Tolerogenic dendritic cells and their applications in transplantation

Rapamycin-modified CD169low/-tolDC promotes skin graft survival in mice via IL-10+Breg

Skin allografts are prone to rejection because of their high immunogenicity. By achieving immune tolerance, the long-term survival of skin allografts can be extended without the need for immunosuppressants or with only short-term low-dose dependency. Tolerogenic dendritic cells (tolDCs) show a strong potential for graft tolerance. We explored the mechanism whereby rapamycin-modified CD169low/-tolDCs regulate interleukin-10 (IL-10) B regulatory (IL-10+ Breg) cell production and mediate the long-term survival of skin allografts in mice. CD169low/-tolDCs were obtained through flow cytometry sorting after treating the mesenchymal stem cell (MSC)-derived dendritic cells with a low dose of GM-CSF. A treatment regimen combining preoperative stimulation and postoperative adoptive infusion of CD169low/-tolDCs was used to treat an acute rejection (AR) mouse skin transplantation model-the adoptive infusion group. An equivalent dose of saline was administered to the control group. Survival and graft rejection rates were assessed. Mixed lymphocyte culture, flow cytometry, immunohistochemistry (IHC), and western blotting (WB) were used to elucidate the expression of different IL-10+ Breg subsets in mice treated with adoptive infusion therapy and the molecular mechanisms whereby CD169low/-tolDCs induce IL-10+ Breg production to mediate tolerance. Adoptive infusion of CD169low/-tol DCs markedly prolonged the rejection time after skin transplantation in mice and promoted graft survival. A significant increase was observed in local blood flow signals in the transplanted skin, along with mild local inflammation. Flow cytometric analysis revealed a positive correlation between high expression of IL-10+ Breg and the changes in Foxp3+ Tregs in vivo, primarily enriched in the CD19 + CD24 + CD27+ mBreg and CD19 + CD23 + CD27-CD24+ Breg subsets, with higher levels of IgM expression. Significant differences were observed compared with control mice. CD79b/NF-κB pathway was found to be involved in Breg production. CD24, CD23, CD79, BTK, NF-κB p50/p65, CD40, and IKKα levels in the adoptive infusion group were significantly increased compared with those in the control group. Adoptive infusion of CD169low/-MSCs/tolDCs may activate the NF-κB pathway through CD79/BTK-dependent and CD40/IKKα-independent pathways, inducing high expression of IL-10 + Breg and promoting graft survival of mouse skin transplantation.

CXCL12+ fibroblastic reticular cells in lymph nodes facilitate immune tolerance by regulating T cell-mediated alloimmunity

Fibroblastic reticular cells (FRCs) are the master regulators of the lymph node (LN) microenvironment. However, the role of specific FRC subsets in controlling alloimmune responses remains to be studied. Single-cell RNA sequencing (scRNA-Seq) of naive and draining LNs (DLNs) of heart-transplanted mice and human LNs revealed a specific subset of CXCL12hi FRCs that expressed high levels of lymphotoxin-β receptor (LTβR) and are enriched in the expression of immunoregulatory genes. CXCL12hi FRCs had high expression of CCL19, CCL21, indoleamine 2,3-dioxygenase (IDO), IL-10, and TGF-β1. Adoptive transfer of ex vivo-expanded FRCs resulted in their homing to LNs and induced immunosuppressive environments in DLNs to promote heart allograft acceptance. Genetic deletion of LTβR and Cxcl12 in FRCs increased alloreactivity, abrogating the effect of costimulatory blockade in prolonging heart allograft survival. As compared with WT recipients, CXCL12+ FRC-deficient recipients exhibited increased differentiation of CD4+ T cells into Th1 cells. Nano delivery of CXCL12 to DLNs improved allograft survival in heart-transplanted mice. Our study highlights the importance of DLN CXCL12hi FRCs in promoting transplant tolerance.

Dendritic Cells in Xenotransplantation: Shaping the Cellular Immune Response Toward Tolerance

The molecular barriers that cause acute xenograft rejection have been identified and addressed by generating genetically modified (GM) animals, knocked out for specific xenoantigens (xenoAgs), and expressing regulatory molecules for both complement and coagulation pathways among others. The focus of xenotransplantation research now lies in delayed xenograft rejection. Dendritic cells (DC) are a specific subpopulation of professional antigen-presenting cells (APC) that play a crucial role in the context of organ transplantation. DCs, originating from both the xenograft and the recipient, have the capacity to present xenoAgs to the recipient's immune system via their respective major histocompatibility complex (MHC) molecules leading to rejection. These processes are known as direct and indirect presentation, respectively. However, under certain microenvironmental conditions, DC develops into anti-inflammatory regulatory cells that can induce immunological tolerance. The purpose of this review is to summarize current knowledge on the general characteristics and functions of DC from species relevant to xenotransplantation, specifically humans, non-human primates (NHP), and pigs. It will also cover the process of xenoAg presentation, different methods for generating DC with regulatory properties in vitro, and finally, discuss the current strategies for using regulatory DC to improve xenograft acceptance by inducing tolerance.

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.

Drug delivery strategies for local immunomodulation in transplantation: Bridging the translational gap

Drug delivery strategies for local immunomodulation hold tremendous promise compared to current clinical gold-standard systemic immunosuppression as they could improve the benefit to risk ratio of life-saving or life-enhancing transplants. Such strategies have facilitated prolonged graft survival in animal models at lower drug doses while minimizing off-target effects. Despite the promising outcomes in preclinical animal studies, progression of these strategies to clinical trials has faced challenges. A comprehensive understanding of the translational barriers is a critical first step towards clinical validation of effective immunomodulatory drug delivery protocols proven for safety and tolerability in pre-clinical animal models. This review overviews the current state-of-the-art in local immunomodulatory strategies for transplantation and outlines the key challenges hindering their clinical translation.

Dissection of pro-tumoral macrophage subtypes and immunosuppressive cells participating in M2 polarization

Alternatively activated macrophage (M2) polarization can result in one of four subtypes based on cytokines and signaling pathways associated with macrophage activation: M2a, M2b, M2c, and M2d macrophages. The majority of M2 subtypes are anti-inflammatory and pro-angiogenic, secreting growth factors (VEGF, PDGF) and matrix metalloproteinases (MMP2, MMP9) which boost tumor growth, metastasis, and invasion. M2-polarized macrophages are associated with immune suppressor cells harboring Myeloid derived suppressor cells, Regulatory T cells (Tregs), Regulatory B cells as well as alternatively activated (N2) neutrophils. Treg cells selectively support the metabolic stability, mitochondrial integrity, and survival rate of M2-like TAMs in an indirect environment. Also, the contribution of Breg cells influences macrophage polarization towards the M2 direction. TAM is activated when TAN levels in the tumor microenvironment are insufficient or vice versa, suggesting that macrophage and its polarization are fine-tuned. Understanding the functions of immune suppressive cells, mediators, and signaling pathways involved with M2 polarization will allow us to identify potential strategies for targeting the TAM repolarization phenotype for innovative immunotherapy approaches. In this review, we have highlighted the critical factors for M2 macrophage polarization, differential cytokine/chemokine profiles of M1 and M2 macrophage subtypes, and other immune cells' impact on the polarization within the immunosuppressive niche.

