent cells located within the stroma of bone marrow (BM), but they can be isolated from virtually all organs. Extracellular vesicles and exosomes are released from inflammatory cells and act as messengers enabling communication between cells. To investigate the effects of MSC‐derived exosomes on the induction of mouse tolDCs, murine adipose‐derived MSCs were isolated from C57BL/6 mice and exosomes isolated by ExoQuick‐TC kits. BM‐derived DCs (BMDCs) were prepared and cocultured with MSCs‐derived exosomes (100 μg/ml) for 72 hr. Mature BMDCs were derived by adding lipopolysaccharide (LPS; 0.1μg/ml) at Day 8 for 24 hr. The study groups were divided into (a) immature DC (iDC, Ctrl), (b) iDC + exosome (Exo), (c) iDC + LPS (LPS), and (d) iDC + exosome + LPS (EXO + LPS). Expression of CD11c, CD83, CD86, CD40, and MHCII on DCs was analyzed at Day 9. DC proliferation was assessed by coculture with carboxyfluorescein succinimidyl ester‐labeled BALB/C‐derived splenocytes p. Interleukin‐6 (IL‐6), IL‐10, and transforming growth factor‐β (TGF‐β) release were measured by enzyme‐linked immunosorbent assay. MSC‐derived exosomes decrease DC surface marker expression in cells treated with LPS, compared with control cells ( ≤ .05). MSC‐derived exosomes decrease IL‐6 release but augment IL‐10 and TGF‐β release (p ≤ .05). Lymphocyte proliferation was decreased (p ≤ .05) in the presence of DCs treated with MSC‐derived exosomes. CMSC‐derived exosomes suppress the maturation of BMDCs, suggesting that they may be important modulators of DC‐induced immune responses.

Tolerogenic Dendritic Cells Generated by BAFF Silencing Ameliorate Collagen-Induced Arthritis by Modulating the Th17/Regulatory T Cell Balance

Tolerogenic dendritic cells (tolDCs) have received much attention because of their capacity to restore immune homeostasis. RNA interference techniques have been used in several studies to generate tolDCs by inactivating certain molecules that regulate DC maturation and immunologic function. BAFF is a key B cell survival factor that is not only essential for B cell function but also T cell costimulation, and DCs are the major source of BAFF. In this study, we determined whether BAFF gene silencing in mature DCs could lead to a tolerogenic phenotype as well as the potential therapeutic effect of BAFF-silenced DCs on collagen-induced arthritis (CIA) in mice. Meanwhile, CRISPR/Cas9-mediated BAFF^-/- DC2.4 cells were generated to verify the role of BAFF in DC maturation and functionality. BAFF-silenced DCs and BAFF^-/- DC2.4 cells exhibited an immature phenotype and functional state. Further, the transplantation of BAFF-silenced DCs significantly alleviated CIA severity in mice, which correlated with a reduction in Th17 populations and increased regulatory T cells. In vitro, BAFF-silenced DCs promoted Foxp3 mRNA and IL-10 expression but inhibited ROR-γt mRNA and IL-17A expression in CD4⁺ T cells. Together, BAFF-silenced DCs can alleviate CIA, partly by inducing Foxp3⁺ regulatory T cells and suppressing Th17 subsets. Collectively, BAFF plays an important role in interactions between DCs and T cells, which might be a promising genetic target to generate tolDCs for autoimmune arthritis treatment.

Immunobiology of Atherosclerosis: A Complex Net of Interactions

Cardiovascular disease is the leading cause of mortality worldwide, and atherosclerosis the principal factor underlying cardiovascular events. Atherosclerosis is a chronic inflammatory disease characterized by endothelial dysfunction, intimal lipid deposition, smooth muscle cell proliferation, cell apoptosis and necrosis, and local and systemic inflammation, involving key contributions to from innate and adaptive immunity. The balance between proatherogenic inflammatory and atheroprotective anti-inflammatory responses is modulated by a complex network of interactions among vascular components and immune cells, including monocytes, macrophages, dendritic cells, and T, B, and foam cells; these interactions modulate the further progression and stability of the atherosclerotic lesion. In this review, we take a global perspective on existing knowledge about the pathogenesis of immune responses in the atherosclerotic microenvironment and the interplay between the major innate and adaptive immune factors in atherosclerosis. Studies such as this are the basis for the development of new therapies against atherosclerosis.

Dendritic cells generated in the presence of interferon-α and modulated with dexamethasone as a novel tolerogenic vaccine platform

BACKGROUND

Tolerogenic dendritic cells (tDCs) are considered a novel therapeutic tool in treating autoimmune diseases, allergies, and transplantation reactions. Among numerous pharmacological immune modulators, dexamethasone (Dex) is known to induce potent tolerogenicity in DCs generated from human monocytes with granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-4 (IL-4), and these cells (IL-4-DCs/Dex) are being appraised as a tDC-based platform in clinical settings. Interferon-α (IFNα) represents another powerful inducer of monocyte-derived DCs, which possess higher migratory activity and stability. However, the functions of IFN-DCs/Dex have not been sufficiently analyzed and there are no comparative studies of the tolerogenicity of IFN-DCs/Dex and IL-4-DCs/Dex. This study aimed to investigate the properties of IFN-DCs/Dex in comparison with IL-4-DCs/Dex.

