Differential role of all-trans retinoic acid in promoting the development of CD4+ and CD8+ regulatory T cells

Exploring risk factors for autoimmune diseases complicated by non-hodgkin lymphoma through regulatory T cell immune-related traits: a Mendelian randomization study

Background

The effect of immune cells on autoimmune diseases (ADs) complicated by non-Hodgkin lymphoma (NHL) has been widely recognized, but a causal relationship between regulatory T cell (Treg) immune traits and ADs complicated by NHL remains debated.

Methods

Aggregate data for 84 Treg-related immune traits were downloaded from the Genome-Wide Association Study (GWAS) catalog, and GWAS data for diffuse large B-cell lymphoma (DLBCL; n=315243), follicular lymphoma (FL; n=325831), sjögren's syndrome (SS; n=402090), rheumatoid arthritis (RA; n=276465), dermatopolymyositis (DM; n=311640), psoriasis (n=407876), atopic dermatitis (AD; n=382254), ulcerative colitis (UC; n=411317), crohn's disease(CD; n=411973) and systemic lupus erythematosus (SLE; n=307587) were downloaded from the FinnGen database. The inverse variance weighting (IVW) method was mainly used to infer any causal association between Treg-related immune traits and DLBCL, FL, SS, DM, RA, Psoriasis, AD, UC, CD and SLE, supplemented by MR-Egger, weighted median, simple mode, and weighted mode. Moreover, we performed sensitivity analyses to assess the validity of the causal relationships.

Results

There was a potential genetic predisposition association identified between CD39+ CD8br AC, CD39+ CD8br % T cell, and the risk of DLBCL (OR=1.51, p<0.001; OR=1.25, p=0.001) (adjusted FDR<0.1). Genetic prediction revealed potential associations between CD25++ CD8br AC, CD28- CD25++ CD8br % T cell, CD39+ CD8br % CD8br, and the risk of FL (OR=1.13, p=0.022; OR=1.28, p=0.042; OR=0.90, p=0.016) (adjusted FDR>0.1). Furthermore, SLE and CD exhibited a genetically predicted potential association with the CD39+ CD8+ Tregs subset. SS and DM were possibly associated with an increase in the quantity of the CD4+ Tregs subset; RA may have reduced the quantity of the CD39+ CD8+ Tregs subset, although no causal relationship was identified. Sensitivity analyses supported the robustness of our findings.

Conclusions

There existed a genetically predicted potential association between the CD39+ CD8+ Tregs subset and the risk of DLBCL, while SLE and CD were genetically predicted to be potentially associated with the CD39+ CD8+ Tregs subset. The CD39+ CD8+ Tregs subset potentially aided in the clinical diagnosis and treatment of SLE or CD complicated by DLBCL.

Metformin reduces hepatocarcinogenesis by inducing downregulation of Cyp26a1 and CD8+ T cells

BACKGROUND

Hepatocellular carcinoma (HCC) is a highly heterogeneous cancer with major challenges in both prevention and therapy. Metformin, adenosine monophosphate-activated protein kinase (AMPK) activator, has been suggested to reduce the incidence of HCC when used for patients with diabetes in preclinical and clinical studies. However, the possible effects of metformin and their mechanisms of action in non-diabetic HCC have not been adequately investigated.

METHODS

Fah-/-  mice were used to construct a liver-injury-induced non-diabetic HCC model for exploring hepatocarcinogenesis and therapeutic potential of metformin. Changes in relevant tumour and biochemical indicators were measured. Bulk and single-cell RNA-sequencing analyses were performed to validate the crucial role of proinflammatory/pro-tumour CD8+ T cells. In vitro and in vivo experiments were performed to confirm Cyp26a1-related antitumour mechanisms of metformin.

RESULTS

RNA-sequencing analysis showed that chronic liver injury led to significant changes in AMPK-, glucose- and retinol metabolism-related pathways in Fah-/- mice. Metformin prevented the formation of non-diabetic HCC in Fah-/- mice with chronic liver injury. Cyp26a1 ddexpression in hepatocytes was significantly suppressed after metformin treatment. Moreover, downregulation of Cyp26a1 occurred in conjunction with increased levels of all-trans-retinoic acid (atRA), which is involved in the activation of metformin-suppressed hepatocarcinogenesis in Fah-/- mice. In contrast, both CD8+  T-cell infiltration and proinflammatory/pro-tumour cytokines in the liver were significantly upregulated in Fah-/- mice during chronic liver injury, which was notably reversed by either metformin or atRA treatment. Regarding mechanisms, metformin regulated the decrease in Cyp26a1 enzyme expression and increased atRA expression via the AMPK/STAT3/Gadd45β/JNK/c-Jun pathway.