Sensing of an HIV-1-Derived Single-Stranded RNA-Oligonucleotide Induces Arginase 1-Mediated Tolerance

Small synthetic oligodeoxynucleotides (ODNs) can mimic microbial nucleic acids by interacting with receptor systems and promoting immunostimulatory activities. Nevertheless, some ODNs can act differently on the plasmacytoid dendritic cell (pDC) subset, shaping their immunoregulatory properties and rendering them suitable immunotherapeutic tools in several clinical settings for treating overwhelming immune responses. We designed HIV-1-derived, DNA- and RNA-based oligonucleotides (gag, pol, and U5 regions) and assessed their activity in conferring a tolerogenic phenotype to pDCs in skin test experiments. RNA-but not DNA-oligonucleotides are capable of inducing tolerogenic features in pDCs. Interestingly, sensing the HIV-1-derived single-stranded RNA-gag oligonucleotide (RNA-gag) requires both TLR3 and TLR7 and the engagement of the TRIF adaptor molecule. Moreover, the induction of a suppressive phenotype in pDCs by RNA-gag is contingent upon the induction and activation of the immunosuppressive enzyme Arginase 1. Thus, our data suggest that sensing of the synthetic RNA-gag oligonucleotide in pDCs can induce a suppressive phenotype in pDCs, a property rendering RNA-gag a potential tool for therapeutic strategies in allergies and autoimmune diseases.

Optimal conditions for adenoviral transduction of immature dendritic cells without affecting the tolerogenic activity of DC-based immunotherapy

Dendritic cells (DCs) play a pivotal role in maintaining immune tolerance. Using recombinant adenovirus (rAd) to deliver vectors to immature dendritic cells (imDCs) is an important method for studying the tolerogenic function of DCs. We found that using RPMI medium and a higher MOI during transduction increased the expression of CD80, CD86, and MHC-II on the surface of imDCs. Our data reveal a significant increase in the secretion of the pro-inflammatory cytokine IL-6 in the group showing the most pronounced phenotypic changes. In the mouse heart transplant model, imDCs with unstable phenotype and function due to adenoviral transduction resulted in an increased proportion of Th1 and Th17 cells in recipients. However, these effects can be managed, and our proposed optimized transduction strategy significantly minimizes these adverse effects. Our study holds significant implications for the development and optimization of immunotherapy utilizing tolerogenic dendritic cells.

Tumor Microenvironment Modulation by Cancer-Derived Extracellular Vesicles

The tumor microenvironment (TME) plays an important role in the process of tumorigenesis, regulating the growth, metabolism, proliferation, and invasion of cancer cells, as well as contributing to tumor resistance to the conventional chemoradiotherapies. Several types of cells with relatively stable phenotypes have been identified within the TME, including cancer-associated fibroblasts (CAFs), tumor-associated macrophages (TAMs), neutrophils, and natural killer (NK) cells, which have been shown to modulate cancer cell proliferation, metastasis, and interaction with the immune system, thus promoting tumor heterogeneity. Growing evidence suggests that tumor-cell-derived extracellular vesicles (EVs), via the transfer of various molecules (e.g., RNA, proteins, peptides, and lipids), play a pivotal role in the transformation of normal cells in the TME into their tumor-associated protumorigenic counterparts. This review article focuses on the functions of EVs in the modulation of the TME with a view to how exosomes contribute to the transformation of normal cells, as well as their importance for cancer diagnosis and therapy.

Cell-mediated barriers in cancer immunosurveillance

The immune cells within the tumor microenvironment (TME) exert multifaceted functions ranging from tumor-antagonizing or tumor-promoting activities. During the initial phases of tumor development, the tumor-antagonizing immune cells in the TME combat cancer cells in an immune surveillance process. However, with time, cancer cells can evade detection and impede the immune cells' effectiveness through diverse mechanisms, such as decreasing immunogenic antigen presentation on their surfaces and/or secreting anti-immune factors that cause tolerance in TME. Moreover, some immune cells cause immunosuppressive situations and inhibit antitumoral immune responses. Physical and cellular-mediated barriers in the TME, such as cancer-associated fibroblasts, tumor endothelium, the altered lipid composition of tumor cells, and exosomes secreted from cancer cells, also mediate immunosuppression and prevent extravasation of immune cells. Due to successful clinical outcomes of cancer treatment strategies the potential barriers must be identified and addressed. We need to figure out how to optimize cancer immunotherapy strategies, and how to combine therapeutic approaches for maximum clinical benefit. This review provides a detailed overview of various cells and molecules in the TME, their association with escaping from immune surveillance, therapeutic targets, and future perspectives for improving cancer immunotherapy.

Mechanism of Action of Oral Salmonella-Based Vaccine to Prevent and Reverse Type 1 Diabetes in NOD Mice

A combination therapy of preproinsulin (PPI) and immunomodulators (TGFβ+IL10) orally delivered via genetically modified Salmonella and anti-CD3 promoted glucose balance in in NOD mice with recent onset diabetes. The Salmonella bacteria were modified to express the diabetes-associated antigen PPI controlled by a bacterial promoter in conjunction with over-expressed immunomodulating molecules. The possible mechanisms of action of this vaccine to limit autoimmune diabetes remained undefined. In mice, the vaccine prevented and reversed ongoing diabetes. The vaccine-mediated beneficial effects were associated with increased numbers of antigen-specific CD4+CD25+Foxp3+ Tregs, CD4+CD49b+LAG3+ Tr1-cells, and tolerogenic dendritic-cells (tol-DCs) in the spleens and lymphatic organs of treated mice. Despite this, the immune response to Salmonella infection was not altered. Furthermore, the vaccine effects were associated with a reduction in islet-infiltrating lymphocytes and an increase in the islet beta-cell mass. This was associated with increased serum levels of the tolerogenic cytokines (IL10, IL2, and IL13) and chemokine ligand 2 (CCL2) and decreased levels of inflammatory cytokines (IFNγ, GM-CSF, IL6, IL12, and TNFα) and chemokines (CXCL1, CXCL2, and CXCL5). Overall, the data suggest that the Salmonella-based vaccine modulates the immune response, reduces inflammation, and promotes tolerance specifically to an antigen involved in autoimmune diabetes.

Exopolysaccharide-Treated Dendritic Cells Effectively Ameliorate Acute Graft-versus-Host Disease

Graft-versus-host disease (GVHD) is a primary and often lethal complication of allogenic hematopoietic stem cell transplantation (HSCT). Prophylactic regimens for GVHD are given as standard pretransplantation therapy; however, up to 50% of these patients develop acute GVHD (aGVHD) and require additional immunosuppressive intervention. Using a mouse GVHD model, we previously showed that injecting mice with exopolysaccharide (EPS) from Bacillus subtilis prior to GVHD induction significantly increased 80-day survival after transplantation of complete allogeneic major histocompatibility complex-mismatched cells. To ask whether EPS might also inhibit GVHD in humans, we used humanized NSG-HLA-A2 mice and induced GVHD by i.v. injection of A2neg human peripheral blood mononuclear cells (PBMCs). Because we could not inject human donors with EPS, we transferred EPS-pretreated dendritic cells (DCs) to inhibit aGVHD. We derived these DCs from CD34+ human cord blood cells, treated them with EPS, and then injected them together with PBMCs into the NSG-HLA-A2 mice. We found that all mice that received untreated DCs were dead by day 35, whereas 25% of mice receiving EPS-treated DCs (EPS-DCs) survived. This DC cell therapy could be readily translatable to humans, because we can generate large numbers of human EPS-DCs and use them as an "off the shelf" treatment for patients undergoing HSCT.

