Tolerogenic dendritic cells and their potential applications

Tailoring Biomaterials Ameliorate Inflammatory Bone Loss

Inflammatory diseases, such as rheumatoid arthritis, periodontitis, chronic obstructive pulmonary disease, and celiac disease, disrupt the delicate balance between bone resorption and formation, leading to inflammatory bone loss. Conventional approaches to tackle this issue encompass pharmaceutical interventions and surgical procedures. Nevertheless, pharmaceutical interventions exhibit limited efficacy, while surgical treatments impose trauma and significant financial burden upon patients. Biomaterials show outstanding spatiotemporal controllability, possess a remarkable specific surface area, and demonstrate exceptional reactivity. In the present era, the advancement of emerging biomaterials has bestowed upon more efficacious solutions for combatting the detrimental consequences of inflammatory bone loss. In this review, the advances of biomaterials for ameliorating inflammatory bone loss are listed. Additionally, the advantages and disadvantages of various biomaterials-mediated strategies are summarized. Finally, the challenges and perspectives of biomaterials are analyzed. This review aims to provide new possibilities for developing more advanced biomaterials toward inflammatory bone loss.

Calcitriol restrains microglial M1 polarization and alleviates dopaminergic degeneration in hemiparkinsonian mice by boosting regulatory T-cell expansion

OBJECTIVE

Vitamin D deficiency is a risk factor for Parkinson's disease (PD) and vitamin D supplementation robustly alleviates neurodegeneration in PD models. However, the mechanisms underlying this effect require further clarification. Current evidence suggests that harnessing regulatory T cells (Treg) may mitigate neuronal degeneration. In this study, we investigated the therapeutic effects of vitamin D receptor activation by calcitriol on PD, specifically focusing on its role in Treg.

METHODS

Hemiparkinsonian mice model was established through the injection of 6-OHDA into the striatum. Mice were pretreated with calcitriol before 6-OHDA injection. The motor performance, dopaminergic neuronal survival, contents of dopamine, and dopamine metabolites were evaluated. The pro-inflammatory cytokines levels, T-cell infiltration, mRNA expression of indicated microglial M1/M2 phenotypic markers, and microglial marker in the midbrain were detected. Populations of Treg in the splenic tissues were assessed using a flow cytometry assay. PC61 monoclonal antibody was applied to deplete Treg in vivo.

RESULTS

We show that calcitriol supplementation notably improved motor performance and reduced dopaminergic degeneration in the 6-OHDA-induced PD model. Mechanistically, calcitriol promoted anti-inflammatory/neuroprotective Treg and inhibited pro-inflammatory/neurodestructive effector T-cell generation in this model. This process significantly inhibited T-cell infiltration in the midbrain, restrained microglial activation, microglial M1 polarization, and decreased pro-inflammatory cytokines release. This more favorable inflammatory microenvironment rescued dopaminergic degeneration. To further verify that the anti-inflammatory effects of calcitriol are associated with Treg expansion, we applied an antibody-mediated Treg depletion assay. As predicted, the anti-inflammatory effects of calcitriol in the PD model were diminished following Treg depletion.

CONCLUSION

These findings suggest that calcitriol's anti-inflammatory and neuroprotective effects in PD are associated with its potential to boost Treg expansion.

Tolerogenic dendritic cells and TLR4/IRAK4/NF-κB signaling pathway in allergic rhinitis

Dendritic cells (DCs), central participants in the allergic immune response, can capture and present allergens leading to allergic inflammation in the immunopathogenesis of allergic rhinitis (AR). In addition to initiating antigen-specific immune responses, DCs induce tolerance and modulate immune homeostasis. As a special type of DCs, tolerogenic DCs (tolDCs) achieve immune tolerance mainly by suppressing effector T cell responses and inducing regulatory T cells (Tregs). TolDCs suppress allergic inflammation by modulating immune tolerance, thereby reducing symptoms of AR. Activation of the TLR4/IRAK4/NF-κB signaling pathway contributes to the release of inflammatory cytokines, and inhibitors of this signaling pathway induce the production of tolDCs to alleviate allergic inflammatory responses. This review focuses on the relationship between tolDCs and TLR4/IRAK4/NF-κB signaling pathway with AR.

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.

Vitamin D and estrogen steroid hormones and their immunogenetic roles in Infectious respiratory (TB and COVID-19) diseases

The role of steroid hormones against infectious diseases has been extensively studied. From immunomodulatory action to direct inhibition of microorganism growth, hormones D3 (VD3) and 17β-estradiol (E2), and the genetic pathways modulated by them, are key targets for a better understanding pathogenesis of infectious respiratory diseases (IRD) such as tuberculosis (TB) and the coronavirus disease-19 (COVID-19). Currently, the world faces two major public health problems, the outbreak of COVID-19, accounting for more than 6 million so far, and TB, more than 1 million deaths per year. Both, although resulting from different pathogens, the Mtb and the SARS-CoV-2, respectively, are considered serious and epidemic. TB and COVID-19 present similar infection rates between men and women, however the number of complications and deaths resulting from the two infections is higher in men when compared to women in childbearing age, which may indicate a role of the sex hormone E2 in the context of these diseases. E2 and VD3 act upon key gene pathways as important immunomodulatory players and supporting molecules in IRDs. This review summarizes the main roles of these hormones (VD3 and E2) in modulating immune and inflammatory responses and their relationship with TB and COVID-19.

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.

Heterogeneity of adherent and non‑adherent JAWS II dendritic cells

Dendritic cells (DCs) are crucial in the development of immune responses. DC JAWS II is a murine cell line frequently used in DC studies. These cells are grown in two cell fractions: Adherent and non-adherent. The present study aimed to compare these two fractions in both immature and lipopolysaccharide (LPS)-activated JAWS II cells. The present study analysed the condition, phenotype, antigen uptake capability, signalling properties and the influence on the activity of T cells using flow cytometry, mixed cell reaction and ELISA methods. Adherent immature JAWS II cells exhibited increased endocytosis and decreased activation of the Pi3K signalling pathway. After LPS activation, adherent JAWS II cells exhibited increased expression levels of CD80 and CD86 costimulatory molecules, increased endocytosis and an elevated ability to induce T cell proliferation, compared with non-adherent cells. These results demonstrated that the two fractions of JAWS II adherent and non-adherent cells exhibited different properties and this should be taken into account in the planning of research.

The Mechanism of Delayed Ischemic Preconditioning in Alleviating Acute Ischemia/Reperfusion Renal Injury through Treg Mediated by Immature CD11c+ Dendritic Cells

Introduction

Renal ischemia-reperfusion injury (IRI) is one of the major causes of acute kidney injury, and its mechanism is complex involving multiple factors, while delayed ischemic preconditioning (DIPC) has a protective effect on the above process. In our previous study, we found that DIPC can exert its protection on renal IRI by inhibiting the maturation of dendritic cells (DCs), but the mechanism has not been clarified. This study aimed to investigate the protective mechanism of DIPC on renal IRI in mice through Treg mediated by immature DCs (imDCs).

