Regulatory dendritic cell therapy: from rodents to clinical application. Immunol Lett. 2014;161:216-221. [PMID: 24316407 DOI: 10.1016/j.imlet.2013.11.016]

Adipose-derived stem cell modulate tolerogenic dendritic cell-induced T cell regulation is correlated with activation of Notch-NFκB signaling

BACKGROUND

Adipose-derived stem cells (ASCs) are recognized for their potential immunomodulatory properties. In the immune system, tolerogenic dendritic cells (DCs), characterized by an immature phenotype, play a crucial role in inducing regulatory T cells (Tregs) and promoting immune tolerance. Notch1 signaling has been identified as a key regulator in the development and function of DCs. However, the precise involvement of Notch1 pathway in ASC-mediated modulation of tolerogenic DCs and its impact on immune modulation remain to be fully elucidated. This study aims to investigate the interplay between ASCs and DCs, focusing the role of Notch1 signaling and downstream pathways in ASC-modulated tolerogenic DCs.

METHODS

Rat bone marrow-derived myeloid DCs were directly co-cultured with ASCs to generate ASC-treated DCs (ASC-DCs). Notch signaling was inhibited using DAPT, while NFκB pathways were inhibited by NEMO binding domain peptide and si-NIK. Flow cytometry assessed DC phenotypes. Real-time quantitative PCR, Western blotting and immunofluorescence determined the expression of Notch1, Jagged1 and the p52/RelB complex in ASC- DCs.

RESULTS

Notch1 and Jagged1 were highly expressed on both DCs and ASCs. ASC-DCs displayed significantly reduced levels of CD80, CD86 and MHC II compared to mature DCs. Inhibiting the Notch pathway with DAPT reversed the dedifferentiation effects. The percentage of induced CD25+/FOXP3+/CD4+ Tregs decreased when ASC-DCs were treated with DAPT (inhibition of the Notch pathway) and si-NIK (inhibition of the non-canonical NFκB pathway).

CONCLUSIONS

ASCs induce DC tolerogenicity by inhibiting maturation and promoting downstream Treg generation, involving the Notch and NFκB pathways. ASC-induced tolerogenic DCs can be a potential immunomodulatory tool for clinical application.

Current state of knowledge and challenges for harnessing the power of dendritic cells in cancer immunotherapy

DCs have great promise for cancer immunotherapy and are essential for coordinating immune responses. In the battle against cancer, using DCs' ability to stimulate the immune system and focus it on tumor cells has shown to be a viable tactic. This study offers a thorough summary of recent developments as well as potential future paths for DC-based immunotherapy against cancer. This study reviews the many methods used in DC therapy, such as vaccination and active cellular immunotherapy. The effectiveness and safety of DC-based treatments for metastatic castration-resistant prostate cancer and non-small cell lung cancer are highlighted in these investigations. The findings indicate longer survival times and superior results for particular patient groups. We are aware of the difficulties and restrictions of DC-based immunotherapy, though. These include the immunosuppressive tumor microenvironment, the intricacy of DC production, and the heterogeneity within DC populations. More study and development are needed to overcome these challenges to enhance immunological responses, optimize treatment regimens, and increase scalability.

Dendritic cells in liver transplantation immune response

Dendritic cells (DCs) are the most powerful antigen presenting cells (APCs), they are considered one of the key regulatory factors in the liver immune system. There is currently much interest in modulating DC function to improve transplant immune response. In liver transplantation, DCs participate in both the promotion and inhibition of the alloreponse by adopting different phenotypes and function. Thus, in this review, we discussed the origin, maturation, migration and pathological effects of several DC subsets, including the conventional DC (cDC), plasmacytoid DC (pDC) and monocyte-derived DC (Mo-DC) in liver transplantation, and we summarized the roles of these DC subsets in liver transplant rejection and tolerance. In addition, we also outlined the latest progress in DC-based related treatment regimens. Overall, our discussion provides a beneficial resource for better understanding the biology of DCs and their manipulation to improve the immune adaptability of patients in transplant status.

IL-10-Functionalized Hydrogels Support Immunosuppressive Dendritic Cell Phenotype and Function

Biomaterial systems such as hydrogels enable localized delivery and postinjection modulation of cellular therapies in a wide array of contexts. Biomaterials as adjuvants have been an active area of investigation, but the study of functionalized biomaterials supporting immunosuppressive cell therapies for tolerogenic applications is still nascent. Here, we developed a 4-arm poly(ethylene-glycol)-maleimide (PEG-4MAL) hydrogel functionalized with interleukin-10 (IL-10) to improve the local delivery and efficacy of a cell therapy against autoimmune disease. The biophysical and biochemical properties of PEG-4MAL hydrogels were optimized to support dendritic cell (DC) viability and an immature phenotype. IL-10-functionalized PEG-4MAL (PEG-IL10) hydrogels exhibited controlled IL-10 release, extended the duration of DC support, and protected DCs from inflammatory assault. After incorporation in PEG-IL10 hydrogels, these DCs induced CD25+FoxP3+ regulatory T cells (Tregs) during in vitro coculture. These studies serve as a proof-of-concept for improving the efficacy of immunosuppressive cell therapies through biomaterial delivery. The flexible nature of this system enables its widespread application across a breadth of other tolerogenic applications for future investigation.

Advancements in cell membrane camouflaged nanoparticles: A bioinspired platform for cancer therapy

The idea of employing natural cell membranes as a coating medium for nanoparticles (NPs) endows man-made vectors with natural capabilities and benefits. In addition to retaining the physicochemical characteristics of the NPs, the biomimetic NPs also have the functionality of source cell membranes. It has emerged as a promising approach to enhancing the properties of NPs for drug delivery, immune evasion, imaging, cancer-targeting, and phototherapy sensitivity. Several studies have been reported with a multitude of approaches to reengineering the surface of NPs using biological membranes. Owing to their low immunogenicity and intriguing biomimetic properties, cell-membrane-based biohybrid delivery systems have recently gained a lot of interest as therapeutic delivery systems. This review summarises different kinds of biomimetic NPs reported so far, their fabrication aspects, and their application in the biomedical field. Finally, it briefs on the latest advances available in this biohybrid concept.

Anti-Mouse CD83 Monoclonal Antibody Targeting Mature Dendritic Cells Provides Protection Against Collagen Induced Arthritis

Antibodies targeting the activation marker CD83 can achieve immune suppression by targeting antigen-presenting mature dendritic cells (DC). This study investigated the immunosuppressive mechanisms of anti-CD83 antibody treatment in mice and tested its efficacy in a model of autoimmune rheumatoid arthritis. A rat anti-mouse CD83 IgG2a monoclonal antibody, DCR-5, was developed and functionally tested in mixed leukocyte reactions, demonstrating depletion of CD83⁺ conventional (c)DC, induction of regulatory DC (DCreg), and suppression of allogeneic T cell proliferation. DCR-5 injection into mice caused partial splenic cDC depletion for 2-4 days (mostly CD8⁺ and CD83⁺ cDC affected) with a concomitant increase in DCreg and regulatory T cells (Treg). Mice with collagen induced arthritis (CIA) treated with 2 or 6 mg/kg DCR-5 at baseline and every three days thereafter until euthanasia at day 36 exhibited significantly reduced arthritic paw scores and joint pathology compared to isotype control or untreated mice. While both doses reduced anti-collagen antibodies, only 6 mg/kg achieved significance. Treatment with 10 mg/kg DCR-5 was ineffective. Immunohistological staining of spleens at the end of CIA model with CD11c, CD83, and FoxP3 showed greater DC depletion and Treg induction in 6 mg/kg compared to 10 mg/kg DCR-5 treated mice. In conclusion, DCR-5 conferred protection from arthritis by targeting CD83, resulting in selective depletion of mature cDC and subsequent increases in DCreg and Treg. This highlights the potential for anti-CD83 antibodies as a targeted therapy for autoimmune diseases.