Circular RNA MAP2K2-modified immunosuppressive dendritic cells for preventing alloimmune rejection in organ transplantation

Long-term patient and graft survival has been achieved in organ transplantation but at the expense of toxic side effects that are associated with long-term use of nonspecific immunosuppressive drugs. Discovering new regulators of dendritic cells is the key for development of an ideal treatment to prevent immune rejection. We hypothesized that knockdown of circMAP2K2 induces immunosuppressive DCs and that treatment with circMAP2K2 silenced-DCs can prevent alloimmune rejection. DCs were cultured and transfected with siRNA for circMAP2K2. circMAP2K2 levels were measured by qRT-PCR. DC's maturation and immune function were assessed by flow cytometry and mixed lymphocyte reactions. The function of circMAP2K2 was illustrated by a series of RIP and IP. The therapeutics of engineered DCs was tested in a mouse heart transplantation model. We found that circMAP2K2 was highly expressed in mature DCs. Knockdown of circMAP2K2 reduced expression of MHCII, CD40 and CD80, attenuated the ability of DCs to activate allogeneic naïve T cells, and enhanced CD4+CD25+FOXP3+ regulatory T cells (Treg). circMAP2K2-induced immunosuppressive DCs by interacting with SENP3. Treatment with circMAP2K2-knockdown DCs attenuated alloimmune rejection and prolonged allograft survival in a murine heart transplantation model. The immune suppression induced in vivo was donor-antigen specific. In conclusion, knockdown of circMAP2K2 can induce immunosuppressive DCs which are able to inhibit overactive immune response, highlighting a new promising therapeutic approach for immune disorder diseases.

Co-delivery of vitamin D3 and Lkb1 siRNA by cationic lipid-assisted PEG-PLGA nanoparticles to effectively remodel the immune system in vivo

The imbalance of the immune system can lead to the occurrence of autoimmune diseases. Controlling and regulating the proliferation and function of effector T (Teff) cells and regulatory T (Treg) cells becomes the key to treating these diseases. Dendritic cells (DCs), as dedicated antigen-presenting cells, play a key role in inducing the differentiation of naive CD4+ T cells. In this study, we designed a cationic lipid-assisted PEG-PLGA nanoparticle (NPs/VD3/siLkb1) to deliver 1,25-dihydroxyvitamin D3 (VD3) and small interfering RNA (siRNA) to DC cells in the draining lymph nodes. By modulating the phenotypic changes of DC cells, this approach expands Treg cells and reduces the occurrence of autoimmune diseases. Thus, this study provides a novel approach to alleviating the occurrence and development of autoimmune diseases while also minimizing the risk of unwanted complications.

Innovative biomaterials for the treatment of periodontal disease

Periodontitis is a multifactorial disease that involves the destruction of hard and soft tissues surrounding the tooth. Routine periodontal treatment includes mechanical debridement (surgical and non-surgical) and the systemic administration of antibiotics. In contrast, severe and chronic periodontitis involves aggressive tissue destruction and bone resorption, and the damage is usually irreversible. In these severe cases, bone grafts, the delivery of growth hormones, and guided tissue regeneration can all be used to stimulate periodontal regeneration. However, these approaches do not result in consistent and predictable treatment outcomes. As a result, advanced biomaterials have evolved as an adjunctive approach to improve clinical performance. These novel biomaterials are designed to either prolong the release of antibacterial agents or osteogenic molecules, or to act as immunomodulators to promote healing. The first half of this review briefly summarizes the key immune cells and their underlying cellular pathways implicated in periodontitis. Advanced biomaterials designed to promote periodontal regeneration will be highlighted in the second half. Finally, the limitations of the current experimental design and the challenges of translational science will be discussed.

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.

Pairing of single-cell RNA analysis and T cell antigen receptor profiling indicates breakdown of T cell tolerance checkpoints in atherosclerosis

Atherosclerotic plaques form in the inner layer of arteries triggering heart attacks and strokes. Although T cells have been detected in atherosclerosis, tolerance dysfunction as a disease driver remains unexplored. Here we examine tolerance checkpoints in atherosclerotic plaques, artery tertiary lymphoid organs and lymph nodes in mice burdened by advanced atherosclerosis, via single-cell RNA sequencing paired with T cell antigen receptor sequencing. Complex patterns of deteriorating peripheral T cell tolerance were observed being most pronounced in plaques followed by artery tertiary lymphoid organs, lymph nodes and blood. Affected checkpoints included clonal expansion of CD4+, CD8+ and regulatory T cells; aberrant tolerance-regulating transcripts of clonally expanded T cells; T cell exhaustion; Treg-TH17 T cell conversion; and dysfunctional antigen presentation. Moreover, single-cell RNA-sequencing profiles of human plaques revealed that the CD8+ T cell tolerance dysfunction observed in mouse plaques was shared in human coronary and carotid artery plaques. Thus, our data support the concept of atherosclerosis as a bona fide T cell autoimmune disease targeting the arterial wall.

The role of tolerogenic dendritic cells in systematic lupus erythematosus progression and remission

Systematic lupus erythematosus (SLE) is an autoimmune disease reflecting an imbalance between effector and regulatory immune responses. Dendritic cells (DC) are a link between innate and adaptive immunity. Inflammatory DCs (inflDC) can initiate and trigger lymphocyte responses in SLE with over-expression of surface molecules and pro-inflammatory cytokine, including Interferon (IFN) α, Interleukin (IL) 1α, IL-1β, and IL-6, resulting in the overreaction of T helper cells (Th), and B cells immune responses. On the opposite side, tolerogenic DCs (tolDC) express inhibitory interacting surface molecules and repressive mediators, such as IL-10, Transforming growth factor beta (TGF-β), and Indoleamine 2, 3-dioxygenase (IDO), which can maintain self-tolerance in SLE by induction of regulatory T cells (Treg), T cells deletion and anergy. Hence, tolDCs can be a therapeutic candidate for patients with SLE to suppress their systematic inflammation. Recent pre-clinical and clinical studies showed the efficacy of tolDCs therapy in autoimmune diseases. In this review, we provide a wide perspective on the effect of inflDCs in promoting inflammation and the role of tolDC in the suppression of immune cells' overreaction in SLE. Furthermore, we reviewed the finding of clinical trials and experimental studies related to autoimmune diseases, particularly SLE.

The Combination of Rhodosin and MMF Prolongs Cardiac Allograft Survival by Inhibiting DC Maturation by Promoting Mitochondrial Fusion

Despite being the gold-standard treatment for end-stage heart disease, heart transplantation is associated with acute cardiac rejection within 1 year of transplantation. The continuous application of immunosuppressants may cause side effects such as hepatic and renal toxicity, infection, and malignancy. Developing new pharmaceutical strategies to alleviate acute rejection after heart transplantation effectively and safely is of critical importance. In this study, we performed a murine model of MHC-full mismatch cardiac transplantation and showed that the combination of Rhodosin (Rho) and mycophenolate mofetil (MMF) could prevent acute rejection and oxidative stress injury and prolong the survival time of murine heart transplants. The use of Rho plus MMF in allografts improved the balance of Tregs/Teff cells, which had a protective effect on allotransplantation. We also isolated bone marrow-derived dendritic cells (BMDCs) and determined that Rho inhibited DC maturation by promoting mitochondrial fusion mainly through the mitochondrial fusion-related protein MFN1. Herein, we demonstrated that Rho, an active ingredient isolated from the plant Rhodiola rosea with antioxidant and anti-inflammatory activities, could efficiently alleviate acute rejection and significantly prolong murine heart allograft survival when used with a low dose of MMF. More importantly, we found that Rho restrained DC maturation by promoting mitochondrial fusion and decreasing reactive oxygen species (ROS) levels, which then alleviated acute rejection in murine cardiac transplantation. Interestingly, as a novel immunosuppressant, Rho has almost no side effects compared with other traditional immunosuppressants. Taken together, these results suggest that Rho has good clinical auxiliary applications as an effective immunosuppressant and antioxidant, and this study provides an efficient strategy to overcome the side effects of immunosuppressive agents that are currently used in organ transplantation.