Methods

The IRI mice model, DIPC treatment, and conditional CD11c⁺ DCs (CD11c-DTR) knockout mice were used to perform our study. The maturation and differentiation of DCs and Treg cells in the kidney and spleen were analyzed by flow cytometry. HE staining was used to evaluate the pathology of the kidney tissue. The level of creatinine (Cr), oxidative stress factors (SOD, MDA), and inflammatory factors (TNF-α, IL-10, IL-4) were also measured. Then, imDCs were co-cultured with HK-2 cells, and apoptosis was analyzed with flow cytometry and PI-Hoechst 33,342 fluorescence staining to assess the apoptosis rate of HK-2 cells under hypoxic-reoxygenated (H/R) conditions.

Results

DIPC could decrease renal Cr levels, alleviate pathological renal damage, and reduce oxidative stress and inflammation caused by IRI. Moreover, DIPC could decrease the number of mature DCs (mDCs) and increase Treg lymphocyte infiltration in the kidney tissue, while the reduction of DCs reversed this process. In addition, our in vitro experiment found that in the H/R model, the apoptosis of HK-2 cells decreased which were co-cultured with imDCs.

Conclusion

DIPC can regulate the differentiation of DCs into imDCs, thus affecting the differentiation level and distribution of Treg cells to exert its protective effect on renal IRI.

Vitamin D-Dimer: A Possible Biomolecule Modulator in Cytotoxic and Phagocytosis Processes?

Background: Vitamin D3 complexed to deglycosylated vitamin D binding protein (VitD-dgVDBP) is a water-soluble vitamin D dimeric compound (VitD-dgVDBP). It is not clear how VitD-dgVDBP affects circulating monocytes, macrophages, other immune cell systems, including phagocytosis and apoptosis, and the generation of reactive oxygen species (ROS) compared to dgVDBP. Methods: Flow cytometry was used to measure superoxide anion radical (O2*−) levels and macrophage activity in the presence of VitD-dgVDBP or dgVDBP. VitD-dgVDBP was incubated with normal human lymphocytes (nPBMCs), and several clusters of determination (CDs) were estimated. dgVDBP and VitD-dgVDBP apoptosis was estimated on malignant prostatic cells. Results: The macrophage activity was 2.8-fold higher using VitD-dgVDBP (19.8·106 counts) compared to dgVDBP (7.0·106 counts), but O2*− production was 1.8-fold lower in favor of VitD-dgVDBP (355·103 counts) compared to dgVDBP (630·106 counts). The calculated ratio of the radical/macrophage activity was 5-fold lower compared to that of dgVDBP. Only VitD-dgVDBP activated caspase-3 (8%), caspase-9 (13%), and cytochrome-C (11%) on prostatic cancer cells. PE-Cy7-labeled VitD-dgVDBP was found to bind to cytotoxic suppressor cells, monocytes/macrophages, dendritic and natural killer cells (CD8+), and helper cells (CD4+). After 12 h of co-incubation of nPBMCs with VitD-dgVDBP, significant activation and expression were measured for CD16++/CD16 (0.6 ± 0.1% vs. 0.4 ± 0.1%, p < 0.05), CD45k+ (96.0 ± 6.0% vs. 84.7 ± 9.5%, p < 0.05), CD85k+ (24.3 ± 13.2% vs. 3.8 ± 3.2%, p < 0.05), and CD85k+/CD123+ (46.8 ± 8.1% vs. 3.5 ± 3.7%, p < 0.001) compared to the control experiment. No significant difference was found using CD3+, CD4+, CD8+, CD4/CD8, CD4/CD8, CD16+, CD16++, CD14+, or CD123+. A significant decline in CD14+/CD16+ was obtained in the presence of VitD-dgVDBP (0.7 ± 0.2% vs. 3.1 ± 1.7%; p < 0.01). Conclusion: The newly developed water-soluble VitD3 form VitD-dgVDBP affected cytotoxic suppressor cells by activating the low radical-dependent CD16 pathway and seemed to induce apoptosis in malignant prostatic cells.

Recent progress in therapeutic strategies and biomimetic nanomedicines for rheumatoid arthritis treatment

INTRODUCTION

Rheumatoid arthritis (RA) is an autoimmune systemic disease in which inflammatory and immune cells accumulate in inflamed joints. Researchers aimed at the characteristics of RA to achieve the effect of treating RA through different therapeutic strategies, and have used various endogenous materials to design drug-loaded nanoparticles that can target RA by binding to cell adhesion molecules or chemokines. In some cases, the nanoparticles can respond to the characteristics of the microenvironment.

AREAS COVERED

This article reviews the recent advances in the treatment of RA from two aspects of therapeutic strategies and delivery strategies. Therapeutic strategies mainly include neutralization of inflammatory factors, promotion of inflammatory cell apoptosis, ROS scavenger, immunosuppression, and bone tissue repair. The drug delivery strategy is mainly described from two aspects: chemically functionalized biomimetic nanoparticles and endogenous nanoparticles.

EXPERT OPINION

Biomimetic NPs may be effective drug carriers for targeted RA treatment. NPs can reduce the clearance of mononuclear phagocytes, prolong the blood circulation time, and improve the targeting ability. With the deepening of research, more and more biomimetic NPs have entered the clinical trial stage. However, safe and scalable preparation methods are needed to improve their clinical applicability.

Combined Therapy of Vitamin D3-Tolerogenic Dendritic Cells and Interferon-β in a Preclinical Model of Multiple Sclerosis

Autologous antigen-specific therapies based on tolerogenic dendritic cells (tolDC) offer the possibility to treat autoimmune diseases by restoring homeostasis and targeting specifically autoreactive responses. Here, we explore the hypothesis that systemic inflammation occurring in autoimmune diseases, such as multiple sclerosis (MS), can generate a disease-specific environment able to alter the functionality of tolDC. In this context in fact, a combined therapy of tolDC with an immunomodulatory treatment could potentiate the beneficial effect of this antigen-specific cell therapy. For this purpose, we analyzed the efficacy of a combined therapy based on the use of vitamin D3 (VitD3)-tolDC plus interferon beta (IFN-beta) in MS. VitD3-tolDC were generated from healthy donors and MS patients and co-cultured with allogeneic peripheral blood mononuclear cells, in the presence or absence of IFN-beta. In vitro, VitD3-tolDC treatment reduced the percentage of activated T cells and allogeneic proliferation, whereas VitD3-tolDC+IFN-beta treatment enhanced the suppressive ability of VitD3-tolDC and, additionally, induced a shift towards a Th2 profile. To determine the clinical benefit of the combined therapy, C57BL/6-experimental autoimmune encephalomyelitis (EAE)-induced mice were treated with antigen-specific VitD3-tolDC and/or IFN-beta. Treatment of EAE mice with combined therapy ameliorated the disease course compared to each monotherapy. These results suggest that a combined therapy based on antigen-specific VitD3-tolDC and IFN-beta may represent a promising strategy for MS patients.