CONCLUSIONS

Metformin inhibits non-diabetic HCC by upregulating atRA levels and downregulating CD8+ T cells. This is the first reporting that the traditional drug metformin regulates the metabolite atRA via the Cyp26a1-involved pathway. The present study provides a potential application of metformin and atRA in non-diabetic HCC.

CD8+iTregs mediate the protective effect of rapamycin against graft versus host disease in a humanized murine model

CD8⁺Tregs are important immunoregulatory cells that participate in immunopathological processes in many diseases. Rapamycin (Rapa) is a macrolide immunosuppressant that inhibits the mammalian target of rapamycin (mTOR) and has been shown to improve CD4⁺-induced Tregs (iTregs) generation. This study aimed to evaluate the role of Rapa in the generation and function of CD8⁺iTregs. Human CD8 + CD25-CD45RA + T cells were divided into two groups, one with Rapa and the other without Rapa, and both groups were cultured under Treg-induced conditions. Rapa significantly improved Foxp3 expression and the suppressive function of CD8⁺iTregs in vitro. Further studies showed that Rapa suppressed inflammatory cytokine expression and enhanced anti-inflammatory cytokine expression. Under inflammatory conditions in vitro, Rapa-CD8 + iTregs sustained Foxp3 and anti-inflammatory cytokine expression. An in-depth study showed that Rapa regulated CpG demethylation in the Foxp3 region and STAT1 and STAT3 phosphorylation in CD8⁺iTregs. Finally, we compared the regulatory ability of Rapa and all-trans retinoic acid, another reagent that stimulates CD4⁺ iTreg generation in vitro, which showed that Rapa, but not all-trans retinoic acid, improved CD8⁺ iTreg induction and suppressed CD4⁺T cell expansion in vitro and protected against graft-versus-host disease in a humanized murine model in vivo. These results strongly suggest that CD8⁺iTregs initiated by Rapa may represent a new therapeutic strategy for inflammatory and autoimmune diseases.

Immune Impairment Associated with Vitamin A Deficiency: Insights from Clinical Studies and Animal Model Research

Vitamin A (VA) is critical for many biological processes, including embryonic development, hormone production and function, the maintenance and modulation of immunity, and the homeostasis of epithelium and mucosa. Specifically, VA affects cell integrity, cytokine production, innate immune cell activation, antigen presentation, and lymphocyte trafficking to mucosal surfaces. VA also has been reported to influence the gut microbiota composition and diversity. Consequently, VA deficiency (VAD) results in the imbalanced production of inflammatory and immunomodulatory cytokines, intestinal inflammation, weakened mucosal barrier functions, reduced reactive oxygen species (ROS) and disruption of the gut microbiome. Although VAD is primarily known to cause xerophthalmia, its role in the impairment of anti-infectious defense mechanisms is less defined. Infectious diseases lead to temporary anorexia and lower dietary intake; furthermore, they adversely affect VA status by interfering with VA absorption, utilization and excretion. Thus, there is a tri-directional relationship between VAD, immune response and infections, as VAD affects immune response and predisposes the host to infection, and infection decreases the intestinal absorption of the VA, thereby contributing to secondary VAD development. This has been demonstrated using nutritional and clinical studies, radiotracer studies and knockout animal models. An in-depth understanding of the relationship between VAD, immune response, gut microbiota and infections is critical for optimizing vaccine efficacy and the development of effective immunization programs for countries with high prevalence of VAD. Therefore, in this review, we have comprehensively summarized the existing knowledge regarding VAD impacts on immune responses to infections and post vaccination. We have detailed pathological conditions associated with clinical and subclinical VAD, gut microbiome adaptation to VAD and VAD effects on the immune responses to infection and vaccines.