Concanavalin A-induced autoimmune hepatitis model in mice: Mechanisms and future outlook

The concanavalin A (Con A)-induced liver injury mouse model is a typical animal model focusing on T cell-dependent hepatic damage in the field of autoimmune hepatitis (AIH). However, the underlying mechanism of hepatic dysfunction due to cell activation or signaling pathways triggered by Con A has not been fully clarified. Therefore, the controversy on this model remains in the academic community. In this article, we first summarized the merit and demerit of this contentious model from the perspectives of cell dysfunction, microcirculation disturbance, involved signaling pathways, as well as the properties of Con A. Then, we summed up the scientific implications of the model in elucidating the pathogenesis of AIH, and the shortcomings of this model were also summarized to elucidate the pathogenesis and application prospect of this classical liver injury mouse model in the study of AIH.

Interleukin-10 and Transforming Growth Factor-β Cytokines Decrease Immune Activation During Normothermic Ex Vivo Machine Perfusion of the Rat Liver

Normothermic ex vivo liver perfusion (NEVLP) is a novel system for organ preservation that may improve over static cold storage clinically and offers the chance for graft modification prior to transplantation. Although recent studies have shown the presence of inflammatory molecules during perfusion, none have yet shown the effects of NEVLP on liver-resident immune cell activation. We investigated the effects of NEVLP on liver-resident immune cell activation and assessed the ability of anti-inflammatory cytokines interleukin 10 (IL10) and transforming growth factor β (TGF-β) to improve organ function and reduce immune activation during perfusion. Rat livers were perfused for 4 hours at 37°C with or without the addition of 20 ng/mL of each IL10 and TGF-β (n = 7). Naïve and cold storage (4 hours at 4°C) livers served as controls (n = 4). Following preservation, gene expression profiles were assessed through single-cell RNA sequencing; dendritic cell and macrophage activation was measured by flow cytometry; and cytokine production was assessed by enzyme-linked immunosorbent assay. NEVLP induced a global inflammatory gene expression signature, most notably in liver-resident macrophages and dendritic cells, which was accompanied by an increase in cell-surface levels of major histocompatibility complex (MHC) II, CD40, and CD86. Immune activation was partially ameliorated by IL10 and TGF-β treatment, but no changes were observed in inflammatory cytokine production. Overall levels of liver damage and cellular apoptosis from perfusion were low, and liver function was improved with IL10 and TGF-β treatment. This is the first study to demonstrate that liver-resident immune cells gain an activated phenotype during NEVLP on both the gene and protein level and that this activation can be reduced through therapeutic intervention with IL10 and TGF-β.

The immune niche of the liver

The liver is an essential organ that is critical for the removal of toxins, the production of proteins, and the maintenance of metabolic homeostasis. Behind each liver functional unit, termed lobules, hides a heterogeneous, complex, and well-orchestrated system. Despite parenchymal cells being most commonly associated with the liver's primary functionality, it has become clear that it is the immune niche of the liver that plays a central role in maintaining both local and systemic homeostasis by propagating hepatic inflammation and orchestrating its resolution. As such, the immunological processes that are at play in healthy and diseased livers are being investigated thoroughly in order to understand the underpinnings of inflammation and the potential avenues for restoring homeostasis. This review highlights recent advances in our understanding of the immune niche of the liver and provides perspectives for how the implementation of new transcriptomic, multimodal, and spatial technologies can uncover the heterogeneity, plasticity, and location of hepatic immune populations. Findings from these technologies will further our understanding of liver biology and create a new framework for the identification of therapeutic targets.

Transfection of Vitamin D3-Induced Tolerogenic Dendritic Cells for the Silencing of Potential Tolerogenic Genes. Identification of CSF1R-CSF1 Signaling as a Glycolytic Regulator

The use of autologous tolerogenic dendritic cells (tolDC) has become a promising strategy to re-establish immune tolerance in autoimmune diseases. Among the different strategies available, the use of vitamin D3 for the generation of tolDC (VitD3-tolDC) has been widely tested because of their immune regulatory properties. To identify molecules and pathways involved in the generation of VitD3-tolDC, we established an easy and fast gene silencing method based on the use of Viromer blue to introduce siRNA into monocytes on day 1 of culture differentiation. The analysis of the effect of CD209 (DC-SIGN) and CD115 (CSF1R) down-modulation on the phenotype and functionality of transfected VitD3-tolDC revealed a partial role of CD115 in their tolerogenicity. Further investigations showed that CSF1R-CSF1 signaling is involved in the induction of cell metabolic reprogramming, triggering glycolysis to produce high amounts of lactate, a novel suppressive mechanism of T cell proliferation, recently found in autologous tolerogenic dendritic cells (ATDCs).

Rapamycin Alternatively Modifies Mitochondrial Dynamics in Dendritic Cells to Reduce Kidney Ischemic Reperfusion Injury

Dendritic cells (DCs) are unique immune cells that can link innate and adaptive immune responses and Immunometabolism greatly impacts their phenotype. Rapamycin is a macrolide compound that has immunosuppressant functions and is used to prevent graft loss in kidney transplantation. The current study evaluated the therapeutic potential of ex-vivo rapamycin treated DCs to protect kidneys in a mouse model of acute kidney injury (AKI). For the rapamycin single (S) treatment (Rapa-S-DC), Veh-DCs were treated with rapamycin (10 ng/mL) for 1 h before LPS. In contrast, rapamycin multiple (M) treatment (Rapa-M-DC) were exposed to 3 treatments over 7 days. Only multiple ex-vivo rapamycin treatments of DCs induced a persistent reprogramming of mitochondrial metabolism. These DCs had 18-fold more mitochondria, had almost 4-fold higher oxygen consumption rates, and produced more ATP compared to Veh-DCs (Veh treated control DCs). Pathway analysis showed IL10 signaling as a major contributing pathway to the altered immunophenotype after Rapamycin treatment compared to vehicle with significantly lower cytokines Tnfa, Il1b, and Il6, while regulators of mitochondrial content Pgc1a, Tfam, and Ho1 remained elevated. Critically, adoptive transfer of rapamycin-treated DCs to WT recipients 24 h before bilateral kidney ischemia significantly protected the kidneys from injury with a significant 3-fold improvement in kidney function. Last, the infusion of DCs containing higher mitochondria numbers (treated ex-vivo with healthy isolated mitochondria (10 µg/mL) one day before) also partially protected the kidneys from IRI. These studies demonstrate that pre-emptive infusion of ex-vivo reprogrammed DCs that have higher mitochondria content has therapeutic capacity to induce an anti-inflammatory regulatory phenotype to protect kidneys from injury.