A New Generation of Cell Therapies Employing Regulatory T Cells (Treg) to Induce Immune Tolerance in Pediatric Transplantation

Kidney transplantation is the most common solid organ transplant and the preferred treatment for pediatric patients with end-stage renal disease, but it is still not a definitive solution due to immune graft rejection. Regulatory T cells (Treg) and their control over effector T cells is a crucial and intrinsic tolerance mechanism in limiting excessive immune responses. In the case of transplants, Treg are important for the survival of the transplanted organ, and their dysregulation could increase the risk of rejection in transplanted children. Chronic immunosuppression to prevent rejection, for which Treg are especially sensitive, have a detrimental effect on Treg counts, decreasing the Treg/T-effector balance. Cell therapy with Treg cells is a promising approach to restore this imbalance, promoting tolerance and thus increasing graft survival. However, the strategies used to date that employ peripheral blood as a Treg source have shown limited efficacy. Moreover, it is not possible to use this approach in pediatric patients due to the limited volume of blood that can be extracted from children. Here, we outline our innovative strategy that employs the thymus removed during pediatric cardiac surgeries as a source of therapeutic Treg that could make this therapy accessible to transplanted children. The advantageous properties and the massive amount of Treg cells obtained from pediatric thymic tissue (thyTreg) opens a new possibility for Treg therapies to prevent rejection in pediatric kidney transplants. We are recruiting patients in a clinical trial to prevent rejection in heart-transplanted children through the infusion of autologous thyTreg cells (NCT04924491). If its efficacy is confirmed, thyTreg therapy may establish a new paradigm in preventing organ rejection in pediatric transplants, and their allogeneic use would extend its application to other solid organ transplantation.

CXCR4 blockade reduces the severity of murine heart allograft rejection by plasmacytoid dendritic cell-mediated immune regulation

Allograft-specific regulatory T cells (T_reg cells) are crucial for long-term graft acceptance after transplantation. Although adoptive T_reg cell transfer has been proposed, major challenges include graft-specificity and stability. Thus, there is an unmet need for the direct induction of graft-specific T_reg cells. We hypothesized a synergism of the immunotolerogenic effects of rapamycin (mTOR inhibition) and plerixafor (CXCR4 antagonist) for T_reg cell induction. Thus, we performed fully-mismatched heart transplantations and found combination treatment to result in prolonged allograft survival. Moreover, fibrosis and myocyte lesions were reduced. Although less CD3⁺ T cell infiltrated, higher T_reg cell numbers were observed. Noteworthy, this was accompanied by a plerixafor-dependent plasmacytoid dendritic cells-(pDCs)-mobilization. Furthermore, in vivo pDC-depletion abrogated the plerixafor-mediated T_reg cell number increase and reduced allograft survival. Our pharmacological approach allowed to increase T_reg cell numbers due to pDC-mediated immune regulation. Therefore pDCs can be an attractive immunotherapeutic target in addition to plerixafor treatment.

Myeloid and Mesenchymal Stem Cell Therapies for Solid Organ Transplant Tolerance

Transplantation is now performed globally as a routine procedure. However, the increased demand for donor organs and consequent expansion of donor criteria has created an imperative to maximize the quality of these gains. The goal is to balance preservation of allograft function against patient quality-of-life, despite exposure to long-term immunosuppression. Elimination of immunosuppressive therapy to avoid drug toxicity, with concurrent acceptance of the allograft-so-called operational tolerance-has proven elusive. The lack of recent advances in immunomodulatory drug development, together with advances in immunotherapy in oncology, has prompted interest in cell-based therapies to control the alloimmune response. Extensive experimental work in animals has characterized regulatory immune cell populations that can induce and maintain tolerance, demonstrating that their adoptive transfer can promote donor-specific tolerance. An extension of this large body of work has resulted in protocols for manufacture, as well as early-phase safety and feasibility trials for many regulatory cell types. Despite the excitement generated by early clinical trials in autoimmune diseases and organ transplantation, there is as yet no clinically validated, approved regulatory cell therapy for transplantation. In this review, we summarize recent advances in this field, with a focus on myeloid and mesenchymal cell therapies, including current understanding of the mechanisms of action of regulatory immune cells, and clinical trials in organ transplantation using these cells as therapeutics.

Cyclosporine A, in Contrast to Rapamycin, Affects the Ability of Dendritic Cells to Induce Immune Tolerance Mechanisms

Following organ transplantation, it is essential that immune tolerance is induced in the graft recipient to reduce the risk of rejection and avoid complications associated with the long-term use of immunosuppressive drugs. Immature dendritic cells (DCs) are considered to promote transplant tolerance and may minimize the risk of graft rejection. The aim of the study was to evaluate the effects of immunosuppressive agents: rapamycin (Rapa) and cyclosporine A (CsA) on generation of human tolerogenic DCs (tolDCs) and also to evaluate the ability of these cells to induce mechanisms of immune tolerance. tolDCs were generated in the environment of Rapa or CsA. Next, we evaluated the effects of these agents on surface phenotypes (CD11c, MHC II, CD40, CD80, CD83, CD86, CCR7, TLR2, TLR4), cytokine production (IL-4, IL-6, IL-10, IL-12p70, TGF-β), phagocytic capacity and resistant to lipopolysaccharide activation of these DCs. Moreover, we assessed ability of such tolDCs to induce T cell activation and apoptosis, Treg differentiation and production of Th1- and Th2-characteristic cytokine profile. Data obtained in this study demonstrate that rapamycin is effective at generating maturation-resistant tolDCs, however, does not change the ability of these cells to induce mechanisms of immune tolerance. In contrast, CsA affects the ability of these cells to induce mechanisms of immune tolerance, but is not efficient at generating maturation-resistant tolDCs.

Immunomodulatory bioactive glasses for tissue regeneration

The regulatory functions of the immune response in tissue healing, repair, and regeneration have been evidenced in the last decade. Immune cells play central roles in immune responses toward inducing favorable tissue regenerative processes. Modulating and controlling the immune cell responses (particularly macrophages) is an emerging approach to enhance tissue regeneration. Bioactive glasses (BGs) are multifunctional materials exhibiting osteogenic, angiogenic, and antibacterial properties, being increasingly investigated for various tissue regeneration scenarios, including bone regeneration and wound healing. On the other hand, the immunomodulatory effects of BGs in relation to regenerating tissues have started to be understood, and key knowledge is emerging. This is the first review article summarizing the immunomodulatory effects of BGs for tissue repair and regeneration. The immune response to BGs is firstly introduced, discussing potential mechanisms regarding the immunomodulation effects induced by BGs. Moreover, the interactions between the immune cells involved in the immunomodulation process and BGs (dissolution products) are summarized in detail. Particularly, a well-regulated and timely switch of macrophage phenotype from pro-inflammatory to anti-inflammatory is crucial to constructive tissue regeneration through modulating osteogenesis, osteoclastogenesis, and angiogenesis. The influence of BG characteristics on macrophage responses is discussed. We highlight the strategies employed to harness macrophage responses for enhanced tissue regeneration, including the incorporation of active ions, surface functionalization, and controlled release of immunomodulatory molecules. Finally, we conclude with our perspectives on future research challenges and directions in the emerging field of immunomodulatory BGs for tissue regeneration. STATEMENT OF SIGNIFICANCE: Immunomodulatory effects of bioactive glasses (BGs) in relation to bone regeneration and wound healing have started to be understood. We summarize those studies which have focused on immunomodulatory BGs for tissue regeneration. We first introduce the potential mechanisms of the immunomodulation effects induced by BGs. Interactions between the cells involved in immunomodulation processes and BGs (and their dissolution products, biologically active ions) are elaborated. We highlight the strategies employed to modulate macrophage responses for enhancing tissue regeneration, including incorporation of active ions, surface functionalization, and controlled release of immunomodulatory agents. This is the first review article summarizing and outlining the immunomodulatory effects of BGs for tissue regeneration. We anticipate that increasing research efforts will start to emerge in the area of immunomodulatory BGs.