RESULTS

DCs were obtained by cultivation of an adherent fraction of peripheral blood mononuclear cells (MNCs) in the presence of GM-CSF and IFNα or IL-4 with subsequent lipopolysaccharide-driven maturation. Dex (10^-6 M) was added to the cultures at day 3. We showed that generation of IFN-DCs with Dex resulted in decrease in percentage of CD83⁺ and CD86⁺ DCs and increase in numbers of CD14⁺, B7-H1⁺, and Toll-like receptor 2 (TLR2⁺) DCs. Treatment with Dex downregulated pro-inflammatory cytokine production, reduced DC allostimulatory activity, and inhibited DC capacity to stimulate Th1/pro-inflammatory cytokine production, altogether evidencing the induction of a tolerogenic phenotype. As compared to IL-4-DCs/Dex, IFN-DCs/Dex were characterized by larger proportion of TLR2⁺ and CD14⁺ cells, higher production of IL-10 and lower TNFα/IL-10 ratio, more potent capacity to induce T cell anergy, and more efficiently skewed T cell cytokine balance towards Th2/anti-inflammatory profile.

CONCLUSIONS

The data obtained indicate that potent tDCs could be generated by treating IFN-DCs with dexamethasone. The tolerogenic properties of IFN-DCs/Dex are better than or at least equal to those of the IL-4-DCs/Dex, as assessed by in vitro phenotypic and functional assays, suggesting these cells as a new tolerogenic vaccine platform.

Role of extracellular vesicles in stem cell biology

The extracellular vesicles (EVs) are membrane vesicles carrying proteins, nucleic acids, and bioactive lipids of the cell of origin. These vesicles released within the extracellular space and entering into the circulation may transfer their cargo to neighboring or distant cells and induce phenotypical and functional changes that may be relevant in several physiopathological conditions. In an attempt to define the biological properties of EVs, several investigations have focused on their cargo and on the effects elicited in recipient cells. EVs have been involved in modulation of tumor microenvironment and behavior, as well as in the immune and inflammatory response. In the present review, we address the paracrine action of EVs released by stem cells and their potential involvement in the activation of regenerative programs in injured cells.

Advances in therapeutic applications of extracellular vesicles

Extracellular vesicles (EVs) are nanometer-sized, lipid membrane-enclosed vesicles secreted by most, if not all, cells and contain lipids, proteins, and various nucleic acid species of the source cell. EVs act as important mediators of intercellular communication that influence both physiological and pathological conditions. Given their ability to transfer bioactive components and surmount biological barriers, EVs are increasingly being explored as potential therapeutic agents. EVs can potentiate tissue regeneration, participate in immune modulation, and function as potential alternatives to stem cell therapy, and bioengineered EVs can act as delivery vehicles for therapeutic agents. Here, we cover recent approaches and advances of EV-based therapies.

Regulatory dendritic cells for human organ transplantation

Current immunosuppressive (IS) regimens used to prevent organ allograft rejection have well-recognized side effects, that include enhanced risk of infection and certain types of cancer, metabolic disorders, cardiovascular disease, renal complications and failure to control chronic allograft rejection. The life-long dependency of patients on these IS agents reflects their inability to induce donor-specific tolerance. Extensive studies in rodent and non-human primate models have demonstrated the ability of adoptively-transferred regulatory immune cells (either regulatory myeloid cells or regulatory T cells) to promote transplant tolerance. Consequently, there is considerable interest in the potential of regulatory immune cell therapy to allow safe minimization/complete withdrawal of immunosuppression and the promotion of organ transplant tolerance in the clinic. Here, we review the properties of regulatory dendritic cells (DCreg) with a focus on the approaches being taken to generate human DCreg for clinical testing. We also document the early phase clinical trials that are underway to assess DCreg therapy in clinical organ transplantation as well as in autoimmune disorders.

Citrullination Controls Dendritic Cell Transdifferentiation into Osteoclasts

An increased repertoire of potential osteoclast (OC) precursors could accelerate the development of bone-erosive OCs and the consequent bone damage in rheumatoid arthritis (RA). Immature dendritic cells (DCs) can develop into OCs, however, the mechanisms underlying this differentiation switch are poorly understood. We investigated whether protein citrullination and RA-specific anti-citrullinated protein Abs (ACPAs) could regulate human blood-derived DC-OC transdifferentiation. We show that plasticity toward the OC lineage correlated with peptidyl arginine deiminase (PAD) activity and protein citrullination in DCs. Citrullinated actin and vimentin were present in DCs and DC-derived OCs, and both proteins were deposited on the cell surface, colocalizing with ACPAs binding to the cells. ACPAs enhanced OC differentiation from monocyte-derived or circulating CD1c⁺ DCs by increasing the release of IL-8. Blocking IL-8 binding or the PAD enzymes completely abolished the stimulatory effect of ACPAs, whereas PAD inhibition reduced steady-state OC development, as well, suggesting an essential role for protein citrullination in DC-OC transdifferentiation. Protein citrullination and ACPA binding to immature DCs might thus promote differentiation plasticity toward the OC lineage, which can facilitate bone erosion in ACPA-positive RA.