Clinical translation of immunomodulatory therapeutics

Immunomodulatory therapeutics represent a unique class of drug products that have tremendous potential to rebalance malfunctioning immune systems and are quickly becoming one of the fastest-growing areas in the pharmaceutical industry. For these drugs to become mainstream medicines, they must provide greater therapeutic benefit than the currently used treatments without causing severe toxicities. Immunomodulators, cell-based therapies, antibodies, and viral therapies have all achieved varying amounts of success in the treatment of cancers and/or autoimmune diseases. However, many challenges related to precision dosing, off-target effects, and manufacturing hurdles will need to be addressed before we see widespread adoption of these therapies in the clinic. This review provides a perspective on the progress of immunostimulatory and immunosuppressive therapies to date and discusses the opportunities and challenges for clinical translation of the next generation of immunomodulatory therapeutics.

Revisiting the Mechanisms of Immune Evasion Employed by Human Parasites

For the establishment of a successful infection, i.e., long-term parasitism and a complete life cycle, parasites use various diverse mechanisms and factors, which they may be inherently bestowed with, or may acquire from the natural vector biting the host at the infection prelude, or may take over from the infecting host, to outmaneuver, evade, overcome, and/or suppress the host immunity, both innately and adaptively. This narrative review summarizes the up-to-date strategies exploited by a number of representative human parasites (protozoa and helminths) to counteract the target host immune defense. The revisited information should be useful for designing diagnostics and therapeutics as well as vaccines against the respective parasitic infections.

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.

Lung CD103+ Dendritic cells of mice infected with Paracoccidioides brasiliensis contribute to Treg differentiation

The DC subsets that express αE integrin (CD103) have been described to exert antagonistic functions, driving T cells towards either an inflammatory (Th1/Th17) or immunosuppressive phenotype (regulatory T cells - Treg). These functions depend on the tissue they reside and microenvironment factors or stimuli that this Antigen-presenting cell (APC) subpopulation receive. In this regard, immunoregulatory phenotype has been described in small subsets of CD103⁺ DCs from lung and intestinal mucosa. The function of this APC subpopulation in pulmonary Paracoccidioides brasiliensis infection is poorly described. Here, we showed that lung CD103⁺ DCs contribute to Treg differentiation in a pulmonary P. brasiliensis infection model, which was attributed to downregulation of costimulatory molecules analyzed in these APC subtypes 21 days post-infection. Overall, this data suggests that P. brasiliensis infection caused an immunosuppression that has also been observed in patients with the most severe form of Paracoccidioidomycosis (PCM) - a sickness caused by this fungus genus. Furthermore, these results open new perspectives for knowledge of the mechanisms that underlie the higher percentage of Treg cells found in peripheral blood of PCM patients.

Steroid-Peptide Immunoconjugates for Attenuating T Cell Responses in an Experimental Autoimmune Encephalomyelitis Murine Model of Multiple Sclerosis

Diseases of immunity, including autoimmune diseases such as multiple sclerosis, transplantation graft rejection, allergy, and asthma, are prevalent and increasing in prevalence. They contribute to significant morbidity and mortality; however, few if any curative therapies exist, and those that are available lack either potency or specificity. Dendritic cells (DCs) are sentinels of the immune system that connect the innate and adaptive immune system and are critical regulators of both immunity and tolerance. We posited that the tolerogenic potential of DC could be harnessed to develop more specific and potent therapies for diseases of immunity by delivering autoantigen to a sufficient number of tolerogenic DCs in situ that could then inhibit pathogenic effector T cell responses. Specifically, we hypothesized that the steroid dexamethasone covalently coupled to a peptide antigen could be processed by DCs, induce tolerogenic DCs, and attenuate antigen-specific pathogenic T cell responses. To test this hypothesis, we synthesized a series of dexamethasone-peptide immunoconjugates by standard solid-phase peptide synthesis. The antigenic portion of the immunoconjugate could be presented by DCs, and the immunoconjugate induced a tolerogenic phenotype in DCs that then inhibited antigen-specific T cell proliferation in vitro. When the immunoconjugate was administered prophylactically in the murine experimental autoimmune encephalomyelitis model of multiple sclerosis, disease was attenuated compared to dexamethasone and peptide delivered as uncoupled components. Together, this work demonstrates the utility of immunoconjugates for inducing tolerance while establishing the foundation for future studies exploring methods to enrich and target DCs for tolerogenic therapies.

Depletion of miR-21 in dendritic cells aggravates renal ischemia-reperfusion injury

Dendritic cells (DCs) play an important role in the pathophysiology of renal ischemia-reperfusion injury (IRI). The mechanisms underlying DCs phenotypic modulation and their function are not fully understood. In this study, we examined the effect of miR-21 on the phenotypic modulation of DCs in vitro and in vivo, and further investigated the impact of miR-21-overexpression DC or miR-21-deficient DC on renal IRI. We found that treatment with hypoxia/reoxygenation (H/R) suppressed miR-21 expression in bone marrow-derived dendritic cells (BMDCs), and significantly increased the percentage of mature DCs (CD11c⁺ /MHC-II⁺ /CD80⁺ ). Using a selection of microRNA mimics, we successfully induced the upregulation of miR-21 in BMDCs, which induced immature DC phenotype and an anti-inflammatory DC response. However, deletion of miR-21 in BMDCs promoted maturation of DCs under H/R. Adoptive transfer of miR-21-overexpression BMDCs could alleviate renal IR-induced pro-inflammatory cytokines production and acute kidney injury (AKI). Mice with miR-21 deficiency in DCs subjected to renal IR showed more severe renal dysfunction and inflammatory response compared with wild-type mice. In addition, chemokine C receptor 7 (CCR7), a surface marker of mature DC, was a target gene of miR-21, and silencing of CCR7 in BMDCs led to reduced mature DCs under H/R. In conclusion, our findings highlight miR-21 as a key regulator of DCs subset phenotype and a potential therapeutic target in renal IRI.

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.

Vitamin D and microbiota: Two sides of the same coin in the immunomodulatory aspects

The gut microbiota is crucial for host immune response, vitamin synthesis, short chain fatty acids (SCFAs) production, intestinal permeability, nutrient digestion energy metabolism and protection from pathogens. Therefore, gut microbiota guarantees the host's predisposition to gastrointestinal diseases. Intestinal microbiota may be damaged by environmental components with negative health conditions. Dysbiosis consisting in alteration in the gut microbiota has been involved in several disorders including inflammation, allergic reactions, autoimmune diseases, heart diseases, obesity, and metabolic syndrome and even in the state of malignant carcinogenesis existing in humans. Several epidemiological studies have shown that inadequate solar exposure results in vitamin D insufficiency/deficiency which has a strong impact on different immune responses and the occurrence of a wide range of pathological conditions. Additionally, new evidence indicates that the vitamin D pathway plays a key role in gut homeostasis. Due to the strong connection between vitamin D and microbiota, herein we focus on the new findings about intestinal bacteria-immune crosstalk and the impact of vitamin D in gut microbiota regulation, in order to offer new clarifications on their interaction. Understanding the mechanism by which vitamin D can affect the gut microbiota composition and its dynamic activities, as well as the innate and adaptive state of the immune system, is not only a fundamental research but also an opportunity to improve health status.