Hepatic Inflammation Confers Protective Immunity Against Liver Stages of Malaria Parasite

Deciphering the mechanisms by which Plasmodium parasites develop inside hepatocytes is an important step toward the understanding of malaria pathogenesis. We propose that the nature and the magnitude of the inflammatory response in the liver are key for the establishment of the infection. Here, we used mice deficient in the multidrug resistance-2 gene (Mdr2-/-)-encoded phospholipid flippase leading to the development of liver inflammation. Infection of Mdr2-/- mice with Plasmodium berghei ANKA (PbANKA) sporozoites (SPZ) resulted in the blockade of hepatic exo-erythrocytic forms (EEFs) with no further development into blood stage parasites. Interestingly, cultured primary hepatocytes from mutant and wild-type mice are equally effective in supporting EEF development. The abortive infection resulted in a long-lasting immunity in Mdr2-/- mice against infectious SPZ where neutrophils and IL-6 appear as key effector components along with CD8+ and CD4+ effector and central memory T cells. Inflammation-induced breakdown of liver tolerance promotes anti-parasite immunity and provides new approaches for the design of effective vaccines against malaria disease.

Intranasal administration of regulatory dendritic cells is useful for the induction of nasal mucosal tolerance in a mice model of allergic rhinitis

Background

Intranasally administered dendritic cells (DCs) migrate into blood and thymus to induce immune responses. Regulatory dendritic cells (DCs) are also useful agents for allergy control. However, to the best of our knowledge, the effects of intranasal administration of regulatory DCs on allergy have not been reported until now. Therefore, we examined the effects of intranasal route of administration of CD40-silenced DCs on allergic responses and compared these with the effects of other administration routes, based on our previous findings on the inhibitory effects of CD40-silenced DCs on allergic responses.

Methods

Mice with allergic rhinitis were treated intranasally, subcutaneously, intraperitoneally, or intravenously with CD40-silenced ovalbumin (OVA)-pulsed DCs that were transfected with CD40 siRNAs and pulsed with OVA antigen. The effects of these DCs on allergic reactions and symptoms were estimated.

Results

Intranasal, subcutaneous, intraperitoneal, or intravenous administration of OVA-pulsed CD40-silenced DCs inhibited allergic responses and symptoms in mice. Furthermore, intranasal administration of OVA-pulsed CD40-silenced DCs significantly reduced allergic symptoms and the number of eosinophils in the nasal mucosa compared with subcutaneous, intraperitoneal, or intravenous administration of these DCs. Intranasal administration of OVA-pulsed CD40-silenced DCs resulted in significantly up-regulated IL-10, IL-35, and Foxp3 expression, and enhanced the percentage of CD11c⁺CD40⁻ and CD4⁺CD25⁺ cells within the cervical lymph nodes compared to subcutaneous, intraperitoneal, or intravenous routes of administration.

Conclusions

We believe that this is the first report to demonstrate that regulatory DCs infiltrate into the cervical lymph nodes after intranasal administration of these cells and that intranasal administration of regulatory DCs is more effective for the induction of tolerance in the nasal mucosa than subcutaneous, intraperitoneal, or intravenous administration.

Enabling allogeneic therapies: CIRM-funded strategies for immune tolerance and immune evasion

A major goal for the field of regenerative medicine is to enable the safe and durable engraftment of allogeneic tissues and organs. In contrast to autologous therapies, allogeneic therapies can be produced for many patients, thus reducing costs and increasing availability. However, the need to overcome strong immune system barriers to engraftment poses a significant biological challenge to widespread adoption of allogeneic therapies. While the use of powerful immunosuppressant drugs has enabled the engraftment of lifesaving organ transplants, these drugs have serious side effects and often the organ is eventually rejected by the recipient immune system. Two conceptually different strategies have emerged to enable durable engraftment of allogeneic therapies in the absence of immune suppression. One strategy is to induce immune tolerance of the transplant, either by creating “mixed chimerism” in the hematopoietic system, or by retraining the immune system using modified thymic epithelial cells. The second strategy is to evade the immune system altogether, either by engineering the donor tissue to be “invisible” to the immune system, or by sequestering the donor tissue in an immune impermeable barrier. We give examples of research funded by the California Institute for Regenerative Medicine (CIRM) in each of these areas, ranging from early discovery‐stage work through clinical trials. The advancements that are being made in this area hold promise that many more patients will be able to benefit from regenerative medicine therapies in the future.

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.

FTY720 Regulates Mitochondria Biogenesis in Dendritic Cells to Prevent Kidney Ischemic Reperfusion Injury

Dendritic cells (DCs) are central in regulating immune responses of kidney ischemia-reperfusion injury (IRI), and strategies to alter DC function may provide new therapeutic opportunities. Sphingosine 1-phosphate (S1P) modulates immunity through binding to its receptors (S1P1-5), and protection from kidney IRI occurs in mice treated with S1PR agonist, FTY720 (FTY). We tested if ex vivo propagation of DCs with FTY could be used as cellular therapy to limit the off-target effects associated with systemic FTY administration in kidney IRI. DCs have the ability of regulate innate and adaptive responses and we posited that treatment of DC with FTY may underlie improvements in kidney IRI. Herein, it was observed that treatment of bone marrow derived dendritic cells (BMDCs) with FTY induced mitochondrial biogenesis, FTY-treated BMDCs (FTY-DCs) showed significantly higher oxygen consumption rate and ATP production compared to vehicle treated BMDCs (Veh-DCs). Adoptive transfer of FTY-DCs to mice 24 h before or 4 h after IRI significantly protected the kidneys from injury compared to mice treated with Veh-DCs. Additionally, allogeneic adoptive transfer of C57BL/6J FTY-DCs into BALB/c mice equally protected the kidneys from IRI. FTY-DCs propagated from S1pr1-deficient DCs derived from CD11cCreS1pr1^fl/fl mice as well as blunting mitochondrial oxidation in wildtype (WT) FTY-DCs prior to transfer abrogated the protection observed by FTY-DCs. We queried if DC mitochondrial content alters kidney responses after IRI, a novel but little studied phenomenon shown to be integral to regulation of the immune response. Transfer of mitochondria rich FTY-DCs protects kidneys from IRI as transferred FTY-DCs donated their mitochondria to recipient splenocytes (i.e., macrophages) and prior splenectomy abrogated this protection. Adoptive transfer of FTY-DCs either prior to or after ischemic injury protects kidneys from IRI demonstrating a potent role for donor DC-mitochondria in FTY's efficacy. This is the first evidence, to our knowledge, that DCs have the potential to protect against kidney injury by donating mitochondria to splenic macrophages to alter their bioenergetics thus making them anti-inflammatory. In conclusion, the results support that ex vivo FTY720-induction of the regulatory DC phenotype could have therapeutic relevance that can be preventively infused to reduce acute kidney injury.

Toll-Like Receptor 3 Activator Preconditioning Enhances Modulatory Function of Adipose‑Derived Mesenchymal Stem Cells in a Fully MHC-Mismatched Murine Model of Heterotopic Heart Transplantation

Background

Donor-specific tolerance is the ultimate goal in organ transplantation. Diverse approaches, including the use of mesenchymal stem cells (MSCs), have been investigated to induce graft tolerance. Non-stimulated MSCs showed limited regulatory functions through interaction with multiple immune-regulatory cells, such as regulatory T cells (Tregs). To augment their functions, MSCs have been preconditioned with toll-like receptor (TLR3/4) agonist in autoimmune disease models, but results were conflicting.

Material/Methods

We evaluated the immunomodulatory effects of mouse adipose-derived mesenchymal stem cells (ADSCs) preconditioned with various combinations of TLR3/4 agonist and antagonists, including polyinosinic-polycytidylic acid poly(I:C)-TLR3 agonist, lipopolysaccharide (LPS) -TLR4 agonist, and TAK242-TLR4 antagonist. In vitro and in vivo experiments including mixed lymphocyte reaction, cytokines measurement, Tregs analysis, and a fully mismatched MHC heterotopic heart transplantation in mice (BALB/c to C57BL/6) were conducted.