Ways Forward for Tolerance-Inducing Cellular Therapies- an AFACTT Perspective

Clinical studies with cellular therapies using tolerance-inducing cells, such as tolerogenic antigen-presenting cells (tolAPC) and regulatory T cells (Treg) for the prevention of transplant rejection and the treatment of autoimmune diseases have been expanding the last decade. In this perspective, we will summarize the current perspectives of the clinical application of both tolAPC and Treg, and will address future directions and the importance of immunomonitoring in clinical studies that will result in progress in the field.

Tolerogenic Dendritic Cells and T-Regulatory Cells at the Clinical Trials Crossroad for the Treatment of Autoimmune Disease; Emphasis on Type 1 Diabetes Therapy

Tolerogenic dendritic cells and T-regulatory cells are two immune cell populations with the potential to prevent the onset of clinical stage type 1 diabetes, and manage the beginning of underlying autoimmunity, at the time-at-onset and onwards. Initial phase I trials demonstrated that the administration of a number of these cell populations, generated ex vivo from peripheral blood leukocytes, was safe. Outcomes of some of these trials also suggested some level of autoimmunity regulation, by the increase in the numbers of regulatory cells at different points in a network of immune regulation in vivo. As these cell populations come to the cusp of pivotal phase II efficacy trials, a number of questions still need to be addressed. At least one mechanism of action needs to be verified as operational, and through this mechanism biomarkers predictive of the underlying autoimmunity need to be identified. Efficacy in the regulation of the underlying autoimmunity also need to be monitored. At the same time, the absence of a common phenotype core among the different dendritic cell and T-regulatory cell populations, that have completed phase I and early phase II trials, necessitates a better understanding of what makes these cells tolerogenic, especially if a uniform phenotypic core cannot be identified. Finally, the inter-relationship of tolerogenic dendritic cells and T-regulatory cells for survival, induction, and maintenance of a tolerogenic state that manages the underlying diabetes autoimmunity, raises the possibility to co-administer, or even to serially-administer tolerogenic dendritic cells together with T-regulatory cells as a cellular co-therapy, enabling the best possible outcome. This is currently a knowledge gap that this review aims to address.

The Challenge of the Pathogenesis of Parkinson's Disease: Is Autoimmunity the Culprit?

The role of autoimmunity in Parkinson's disease (PD), as one of the most popular research subjects, has been intensively investigated in recent years. Although the ultimate cause of PD is unknown, one major area of interest remains identifying new therapeutic targets and options for patients suffering from PD. Herein, we present a comprehensive review of the impacts of autoimmunity in neurodegenerative diseases, especially PD, and we have composed a logical argument to substantiate that autoimmunity is actively involved in the pathogenesis of PD through several proteins, including α-synuclein, DJ-1, PINK1, and Parkin, as well as immune cells, such as dendritic cells, microglia, T cells, and B cells. Furthermore, a detailed analysis of the relevance of autoimmunity to the clinical symptoms of PD provides strong evidence for the close correlation of autoimmunity with PD. In addition, the previously identified relationships between other autoimmune diseases and PD help us to better understand the disease pattern, laying the foundation for new therapeutic solutions to PD. In summary, this review aims to integrate and present currently available data to clarify the pathogenesis of PD and discuss some controversial but innovative research perspectives on the involvement of autoimmunity in PD, as well as possible novel diagnostic methods and treatments based on autoimmunity targets.

Nrf2-mediated metabolic reprogramming of tolerogenic dendritic cells is protective against aplastic anemia

Aplastic anemia (AA) is a rare disease characterized by immune-mediated suppression of bone marrow (BM) function resulting in progressive pancytopenia. Stem cell transplant and immunosuppressive therapies remain the major treatment choices for AA patients with limited benefit and undesired side effects. Here, we report for the first time the therapeutic utility of Nrf2-induced metabolically reprogrammed tolerogenic dendritic cells (TolDCs) in the suppression of AA in mice. CDDO-DFPA-induced Nrf2 activation resulted in a TolDC phenotype as evidenced by induction of IL-4, IL-10, and TGF-β and suppression of TNFα, IFN-γ, and IL-12 levels in Nrf2^+/+ but not Nrf2^-/- DCs. Cellular metabolism holds the key to determining DC immunogenic or tolerogenic cell fate. Although immature and LPS-induced (mature) Nrf2^+/+ and Nrf2^-/- DCs exhibited similar patterns of oxidative phosphorylation (OXPHOS) and glycolysis, only Nrf2^+/+ DCs partially restored OXPHOS and reduced glycolysis during CDDO-DFPA-induced Nrf2 activation. These results were further confirmed by altered glucose uptake and lactate production. We observed significantly enhanced HO-1 and reduced iNOS/NO production in Nrf2^+/+ compared to Nrf2^-/- DCs, suggesting Nrf2-dependent TolDC induction is linked to suppression of the inhibitory effect of NO on OXPHOS. Furthermore, Nrf2^-/- DCs demonstrated higher antigen-specific T cell proliferation. Lastly, TolDC administration improved hematopoiesis and survival in AA murine model, with decreased Th17 and increased Treg cells. Concomitantly, immunohistochemical analysis of AA patient BM biopsies displayed higher DCs, T cells, and iNOS expression accompanied with lower Nrf2 and HO-1 expression when compared to normal subjects. These results provide new insight into the therapeutic utility of metabolically reprogrammed TolDCs by CDDO-DFPA induced Nrf2 signaling in the treatment of AA.