Human Memory Th17 Cell Populations Change Into Anti-inflammatory Cells With Regulatory Capacity Upon Exposure to Active Vitamin D

Autoimmune diseases are characterized by an aberrantly activated immune system, resulting in tissue damage and functional disability in patients. An important therapeutic goal is to restore the deregulated immunological balance between pro- and anti-inflammatory T cells. This imbalance is illustrated by elevated levels and activity of memory Th17 cell populations, such as Th17, Th1/Th17, and Th17.1 cells, in various autoimmune diseases. These cells are characterized by the chemokine receptor CCR6, RORC expression and production of IL-17A, IFNγ, and TNFα. Using rheumatoid arthritis (RA) as a model of autoimmune disease, we here demonstrate that pro-inflammatory memory CCR6+ Th cells can switch into anti-inflammatory cells with regulatory capacity using the active vitamin D metabolite 1,25(OH)₂D₃. Memory CCR6+ Th cells, excluding Tregs, were sorted from healthy controls or treatment-naïve patients with early rheumatoid arthritis (RA) and cultured with or without 1,25(OH)₂D₃. Treatment with 1,25(OH)₂D₃ inhibited pro-inflammatory cytokines such as IL-17A, IL-17F, IL-22 and IFNγ in memory CCR6+ Th cells from both healthy controls and RA patients. This was accompanied by induction of anti-inflammatory factors, including IL-10 and CTLA4. Interestingly, these formerly pathogenic cells suppressed proliferation of autologous CD3+ T cells similar to classical Tregs. Importantly, the modulated memory cells still migrated toward inflammatory milieus in vitro, modeled by RA synovial fluid, and retained their suppressive capacity in this environment. These data show the potential to reset the pathogenic profile of human memory Th cells into non-pathogenic cells with regulatory capacity.

Beneficial effect of atorvastatin-modified dendritic cells pulsed with myelin oligodendrocyte glycoprotein autoantigen on experimental autoimmune encephalomyelitis

It is well known that dendritic cells play a key role in producing antigen-specific responses. Inversely, tolerogenic dendritic cells (TolDCs), a specialized subset, induce immune tolerance and negatively regulate autoimmune responses. Statins, the inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase in the mevalonate pathway for cholesterol biosynthesis, might be a promising inductive agent for inducing TolDCs. This study aimed to investigate the effectiveness of TolDCs induced by atorvastatin pulsed with myelin oligodendrocyte glycoprotein 35-55 peptide (MOG35-55) in experimental autoimmune encephalomyelitis mice established by MOG35-55 immunization and to investigate the potential effects on Th17/Treg balance in the murine model of multiple sclerosis. Our results showed that atorvastatin-treated dendritic cells maintained a steady semimature phenotype with a low level of costimulatory molecules and proinflammatory cytokines. Upon an intraperitoneal injection into experimental autoimmune encephalomyelitis mice, TolDCs pulsed with MOG (TolDCs-MOG) significantly alleviated disease activity and regulated Th17/Treg balance with a marked decrease in Th17 cells and an obvious increase in regulatory T cells. Taken together, TolDCs-MOG modified by atorvastatin showed a characteristic tolerogenic phenotype and the antigen-specific TolDCs might represent a new promising strategy for the future treatments for multiple sclerosis.

Jagged1-expressing adenovirus-infected dendritic cells induce expansion of Foxp3+ regulatory T cells and alleviate T helper type 2-mediated allergic asthma in mice

Dendritic cells (DCs) are professional antigen-presenting cells that play a key role in directing T-cell responses. Regulatory T (Treg) cells possess an immunosuppressive ability to inhibit effector T-cell responses, and Notch ligand Jagged1 (Jag1) is implicated in Treg cell differentiation. In this study, we evaluated whether bone marrow-derived DCs genetically engineered to express Jag1 (Jag1-DCs) would affect the maturation and function of DCs in vitro and further investigated the immunoregulatory ability of Jag1-DCs to manipulate T helper type 2 (Th2) -mediated allergic asthma in mice. We produced Jag1-DCs by adenoviral transduction. Overexpression of Jag1 by ovalbumin (OVA) -stimulated Jag1-DCs exhibited increased expression of programmed cell death ligand 1 (PD-L1) and OX40L molecules. Subsequently, co-culture of these OVA-pulsed Jag1-DCs with allogeneic or syngeneic CD4⁺ T cells promoted the generation of Foxp3⁺ Treg cells, and blocking PD-L1 using specific antibodies partially reduced Treg cell expansion. Furthermore, adoptive transfer of OVA-pulsed Jag1-DCs to mice with OVA-induced asthma reduced allergen-specific immunoglobulin E production, airway hyperresponsiveness, airway inflammation, and secretion of Th2-type cytokines (interleukin-4, interleukin-5, and interleukin-13). Notably, an increased number of Foxp3⁺ Treg cells associated with enhanced levels of transforming growth factor-β production was observed in Jag1-DC-treated mice. These data indicate that transgenic expression of Jag1 by DCs promotes induction of Foxp3⁺ Treg cells, which ameliorated Th2-mediated allergic asthma in mice. Our study supports an attractive strategy to artificially generate immunoregulatory DCs and provides a novel approach for manipulating Th2 cell-driven deleterious immune diseases.

Vitamin D: Nutrient, Hormone, and Immunomodulator

The classical functions of vitamin D are to regulate calcium-phosphorus homeostasis and control bone metabolism. However, vitamin D deficiency has been reported in several chronic conditions associated with increased inflammation and deregulation of the immune system, such as diabetes, asthma, and rheumatoid arthritis. These observations, together with experimental studies, suggest a critical role for vitamin D in the modulation of immune function. This leads to the hypothesis of a disease-specific alteration of vitamin D metabolism and reinforces the role of vitamin D in maintaining a healthy immune system. Two key observations validate this important non-classical action of vitamin D: first, vitamin D receptor (VDR) is expressed by the majority of immune cells, including B and T lymphocytes, monocytes, macrophages, and dendritic cells; second, there is an active vitamin D metabolism by immune cells that is able to locally convert 25(OH)D₃ into 1,25(OH)₂D₃, its active form. Vitamin D and VDR signaling together have a suppressive role on autoimmunity and an anti-inflammatory effect, promoting dendritic cell and regulatory T-cell differentiation and reducing T helper Th 17 cell response and inflammatory cytokines secretion. This review summarizes experimental data and clinical observations on the potential immunomodulating properties of vitamin D.

Identification of a Novel OX40L+ Dendritic Cell Subset That Selectively Expands Regulatory T cells

We have previously shown GM-CSF derived bone-marrow dendritic cells (G-BMDCs) can induce the selective expansion of Tregs through the surface-bound molecule OX40L; however, the physiological role of this ex vivo derived DC subset remained to be elucidated. We determined GM-CSF administration to mice induced the generation of in vivo derived OX40L⁺ DCs, phenotypically similar to ex vivo OX40L⁺G-BMDCs, in the spleen, brachial lymph nodes and liver. The generation of OX40L⁺ DCs correlated with increased percentages of functionally suppressive Tregs in the spleen, brachial lymph nodes, and liver of GM-CSF treated mice. DCs from GM-CSF treated mice expanded Tregs in CD4⁺ T-cell co-cultures in an OX40L dependent manner, suggesting OX40L⁺ DCs may play a role in peripheral Treg homeostasis. Furthermore, comparing the transcriptome data of OX40L⁺ DCs to that of all immune cell types revealed OX40L⁺ DCs to be distinct from steady-state immune cells and, microarray analysis of OX40L⁺G-BMDCs and OX40L⁻G-BMDCs revealed higher expression of molecules that are associated with tolerogenic phenotype and could play important roles in the function of OX40L⁺ DCs. These findings suggest that OX40L⁺ DCs may represent a unique DC subset induced under inflammatory conditions that may play an essential role in maintaining Treg homeostasis.