Interplay of Immunometabolism and Epithelial-Mesenchymal Transition in the Tumor Microenvironment

Epithelial–mesenchymal transition (EMT) and metabolic reprogramming in cancer cells are the key hallmarks of tumor metastasis. Since the relationship between the two has been well studied, researchers have gained increasing interest in the interplay of cancer cell EMT and immune metabolic changes. Whether the mutual influences between them could provide novel explanations for immune surveillance during metastasis is worth understanding. Here, we review the role of immunometabolism in the regulatory loop between tumor-infiltrating immune cells and EMT. We also discuss the challenges and perspectives of targeting immunometabolism in cancer treatment.

Oxymatrine protects cardiac allografts by regulating immunotolerant cells

Organ transplantation is an effective treatment strategy for patients with irreversible organ failure or congenital organ dysfunction. Oxymatrine (OMT) is a quinolizidine alkaloid with protective and anti-inflammatory effects on tissues and organs. The objective of this study was to investigate whether OMT could exert protective effects in cardiac allografts by regulating immune cells. In vitro cell proliferation and co-culture experiments were used to measure the effects of OMT on splenocyte proliferation and differentiation. In the in vivo study, C57BL/6 mice transplanted with BALB/c cardiac grafts were randomly divided into untreated, low-dose OMT treated, middle-dose OMT treated, high-dose OMT treated, and rapamycin-treated groups. Haematoxylin and eosin and immunohistochemical staining were used to assess pathological changes in the grafts, and fluorescence-activated cell sorting analysis was performed to measure the percentages of immune cells. The results showed that, in the in vitro study, OMT inhibited splenocyte proliferation, decreased the percentage of mature dendritic cells (DCs), and increased the percentage of regulatory T cells (Tregs) and regulatory B cells (Bregs). In the in vivo study, OMT exerted allograft protective effects by prolonging survival time, alleviating pathological damages to the cardiac allograft, decreasing intragraft CD3⁺ cell and increasing intragraft Foxp3⁺ cell infiltration, decreasing the percentages of mature DCs, increasing the percentages of Tregs and Bregs, and inhibiting the function of DCs. In conclusion, our study demonstrates that OMT exerted a protective effect on cardiac allografts by regulating immunotolerant cells. More in-depth studies of OMT may provide additional insight into the use of immunosuppressive drugs as a post-transplantation treatment strategy.

Reactive oxygen species-responsive dendritic cell-derived exosomes for rheumatoid arthritis

Although tolerogenic dendritic cell-derived exosomes (TolDex) have emerged as promising therapeutics for rheumatoid arthritis (RA), their clinical applications have been hampered by their poor in vivo disposition after systemic administration. Herein, we report the development of stimuli-responsive TolDex that induces lesion-specific immunoregulation in RA. Responsiveness to reactive oxygen species (ROS), a physiological stimulus in the RA microenvironment, was conferred on TolDex by introducing a thioketal (TK) linker-embedded poly(ethylene glycol) (PEG) on TolDex surface via hydrophobic insertion. The detachment of PEG following overproduction of ROS facilitates the cellular uptake of ROS-responsive TolDex (TKDex) into activated immune cells. Notably, TolDex and TKDex downregulated CD40 in mature dendritic cells (mDCs) and regulated secretion of pro-inflammatory cytokines, including tumor necrosis factor (TNF)-α and interleukin-6 (IL-6) at the cellular level. In the collagen-induced arthritis (CIA) mouse model, PEG prolonged the blood circulation of TKDex following intravenous administration and enhanced their accumulation in the joints. In addition, TKDex decreased IL-6, increased transforming growth factor-β, and induced the CD4⁺CD25⁺Foxp3⁺ regulatory T cells in CIA mice. Overall, ROS-responsive TolDex might have potential as therapeutic agents for RA. STATEMENT OF SIGNIFICANCE: Tolerogenic dendritic cell-derived exosomes (TolDex) are emerging immunoregulators of autoimmune diseases, including rheumatoid arthritis (RA). However, their lack of long-term stability and low targetability are still challenging. To overcome these issues, we developed reactive oxygen species (ROS)-responsive TolDex (TKDex) by incorporating the ROS-sensitive functional group-embedded poly(ethylene glycol) linker into the exosomal membrane of TolDex. Surface-engineered TKDex were internalized in mature DCs because of high ROS-sensitivity and enhanced accumulation in the inflamed joint in vivo. Further, for the first time, we investigated the potential mechanism of action of TolDex relevant to CD40 downregulation and attenuation of tumor necrosis factor (TNF)-α secretion. Our strategy highlighted the promising nanotherapeutic effects of stimuli-sensitive TolDex, which induces immunoregulation.

Fa(c)t checking: How fatty acids shape metabolism and function of macrophages and dendritic cells

In recent years there have been major advances in our understanding of the role of free fatty acids (FAs) and their metabolism in shaping the functional properties of macrophages and DCs. This review presents the most recent insights into how cell intrinsic FA metabolism controls DC and macrophage function, as well as the current evidence of the importance of various exogenous FAs (such as polyunsaturated FAs and their oxidation products—prostaglandins, leukotrienes, and proresolving lipid mediators) in affecting DC and macrophage biology, by modulating their metabolic properties. Finally, we explore whether targeted modulation of FA metabolism of myeloid cells to steer their function could hold promise in therapeutic settings.

Immune metabolism: a bridge of dendritic cells function

An increasing number of researches have shown that cell metabolism regulates cell function. Dendritic cells (DCs), a professional antigen presenting cells, connect innate and adaptive immune responses. The preference of DCs for sugar or lipid affects its phenotypes and functions. In many diseases such as atherosclerosis (AS), diabetes mellitus and tumor, altered glucose or lipid level in microenvironment makes DCs exert ineffective or opposite immune roles, which accelerates the development of these diseases. In this article, we review the metabolism pathways of glucose and cholesterol in DCs, and the effects of metabolic changes on the phenotype and function of DCs. In addition, we discuss the effects of changes in glucose and lipid levels on DCs in the context of different diseases for better understanding the relationship between DCs and diseases. The immune metabolism of DCs may be a potential intervention link to treat metabolic-related immune diseases.

Immune function of miR-214 and its application prospects as molecular marker

MicroRNAs are a class of evolutionary conserved non-coding small RNAs that play key regulatory roles at the post-transcriptional level. In recent years, studies have shown that miR-214 plays an important role in regulating several biological processes such as cell proliferation and differentiation, tumorigenesis, inflammation and immunity, and it has become a hotspot in the miRNA field. In this review, the regulatory functions of miR-214 in the proliferation, differentiation and functional activities of immune-related cells, such as dendritic cells, T cells and NK cells, were briefly reviewed. Also, the mechanisms of miR-214 involved in tumor immunity, inflammatory regulation and antivirus were discussed. Finally, the value and application prospects of miR-214 as a molecular marker in inflammation and tumor related diseases were analyzed briefly. We hope it can provide reference for further study on the mechanism and application of miR-214.