T Cell-Mediated Chronic Inflammatory Diseases Are Candidates for Therapeutic Tolerance Induction with Heat Shock Proteins

Failing immunological tolerance for critical self-antigens is the problem underlying most chronic inflammatory diseases of humans. Despite the success of novel immunosuppressive biological drugs, the so-called biologics, in the treatment of diseases such rheumatoid arthritis (RA) and type 1 diabetes, none of these approaches does lead to a permanent state of medicine free disease remission. Therefore, there is a need for therapies that restore physiological mechanisms of self-tolerance. Heat shock proteins (HSPs) have shown disease suppressive activities in many models of experimental autoimmune diseases through the induction of regulatory T cells (Tregs). Also in first clinical trials with HSP-based peptides in RA and diabetes, the induction of Tregs was noted. Due to their exceptionally high degree of evolutionary conservation, HSP protein sequences (peptides) are shared between the microbiota-associated bacterial species and the self-HSP in the tissues. Therefore, Treg mechanisms, such as those induced and maintained by gut mucosal tolerance for the microbiota, can play a role by targeting the more conserved HSP peptide sequences in the inflamed tissues. In addition, the stress upregulated presence of HSP in these tissues may well assist the targeting of the HSP induced Treg specifically to the sites of inflammation.

Therapeutic Potential of Secreted Molecules Derived from Human Amniotic Fluid Mesenchymal Stem/Stroma Cells in a Mice Model of Colitis

Inflammatory bowel diseases (IBDs) are the result of pathological immune responses due to environmental factors or microbial antigens into a genetically predisposed individual. Mainly due to their trophic properties, a mounting interest is focused on the use of human mesenchymal stem/stromal cells (hMSCs) to treat IBD disease in animal models. The aim of the study is to test whether the secreted molecules, derived from a specific population of second trimester amniotic fluid mesenchymal stem/stromal cells, the spindle-shaped MSCs (SS-AF-MSCs), could be utilized as a novel therapeutic, cell free approach for IBD therapy. Induction of colitis was achieved by oral administration of dextran sulphate sodium (DSS) (3 % w/v in tap water), for 5 days, to 8-week-old NOD/SCID mice. The progression of colitis was assessed on a daily basis through recording the body weight, stool consistency and bleeding. Conditioned media (CM) derived from SS-AF-MSCs were collected, concentrated and then delivered intraperitoneally into DSS treated mice. To evaluate and determine the inflammatory cytokine levels, histopathological approach was applied. Administration of CM derived from SS-AF-MSCs cells reduced the severity of colitis in mice. More importantly, TGFb1 protein levels were increased in the mice received CM, while TNFa and MMP2 protein levels were decreased, respectively. Accordingly, IL-10 was significantly increased in mice received CM, whereas TNFa and IL-1b were decreased at mRNA level. Our results demonstrated that CM derived from SS-AF-MSCs cells is able to ameliorate DSS-induced colitis in immunodeficient colitis mouse model, and thus, it has a potential for use in IBD therapy.

Clinical Tolerogenic Dendritic Cells: Exploring Therapeutic Impact on Human Autoimmune Disease

Tolerogenic dendritic cell (tDC)-based clinical trials for the treatment of autoimmune diseases are now a reality. Clinical trials are currently exploring the effectiveness of tDC to treat autoimmune diseases of type 1 diabetes mellitus, rheumatoid arthritis, multiple sclerosis (MS), and Crohn's disease. This review will address tDC employed in current clinical trials, focusing on cell characteristics, mechanisms of action, and clinical findings. To date, the publicly reported human trials using tDC indicate that regulatory lymphocytes (largely Foxp3+ T-regulatory cell and, in one trial, B-regulatory cells) are, for the most part, increased in frequency in the circulation. Other than this observation, there are significant differences in the major phenotypes of the tDC. These differences may affect the outcome in efficacy of recently launched and impending phase II trials. Recent efforts to establish a catalog listing where tDC converge and diverge in phenotype and functional outcome are an important first step toward understanding core mechanisms of action and critical "musts" for tDC to be therapeutically successful. In our view, the most critical parameter to efficacy is in vivo stability of the tolerogenic activity over phenotype. As such, methods that generate tDC that can induce and stably maintain immune hyporesponsiveness to allo- or disease-specific autoantigens in the presence of powerful pro-inflammatory signals are those that will fare better in primary endpoints in phase II clinical trials (e.g., disease improvement, preservation of autoimmunity-targeted tissue, allograft survival). We propose that pre-treatment phenotypes of tDC in the absence of functional stability are of secondary value especially as such phenotypes can dramatically change following administration, especially under dynamic changes in the inflammatory state of the patient. Furthermore, understanding the outcomes of different methods of cell delivery and sites of delivery on functional outcomes, as well as quality control variability in the functional outcomes resulting from the various approaches of generating tDC for clinical use, will inform more standardized ex vivo generation methods. An understanding of these similarities and differences, with a reference point the large number of naturally occurring tDC populations with different immune profiles described in the literature, could explain some of the expected and unanticipated outcomes of emerging tDC clinical trials.