Results

ADSCs preconditioned with poly(I:C) showed the highest efficiency in inhibiting lymphocyte proliferation, which was correlated with the upregulation of fibrinogen-like protein 2 (FGL2), an effector molecule of Tregs. The mean survival of cardiac allografts was extended from 8 to 12 days by intravenous injection of a single dose of ADSCs preconditioned with TLR3 agonist. The proportion of Tregs in the recipient’s spleen was significantly increased by injecting the poly(I:C)-stimulated ADSCs.

Conclusions

These results show that short-term TLR3 agonist preconditioning enhances the immunomodulatory efficacy of ADSCs, which can induce the generation of Tregs and upregulate the expression of FGL2, thereby improving the outcome of patients receiving organ transplantation.

Deficiency of canonical Wnt/β-catenin signalling in hepatic dendritic cells triggers autoimmune hepatitis

BACKGROUND & AIMS

Autoimmune hepatitis (AIH) is a chronic inflammatory liver disease manifested with the aberrant activation of hepatic dendritic cells (HDCs) and the subsequent breakdown of immune homeostasis. As an important player, HDC maintains immunological balance between tolerance to self-antigens versus destruction against pathogens in liver. However, the intracellular signalling networks that program HDC remain unclear. We have now found the role of canonical Wnt/β-catenin signalling in HDCs.

METHODS

Liver sections from AIH patients and healthy subjects were stained for the markers of Wnt/β-catenin signalling. Concanavalin A (ConA) and HDC/Hepa1-6 vaccine-induced AIH mouse models were examined for liver injury, inflammation and immune cell functions by serum biochemistry, histology, quantitative reverse transcription polymerase chain reaction (qRT-PCR), enzyme-linked immunosorbent assay (ELISA) and flow cytometry analysis. Wnt/β-catenin signalling expression was measured using immunoblot and qRT-PCR.

RESULTS

Canonical Wnt/β-catenin signalling in HDC is deficient in AIH patients and a mouse model, which coincides with the immunogenic function of HDCs. Furthermore, Wnt ligand engagement reactivates Wnt/β-catenin signalling and recovers the immunoregulatory phenotype of HDCs, in turn alleviating the severity of AIH. Likewise, pharmacologic activation of Wnt/β-catenin signalling attenuates AIH progression.

CONCLUSIONS

We report here that the constitutively active canonical Wnt/β-catenin signalling confers HDCs tolerogenicity under steady-state conditions. Deficiency of this pathway gives rise to T cell-mediated immune response and incidence of AIH. It may act as a new pathogenesis and treatment target for AIH.

Characterization and functional prediction of the microRNAs differentially expressed in a mouse model of concanavalin A-induced autoimmune hepatitis

In order to investigate the altered expression of microRNAs (miRNAs) in the development of autoimmune hepatitis (AIH), the aberrantly expressed miRNAs in the concanavalin A (Con A)-induced AIH mouse model were identified for the first time with microarray in this study. A total of 49 miRNAs (31 up- and 18 down-regulated) were screened out, and the qRT-PCR validation results of 12 chosen miRNAs were consistent with the microarray data. Combined with the profiling of differently expressed mRNAs in the same model (data not shown), 959 predicted target genes (601 for up- and 358 for down-regulated miRNAs) were obtained according to the intersection of databases miRWalk and miRDB, and several hub genes were obtained from the regulatory networks, including Cadm1 and Mier3. These target genes were significantly enriched in the Gene ontology (GO) terms of "transcription, DNA-templated", and were annotated in 47 signaling pathways, comprising "Wnt signaling pathway", "Hippo signaling pathway", "Ferroptosis" and "mitogen-activated protein kinase (MAPK) signaling pathway", according to the GO and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. In the miRNA-GO-network, mmu-miR-193b-3p were exhibited in 33 GO terms of biological processes (BP), and the most significantly regulated GO term in BP categories was "regulation of transcription, DNA-templated". While in the miRNA-pathway-network, mmu-miR-7005-5p were enriched in 37 pathways, which was more than the other specifically expressed miRNAs, and the most significantly enriched pathways were "Endocytosis" and "MAPK signaling pathway". In conclusion, these differently expressed miRNAs seemed to be associated with the onset of AIH, and have the potential to serve as the new targets on the treatment of this disease.

Key genes and pathways in tumor-educated dendritic cells by bioinformatical analysis

Specific tumor microenvironment signaling might prevent the maturation of dendritic cells (DCs) with tolerogenic and immunosuppressive potential accounting for antigen-specific unresponsiveness in the lymphoid organs and in the periphery. In the present study, dendritic cells treated with LLC lung cancer cell or 4T1 breast cancer cell culture supernatants significantly down-regulated the expression of co-stimulatory molecules MHC-II, CD40, CD80, but up-regulated the inhibitory molecule PD-L1/L2, VISTA, and increased the messengerRNA levels of interleukin (IL)-6, arginase I, and IL-10, but decreased tumor necrosis factor-α and IL-12a. RNA was isolated from the dendritic cells with or without tumor supernatant stimulation and RNA sequencing was done. Then the differential expression genes were sorted, the candidate genes were analyzed and pathway enrichment analysis was done, and the associated protein-protein interaction network (PPI) was established. After integrated bioinformatical analysis, 405 (279 up-regulated and 126 down-regulated) consistently differential expression genes were identified. Using gene ontology and pathway analysis, it was found that differential expression genes were mainly enriched in the immune response, cell-cell interaction, hemostasis, and cell surface interactions with the vascular wall. The PPI data demonstrated that 236 nodes were classified with 1072 edges, and the most remarkable three modules involved 53 central node genes associated with cell survival, cell-substrate adhesion, chemotaxis, migration, immune response, and complement receptor mediated signaling pathway. These findings revealed the immune status of dendritic cells in the tumor environment.

Liver induced transgene tolerance with AAV vectors

Immune tolerance is a vital component of immunity, as persistent activation of immune cells causes significant tissue damage and loss of tolerance leads to autoimmunity. Likewise, unwanted immune responses can occur in inherited disorders, such as hemophilia and Pompe disease, in which patients lack any expression of protein, during treatment with enzyme replacement therapy, or gene therapy. While the liver has long been known as being tolerogenic, it was only recently appreciated in the last decade that liver directed adeno-associated virus (AAV) gene therapy can induce systemic tolerance to a transgene. In this review, we look at the mechanisms behind liver induced tolerance, discuss different factors influencing successful tolerance induction with AAV, and applications where AAV mediated tolerance may be helpful.

Immune tolerance in multiple sclerosis and neuromyelitis optica with peptide-loaded tolerogenic dendritic cells in a phase 1b trial

Application of antigen-specific immune tolerance in autoimmune disease is a long-sought goal. We studied diseases with abundant information on the autoimmune target: in multiple sclerosis (MS), various myelin antigens are known targets of T cells and antibodies, whereas in neuromyelitis optica (NMO), the aquaporin-4 channel is attacked by T cells and antibodies. We tested whether engineered dendritic cells might induce a tolerogenic immune response in these two conditions. In this in-human clinical study, individual regulatory T cells, secreting IL-10, a key tolerogenic cytokine, were detected after treatment. These results might lead to more extensive trials with this approach in autoimmune conditions where the antigenic target has been identified, including MS, NMO, myasthenia gravis, and Graves disease.