Tumour heterogeneity and intercellular networks of nasopharyngeal carcinoma at single cell resolution

The heterogeneous nature of tumour microenvironment (TME) underlying diverse treatment responses remains unclear in nasopharyngeal carcinoma (NPC). Here, we profile 176,447 cells from 10 NPC tumour-blood pairs, using single-cell transcriptome coupled with T cell receptor sequencing. Our analyses reveal 53 cell subtypes, including tumour-infiltrating CD8+ T, regulatory T (Treg), and dendritic cells (DCs), as well as malignant cells with different Epstein-Barr virus infection status. Trajectory analyses reveal exhausted CD8+ T and immune-suppressive TNFRSF4+ Treg cells in tumours might derive from peripheral CX3CR1+CD8+ T and naïve Treg cells, respectively. Moreover, we identify immune-regulatory and tolerogenic LAMP3+ DCs. Noteworthily, we observe intensive inter-cell interactions among LAMP3+ DCs, Treg, exhausted CD8+ T, and malignant cells, suggesting potential cross-talks to foster an immune-suppressive niche for the TME. Collectively, our study uncovers the heterogeneity and interacting molecules of the TME in NPC at single-cell resolution, which provide insights into the mechanisms underlying NPC progression and the development of precise therapies for NPC.

Soluble CD83 inhibits acute rejection by up regulating TGF-β and IDO secretion in rat liver transplantation

BACKGROUND

Allogeneic transplantation immune tolerance is currently a hot research issue and soluble CD83(sCD83) is a novel immunomodulator with great potential in inducing transplantation tolerance.

OBJECTIVE

To investigate the mechanism of the immune tolerance effect of sCD83 on rat liver transplantation.

METHOD

A rat liver transplantation model was established to study the effects of sCD83 on the expression levels of IL-2, IL-10, and TGF-β in peripheral blood and the mRNA expressions of foxp3, TGF-β, and Indoleamine 2,3-dioxygenase (IDO) in liver. The expression changes of costimulatory molecules CD80, CD86, and MHC-II on the surface of DC cells and the expressions of IDO + DC cell, TGF-β + CD4 + T cell, and CD4 + CD25 + Foxp3 + T cell were analyzed and compared.

RESULTS

sCD83 alleviated the rejection activity index (RAI) of rat liver transplantation in the early stage, increased the expressions of TGF-β, IL-10 in peripheral blood and the mRNAs of IDO, TGF-β and foxp3 in the transplanted liver, and down-regulated the expressions of MHC-II, CD86, and CD80 in DC cells, resulting in significant increased numbers of tolerogenic TGF-β + CD4 + T cells, Treg cells, and IDO + DC cells with low expression.

CONCLUSION

sCD83 inhibited acute rejection after liver transplantation in an allogeneic rat, and the mechanism was associated with the effect that sCD83 increased the expression of TGF-β, activated IDO immunosuppressive pathway, and increased tolerogenic DC cells and Treg cells.

DiR-labeled tolerogenic dendritic cells for targeted imaging in collagen- induced arthritis rats

Tolerogenic dendritic cells (tolDCs) are immunosuppressive cells and play an important role in rheumatoid arthritis (RA) as immunotherapeutic tools. We aimed to investigate whether allogeneic tolDCs (allo-tolDCs) and autologous tolDCs (auto-tolDCs) had long-time tolerogenic potential in vivo and improve arthritis in collagen-induced arthritis (CIA) rats. TolDCs were induced by NF-κB Decoy ODN, and loaded with Bovine Type II collagen (CII- loaded tolDCs) and identified by flow cytometry, and labeled with DiR and injected into CIA rats. The biodistribution of DiR-labeled tolDCs was monitored by IVIS imaging at different time points. Major organs were harvested and analyzed by ex-in vivo cell imaging. The tolDCs were successfully constructed, along with expressing low levels of CD80 and CD86 compared to DCs. The fluorescent signals of all DiR (+) groups were observed at least 25 days, and as long as 35 days. DiR (+) CII- loaded allo-and auto-tolDCs at post injection mainly distributed in the chest and abdomen and gradually moved to limb joints over time. The allo- and auto-tolDCs decreased the expression of IFN-γ and IL-2 in CIA rats with different severity compared to CIA rats without tolDCs treatment, while significantly increased the expression of IL-4 and IL-10. Additionally, these tolDCs ameliorated the ankle joints injury in CIA rats with different severity. The both allo- and auto-tolDCs showed long-time tolerogenic potential in vivo and ameliorated arthritis in CIA rats with different severity.

Haploidentical mixed chimerism cures autoimmunity in established type 1 diabetic mice

Clinical trials are currently testing whether induction of haploidentical mixed chimerism (Haplo-MC) induces organ transplantation tolerance. Whether Haplo-MC can be used to treat established autoimmune diseases remains unknown. Here, we show that established autoimmunity in euthymic and adult-thymectomized NOD (H-2g7) mice was cured by induction of Haplo-MC under a non-myeloablative anti-thymocyte globulin-based conditioning regimen and infusion of CD4+ T cell-depleted hematopoietic graft from H-2b/g7 F1 donors that expressed autoimmune-resistant H-2b or from H-2s/g7 F1 donors that expressed autoimmune-susceptible H-2s. The cure was associated with enhanced thymic negative selection, increased thymic Treg (tTreg) production, and anergy or exhaustion of residual host-type autoreactive T cells in the periphery. The peripheral tolerance was accompanied by expansion of donor- and host-type CD62L-Helios+ tTregs as well as host-type Helios-Nrp1+ peripheral Tregs (pTregs) and PD-L1hi plasmacytoid DCs (pDCs). Depletion of donor- or host-type Tregs led to reduction of host-type PD-L1hi pDCs and recurrence of autoimmunity, whereas PD-L1 deficiency in host-type DCs led to reduction of host-type pDCs and Helios-Nrp1+ pTregs. Thus, induction of Haplo-MC reestablished both central and peripheral tolerance through mechanisms that depend on allo-MHC+ donor-type DCs, PD-L1hi host-type DCs, and the generation and persistence of donor- and host-type tTregs and pTregs.

Exosomes from dendritic cells with Mettl3 gene knockdown prevent immune rejection in a mouse cardiac allograft model

We have previously demonstrated that Mettl3-silencing dendritic cells (DCs) exhibited immature properties and prolonged allograft survival in a murine heart transplantation model. Exosomes derived from donor DCs (Dex) are involved in the immune rejection of organ transplantation, and blocking Dex transfer may suppress immune rejection. Herein, this study aimed to investigate whether Mettl3 knockdown inhibits the secretion and activity of donor Dex, thereby inhibiting donor Dex-mediated immune rejection. The imDex, mDex, shCtrl-mDex, and shMettl3-mDex were obtained from the culture supernatant of DCs (immature DCs, mature DCs, shCtrl-infected mature DCs, shMettl3-infected mature DCs) derived from donor BALB/c mouse bone marrow and then co-cultured with splenic T cell lymphocyte suspension from recipient C57BL/6 mice in vitro or injected into recipient C57BL/6 mice before the cardiac transplantation. Donor shMettl3-mDex expressed lower concentration of exosomes and lower expression of Mettl3, Dex markers (ICAM-1, MHC-I, MHC-II), as well as lower ability to activate T cell immune response than shCtrl-mDex. Administration of donor shMettl3-mDex attenuated immune rejection after mouse heart transplantation and prolonged the allograft survival. In summary, Mettl3 knockdown inhibits the immune rejection of Dex in a mouse cardiac allograft model.