Targeting of tolerogenic dendritic cells towards heat-shock proteins: a novel therapeutic strategy for autoimmune diseases?

Tolerogenic dendritic cells (tolDCs) are a promising therapeutic tool to restore immune tolerance in autoimmune diseases. The rationale of using tolDCs is that they can specifically target the pathogenic T-cell response while leaving other, protective, T-cell responses intact. Several ways of generating therapeutic tolDCs have been described, but whether these tolDCs should be loaded with autoantigen(s), and if so, with which autoantigen(s), remains unclear. Autoimmune diseases, such as rheumatoid arthritis, are not commonly defined by a single, universal, autoantigen. A possible solution is to use surrogate autoantigens for loading of tolDCs. We propose that heat-shock proteins may be a relevant surrogate antigen, as they are evolutionarily conserved between species, ubiquitously expressed in inflamed tissues and have been shown to induce regulatory T cells, ameliorating disease in various arthritis mouse models. In this review, we provide an overview on how immune tolerance may be restored by tolDCs, the problem of selecting relevant autoantigens for loading of tolDCs, and why heat-shock proteins could be used as surrogate autoantigens.

Myeloid-derived suppressor cells and myeloid regulatory cells in cancer and autoimmune disorders

Myeloid-derived suppressor cells (MDSCs) were originally described as a heterogeneous population of immature cells derived from myeloid progenitors with immune-suppressive functions in tumor-bearing hosts. In recent years, increasing number of studies have described various populations of myeloid cells with MDSC-like properties in murine models of cancer and autoimmune diseases. These studies have observed that the populations of MDSCs are increased during inflammation and autoimmune conditions. In addition, MDSCs can effectively suppress T cell responses and modulate the activity of natural killer cells and other myeloid cells. MDSCs have also been implicated in the induction of regulatory T cell production. Furthermore, these cells have the potential to suppress the autoimmune response, thereby limiting tissue injury. Myeloid regulatory cells (Mregs) are recently attracting increasing attention, since they function in proinflammatory and immune suppression in autoimmune diseases, as well as in various types of cancer. Currently, research focus is directed from MDSCs to Mregs in cancer and autoimmune diseases. The present study reviewed the suppressive roles of MDSCs in various autoimmune murine models, the immune modulation of MDSCs to T helper 17 lymphocytes, as well as the proinflammatory and immunosuppressive roles of Mregs in various types of cancer and autoimmune diseases.

Stem Cell-Derived Extracellular Vesicles and Immune-Modulation

Extra-cellular vesicles (EVs) are bilayer membrane structures enriched with proteins, nucleic acids, and other active molecules and have been implicated in many physiological and pathological processes over the past decade. Recently, evidence suggests EVs to play a more dichotomic role in the regulation of the immune system, whereby an immune response may be enhanced or supressed by EVs depending on their cell of origin and its functional state. EVs derived from antigen (Ag)-presenting cells for instance, have been involved in both innate and acquired (or adaptive) immune responses, as Ag carriers or presenters, or as vehicles for delivering active signaling molecules. On the other hand, tumor and stem cell derived EVs have been identified to exert an inhibitory effect on immune responses by carrying immuno-modulatory effectors, such as transcriptional factors, non-coding RNA (Species), and cytokines. In addition, stem cell-derived EVs have also been reported to impair dendritic cell maturation and to regulate the activation, differentiation, and proliferation of B cells. They have been shown to control natural killer cell activity and to suppress the innate immune response (IIR). Studies reporting the role of EVs on T lymphocyte modulation are controversial. Discrepancy in literature may be due to stem cell culture conditions, methods of EV purification, EV molecular content, and functional state of both parental and target cells. However, mesenchymal stem cell-derived EVs were shown to play a more suppressive role by shifting T cells from an activated to a T regulatory phenotype. In this review, we will discuss how stem cell-derived EVs may contribute toward the modulation of the immune response. Collectively, stem cell-derived EVs mainly exhibit an inhibitory effect on the immune system.