Role of myeloid-derived suppressor cells in the formation of pre-metastatic niche

Metastasis is a complex process, which depends on the interaction between tumor cells and host organs. Driven by the primary tumor, the host organ will establish an environment suitable for the growth of tumor cells before their arrival, which is called the pre-metastasis niche. The formation of pre-metastasis niche requires the participation of a variety of cells, in which myeloid-derived suppressor cells play a very important role. They reach the host organ before the tumor cells, and promote the establishment of the pre-metastasis niche by influencing immunosuppression, vascular leakage, extracellular matrix remodeling, angiogenesis and so on. In this article, we introduced the formation of the pre-metastasis niche and discussed the important role of myeloid-derived suppressor cells. In addition, this paper also emphasized the targeting of myeloid-derived suppressor cells as a therapeutic strategy to inhibit the formation of pre-metastasis niche, which provided a research idea for curbing tumor metastasis.

The role of myeloid-derived suppressor cells in lung cancer and targeted immunotherapies

INTRODUCTION

Lung cancer is the deadliest cancer in both sexes combined globally due to significant delays in diagnosis and poor survival. Despite advances in the treatment of lung cancer, the overall outcomes remain poor and traditional chemotherapy fails to provide long-term benefits for many patients. Therefore, new treatment strategies are needed to increase overall survival. Myeloid-derived suppressor cells (MDSCs) are immunosuppressive cells taking part in lung cancer, as has been described in other types of tumors. MDSCs immunosuppressive activity is mediated by arginases (ARG-1 and ARG-2), nitric oxide (NO), reactive oxygen species (ROS), peroxynitrite, PD-1/PD-L1 axis, and different cytokines. MDSCs can be a target for lung cancer immunotherapy by inducing their differentiation into mature myeloid cells, elimination, attenuation of their function, and inhibition of their accumulation.

AREAS COVERED

In this review, the immunosuppressive function of MDSCs, their role in lung cancer, and strategies to target them, which could result in increased efficacy of immunotherapy in patients with lung cancer, are discussed.

EXPERT OPINION

Identification of important mechanisms and upstream pathways involved in MDSCs functions paves the way for further preclinical and clinical lung cancer research, which could lead to the development of novel therapeutic approaches.

Newly Found Peacekeeper: Potential of CD8+ Tregs for Graft-Versus-Host Disease

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains the most effective and potentially curative treatment for a variety of hematologic malignancies. However, graft-versus-host disease (GVHD) is a major obstacle that limits wide application of allo-HSCT, despite the development of prophylactic strategies. Owing to experimental and clinical advances in the field, GVHD is characterized by disruption of the balance between effector and regulatory immune cells, resulting in higher inflammatory cytokine levels. A reduction in regulatory T cells (Tregs) has been associated with limiting recalibration of inflammatory overaction and maintaining immune tolerance. Moreover, accumulating evidence suggests that immunoregulation may be useful for preventing GVHD. As opposed to CD4⁺ Tregs, the CD8⁺ Tregs population, which constitutes an important proportion of all Tregs, efficiently attenuates GVHD while sparing graft-versus-leukemic (GVL) effects. CD8⁺ Tregs may provide another form of cellular therapy for preventing GVHD and preserving GVL effects, and understanding the underlying mechanisms that different from those of CD4⁺ Tregs is significant. In this review, we summarize preclinical experiments that have demonstrated the role of CD8⁺ Tregs during GVHD and attempted to obtain optimized CD8⁺ Tregs. Notably, although optimized CD8⁺ Tregs have obvious advantages, more exploration is needed to determine how to apply them in the clinic.

CD8+ T regulatory cells in lupus

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

Intestinal cDC1 drive cross-tolerance to epithelial-derived antigen via induction of FoxP3+CD8+ Tregs

Although CD8⁺ T cell tolerance to tissue-specific antigen (TSA) is essential for host homeostasis, the mechanisms underlying peripheral cross-tolerance and whether they may differ between tissue sites remain to be fully elucidated. Here, we demonstrate that peripheral cross-tolerance to intestinal epithelial cell (IEC)-derived antigen involves the generation and suppressive function of FoxP3⁺CD8⁺ T cells. FoxP3⁺CD8⁺ T_reg generation was dependent on intestinal cDC1, whose absence led to a break of tolerance and epithelial destruction. Mechanistically, intestinal cDC1-derived PD-L1, TGFβ, and retinoic acid contributed to the generation of gut-tropic CCR9⁺CD103⁺FoxP3⁺CD8⁺ T_regs Last, CD103-deficient CD8⁺ T cells lacked tolerogenic activity in vivo, indicating a role for CD103 in FoxP3⁺CD8⁺ T_reg function. Our results describe a role for FoxP3⁺CD8⁺ T_regs in cross-tolerance in the intestine for which development requires intestinal cDC1.