There are adaptive T-cell and antibody autoimmune responses to myelin-derived peptides in multiple sclerosis (MS) and to aquaporin-4 (AQP4) in neuromyelitis optica spectrum disorders (NMOSDs). Strategies aimed at antigen-specific tolerance to these autoantigens are thus indicated for these diseases. One approach involves induction of tolerance with engineered dendritic cells (tolDCs) loaded with specific antigens. We conducted an in-human phase 1b clinical trial testing increasing concentrations of autologous tolDCs loaded with peptides from various myelin proteins and from AQP4. We tested this approach in 12 patients, 8 with MS and 4 with NMOSD. The primary end point was the safety and tolerability, while secondary end points were clinical outcomes (relapses and disability), imaging (MRI and optical coherence tomography), and immunological responses. Therapy with tolDCs was well tolerated, without serious adverse events and with no therapy-related reactions. Patients remained stable clinically in terms of relapse, disability, and in various measurements using imaging. We observed a significant increase in the production of IL-10 levels in PBMCs stimulated with the peptides as well as an increase in the frequency of a regulatory T cell, known as Tr1, by week 12 of follow-up. In this phase 1b trial, we concluded that the i.v. administration of peptide-loaded dendritic cells is safe and feasible. Elicitation of specific IL-10 production by peptide-specific T cells in MS and NMOSD patients indicates that a key element in antigen specific tolerance is activated with this approach. The results warrant further clinical testing in larger trials.

On-target and direct modulation of alloreactive T cells by a nanoparticle carrying MHC alloantigen, regulatory molecules and CD47 in a murine model of alloskin transplantation

Biomimetic nanoparticles have been reported as immune modulators in autoimmune diseases and allograft rejections by numerous researchers. However, most of the therapeutics carrying antigens, toxins or cytokines underlay the mechanism of antigen presentation by cellular uptake of NPs through pinocytosis and phagocytosis. Few researches focus on the direct and antigen-specific modulation on T cells by NPs and combined use of multiple regulatory molecules. Here, polylactic-co-glycolic acid nanoparticles (PLGA-NPs) were fabricated as scaffold to cocoupling H-2K^b-Ig dimer, anti-Fas mAb, PD-L1-Fc, TGF-β and CD47-Fc for the generation of alloantigen-presenting and tolerance-inducing NPs, termed killer NPs and followed by i.v. injection into a single MHC-mismatched murine model of alloskin transplantation. Three infusions prolonged alloskin graft survival for 45 days; depleted most of H-2K^b alloreactive CD8⁺ T cells in peripheral blood, spleen and local graft, in an antigen-specific manner. The killer NPs circulated throughout vasculature into various organs and local allograft, with a retention time up to 30 h. They made contacts with CD8⁺ T cells to facilitate vigorous apoptosis, inhibit the activation and proliferation of alloreactive CD8⁺ T cells and induce regulatory T cells in secondary lymphoid organs, with the greatly minimized uptake by phagocytes. More importantly, the impairment of host overall immune function and visible organ toxicity were not found. Our results provide the first experimental evidence for the direct and on-target modulation on alloreactive T cells by the biodegradable 200-nm killer NPs via co-presentation of alloantigen and multiple regulatory molecules, thus suggest a novel antigen-specific immune modulator for allograft rejections.

Promises and limitations of immune cell-based therapies in neurological disorders

The healthy immune system has natural checkpoints that temper pernicious inflammation. Cells mediating these checkpoints include regulatory T cells, regulatory B cells, regulatory dendritic cells, microglia, macrophages and monocytes. Here, we highlight discoveries on the beneficial functions of regulatory immune cells and their mechanisms of action and evaluate their potential use as novel cell-based therapies for brain disorders. Regulatory immune cell therapies have the potential not only to mitigate the exacerbation of brain injury by inflammation but also to promote an active post-injury brain repair programme. By harnessing the reparative properties of these cells, we can reduce over-reliance on medications that mask clinical symptoms but fail to impede or reverse the progression of brain disorders. Although these discoveries encourage further testing and genetic engineering of regulatory immune cells for the clinical management of neurological disorders, a number of challenges must be surmounted to improve their safety and efficacy in humans.

Beyond the Magic Bullet: Current Progress of Therapeutic Vaccination in Multiple Sclerosis

Multiple sclerosis (MS) is a chronic immune-mediated disease of the central nervous system (CNS) characterized by neuroinflammation, neurodegeneration and impaired repair mechanisms that lead to neurological disability. The crux of MS is the patient's own immune cells attacking self-antigens in the CNS, namely the myelin sheath that protects nerve cells of the brain and spinal cord. Restoring antigen-specific tolerance via therapeutic vaccination is an innovative and exciting approach in MS therapy. Indeed, leveraging the body's attempt to prevent autoimmunity, i.e., tolerization, focuses on the underlying cause of the disease and could be the key to solving neuroinflammation. In this perspective, antigen-specific vaccination targets only the detrimental and aberrant immune response against the specific disease-associated antigen(s) involved while retaining the capacity of the immune system to respond to unrelated antigens. We review the experimental approaches of tolerance-inducing vaccination in relapsing and progressive forms of MS that have reached the clinical development phase, including vaccination with autologous T cells, autologous tolerogenic dendritic cells, T cell receptor peptide vaccination, altered peptide ligand, ATX-MS-1467, cluster of differentiation (CD)-206-targeted liposomal myelin basic protein peptides and DNA vaccination. Failures, successes and future directions are discussed.

Generation of regulatory dendritic cells after treatment with paeoniflorin

Regulatory dendritic cells are a potential therapeutic tool for assessing a variety of immune overreaction diseases. Paeoniflorin, a bioactive glucoside extracted from the Chinese herb white paeony root, has been shown to be effective at inhibiting the maturation and immunostimulatory function of murine bone marrow-derived dendritic cells. However, whether paeoniflorin can program conventional dendritic cells toward regulatory dendritic cells and the underlying mechanism remain unknown. Here, our study demonstrates that paeoniflorin can induce the production of regulatory dendritic cells from human peripheral blood monocyte-derived immature dendritic cells in the absence or presence of lipopolysaccharide (LPS) but not from mature dendritic cells, thereby demonstrating the potential of paeoniflorin as a specific immunosuppressive drug with fewer complications and side effects. These regulatory dendritic cells treated with paeoniflorin exhibited high CD11b/c and low CD80, CD86 and CD40 expression levels as well as enhanced abilities to capture antigen and promote the proliferation of CD4(+)CD25(+) T cells and reduced abilities to migrate and promote the proliferation of CD4(+) T cells, which is associated with the upregulation of endogenous transforming growth factor (TGF)-β-mediated indoleamine 2,3-dioxygenase (IDO) expression. Collectively, paeoniflorin could program immature dendritic cells (imDCs) and imDCs stimulated with LPS toward a regulatory DC fate by upregulating the endogenous TGF-β-mediated IDO expression level, thereby demonstrating its potential as a specific immunosuppressive drug.