Tolerogenic Dendritic Cells as a Promising Antigen-Specific Therapy in the Treatment of Multiple Sclerosis and Neuromyelitis Optica From Preclinical to Clinical Trials

The identification of activated T-lymphocytes restricted to myelin-derived immunogenic peptides in multiple sclerosis (MS) and aquaporin-4 water channel in neuromyelitis optica (NMO) in the blood of patients opened the possibility for developing highly selective and disease-specific therapeutic approaches. Antigen presenting cells and in particular dendritic cells (DCs) represent a strategy to inhibit pro-inflammatory T helper cells. DCs are located in peripheral and lymphoid tissues and are essential for homeostasis of T cell-dependent immune responses. The expression of a particular set of receptors involved in pathogen recognition confers to DCs the property to initiate immune responses. However, in the absence of danger signals different DC subsets have been revealed to induce active tolerance by inducing regulatory T cells, inhibiting pro-inflammatory T helper cells responses or both. Interestingly, several protocols to generate clinical-grade tolerogenic DC (Tol-DC) in vitro have been described, offering the possibility to restore the homeostasis to central nervous system-related antigens. In this review, we discuss about different DC subsets and their role in tolerance induction, the different protocols to generate Tol-DCs and preclinical studies in animal models as well as describe recent characterization of Tol-DCs for clinical application in autoimmune diseases and in particular in MS and NMO patients. In addition, we discuss the clinical trials ongoing based on Tol-DCs to treat different autoimmune diseases.

Latent, Immunosuppressive Nature of Poly(lactic-co-glycolic acid) Microparticles

Use of biomaterials to spatiotemporally control the activation of immune cells is at the forefront of biomedical engineering research. As more biomaterial strategies are employed for immunomodulation, understanding the immunogenicity of biodegradable materials and their byproducts is paramount in tailoring systems for immune activation or suppression. Poly(D,L-lactic-co-glycolic acid) (PLGA), one of the most commonly studied polymers in tissue engineering and drug delivery, has been previously described on one hand as an immune adjuvant, and on the other as a nonactivating material. In this study, the effect of PLGA microparticles (MPs) on the maturation status of murine bone marrow-derived dendritic cells (DCs), the primary initiators of adaptive immunity, was investigated to decipher the immunomodulatory properties of this biomaterial. Treatment of bone marrow-derived DCs from C57BL/6 mice with PLGA MPs led to a time dependent decrease in the maturation level of these cells, as quantified by decreased expression of the positive stimulatory molecules MHCII, CD80, and CD86 as well as the ability to resist maturation following challenge with lipopolysaccharide (LPS). Moreover, this immunosuppression was dependent on the molecular weight of the PLGA used to fabricate the MPs, as higher molecular weight polymers required longer incubation to produce comparable dampening of maturation molecules. These phenomena were correlated to an increase in lactic acid both intracellularly and extracellularly during DC/PLGA MP coculture, which is postulated to be the primary agent behind the observed immune inhibition. This hypothesis is supported by our results demonstrating that resistance to LPS stimulation may be due to the ability of PLGA MP-derived lactic acid to inhibit the phosphorylation of TAK1 and therefore prevent NF-κB activation. This work is significant as it begins to elucidate how PLGA, a prominent biomaterial with broad applications ranging from tissue engineering to pharmaceutics, could modulate the local immune environment and offers insight on engineering PLGA to exploit its evolving immunogenicity.

Down-regulation of TYK2, CBLB and LMP7 genes expression in relapsing-remitting multiple sclerosis patients treated with interferon-beta

This study aimed to examine the expression of TYK2, CBLB and LMP7 genes at both mRNA and protein levels in relapsing-remitting MS (RRMS) patients in compare with healthy controls. Seventy-eight RRMS patients treated with IFNβ-1a and 79 age- and ethnic-matched healthy subjects were studied. The mRNA expression levels of TYK2, CBLB and LMP7 in PBMCs were quantified by real-time PCR and plasma concentrations of three molecules were measured by ELISA. Results were compared between patients and controls, IFNβ-responders and non-responders. Forty-nine of 78 patients were classified as IFNβ-responders and 29 cases were non-responders. Significantly down-regulated expression of TYK2, CBLB and LMP7 genes was found in the patients group versus controls (P<0.001). Decreased plasma levels of three molecules were observed in patients compared to controls (P<0.001). IFNβ-responders had significantly higher expressions for CBLB (P=0.001) and LMP7 (P=0.02) than non-responders. Also, we observed increased expressions of LMP7 (P=0.39) and CBLB (P=0.02) genes in patients under 30y and increased expression of TYK2 in patients >40years (P=0.002). Our results suggest that expression analysis of TYK2, CBLB and LMP7 genes could be useful for evaluation of T cells immunity and clinical response to IFNβ-therapy in RRMS patients.

Identification of 14-dehydroergosterol as a novel anti-inflammatory compound inducing tolerogenic dendritic cells

Tolerogenic dendritic cells (DCs) have the ability to induce regulatory T cells and play an important role in preventing chronic inflammatory and autoimmune diseases. We have identified a novel compound, 14-dehydroergosterol, from Koji, a Japanese traditional food material fermented with fungi. 14-dehydroergosterol is an ergosterol analogue with a conjugated double bond, but the activity of 14-dehydroergosterol is much higher than that of ergosterol. 14-dehydroergosterol induces the conversion of murine bone marrow (BM)-derived DCs and differentiated DCs into tolerogenic DCs, in which the production of IL-12 is suppressed and that of IL-10 is increased. In a co-culture experiment, DCs treated with 14-dehydroergosterol induced the conversion of naïve CD4-positive T cells into regulatory T cells. In a murine model of multiple sclerosis, experimental autoimmune encephalopathy, 14-dehydroergosterol suppressed the clinical score and inflammatory responses of myeloid DCs and T cells to myelin oligodendrocyte glycoprotein. 14-dehydroergosterol-treated human DCs induced from PBMCs also showed a tolerogenic phenotype. This is the first report to identify a novel compound, 14-dehydroergosterol, that induces DCs to convert to a tolerogenic type. 14-dehydroergosterol is contained in various fermented foods based on Koji, so 14-dehydroergosterol might be a helpful aid to prevent chronic inflammatory and autoimmune diseases.

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.