Tregs in Autoimmune Uveitis

Uveitis is a chronic disease with relapsing and remitting ocular attack, which requires corticosteroids and systemic immunosuppression to prevent severe vision loss. Classically, uveitis is referred to an autoimmune disease, mediated by pro-inflammatory Th17 cells and immunosuppressive CD4+CD25+FoxP3+ T-regulatory cells (Tregs). More and more evidence indicates that Tregs are involved in development, resolution, and remission of uveitis. Clinically, many researchers have conducted quantitative and functional analyses of peripheral blood from patients with different subtypes of uveitis, in an attempt to find the changing rules of Tregs. Consistently, using the experimental autoimmune uveitis (EAU) model, researchers have explored the development and resolution mechanism of uveitis in many aspects. In addition, many drug and Tregs therapy investigations have yielded encouraging results. In this chapter, we introduced the current understanding of Tregs, summarized the clinical changes in the number and function of patients with uveitis and the immune mechanism of Tregs involved in EAU model, as well as discussed the progress and shortcomings of Tregs-related drug therapy and Tregs therapy. Although the exact mechanism of Tregs-mediated uveitis protection remains to be elucidated, the strategy of Tregs regulation may provide a specific and meaningful way for the prevention and treatment of uveitis.

Toll Like Receptor 4 Mediated Lymphocyte Imbalance Induces Nec-Induced Lung Injury

Necrotizing enterocolitis (NEC) is the leading cause of death from gastrointestinal disease in premature infants, and is associated with the development of severe lung inflammation. The pathogenesis of NEC-induced lung injury remains unknown, yet infiltrating immune cells may play a role. In support of this possibility, we now show that NEC in mice and humans was associated with the development of profound lung injury that was characterized by an influx of Th17 cells and a reduction in T regulatory lymphocytes (Tregs). Importantly, the adoptive transfer of CD4 T cells isolated from lungs of mice with NEC into the lungs of immune incompetent mice (Rag1 mice) induced profound inflammation in the lung, while the depletion of Tregs exacerbated NEC induced lung injury, demonstrating that imbalance of Th17/Treg in the lung is required for the induction of injury. In seeking to define the mechanisms involved, the selective deletion of toll-like receptor 4 (TLR4) from the Sftpc1 pulmonary epithelial cells reversed lung injury, while TLR4 activation induced the Th17 recruiting chemokine (C-C motif) ligand 25 (CCL25) in the lungs of mice with NEC. Strikingly, the aerosolized inhibition of both CCL25 and TLR4 and the administration of all trans retinoic acid restored Tregs attenuated NEC-induced lung injury. In summary, we show that TLR4 activation in Surfactant protein C-1 (Sftpc1) cells disrupts the Treg/Th17 balance in the lung via CCL25 leading to lung injury after NEC and reveal that inhibition of TLR4 and stabilization of Th17/Treg balance in the neonatal lung may prevent this devastating complication of NEC.

Anti-PD-L1-modified and ATRA-loaded nanoparticles for immuno-treatment of oral dysplasia and oral squamous cell carcinoma

Aim: To develop nanomedicines for immuno-therapy of oral dysplasia and oral squamous cell carcinoma. Materials & methods: All-trans retinoic acid (ATRA)-poly(lactide-co-glycolide acid) (PLGA)-poly(ethylene glycol) (PEG)-programmed death-ligand 1 (PD-L1) nanomedicines were fabricated by loading ATRA into PLGA-PEG nanocarriers and modification using an anti-PD-L1 antibody. Results: ATRA-PLGA-PEG-PD-L1 nanoparticles showed fast cellular uptake, significantly inhibited proliferation and induced apoptosis in DOK and CAL27 cells. Moreover, in C3H tumor-bearing mice, ATRA-PLGA-PEG-PD-L1 nanoparticles more specifically targeted tumor cells, enhanced anticancer activity and reduced side effects when compared with free ATRA. Furthermore, CD8+ T cells were activated around PD-L1 positive cells in the tumor microenvironment after treatment. Conclusion: ATRA-PLGA-PEG-PD-L1 nanoparticles had low toxicity, high biocompatibility and specifically targeted oral dysplasia and squamous carcinoma cells both in vitro and in vivo.