PDGF upregulates CLEC-2 to induce T regulatory cells

The effect of platelet derived growth factor (PDGF) on immune cells is not elucidated. Here, we demonstrate PDGF inhibited the maturation of human DCs and induced IL-10 secretion. Culture of PDGF-DCs with T cells induced the polarization of T cells towards FoxP3 expressing T regulatory cells that secreted IL-10. Gene expression studies revealed that PDGF induced the expression of C-type lectin like receptor member 2, (CLEC-2) receptor on DCs. Furthermore, DCs transfected with CLEC-2 induced T regulatory cells in DC-T cell co-culture. CLEC-2 is naturally expressed on platelets. Therefore, to confirm whether CLEC-2 is responsible for inducing the T regulatory cells, T cells were cultured with either CLEC-2 expressing platelets or soluble CLEC-2. Both conditions resulted in the induction of regulatory T cells. The generation of T regulatory cells was probably due to the binding of CLEC-2 with its ligand podoplanin on T cells, since crosslinking of podoplanin on the T cells also resulted in the induction of T regulatory cells. These data demonstrate that PDGF upregulates the expression of CLEC-2 on cells to induce T regulatory cells.

Cryopreserved vitamin D3-tolerogenic dendritic cells pulsed with autoantigens as a potential therapy for multiple sclerosis patients

Background

Tolerogenic dendritic cells (tolDC) have been postulated as a potent immunoregulatory therapy for autoimmune diseases such as multiple sclerosis (MS). In a previous study, we demonstrated that the administration of antigen-specific vitamin D₃ (vitD3) tolDC in mice showing clinical signs of experimental autoimmune encephalomyelitis (EAE; the animal model of MS) resulted in abrogation of disease progression. With the purpose to translate this beneficial therapy to the clinics, we have investigated the effectivity of vitD3-frozen antigen-specific tolDC pulsed with myelin oligodendrocyte glycoprotein 40-55 peptide (f-tolDC-MOG) since it would reduce the cost, functional variability and number of leukapheresis to perform to the patients.

Methods

Mice showing EAE clinical signs were treated with repetitive doses of f-tolDC-MOG. Tolerogenic mechanisms induced by the therapy were analysed by flow cytometry and T cell proliferation assays.

Results

Treatment with f-tolDC-MOG was effective in ameliorating clinical signs of mice with EAE, inhibiting antigen-specific reactivity and inducing Treg. In addition, the long-term treatment was well tolerated and leading to a prolonged maintenance of tolerogenicity mediated by induction of Breg, reduction of NK cells and activation of immunoregulatory NKT cells.

Conclusions

The outcomes of this study show that the use of antigen-specific f-tolDC promotes multiple and potent tolerogenic mechanisms. Moreover, these cells can be kept frozen maintaining their tolerogenic properties, which is a relevant step for their translation to the clinic. Altogether, vitD3 f-tolDC-MOG is a potential strategy to arrest the autoimmune destruction in MS patients.

Regulation of chronic inflammatory and immune processes by extracellular vesicles

Almost all cell types release extracellular vesicles (EVs), which are derived either from multivesicular bodies or from the plasma membrane. EVs contain a subset of proteins, lipids, and nucleic acids from the cell from which they are derived. EV factors, particularly small RNAs such as miRNAs, likely play important roles in cell-to-cell communication both locally and systemically. Most of the functions associated with EVs are in the regulation of immune responses to pathogens and cancer, as well as in regulating autoimmunity. This Review will focus on the different modes of immune regulation, both direct and indirect, by EVs. The therapeutic utility of EVs for the regulation of immune responses will also be discussed.

Dendritic Cells in Systemic Lupus Erythematosus: From Pathogenic Players to Therapeutic Tools

System lupus erythematosus (SLE) is a multifactorial systemic autoimmune disease with a wide variety of presenting features. SLE is believed to result from dysregulated immune responses, loss of tolerance of CD4 T cells and B cells to ubiquitous self-antigens, and the subsequent production of anti-nuclear and other autoreactive antibodies. Recent research has associated lupus development with changes in the dendritic cell (DC) compartment, including altered DC subset frequency and localization, overactivation of mDCs and pDCs, and functional defects in DCs. Here we discuss the current knowledge on the role of DC dysfunction in SLE pathogenesis, with the focus on DCs as targets for interventional therapies.

Dendritic Cell-based Immunotherapy for Rheumatoid Arthritis: from Bench to Bedside

Dendritic cells (DCs) are professional antigen presenting cells, and play an important role in the induction of antigen-specific adaptive immunity. However, some DC populations are involved in immune regulation and immune tolerance. These DC populations are believed to take part in the control of immune exaggeration and immune disorder, and maintain immune homeostasis in the body. Tolerogenic DCs (tolDCs) can be generated in vitro by genetic or pharmacological modification or by controlling the maturation stages of cytokine-derived DCs. These tolDCs have been investigated for the treatment of rheumatoid arthritis (RA) in experimental animal models. In the last decade, several in vitro and in vivo approaches have been translated into clinical trials. As of 2015, three tolDC trials for RA are on the list of ClinicalTrial.gov (www.clinicaltrials.gov). Other trials for RA are in progress and will be listed soon. In this review, we discuss the evolution of tolDC-based immunotherapy for RA and its limitations and future prospects.