Vitamin D in Autoimmunity: Molecular Mechanisms and Therapeutic Potential

Over the last three decades, it has become clear that the role of vitamin D goes beyond the regulation of calcium homeostasis and bone health. An important extraskeletal effect of vitamin D is the modulation of the immune system. In the context of autoimmune diseases, this is illustrated by correlations of vitamin D status and genetic polymorphisms in the vitamin D receptor with the incidence and severity of the disease. These correlations warrant investigation into the potential use of vitamin D in the treatment of patients with autoimmune diseases. In recent years, several clinical trials have been performed to investigate the therapeutic value of vitamin D in multiple sclerosis, rheumatoid arthritis, Crohn’s disease, type I diabetes, and systemic lupus erythematosus. Additionally, a second angle of investigation has focused on unraveling the molecular pathways used by vitamin D in order to find new potential therapeutic targets. This review will not only provide an overview of the clinical trials that have been performed but also discuss the current knowledge about the molecular mechanisms underlying the immunomodulatory effects of vitamin D and how these advances can be used in the treatment of autoimmune diseases.

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.

The origin of DCs and capacity for immunologic tolerance in central and peripheral tissues

Dendritic cells (DCs) are specialized immune sentinels that play key role in maintaining immune homeostasis by efficiently regulating the delicate balance between protective immunity and tolerance to self. Although DCs respond to maturation signals present in the surrounding milieu, multiple layers of suppression also co-exist that reduce the infringement of tolerance against self-antigens. These tolerance inducing properties of DCs are governed by their origin and a range of other factors including distribution, cytokines, growth factors, and transcriptional programing, that collectively impart suppressive functions to these cells. DCs directing tolerance secrete anti-inflammatory cytokines and induce naïve T cells or B cells to differentiate into regulatory T cells (Tregs) or B cells. In this review, we provide a detailed outlook on the molecular mechanisms that induce functional specialization to govern central or peripheral tolerance. The tolerance-inducing nature of DCs can be exploited to overcome autoimmunity and rejection in graft transplantation.

Nanoencapsulated budesonide in self-stratified polyurethane-polyurea nanoparticles is highly effective in inducing human tolerogenic dendritic cells

The design of innovative strategies to selectively target cells, such antigen-presenting cells and dendritic cells, in vivo to induce immune tolerance is gaining interest and relevance for the treatment of immune-mediated diseases. A novel loaded-nanosystem strategy to generate tolerogenic dendritic cells (tol-DCs) was evaluated. Hence budesonide (BDS) was encapsulated in multiwalled polyurethane-polyurea nanoparticles (PUUa NPs-BDS) based on self-stratified polymers by hydrophobic interactions at the oil-water interface. DCs treated with encapsulated BDS presented a prominent downregulation of costimulatory molecules (CD80, CD83 and MHCII) and upregulation of inhibitory receptors. Moreover, DCs treated with these PUUa NPs-BDS also secreted large amounts of IL-10, a crucial anti-inflammatory cytokine to induce tolerance, and inhibited T lymphocyte activation in a specific manner compared to those cells generated with free BDS. These results demonstrate that PUUa NPs-BDS are a highly specific and efficient system through which to induce DCs with a tolerogenic profile. Given the capacity of PUUa NPs-BDS, this delivery system has a clear advantage for translation to in vivo studies.

Evaluation of Immunomodulatory Effects of Mesenchymal Stem Cells Soluble Factors on miR-155 and miR-23b Expression in Mice Dendritic Cells

Mesenchymal stem cells (MSCs) can modulate dendritic cells (DCs) activation and induce tolerogenic characteristics in DCs. All mechanisms involved in MSCs-induced tolerogenic DCs are not fully understood. MicroRNAs (miRs) play important role in maturation and function of DCs. In this study, we investigated the effects of MSCs culture supernatant (C.S.) on expression of miR-155 and miR-23b in mice DCs. BALB/c mice spleens were used for DCs isolation. MSCs were isolated from the mice bone marrow and cultured in DMEM media. When MSCs expanded to sixth passage, C.S. was collected after 12, 24 and 48 h. Quantitative polymerase chain reaction (QPCR) was used to determine the expression of miR-155 and miR-23b in DCs treated with C.S. after 6 and 12 h. Secretion of IL-23 and TGF- β were detected in DCs treated with C.S. by ELISA after 24 h. miR-23b expression was significantly increased in DCs treated with 12 h C.S. for 12 h compared to negative controls. miR-155 expression did not change in DCs treated with C.S. after 6 and 12 h. miR-23b expression was significantly increased in DCs treated with 12 h C.S. for 12 h, compared to those treated with C.S. for 6 h. Similarly, miR-23b expression was increased in DCs treated with 24 h C.S. for 12 h when compared to those treated for 6 h. Production of TGF-β and IL-23 were not influenced by C.S. In conclusion, miR-23b is considered to be one of the mechanisms involved in tolerogenic DCs induction by C.S. in a time-dependent manner.

Correlation between small intestinal bacterial overgrowth and dendritic cell phenotype and function in cirrhotic patients with hepatitis B

AIM: To investigate the relationship between dendritic cells (DCs) and small intestinal bacterial overgrowth (SIBO) in cirrhotic patients with hepatitis B.

METHODS: Flow cytometry was used to analyze the counts of peripheral blood DCs in 47 cirrhotic patients with HBV infection and 15 healthy volunteers. SIBO was determined by lactulose hydrogen breath test (LHBT).

RESULTS: Of the 47 cirrhotic patients, 22 (46.8%) had SIBO, which was significantly higher than that in healthy controls (6.7%, P = 0.005). The prevalence of SIBO increased with the Child-Pugh classification of cirrhosis (A: 18.2%, B: 43.8% and C: 65%). The prevalence of SIBO in patients with decompensated cirrhosis was significantly higher than that in patients with compensated cirrhosis (55.6% vs 18.2%, P = 0.030). The expression of CD80, CD83, and CD1a on the surface of DCs in cirrhotic patients was significantly lower than that in healthy controls (P < 0.05). The expression rates of CD80, CD83, CD1a and HLA-DR on the surface of DCs in SIBO positive cirrhotic patients were lower than those in SIBO negative cirrhotic patients (17.22% ± 2.08% vs 22.13% ± 2.34%, 24.65% ± 1.47% vs 34.52% ± 2.84%, 14.05% ± 1.33% vs 17.40% ± 3.22%, 81.47% ± 7.56% vs 70.15% ± 6.32%, P < 0.05).

CONCLUSION: The functional abnormality of DCs in cirrhotic patients with hepatitis B is associated with the presence of SIBO.

Decidual soluble factors, through modulation of dendritic cells functions, determine the immune response patterns at the feto-maternal interface

Dendritic cells (DCs) can acquire immunogenic or tolerogenic properties depending on intrinsic and tissue environmental factors. We aimed to determine the immunomodulatory effects of decidual soluble factors from abortion- and non-abortion-prone mice on DC functions. The decidual cell supernatants (DS) were obtained from abortion-prone and non-abortion-prone mice. Splenic DCs were treated with DS and conalbumin (as an antigen) and injected into the palms of the mice. After five days, regional lymph node cells were collected and cultured in the presence and absence of conalbumin. The proliferation of lymphocyte cells, the frequency of regulatory T cells (Tregs), and the production of IL-4 and IFN-γ were measured by [(3)H]thymidine incorporation, flow cytometry, and ELISA respectively. Our results indicated that DS from both abortion- and non-abortion-prone mice decreased the ability of DCs to induce lymphocyte proliferation and IFN-γ production, while enhanced their capacity to induce Tregs compared with non-treated DCs. Another important finding was that the immunosuppressive effects of DS from abortion-prone mice on DCs for inducing proliferative responses, developing Tregs, and producing IFN-γ by primed lymphocytes was less than DS from non-abortion-prone mice. We also found that only DS from non-abortion-prone mice could enhance the capacity of DCs to induce IL-4 production by primed lymphocytes. It can be concluded that decidua-secreted factors, by altering DC functions, can determine the pattern of immune responses at the fetomaternal interface and, subsequently, pregnancy outcome.