Harnessing lipid signaling pathways to target specialized pro-angiogenic neutrophil subsets for regenerative immunotherapy

To gain insights into neutrophil heterogeneity dynamics in the context of sterile inflammation and wound healing, we performed a pseudotime analysis of single-cell flow cytometry data using the spanning-tree progression analysis of density-normalized events algorithm. This enables us to view neutrophil transitional subsets along a pseudotime trajectory and identify distinct VEGFR1, VEGFR2, and CXCR4 high-expressing pro-angiogenic neutrophils. While the proresolving lipid mediator aspirin-triggered resolvin D1 (AT-RvD1) has a known ability to limit neutrophil infiltration, our analysis uncovers a mode of action in which AT-RvD1 leads to inflammation resolution through the selective reprogramming toward a therapeutic neutrophil subset. This accumulation leads to enhanced vascular remodeling in the skinfold window chamber and a proregenerative shift in macrophage and dendritic cell phenotype, resulting in improved wound closure after skin transplantation. As the targeting of functional immune subsets becomes the key to regenerative immunotherapies, single-cell pseudotime analysis tools will be vital in this field.

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.

Mesenchymal stem cells transfected with sFgl2 inhibit the acute rejection of heart transplantation in mice by regulating macrophage activation

BACKGROUND

Mesenchymal stem cells (MSCs) have become a promising candidate for cell-based immune therapy for acute rejection (AR) after heart transplantation due to possessing immunomodulatory properties. In this study, we evaluated the efficacy of soluble fibronectin-like protein 2 (sFgl2) overexpressing mesenchymal stem cells (sFgl2-MSCs) in inhibiting AR of heart transplantation in mice by regulating immune tolerance through inducing M2 phenotype macrophage polarization.

METHODS AND RESULTS

The sFgl2, a novel immunomodulatory factor secreted by regulatory T cells, was transfected into MSCs to enhance their immunosuppressive functions. After being co-cultured for 72 h, the sFgl2-MSCs inhibited M1 polarization whereas promoted M2 of polarization macrophages through STAT1 and NF-κB pathways in vitro. Besides, the sFgl2-MSCs significantly enhanced the migration and phagocytosis ability of macrophages stimulated with interferon-γ (IFN-γ) and lipopolysaccharide (LPS). Further, the application potential of sFgl2-MSCs in AR treatment was demonstrated by heterotopic cardiac transplantation in mice. The tissue damage and macrophage infiltration were evaluated by H&E and immunohistochemistry staining, and the secretion of inflammatory cytokines was analyzed by ELISA. The results showed that sFgl2-MSCs injected intravenously were able to locate in the graft, promote the M2 polarization of macrophages in vivo, regulate the local and systemic immune response, significantly protect tissues from damaging, and finally prolonged the survival time of mice heart grafts.

CONCLUSION

sFgl2-MSCs ameliorate AR of heart transplantation by regulating macrophages, which provides a new idea for the development of anti-AR treatment methods after heart transplantation.

Dendritic cells with METTL3 gene knockdown exhibit immature properties and prolong allograft survival

Maturation of dendritic cells (DCs) initiates adaptive immune responses and thereby provokes allograft rejection. Here, this study aimed to explore the effect of Methyltransferase-like protein 3 (METTL3) silencing on DC function and the role of METTL3-silencing donor DCs in the immune response after mouse heart transplantation. Bone marrow-derived DCs from donor BALB/c mice were infected with lentiviruses expressing METTL3-specific short hairpin RNA (LV-METTL3 shRNA) to silence METTL3. Then METTL3-silencing DCs were treated with lipopolysaccharide (LPS) for another 48 h to induce DC maturation. Recipient C57BL/6 mice were injected with phosphate-buffered saline (PBS), immature DCs, and METTL3 shRNA-DCs prior to the cardiac transplantation involving the transfer of hearts from donor BALB/c mice to recipient C57BL/6 mice. In vitro we demonstrated that METTL3-silencing DCs had lower expression of MHCII, costimulatory molecules (CD80, CD86), and DC-related cytokines (IFN-γ, IL-12) as well as lower ability to activate T-cell proliferation, which were consistent with the characteristics of tolerogenic DCs. In vivo we found that METTL3-silencing donor DCs induced immune tolerance after mouse heart transplantation and prolonged the allograft survival, which might be associated with Th1/Th2 immune deviation. In summary, METTL3-silencing DCs exhibit immature properties and prolong allograft survival.

The Tumor Microenvironment: A Milieu Hindering and Obstructing Antitumor Immune Responses

The success of cancer immunotherapy relies on the knowledge of the tumor microenvironment and the immune evasion mechanisms in which the tumor, stroma, and infiltrating immune cells function in a complex network. The potential barriers that profoundly challenge the overall clinical outcome of promising therapies need to be fully identified and counteracted. Although cancer immunotherapy has increasingly been applied, we are far from understanding how to utilize different strategies in the best way and how to combine therapeutic options to optimize clinical benefit. This review intends to give a contemporary and detailed overview of the different roles of immune cells, exosomes, and molecules acting in the tumor microenvironment and how they relate to immune activation and escape. Further, current and novel immunotherapeutic options will be discussed.

Brief Report: No Evidence for an Association Between Statin Use and Lower Biomarkers of HIV Persistence or Immune Activation/Inflammation During Effective ART

BACKGROUND

Statins exert pleiotropic anti-inflammatory and immune-modulatory effects, which might translate into antiviral activity. We evaluated whether reported current statin exposure is associated with lower levels of markers of HIV persistence and immune activation/inflammation.

METHODS

We compared levels of markers of HIV viral persistence [cell-associated HIV RNA (CA-RNA), CA-DNA, and single copy assay plasma HIV RNA] and immune activation/inflammation (IL-6, IP-10, neopterin, sCD14, sCD163, and TNF-alpha) between statin users and nonusers among participants of ACTG A5321 who initiated antiretroviral therapy (ART) during chronic infection and maintained virologic suppression (HIV-1 RNA levels ≤50 copies/mL) for ≥3 years.

RESULTS

A total of 303 participants were analyzed. Median time on the current statin was 2.9 years (1.2-5.1). There were no differences between statin users and nonusers in levels of CA-DNA (median 650 vs. 540 copies/10 CD4 T cells; P = 0.58), CA-RNA (53 vs. 37 copies/10 CD4 T cells; P = 0.12), or single copy assay (0.4 vs. 0.4 copies/mL; P = 0.45). Similarly, there were no significant differences between statin users and nonusers in markers of inflammation/activation, except for IP-10 (137 vs. 118 pg/mL; P = 0.028). Findings were unchanged after adjustment for factors including pre-ART CD4 and HIV RNA, and years on ART.

CONCLUSIONS

In this cohort of persons on long-term suppressive ART, current statin use was not associated with lower levels of HIV persistence or immune activation/inflammation. These results do not support a major role for statins in reducing HIV persistence, although an early transient effect cannot be excluded. Prospective, randomized studies are needed to confirm these findings.