Prospective Clinical Testing of Regulatory Dendritic Cells in Organ Transplantation

Dendritic cells (DC) are rare, professional antigen-presenting cells with ability to induce or regulate alloimmune responses. Regulatory DC (DCreg) with potential to down-modulate acute and chronic inflammatory conditions that occur in organ transplantation can be generated in vitro under a variety of conditions. Here, we provide a rationale for evaluation of DCreg therapy in clinical organ transplantation with the goal of promoting sustained, donor-specific hyporesponsiveness, while lowering the incidence and severity of rejection and reducing patients’ dependence on anti-rejection drugs. Generation of donor- or recipient-derived DCreg that suppress T cell responses and prolong transplant survival in rodents or non-human primates has been well-described. Recently, good manufacturing practice (GMP)-grade DCreg have been produced at our Institution for prospective use in human organ transplantation. We briefly review experience of regulatory immune therapy in organ transplantation and describe our experience generating and characterizing human monocyte-derived DCreg. We propose a phase I/II safety study in which the influence of donor-derived DCreg combined with conventional immunosuppression on subclinical and clinical rejection and host alloimmune responses will be examined in detail.

Type 1 diabetes genetic susceptibility and dendritic cell function: potential targets for treatment

Type 1 diabetes is an autoimmune disease that results from the defective induction or maintenance of T cell tolerance against islet β cell self-antigens. Under steady-state conditions, dendritic cells with tolerogenic properties are critical for peripheral immune tolerance. Tolerogenic dendritic cells can induce T cell anergy and deletion and, in some contexts, induce or expand regulatory T cells. Dendritic cells contribute to both immunomodulatory effects and triggering of pathogenesis in type 1 diabetes. This immune equilibrium is affected by both genetic and environmental factors that contribute to the development of type 1 diabetes. Genome-wide association studies and disease association studies have identified >50 polymorphic loci that lend susceptibility or resistance to insulin-dependent diabetes mellitus. In parallel, diabetes susceptibility regions known as insulin-dependent diabetes loci have been identified in the nonobese diabetic mouse, a model for human type 1 diabetes, providing a better understanding of potential immunomodulatory factors in type 1 diabetes risk. Most genetic candidates have annotated immune cell functions, but the focus has been on changes to T and B cells. However, it is likely that some of the genomic susceptibility in type 1 diabetes directly interrupts the tolerogenic potential of dendritic cells in the pathogenic context of ongoing autoimmunity. Here, we will review how gene polymorphisms associated with autoimmune diabetes may influence dendritic cell development and maturation processes that could lead to alterations in the tolerogenic function of dendritic cells. These insights into potential tolerogenic and pathogenic roles for dendritic cells have practical implications for the clinical manipulation of dendritic cells toward tolerance to prevent and treat type 1 diabetes.

Clinical Use of Tolerogenic Dendritic Cells-Harmonization Approach in European Collaborative Effort

The number of patients with autoimmune diseases and severe allergies and recipients of transplants increases worldwide. Currently, these patients require lifelong administration of immunomodulatory drugs. Often, these drugs are expensive and show immediate or late-occurring severe side effects. Treatment would be greatly improved by targeting the cause of autoimmunity, that is, loss of tolerance to self-antigens. Accumulating knowledge on immune mechanisms has led to the development of tolerogenic dendritic cells (tolDC), with the specific objective to restrain unwanted immune reactions in the long term. The first clinical trials with tolDC have recently been conducted and more tolDC trials are underway. Although the safety trials have been encouraging, many questions relating to tolDC, for example, cell-manufacturing protocols, administration route, amount and frequency, or mechanism of action, remain to be answered. Aiming to join efforts in translating tolDC and other tolerogenic cellular products (e.g., Tregs and macrophages) to the clinic, a European COST (European Cooperation in Science and Technology) network has been initiated-A FACTT (action to focus and accelerate cell-based tolerance-inducing therapies). A FACTT aims to minimize overlap and maximize comparison of tolDC approaches through establishment of minimum information models and consensus monitoring parameters, ensuring that progress will be in an efficient, safe, and cost-effective way.

Tolerogenic dendritic cells show gene expression profiles that are different from those of immunogenic dendritic cells in DBA/1 mice

Tolerogenic dendritic cells (tDCs) play an important role in inducing peripheral tolerance; however, few tDC-specific markers have been identified. The aims of this study were to examine whether tDCs show a different gene expression profile from that of immunogenic DCs and identify specific gene markers of each cell type, in DBA/1 mice. tDCs were generated by treating immature DCs (imDCs) with TNF-α and type II collagen. The gene expression profiles of mature (m)DCs and tDCs were then investigated by microarray analysis and candidate markers were validated by quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR). Supervised selection identified 75 gene signatures, 63 of which were consistently upregulated in mDCs and 12 of which were upregulated only in tDCs. Additionally, 10 genes were overexpressed or equally expressed in both tDCs and mDCs. Scin (tDC-specific genes) and Orm1, Pdlim4 and Enpp2 (mDC-specific genes) were validated by real-time qRT-PCR. Taken together, these results clearly show that tDCs and mDCs can be identified according to their expression of specific gene markers.