Bioengineering strategies for inducing tolerance in autoimmune diabetes

Type 1 diabetes is an autoimmune disease marked by the destruction of insulin-producing beta cells in the pancreatic islets. Strategies to delay onset or prevent the autoimmune recognition of beta cell antigens or T cell-mediated killing of beta cells have mainly focused on systemic immunomodulation and antigen-specific immunotherapy. To bridge the fields of type 1 diabetes immunology and biomaterials engineering, this article will review recent trends in the etiology of type 1 diabetes immunopathology and will focus on the contributions of emerging bioengineered strategies in the fight against beta cell autoimmunity in type 1 diabetes.

iPSC-Derived Regulatory Dendritic Cells Inhibit Allograft Rejection by Generating Alloantigen-Specific Regulatory T Cells

Regulatory dendritic cell (DCregs)-based immunotherapy is a potential therapeutic tool for transplant rejection. We generated DCregs from murine induced pluripotent stem cells (iPSCs), which could remain in a “stable immature stage” even under strong stimulation. Harnessing this characteristic, we hypothesized that iPS-DCregs worked as a negative vaccine to generate regulatory T cells (Tregs), and induced donor-specific allograft acceptance. We immunized naive CBA (H-2K^k) mice with B6 (H-2K^b) iPS-DCregs and found that Tregs (CD4⁺CD25⁺FOXP3⁺) significantly increased in CBA splenocytes. Moreover, immunized CBA recipients permanently accepted B6 cardiac grafts in a donor-specific pattern. We demonstrated mechanistically that donor-type iPS-DCregs triggered transforming growth factor β1 secretion, under which the donor-antigen peptides directed naive CD4⁺ T cells to differentiate into donor-specific FOXP3⁺ Tregs instead of into effector T cells in vivo. These findings highlight the potential of iPS-DCregs as a key cell therapy resource in clinical transplantation.

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iPS-DCregs keep in stable immature stage that makes them a powerful cellular vaccine

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Donor-type iPS-DCregs lead to permanent acceptance of allogeneic cardiac grafts

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iPS-DCregs reduce CTL and downregulate proinflammatory cytokine

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iPS-DCregs enhance Tregs transmigration capability in a TGF-β1-dependent manner

Old game, new players: Linking classical theories to new trends in transplant immunology

The evolutionary emergence of an efficient immune system has a fundamental role in our survival against pathogenic attacks. Nevertheless, this same protective mechanism may also establish a negative consequence in the setting of disorders such as autoimmunity and transplant rejection. In light of the latter, although research has long uncovered main concepts of allogeneic recognition, immune rejection is still the main obstacle to long-term graft survival. Therefore, in order to define effective therapies that prolong graft viability, it is essential that we understand the underlying mediators and mechanisms that participate in transplant rejection. This multifaceted process is characterized by diverse cellular and humoral participants with innate and adaptive functions that can determine the type of rejection or promote graft acceptance. Although a number of mediators of graft recognition have been described in traditional immunology, recent studies indicate that defining rigid roles for certain immune cells and factors may be more complicated than originally conceived. Current research has also targeted specific cells and drugs that regulate immune activation and induce tolerance. This review will give a broad view of the most recent understanding of the allogeneic inflammatory/tolerogenic response and current insights into cellular and drug therapies that modulate immune activation that may prove to be useful in the induction of tolerance in the clinical setting.

Phosphorylated Radix Cyathulae officinalis Polysaccharides Act as Adjuvant via Promoting Dendritic Cell Maturation

The aim of this study was to investigate whether phosphorylated Radix Cyathulae officinalis Kuan polysaccharides (pRCPS) used as adjuvant with foot-and-mouth disease vaccine (FMDV) can stimulate specific humoral and cellular immune responses in ICR mice. The results demonstrated that pRCPS significantly up-regulated FMDV-specific IgG, IgG1, IgG2b and IgG2a antibody levels and splenocyte proliferation. pRCPS also promoted the killing activities of cytotoxic T lymphocytes (CTL) and natural killer cells (NK). In addition, pRCPS enhanced the expression levels of IL-2, IL-4, and IFN-γ in CD4⁺ T cells and the level of IFN-γ in CD8⁺ T cells. Importantly, pRCPS enhanced the expression of MHCII, CD40⁺, CD86⁺, and CD80⁺ in dendritic cells (DCs). This study indicated that phosphorylation modification could increase immune-enhancing activities of RCPS, and pRCPS could promote humoral and cellular immune responses through facilitating DC maturation.

Regulatory Dendritic Cells

Dendritic cells (DCs) comprise heterogeneous subsets, functionally classified into conventional DCs (cDCs) and plasmacytoid DCs (pDCs). DCs are considered to be essential antigen (Ag)-presenting cells (APCs) that play crucial roles in activation and fine-tuning of innate and adaptive immunity under inflammatory conditions, as well as induction of immune tolerance to maintain immune homeostasis under steady-state conditions. Furthermore, DC functions can be modified and influenced by stimulation with various extrinsic factors, such as ligands for pattern-recognition receptors (PRRs) and cytokines. On the other hand, treatment of DCs with certain immunosuppressive drugs and molecules leads to the generation of tolerogenic DCs that show downregulation of both the major histocompatibility complex (MHC) and costimulatory molecules, and not only show defective T-cell activation, but also possess tolerogenic properties including the induction of anergic T-cells and regulatory T (T_reg) cells. To develop an effective strategy for Ag-specific intervention of T-cell-mediated immune disorders, we have previously established the modified DCs with moderately high levels of MHC molecules that are defective in the expression of costimulatory molecules that had a greater immunoregulatory property than classical tolerogenic DCs, which we therefore designated as regulatory DCs (DC_reg). Herein, we integrate the current understanding of the role of DCs in the control of immune responses, and further provide new information of the characteristics of tolerogenic DCs and DC_reg, as well as their regulation of immune responses and disorders.

Dendritic Cell KLF2 Expression Regulates T Cell Activation and Proatherogenic Immune Responses

Dendritic cells (DCs) have been implicated as important regulators of innate and adaptive inflammation in many diseases, including atherosclerosis. However, the molecular mechanisms by which DCs mitigate or promote inflammatory pathogenesis are only partially understood. Previous studies have shown an important anti-inflammatory role for the transcription factor Krüppel-like factor 2 (KLF2) in regulating activation of various cell types that participate in atherosclerotic lesion development, including endothelial cells, macrophages, and T cells. We used a pan-DC, CD11c-specific cre-lox gene knockout mouse model to assess the role of KLF2 in DC activation, function, and control of inflammation in the context of hypercholesterolemia and atherosclerosis. We found that KLF2 deficiency enhanced surface expression of costimulatory molecules CD40 and CD86 in DCs and promoted increased T cell proliferation and apoptosis. Transplant of bone marrow from mice with KLF2-deficient DCs into Ldlr-/- mice aggravated atherosclerosis compared with control mice, most likely due to heightened vascular inflammation evidenced by increased DC presence within lesions, enhanced T cell activation and cytokine production, and increased cell death in atherosclerotic lesions. Taken together, these data indicate that KLF2 governs the degree of DC activation and hence the intensity of proatherogenic T cell responses.