In Vitro Immunological Effects of CXCR3 Inhibitor AMG487 on Dendritic Cells

AMG 487 is the targeted blocker of chemokine receptor CXCR3 and improves inflammatory symptoms by blocking the inflammatory cycle. Here we investigated whether AMG 487 affects dendritic cell (DC) biology and function. The expression of co-stimulatory markers on DCs was reduced, indicating the semi-mature state of DC when AMG 487 was added throughout the in vitro differentiation period. Additionally, when added solely during the final lipopolysaccharide-induced activation step, AMG 487 inhibited DC activation, as demonstrated by a decreased expression of activation markers. AMG487 also promoted the expression of PD-L2 and impaired the ability to induce antigen-specific T cell responses. Our results demonstrated that AMG 487 significantly affects DC maturity in vitro and function leading to impaired T cell activation, inducing DCs to have characteristics similar to tolerogenic DCs. AMG 487 may directly play an immunomodulatory role during DC development and functional shaping.

Transcriptome profiling of tolerogenic dendritic cells conditioned with dual mTOR kinase inhibitor, AZD8055

Dendritic cells (DCs) can initiate and regulate adaptive immunity depending on their maturation status. Many pharmacological and genetic means have been used in the generation of immature/tolerogenic DCs. However, the key factors controlling DCs tolerogenicity remain obscure. In this work, we demonstrated that AZD8055, an ATP-competitive inhibitor of mammalian target of rapamycin (mTOR), could also lead to a tolerogenic DC phenotype from several lines of evidence, such as suppression of T cell proliferation, promoting the generation of Tregs, and inducing allogeneic T cell apoptosis. Further studies using RNA-seq method identified 430, 1172 and 1436 differentially expressed genes (DEGs) between AZD-DCs vs. Control-DCs, LPS-DCs vs. Control-DCs, and AZD-DCs vs. LPS-DCs, respectively. The 5 most differentially expressed transcripts identified by RNA-seq expression profiles were validated by quantitative RT-PCR assays. NF-κB, p38MAPK, the ribosome and PPAR signaling pathways may be involved in the induction of tolerogenic DCs by AZD8055. Functional annotation showed some genes like MGL2, Cadherin-1, 4-1BB, RhoB and Pdpn, were quite different between AZD-DCs and Control-DCs/LPS-DCs, which might be related to the tolerogenic properties of AZD-DCs. Our work provided the potential underlying molecular mechanisms involved in the generation of tolerogenic DCs. Further functional characterization of individual target gene in DC tolerogenicity will help to develop novel therapeutic modalities in circumstances like transplant tolerance induction and autoimmunity.

BCAP Regulates Dendritic Cell Maturation Through the Dual-Regulation of NF-κB and PI3K/AKT Signaling During Infection

The maturation of dendritic cells (DCs) is essential in adaptive immunity. B cell adapter for phosphoinositide 3-kinase (BCAP) has been shown a divergent activities in cell type dependent manner including B cells, NK cells, macrophages, and plasmacytoid DCs (pDCs), however, its role in conventional DCs (cDCs) remains unknown. Here, we report that BCAP negatively regulates Toll-like receptor-induced cDC maturation and inhibits cDCs from inducing antigen-specific T cell responses, thereby weakening the antibacterial adaptive immune responses of mice in a Listeria monocytogenes-infection model. Furthermore, we demonstrate that BCAP simultaneously modulates the activation of the NF-κB and PI3K/AKT signaling by dynamically interacting with, respectively, MyD88 and the p85α subunit of PI3K. Our study thus reveals non-redundant roles for BCAP in regulating cDC maturation and reveals a bilateral signal transduction mechanism.

Mechanism of indoleamine 2, 3-dioxygenase inhibiting cardiac allograft rejection in mice

Indoleamine 2, 3‐dioxygenase (IDO)‐mediated regulation of tryptophan metabolism plays an important role in immune tolerance in transplantation, but it has not been elucidated which mechanism specifically induces the occurrence of immune tolerance. Our study revealed that IDO exerts immunosuppressive effects through two pathways in mouse heart transplantation, ‘tryptophan depletion’ and ‘tryptophan metabolite accumulation’. The synergism between IDO⁺DC and TC (tryptophan catabolic products) has stronger inhibitory effects on T lymphocyte proliferation and mouse heart transplant rejection than the two intervention factors alone, and significantly prolong the survival time of donor‐derived transplanted skin. This work demonstrates that the combination of IDO⁺DC and TC can induce immune tolerance to a greater extent, and reduce the rejection of transplanted organs.

Lactobacillus pentosus Modulates Immune Response by Inducing IL-10 Producing Tr1 Cells

Several gut commensals have been shown to modulate host immune response. Recently, many food derived microbes have also been reported to affect the immune system. However, a mechanism to identify immunostimulatory and immunoregulatory microbes is needed. Here, we successfully established an in vitro screening system and identified an immunoregulatory bacterium, Lactobacillus pentosus KF340 (LP340), present in various fermented foods. LP340 induced a regulatory phenotype in mice Ag presenting cells which, in turn, induced IL-10 and IFN-γ producing Type 1 regulatory T cells (Tr1 cells) from naïve CD4+ T cells. Naïve CD4+ T cells co-cultured with LP340 treated dendritic cells highly expressed cytokine receptor IL-27R and were CD49b and lymphocyte-activation gene 3 double positive. Oral administration of LP340 in mice with atopic dermatitis reduced cellular infiltration in affected ear lobes and serum IgE levels, thus, ameliorating the disease symptoms. This suggests a systemic immunoregulatory effect of LP340. These findings demonstrate that LP340, a bacterium derived from food, prevents systemic inflammation through the induction of IL-10 producing Tr1 cells.

Tolerogenic dendritic cells in organ transplantation

Dendritic cells (DCs) are specialized cells of the innate immune system that are characterized by their ability to take up, process and present antigens (Ag) to effector T cells. They are derived from DC precursors produced in the bone marrow. Different DC subsets have been described according to lineage-specific transcription factors required for their development and function. Functionally, DCs are responsible for inducing Ag-specific immune responses that mediate organ transplant rejection. Consequently, to prevent anti-donor immune responses, therapeutic strategies have been directed toward the inhibition of DC activation. In addition however, an extensive body of preclinical research, using transplant models in rodents and nonhuman primates, has established a central role of DCs in the negative regulation of alloimmune responses. As a result, DCs have been employed as cell-based immunotherapy in early phase I/II clinical trials in organ transplantation. Together with in vivo targeting through use of myeloid cell-specific nanobiologics, DC manipulation represents a promising approach for the induction of transplantation tolerance. In this review, we summarize fundamental characteristics of DCs and their roles in promotion of central and peripheral tolerance. We also discuss their clinical application to promote improved long-term outcomes in organ transplantation.

Optimal Tolerogenic Dendritic Cells in Type 1 Diabetes (T1D) Therapy: What Can We Learn From Non-obese Diabetic (NOD) Mouse Models?

Tolerogenic dendritic cells (tolDCs) are explored as a promising standalone or combination therapy in type 1 diabetes (T1D). The therapeutic application of tolDCs, including in human trials, has been tested also in other autoimmune diseases, however, T1D displays some unique features. In addition, unlike in several disease-induced animal models of autoimmune diseases, the prevalent animal model for T1D, the NOD mouse, develops diabetes spontaneously. This review compares evidence of various tolDCs approaches obtained from animal (mainly NOD) models of T1D with a focus on parameters of this cell-based therapy such as protocols of tolDC preparation, antigen-specific vs. unspecific approaches, doses of tolDCs and/or autoantigens, application schemes, application routes, the migration of tolDCs as well as their preventive, early pre-onset intervention or curative effects. This review also discusses perspectives of tolDC therapy and areas of preclinical research that are in need of better clarification in animal models in a quest for effective and optimal tolDC therapies of T1D in humans.