Adenosine 2A receptors in acute kidney injury

Acute kidney injury (AKI) is an important clinical problem that may lead to death and for those who survive, the sequelae of AKI include loss of quality of life, chronic kidney disease and end-stage renal disease. The incidence of AKI continues to rise without clear successes in humans for the pharmacological prevention of AKI or treatment of established AKI. Dendritic cells and macrophages are critical early initiators of innate immunity in the kidney and orchestrate inflammation subsequent to ischaemia-reperfusion injury. These innate cells are the most abundant leucocytes present in the kidney, and they represent a heterogeneous population of cells that are capable of responding to cues from the microenvironment derived from pathogens or endogenous inflammatory mediators such as cytokines or anti-inflammatory mediators such as adenosine. Lymphocyte subsets such as natural killer T cells and Tregs also play roles in regulating ischaemic injury by promoting and suppressing inflammation respectively. Adenosine, produced in response to IR, is generally considered as a protective signalling molecule and elicits its physiological responses through four distinct adenosine receptors. However, its short half-life, lack of specificity and rapid metabolism limit the use of adenosine as a therapeutic agent. These adenosine receptors play various roles in regulating the activity of the aforementioned hematopoietic cells in elevated levels of adenosine such as during hypoxia. This review focuses on the importance of one receptor, the adenosine 2A subtype, in blocking inflammation associated with AKI.

Elevated levels of dehydroepiandrosterone as a potential mechanism of dendritic cell impairment during pregnancy

BACKGROUND

This study aimed to test the hypothesis that immune dysfunction and the increased risk of spontaneous abortion in pregnant women with hyperandrogenia (HA) are caused by the reduced tolerogenic potential of dendritic cells (DCs) that results from elevated levels of dehydroepiandrosterone sulfate (DHEAS).

METHODS

The phenotypic and functional properties of monocyte-derived DCs generated from blood monocytes from non-pregnant women, women with a normal pregnancy, or pregnant women with HA, as well as the in vitro effects of DHEAS on DCs in healthy pregnant women were investigated.

RESULTS

In a normal pregnancy, DCs were shown to be immature and are characterized by a reduced number of CD83(+) and CD25(+) DCs, the ability to stimulate type 2 T cell responses and to induce T cell apoptosis. By contrast, DCs from pregnant women with HA had a mature phenotype, were able to stimulate both type 1 (IFN-γ) and type 2 (IL-4) T cell responses, and were characterized by lower B7-H1 expression and cytotoxic activity against CD8(+) T cells. The addition of DHEAS to cultures of DCs from healthy pregnant women induced the maturation of DCs and increased their ability to activate type 1 T cell responses.

CONCLUSION

Our data demonstrated the reduction in the tolerogenic potential of DCs from pregnant women with HA, and revealed new mechanisms involved in the hormonal regulation of DCs mediated by DHEAS.

Beneficial effect of tolerogenic dendritic cells pulsed with MOG autoantigen in experimental autoimmune encephalomyelitis

BACKGROUND

Treatment with tolerogenic dendritic cells (TolDC) is a promising, cell-based strategy to regulate autoimmune diseases such as multiple sclerosis (MS) in an antigen-specific way. This technique involves the use of TolDC from MS patients cultured in the presence of vitamin D(3) (VitD3) and pulsed with myelin peptides to induce a stable hyporesponsiveness in myelin-specific autologous T cells.

AIM

The purpose of this study was to analyze the in vivo effect of VitD3-TolDC treatment on experimental autoimmune encephalomyelitis, an animal model of MS.

METHODS

Bone marrow-derived TolDC cultured in the presence of VitD3 and pulsed with peptide 40-55 of the myelin oligodendrocyte glycoprotein (MOG(40-55)) were administrated preventively, preclinically, and therapeutically to EAE-induced mice.

RESULTS

We found that VitD3-TolDC-MOG treatment showed a beneficial effect, not only decreasing the incidence of the disease but also reducing the severity of the clinical signs mediated by induction of regulatory T cells (Treg), as well as IL-10 production and reduction of Ag-specific lymphoproliferation. Our results support VitD3-TolDC-peptide(s) treatment as a potential strategy to restore tolerance in autoimmune diseases such as MS.

α-1-Antitrypsin (AAT)-modified donor cells suppress GVHD but enhance the GVL effect: a role for mitochondrial bioenergetics

Hematopoietic cell transplantation is curative in many patients. However, graft-versus-host disease (GVHD), triggered by alloreactive donor cells, has remained a major complication. Here, we show an inverse correlation between plasma α-1-antitrypsin (AAT) levels in human donors and the development of acute GVHD in the recipients (n = 111; P = .0006). In murine models, treatment of transplant donors with human AAT resulted in an increase in interleukin-10 messenger RNA and CD8(+)CD11c(+)CD205(+) major histocompatibility complex class II(+) dendritic cells (DCs), and the prevention or attenuation of acute GVHD in the recipients. Ablation of DCs (in AAT-treated CD11c-DTR donors) decreased CD4(+)CD25(+)FoxP3(+) regulatory T cells to one-third and abrogated the anti-GVHD effect. The graft-versus-leukemia (GVL) effect of donor cells (against A20 tumor cells) was maintained or even enhanced with AAT treatment of the donor, mediated by an expanded population of NK1.1(+), CD49B(+), CD122(+), CD335(+) NKG2D-expressing natural killer (NK) cells. Blockade of NKG2D significantly suppressed the GVL effect. Metabolic analysis showed a high glycolysis-high oxidative phosphorylation profile for NK1.1(+) cells, CD4(+)CD25(+)FoxP3(+) T cells, and CD11c(+) DCs but not for effector T cells, suggesting a cell type-specific effect of AAT. Thus, via altered metabolism, AAT exerts effective GVHD protection while enhancing GVL effects.

Tolerogenic dendritic cells and their applications in transplantation

In transplantation immunology, the ultimate goal is always to successfully and specifically induce immune tolerance of allografts. Tolerogenic dendritic cells (tol-DCs) with immunoregulatory functions have attracted much attention as they play important roles in inducing and maintaining immune tolerance. Here, we focused on tol-DCs that have the potential to promote immune tolerance after solid-organ transplantation. We focus on their development and interactions with other regulatory cells, and we also explore various tol-DC engineering protocols. Harnessing tol-DCs represents a promising cellular therapy for promoting long-term graft functional survival in transplant recipients that will most likely be achieved in the future.