IL-10/IFNγ co-expressing CD4(+) T cells induced by IL-10 DC display a regulatory gene profile and downmodulate T cell responses

Induced regulatory T cells (iTreg) are imperative for tolerance induction and spreading of infectious tolerance. Ex vivo generated tolerogenic dendritic cells (tDCs) have strong therapeutic potential to induce antigen-specific iTreg. We previously demonstrated that IL-10 tDC-primed T cells are very suppressive and produce IL-10. Here, we show that the majority of IL-10(+) T cells co-express IFNγ, giving rise to the question whether these cells are proinflammatory or regulatory. Whole genome gene expression analysis revealed a strong regulatory gene profile and a suppressed Th1 gene profile for IL-10/IFNγ co-expressing CD4(+) T cells. Protein analysis confirmed an extensive regulatory phenotype for IL-10(+)/IFNγ(+) T cells, with specific enhanced expression of GARP and PD-1. In line with these data, isolated IL-10(+)/IFNγ(+) T cells displayed potent suppressive capacity. Thus, IL-10/IFNγ co-expressing CD4(+) T cells induced by IL-10 tDC show dominance of immunomodulation over Th1-mediated immunoactivation and can contribute to induction or spreading of immunological tolerance.

The transcription factor MITF is a critical regulator of GPNMB expression in dendritic cells

BACKGROUND

Dendritic cells (DC) are the most potent antigen-presenting cells (APC) with the unique ability to activate naïve T cells and to initiate and maintain primary immune responses. Immunosuppressive and anti-inflammatory stimuli on DC such as the cytokine IL-10 suppress the activity of the transcription factor NF-κB what results in downregulation of costimulatory molecules, MHC and cytokine production. Glycoprotein NMB (GPNMB) is a transmembrane protein, which acts as a coinhibitory molecule strongly inhibiting T cell responses if present on APC. Interestingly, its expression on human monocyte-derived dendritic cells (moDC) is dramatically upregulated upon treatment with IL-10 but also by the BCR-ABL tyrosine kinase inhibitors (TKI) imatinib, nilotinib or dasatinib used for the treatment of chronic myeloid leukemia (CML). However, the molecular mechanisms responsible for GPNMB overexpression are yet unknown.

RESULTS

The immunosuppressive cytokine IL-10 and the BCR-ABL TKI imatinib or nilotinib, that were examined here, concordantly inhibit the PI3K/Akt signaling pathway, thereby activating the downstream serine/threonine protein kinase GSK3ß, and subsequently the microphthalmia-associated transcription factor (MITF) that is phosphorylated and translocated into the nucleus. Treatment of moDC with a small molecule inhibitor of MITF activity reduced the expression of GPNMB at the level of mRNA and protein, indicating that GPNMB expression is in fact facilitated by MITF activation. In line with these findings, PI3K/Akt inhibition was found to result in GPNMB overexpression accompanied by reduced stimulatory capacity of moDC in mixed lymphocyte reactions (MLR) with allogeneic T cells that could be restored by addition of the GPNMB T cell ligand syndecan-4 (SD-4).

CONCLUSIONS

In summary, imatinib, nilotinib or IL-10 congruently inhibit the PI3K/Akt signaling pathway thereby activating MITF in moDC, resulting in a tolerogenic phenotype. These findings extend current knowledge on the molecular mechanisms balancing activating and inhibitory signals in human DC and may facilitate the targeted manipulation of T cell responses in the context of DC-based immunotherapeutic interventions.

Different protein of Echinococcus granulosus stimulates dendritic induced immune response

Cystic echinococcosis is a chronic infectious disease that results from a host/parasite interaction. Vaccination with ferritin derived from Echinococcus granulosus is a potential preventative treatment. To understand whether ferritin is capable of inducing a host immune response, we investigated the response of dendritic cells (DCs) to both recombinant ferritin protein and the hydatid fluid (HF) of E. granulosus. We evaluated the immunomodulatory potential of these antigens by performing, immunocytochemistry, electron microscopy and in vivo imaging of monocyte-derived murine DCs. During antigen stimulation of DCs, ferritin cause DCs maturation and induced higher levels of surface marker expression and activated T-cell proliferation and migration. On contrary, HF failed to induce surface marker expression and to stimulate T-cell proliferation. In response to HF, DCs produced interleukin-6 (IL-6), but no IL-12 and IL-10. DCs stimulated with ferritin produced high levels of cytokines. Overall, HF appears to induce host immunosuppression in order to ensure parasite survival via inhibits DC maturation and promotes Th2-dependent secretion of cytokines. Although ferritin also promoted DC maturation and cytokine release, it also activates CD4+T-cell proliferation, but regard of the mechanism of the Eg.ferritin induce host to eradicate E. granulosus were not clear.