Vitamin A Deficiency in Patients Undergoing Sleeve Gastrectomy and Gastric Bypass: A 2-Year, Single-Center Review

Introduction: Vitamin A deficiency (VAD) is an underreported micronutrient deficiency after bariatric surgery (BS). Objectives: The goal of this study was to characterize VAD prevalence in patients undergoing malabsorptive and restrictive procedures up to 2 years postoperatively. Methods: Primary sleeve gastrectomy (SG; n = 322) and gastric bypass (GB; n = 249) patients were reviewed. Levels for overall VAD (oVAD; retinol <39 mcg/dL) and moderate VAD (mVAD; retinol <30 mcg/dL) were reported preoperatively and 6, 12, and 24 months postoperatively. Differences in demographic, surgical, and postoperative data were tested between these groups. Settings: Single-center academic institution. Results: Serum retinol levels were documented for 56%, 74%, 61%, and 37% of patients for listed time points. Baseline retinol inversely correlated to preop body mass index (BMI) (R = -0.15, P = .007). Both oVAD and mVAD peaked 6 months postoperatively (33% vs. 15%, P < .005; 12% vs. 4%, P = .0004, respectively). oVAD remained elevated at 24 months (22% vs. 15%, P = .03). Compared to SG, oVAD was higher following GB at 6 months (39% vs. 28%, P = .001) and 12 months (26% vs. 17%, P = .04), and mVAD was greater with GB at 6 months (18% vs. 6%, P < .0005). African American patients had higher oVAD/mVAD preoperatively (26% vs. 13%, P = .02; 13% vs. 3%, P = .001, respectively) and at 6 months (19% vs. 10%, P = .04). Prior mild VAD (retinol 1.05-1.35 μM) was significantly associated with mVAD up to 12 months postoperatively. Conclusions: Although higher following LRYGB, VAD is prevalent following both malabsorptive and restrictive procedures. Preoperative serum retinol is inversely correlated to increasing BMI, and African American race and mild VAD are associated with moderate VAD.

All trans-retinoic acid protects against acute ischemic stroke by modulating neutrophil functions through STAT1 signaling

Background and purpose

Regulation of neural inflammation is considered as a vital therapeutic target in ischemic stroke. All-trans retinoic acid (atRA), a potent immune modulator, has raised interest in the field of stroke therapy. However, the immunological mechanisms for atRA-mediated neuroprotection remain elusive. The current study evaluated the impact of atRA on post-stroke neural inflammation and elucidated the mechanisms involved in the regulation of related neutrophil functions.

Methods

atRA was prophylactically administered to mice 1 day before transient middle cerebral artery occlusion (tMCAO, 1 h) and repeated daily immediately after reperfusion for 3 days. Stroke outcomes, neutrophil polarization, and formation of neutrophil extracellular traps (NETs) in the stroke lesion were assessed. Neutrophil depletion was induced with anti-Ly6G antibodies. Primary neutrophil cultures were used to explore the mechanisms of atRA treatment.

Results

Prophylactic atRA treatment reduced infarct volumes and neurological deficits at 1 day after tMCAO. Post-stroke neural inflammation was attenuated and neutrophil accumulation in lesion was downregulated. atRA treatment skewed neutrophil toward N2 phenotype which facilitated its clearance by macrophage and inhibited NETs formation. The functions of neutrophil were indispensable in the protective effects of atRA and were associated with suppression to STAT1 signaling by atRA. Administration of atRA after stroke still provided efficient protection to cerebral ischemia.

Conclusion

atRA displays potent therapeutic efficacy in ischemic stroke by attenuating neural inflammation. Treatment of atRA impeded neutrophil accumulation, favored N2 polarization, and forbade NETs formation in ischemic lesion. STAT1 signaling played a decisive role in the mechanisms of atRA-afforded regulation to neutrophil.

Electronic supplementary material

The online version of this article (10.1186/s12974-019-1557-6) contains supplementary material, which is available to authorized users.