Therapeutic translation in acute kidney injury: the epithelial/endothelial axis

Acute kidney injury (AKI) remains a major clinical event with rising incidence, severity, and cost; it now has a morbidity and mortality exceeding acute myocardial infarction. There is also a documented conversion to and acceleration of chronic kidney disease to end-stage renal disease. The multifactorial nature of AKI etiologies and pathophysiology and the lack of diagnostic techniques have hindered translation of preclinical success. An evolving understanding of epithelial, endothelial, and inflammatory cell interactions and individualization of care will result in the eventual development of effective therapeutic strategies. This review focuses on epithelial and endothelial injury mediators, interactions, and targets for therapy.

Generation and characterization of regulatory dendritic cells derived from murine induced pluripotent stem cells

Regulatory dendritic cells (DCregs) represent a potential therapeutic tool for assessing a variety of immune overreaction conditions; however, current approaches for generating DCregs for therapeutic purposes are limited. We attempted to generate and characterize DCregs from murine induced pluripotent stem (iPS) cells. The iPS cells co-cultured with OP9 cells displayed mesodermally differentiated flat colonies. GM-CSF drove most of the colonies exhibiting a differentiated morphology. Thereafter, cells became morphologically heterologous under the effects of TGF-β and IL-10. Most of the floating cells developed an irregular shape with areas of protrusion. The generated iPS-DCregs demonstrated high CD11b/c and low CD40, CD80, CD86 and MHC-II expressions with a high antigen uptake ability and poor T-cell stimulatory function. Importantly, iPS-DCregs showed immune responsiveness regulation effects both in vitro and in vivo and the ability to generate regulatory T-cells in vitro. Our result illustrates a feasible approach for generating functional DCregs from murine iPS cells.

Cell-extrinsic CTLA4-mediated regulation of dendritic cell maturation depends on STAT3

Regulatory T (Treg) cells suppress immune responses by downregulating the expression of costimulatory molecules CD80 and CD86 on dendritic cells (DCs) through cytotoxic T lymphocyte antigen 4 (CTLA4). However, it is unclear whether inducible Treg (iTreg) cells can hamper immune responses via the same mechanism. Moreover, whether a reverse signal sent by CTLA4 alone is sufficient to prevent maturation of DCs has never been evaluated. Here, we demonstrate that stimulation of DCs with CTLA4, either expressed by inducible Treg cells or by cross-linking with CTLA4Fc fusion protein, can significantly inhibit LPS-induced CD80 and CD86 mRNA and protein expression in both mouse and human DCs. Importantly, CTLA4Fc-treated DCs had reduced ability to stimulate CD4(+) and CD8(+) T-cell proliferation and cytokine production in both syngeneic and allogeneic settings. We also investigated the molecular mechanism involved in the induction of tolerogenic DCs by CTLA4. We determined that the interaction of CTLA4 with its high affinity ligand CD80 on DCs induces STAT3 phosphorylation followed by reduction of NF-κB activity, leading to suppression of CD80 and CD86 gene transcription and protein production. Our work opens new windows for the generation of tolerogenic DCs that could ultimately be used for treating autoimmune diseases and transplant rejection.

Tolerogenic dendritic cells: key regulators of peripheral tolerance in health and disease

Dendritic cells (DCs) as professional antigen-presenting cells are able to induce immunity and tolerance in different conditions, which leads to strong immune responses against hostile agents or tolerance to self-antigens. Although for subsets of DCs, a regulatory function has been shown, the role of the microenvironment is momentous to generate tolerogenic DCs (tDCs). Different microorganisms and tumor cells escape from immune responses by producing mediators and components that influence DCs to show tolerogenic characteristics. In this review, tDC induction was explained in steady state and disease conditions. Moreover, an overview was presented on the efforts to generate in vitro tDCs, their clinical applications and the problems which remain to be solved in this field.

Transplant tolerance: new insights and strategies for long-term allograft acceptance

One of the greatest advances in medicine during the past century is the introduction of organ transplantation. This therapeutic strategy designed to treat organ failure and organ dysfunction allows to prolong the survival of many patients that are faced with no other treatment option. Today, organ transplantation between genetically dissimilar individuals (allogeneic grafting) is a procedure widely used as a therapeutic alternative in cases of organ failure, hematological disease treatment, and some malignancies. Despite the potential of organ transplantation, the administration of immunosuppressive drugs required for allograft acceptance induces severe immunosuppression in transplanted patients, which leads to serious side effects such as infection with opportunistic pathogens and the occurrence of neoplasias, in addition to the known intrinsic toxicity of these drugs. To solve this setback in allotransplantation, researchers have focused on manipulating the immune response in order to create a state of tolerance rather than unspecific immunosuppression. Here, we describe the different treatments and some of the novel immunotherapeutic strategies undertaken to induce transplantation tolerance.

Rejection and regulation: a tight balance

PURPOSE OF REVIEW

Achieving allograft tolerance is the holy grail of transplantation. However, tolerance and rejection are two extreme ends of a scale that can be tipped in either direction. We review the novel effector and regulatory mechanisms involved and factors that tip the balance in favor of rejection or regulation.

RECENT FINDINGS

It is increasingly recognized that established T-cell phenotypes could change their commitments. New data point to the plasticity of Th17 cells in vivo with a reciprocal balance of Th17 cells and regulatory T cells (Tregs) driven by the local cytokine environment. Treg-cell profiles have been linked to acute and chronic allograft outcomes, and emerging data also indicate a novel role of a regulatory B-cell population. Current research efforts are looking into factors that tip the balance toward allograft tolerance by targeting cytokines, novel costimulatory pathways such as T-cell immunoglobulin mucin molecules, and components of innate immunity, particularly dendritic cells.

SUMMARY

The balance of effector and regulatory mechanisms contributing to allograft outcome is very complex. It is likely that targeting multiple pathways will be required to achieve tolerance. Further studies are warranted to define this balance and identify optimal combination of therapeutic interventions.

Application of dendritic cells stimulated with Trichinella spiralis excretory-secretory antigens alleviates experimental autoimmune encephalomyelitis

The parasitic nematode, Trichinella spiralis (T. spiralis), exerts an immunomodulatory effect on the host immune response through excretory-secretory products (ES L1) released from encysted muscle larvae. Our model of combined T. spiralis infection and experimental autoimmune encephalomyelitis (EAE) in Dark Agouti (DA) rats demonstrated a significant reduction in EAE severity in infected animals. Recently, we have created an immune status characteristic for the live infection by in vivo application of dendritic cells (DCs) stimulated with ES L1 products of T. spiralis muscle larvae. Moreover, these cells were able to ameliorate EAE when applied 7 days before EAE induction. ES L1-stimulated DCs increased production of IL-4, IL-10 and TGF-β, and decreased production of IFN-γ and IL-17, both at the systemic level and in target organs. A significant increase in the proportion of CD4+CD25+Foxp3+ T cells was found among spleen cells, and CNS infiltrates from DA rats treated with ES L1-stimulated DCs before EAE induction, compared to controls injected with unstimulated DCs. Regulatory T cells, together with elevated levels of IL-10 and TGF-β, are most likely involved in restraining the production of Th1 and Th17 cytokines responsible for autoimmunity and thus are responsible for the beneficial effect of ES L1-educated DCs on the course of EAE. Our results show that ES L1 antigen-stimulated DCs are able not only to provoke, but also to sustain anti-inflammatory and regulatory responses regardless of EAE induction, with subsequent amelioration of EAE, or even protection from the disease.