Overexpression of Fibrinogen-Like Protein 2 Promotes Tolerance in a Fully Mismatched Murine Model of Heart Transplantation

Fibrinogen-like protein 2 (FGL2) is an immunomodulatory protein that is expressed by regulatory T cells (Tregs). The objective of this study was to determine if recombinant FGL2 (rFGL2) treatment or constitutive FGL2 overexpression could promote transplant tolerance in mice. Although rFGL2 treatment prevented rejection of fully mismatched cardiac allografts, all grafts were rejected after stopping treatment. Next, we generated FGL2 transgenic mice (fgl2(Tg) ) that ubiquitously overexpressed FGL2. These mice developed normally and had no evidence of the autoimmune glomerulonephritis seen in fgl2(-/-) mice. Immune characterization showed fgl2(Tg) T cells were hypoproliferative to stimulation with alloantigens or anti-CD3 and anti-CD28 stimulation, and fgl2(Tg) Tregs had increased immunosuppressive activity compared with fgl2(+/+) Tregs. To determine if FGL2 overexpression can promote tolerance, we transplanted fully mismatched cardiac allografts into fgl2(Tg) recipients. Fifty percent of cardiac grafts were accepted indefinitely in fgl2(Tg) recipients without any immunosuppression. Tolerant fgl2(Tg) grafts had increased numbers and proportions of Tregs and tolerant fgl2(Tg) mice had reduced proliferation to donor but not third party antigens. These data show that tolerance in fgl2(Tg) recipients involves changes in Treg and T cell activity that contribute to a higher intragraft Treg-to-T cell ratio and acceptance of fully mismatched allografts.

Modulation of liver tolerance by conventional and nonconventional antigen-presenting cells and regulatory immune cells

The liver is a tolerogenic organ with exquisite mechanisms of immune regulation that ensure upkeep of local and systemic immune tolerance to self and foreign antigens, but that is also able to mount effective immune responses against pathogens. The immune privilege of liver allografts was recognized first in pigs in spite of major histo-compatibility complex mismatch, and termed the "liver tolerance effect". Furthermore, liver transplants are spontaneously accepted with only low-dose immunosuppression, and induce tolerance for non-hepatic co-transplanted allografts of the same donor. Although this immunotolerogenic environment is favorable in the setting of organ transplantation, it is detrimental in chronic infectious liver diseases like hepatitis B or C, malaria, schistosomiasis or tumorigenesis, leading to pathogen persistence and weak anti-tumor effects. The liver is a primary site of T-cell activation, but it elicits poor or incomplete activation of T cells, leading to their abortive activation, exhaustion, suppression of their effector function and early death. This is exploited by pathogens and can impair pathogen control and clearance or allow tumor growth. Hepatic priming of T cells is mediated by a number of local conventional and nonconventional antigen-presenting cells (APCs), which promote tolerance by immune deviation, induction of T-cell anergy or apoptosis, and generating and expanding regulatory T cells. This review will focus on the communication between classical and nonclassical APCs and lymphocytes in the liver in tolerance induction and will discuss recent insights into the role of innate lymphocytes in this process.

β-glucan restores tumor-educated dendritic cell maturation to enhance antitumor immune responses

Tumors can induce the generation and accumulation of immunosuppressive cells such as myeloid-derived suppressor cells (MDSCs) in a tumor microenvironment, contributing to tumor escape from immunological attack. Although dendritic cell-based cancer vaccines can initiate antitumor immune responses, tumor-educated dendritic cells (TEDCs) involved in the tolerance induction have attracted much attention recently. In this study, we investigated the effect of β-glucan on TEDCs and found that β-glucan treatment could promote the maturation and migration of TEDCs and that the suppressive function of TEDCs was significantly decreased. Treatment with β-glucan drastically decreased the levels of regulatory T (Treg) cells but increased the infiltration of macrophages, granulocytes and DCs in tumor masses, thus elicited Th1 differentiation and cytotoxic T-lymphocyte responses and led to a delay in tumor progression. These findings reveal that β-glucan can inhibit the regulatory function of TEDCs, therefore revealing a novel function for β-glucan in immunotherapy and suggesting its potential clinical benefit. β-Glucan directly abrogated tumor-educated dendritic cells-associated immune suppression, promoted Th1 differentiation and cytotoxic T-lymphocyte priming and improved antitumor responses.

Natural IgM Switches the Function of Lipopolysaccharide-Activated Murine Bone Marrow-Derived Dendritic Cells to a Regulatory Dendritic Cell That Suppresses Innate Inflammation

We have previously shown that polyclonal natural IgM protects mice from renal ischemia/reperfusion injury (IRI) by inhibiting the reperfusion inflammatory response. We hypothesized that a potential mechanism involved IgM modulation of dendritic cells (DC), as we observed high IgM binding to splenic DC. To test this hypothesis, we pretreated bone marrow-derived DC (BMDC) with polyclonal murine or human IgM prior to LPS activation and demonstrated that 0.5 × 10(6) IgM/LPS-pretreated BMDC, when injected into wild-type C57BL/6 mice 24 h before renal ischemia, protect mice from developing renal IRI. We show that this switching of LPS-activated BMDC to a regulatory phenotype requires modulation of BMDC function that is mediated by IgM binding to nonapoptotic BMDC receptors. Regulatory BMDC require IL-10 and programmed death 1 as well as downregulation of CD40 and p65 NF-κB phosphorylation to protect in renal IRI. Blocking the programmed death ligand 1 binding site just before i.v. injection of IgM/LPS-pretreated BMDC or using IL-10 knockout BMDC fails to induce protection. Similarly, IgM/LPS-pretreated BMDC are rendered nonprotective by increasing CD40 expression and phosphorylation of p65 NF-κB. How IgM/LPS regulatory BMDC suppress in vivo ischemia-induced innate inflammation remains to be determined. However, we show that suppression is dependent on other in vivo regulatory mechanisms in the host, that is, CD25(+) T cells, B cells, IL-10, and circulating IgM. There was no increase in Foxp3(+) regulatory T cells in the spleen either before or after renal IRI. Collectively, these findings show that natural IgM anti-leukocyte Abs can switch BMDC to a regulatory phenotype despite the presence of LPS that ordinarily induces BMDC maturation.

Contribution of dendritic cells to the autoimmune pathology of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a heterogeneous disease in which excessive inflammation, autoantibodies and complement activation lead to multisystem tissue damage. The contribution of the individual genetic composition has been extensively studied, and several susceptibility genes related to immune pathways that participate in SLE pathogenesis have been identified. It has been proposed that SLE takes place when susceptibility factors interact with environmental stimuli leading to a deregulated immune response. Experimental evidence suggests that such events are related to the failure of T-cell and B-cell suppression mediated by defects in cell signalling, immune tolerance and apoptotic mechanism promoting autoimmunity. In addition, it has been reported that dendritic cells (DCs) from SLE patients, which are crucial in the modulation of peripheral tolerance to self-antigens, show an increased ratio of activating/inhibitory receptors on their surfaces. This phenotype and an augmented expression of co-stimulatory molecules is thought to be critical for disease pathogenesis. Accordingly, tolerogenic DCs can be a potential strategy for developing antigen-specific therapies to reduce detrimental inflammation without causing systemic immunosuppression. In this review article we discuss the most relevant data relative to the contribution of DCs to the triggering of SLE.

Tolerogenic Dendritic Cells on Transplantation: Immunotherapy Based on Second Signal Blockage

Dendritic cells (DCs), the most important professional antigen-presenting cells (APC), play crucial role in both immunity and tolerance. It is well known that DCs are able to mount immune responses against foreign antigens and simultaneously tolerate self-antigens. Since DCs can be modulated depending on the surrounding microenvironment, they can act as a bridge between innate and adaptive immunity. However, the mechanisms that support this dual role are not entirely clear. Recent studies have shown that DCs can be manipulated ex vivo in order to trigger their tolerogenic profile, what can be a tool to be used in clinical trials aiming the treatment of various diseases and the prevention of transplant rejection. In this sense, the blockage of costimulatory molecules on DC, in the attempt of inhibiting the second signal in the immunological synapse, can be considered as one of the main strategies under development. This review brings an update on current therapies using tolerogenic dendritic cells modulated with costimulatory blockers with the aim of reducing transplant rejection. However, although there are current clinical trials using tolerogenic DC to treat allograft rejection, the actual challenge is to modulate these cells in order to maintain a permanent tolerogenic profile.

Sphingosine 1-Phosphate Receptor 3-Deficient Dendritic Cells Modulate Splenic Responses to Ischemia-Reperfusion Injury

The plasticity of dendritic cells (DCs) permits phenotypic modulation ex vivo by gene expression or pharmacologic agents, and these modified DCs can exert therapeutic immunosuppressive effects in vivo through direct interactions with T cells, either inducing T regulatory cells (T(REG)s) or causing anergy. Sphingosine 1-phosphate (S1P) is a sphingolipid and the natural ligand for five G protein-coupled receptors (S1P1, S1P2, S1P3, S1P4, and S1P5), and S1PR agonists reduce kidney ischemia-reperfusion injury (IRI) in mice. S1pr3(-/-)mice are protected from kidney IRI, because DCs do not mature. We tested the therapeutic advantage of S1pr3(-/-) bone marrow-derived dendritic cell (BMDC) transfers in kidney IRI. IRI produced a rise in plasma creatinine (PCr) levels in mice receiving no cells (NCs) and mice pretreated with wild-type (WT) BMDCs. However, S1pr3(-/-) BMDC-pretreated mice were protected from kidney IRI. S1pr3(-/-) BMDC-pretreated mice had significantly higher numbers of splenic T(REG)s compared with NC and WT BMDC-pretreated mice. S1pr3(-/-) BMDCs did not attenuate IRI in splenectomized, Rag-1(-/-), or CD11c(+) DC-depleted mice. Additionally, S1pr3(-/-) BMDC-dependent protection required CD169(+)marginal zone macrophages and the macrophage-derived chemokine CCL22 to increase splenic CD4(+)Foxp3(+) T(REG)s. Pretreatment with S1pr3(-/-) BMDCs also induced T(REG)-dependent protection against IRI in an allogeneic mouse model. In summary, adoptively transferred S1pr3(-/-) BMDCs prevent kidney IRI through interactions within the spleen and expansion of splenic CD4(+)Foxp3(+) T(REG)s. We conclude that genetically induced deficiency of S1pr3 in allogenic BMDCs could serve as a therapeutic approach to prevent IRI-induced AKI.

Micro and nanoparticle drug delivery systems for preventing allotransplant rejection

Despite decades of advances in transplant immunology, tissue damage caused by acute allograft rejection remains the primary cause of morbidity and mortality in the transplant recipient. Moreover, the long-term sequelae of lifelong immunosuppression leaves patients at risk for developing a host of other deleterious conditions. Controlled drug delivery using micro- and nanoparticles (MNPs) is an effective way to deliver higher local doses of a given drug to specific tissues and cells while mitigating systemic effects. Herein, we review several descriptions of MNP immunotherapies aimed at prolonging allograft survival. We also discuss developments in the field of biomimetic drug delivery that use MNP constructs to induce and recruit our bodies' own suppressive immune cells. Finally, we comment on the regulatory pathway associated with these drug delivery systems. Collectively, it is our hope the studies described in this review will help to usher in a new era of immunotherapy in organ transplantation.

Chuanminshen violaceum polysaccharides improve the immune responses of foot-and-mouth disease vaccine in mice

Water-soluble polysaccharides from Chuanminshen violaceum (CVPS) were evaluated for their physicochemical properties, monosaccharide composition, and adjuvant potential to specific cellular and humoral immune responses in a mouse model of foot-and-mouth disease virus (FMDV) vaccination. The average molecular weight (Mw) of the CVPS was 968.31 kDa. The monosaccharide components of the CVPS was rhamnose, arabinose, fucose, mannose, glucose, and galactose with a relative mass of 6.29%, 21.87%, 16.59%, 12.54%, 13.07%, and 28.05%, respectively. Administering CVPS as an adjuvant significantly enhanced the phagocytic capacity of peritoneal macrophages, splenocyte proliferation, and the activity of NK cells and CTL as well as increased FMDV-specific IgG and IgG subclass antibody titers. Moreover, CVPS increased the expression of IL-2, IFN-γ, and IL-4 in CD4(+) T cells and IFN-γ expression in CD8(+) T cells. Additionally, CVPS enhanced CD40(+), CD80(+), and CD86(+) expression on DCs. Moreover, CVPS upregulated MHC-I/II, TLR-2/4 mRNA levels. In contrast, CVPS downregulated TGF-β mRNA expression and the frequency of CD4(+)CD25(+)Foxp3(+) Treg cells. Taken together, these results indicate that administering CVPS as an adjuvant enhances both cellular and humoral immune responses via the TLR-2 and TLR-4 signalling pathways, thereby promoting DC maturation and suppressing TGF-β expression and Treg frequency.

Advances and challenges in immunotherapy for solid organ and hematopoietic stem cell transplantation

Although major advances have been made in solid organ and hematopoietic stem cell transplantation in the last 50 years, big challenges remain. This review outlines the current immunological limitations for hematopoietic stem cell and solid organ transplantation and discusses new immune-modulating therapies in preclinical development and in clinical trials that may allow these obstacles to be overcome.

Generation of antigen-specific Foxp3+ regulatory T-cells in vivo following administration of diabetes-reversing tolerogenic microspheres does not require provision of antigen in the formulation

We have developed novel antisense oligonucleotide-formulated microspheres that can reverse hyperglycemia in newly-onset diabetic mice. Dendritic cells taking up the microspheres adopt a restrained co-stimulation ability and migrate to the pancreatic lymph nodes when injected into an abdominal region that is drained by those lymph nodes. Furthermore, we demonstrate that the absolute numbers of antigen-specific Foxp3+ T regulatory cells are increased only in the lymph nodes draining the site of administration and that these T-cells proliferate independently of antigen supply in the microspheres. Taken together, our data add to the emerging model where antigen supply may not be a requirement in "vaccines" for autoimmune disease, but the site of administration - subserved by lymph nodes draining the target organ - is in fact critical to foster the generation of antigen-specific regulatory cells. The implications of these observations on "vaccine" design for autoimmunity are discussed and summarized.

Orchestration of transplantation tolerance by regulatory dendritic cell therapy or in-situ targeting of dendritic cells

PURPOSE OF REVIEW

Extensive research in murine transplant models over the past two decades has convincingly demonstrated the ability of regulatory dendritic cells (DCregs) to promote long-term allograft survival. We review important considerations regarding the source of therapeutic DCregs (donor or recipient) and their mode of action, in-situ targeting of DCregs, and optimal therapeutic regimens to promote DCreg function.

RECENT FINDINGS

Recent studies have defined protocols and mechanisms whereby ex-vivo-generated DCregs of donor or recipient origin subvert allogeneic T-cell responses and promote long-term organ transplant survival. Particular interest has focused on how donor antigen is acquired, processed and presented by autologous dendritic cells, on the stability of DCregs, and on in-situ targeting of dendritic cells to promote their tolerogenic function. New evidence of the therapeutic efficacy of DCregs in a clinically relevant nonhuman primate organ transplant model and production of clinical grade DCregs support early evaluation of DCreg therapy in human graft recipients.

SUMMARY

We discuss strategies currently used to promote dendritic cell tolerogenicity, including DCreg therapy and in-situ targeting of dendritic cells, with a view to improved understanding of underlying mechanisms and identification of the most promising strategies for therapeutic application.