Translational Potential of Therapeutics Targeting Regulatory Myeloid Cells in Tuberculosis

Despite recent advances in tuberculosis (TB) drug development and availability, successful antibiotic treatment is challenged by the parallel development of antimicrobial resistance. As a result, new approaches toward improving TB treatment have been proposed in an attempt to reduce the high TB morbidity and mortality rates. Host-directed therapies (HDTs), designed to modulate host immune components, provide an alternative approach for improving treatment outcome in both non-communicable and infectious diseases. Many candidate immunotherapeutics, designed to target regulatory myeloid immune components in cancer, have so far proven to be of value as repurposed HDT in TB. Several of these studies do however lack detailed description of the mechanism or host pathway affected by TB HDT treatment. In this review, we present an argument for greater appreciation of the role of regulatory myeloid cells, such as myeloid-derived suppressor cells (MDSC), as potential targets for the development of candidate TB HDT compounds. We discuss the role of MDSC in the context of Mycobacterium tuberculosis infection and disease, focussing primarily on their specific cellular functions and highlight the impact of HDTs on MDSC frequency and function.

Role of Vitamin A in the Immune System

Vitamin A (VitA) is a micronutrient that is crucial for maintaining vision, promoting growth and development, and protecting epithelium and mucus integrity in the body. VitA is known as an anti-inflammation vitamin because of its critical role in enhancing immune function. VitA is involved in the development of the immune system and plays regulatory roles in cellular immune responses and humoral immune processes. VitA has demonstrated a therapeutic effect in the treatment of various infectious diseases. To better understand the relationship between nutrition and the immune system, the authors review recent literature about VitA in immunity research and briefly introduce the clinical application of VitA in the treatment of several infectious diseases.

TGF-β-Induced CD8+CD103+ Regulatory T Cells Show Potent Therapeutic Effect on Chronic Graft-versus-Host Disease Lupus by Suppressing B Cells

Lupus nephritis is one of most severe complications of systemic erythematosus lupus and current approaches are not curative for lupus nephritis. Although CD4⁺Foxp3⁺ regulatory T cells (Treg) are crucial for prevention of autoimmunity, the therapeutic effect of these cells on lupus nephritis is not satisfactory. We previously reported that CD8⁺CD103⁺ Treg induced ex vivo with TGF-β1 and IL-2 (CD8⁺CD103⁺ iTreg), regardless of Foxp3 expression, displayed potent immunosuppressive effect on Th cell response and had therapeutic effect on Th cell-mediated colitis. Here, we tested whether CD8⁺CD103⁺ iTreg can ameliorate lupus nephritis and determined potential molecular mechanisms. Adoptive transfer of CD8⁺CD103⁺ iTreg but not control cells to chronic graft-versus-host disease with a typical lupus syndrome showed decreased levels of autoantibodies and proteinuria, reduced renal pathological lesions, lowered renal deposition of IgG/C3, and improved survival. CD8⁺CD103⁺ iTreg cells suppressed not only T helper cells but also B cell responses directly that may involve in both TGF-β and IL-10 signals. Using RNA-seq, we demonstrated CD8⁺CD103⁺ iTreg have its own unique expression profiles of transcription factors. Thus, current study has identified and extended the target cells of CD8⁺CD103⁺ iTreg and provided a possible application of this new iTreg subset on lupus nephritis and other autoimmune diseases.

Unleashing the immune response against childhood solid cancers

Tumor immunotherapy has come to the fore fuelled by impressive clinical responses to checkpoint inhibitor antibodies in a range of adult malignancies and by the success of chimeric antigen receptor T cells targeting adult and pediatric B-cell malignancies. Clearly, if appropriately fine-tuned, the immune system has the capability to seek out and destroy cancer. Studies in pediatric solid cancers so far have not shown the therapeutic potential checkpoint inhibitors described in adult cancers and this may reflect fewer tumor-associated antigens or different immune evasion mechanisms. One potential approach to overcome these limitations will be to combine interventions to undermine immune evasion mechanisms with engineered T-cell adoptive transfer.

Single and combined effect of retinoic acid and rapamycin modulate the generation, activity and homing potential of induced human regulatory T cells

Adoptive transfer of CD4+CD25+FOXP3+ regulatory T cells (Treg cells) has been successfully utilized to treat graft versus host disease and represents a promising strategy for the treatment of autoimmune diseases and transplant rejection. The aim of this study was to evaluate the effects of all-trans retinoic acid (atRA) and rapamycin (RAPA) on the number, phenotype, homing markers expression, DNA methylation, and function of induced human Treg cells in short-term cultures. Naive T cells were polyclonally stimulated and cultured for five days in the presence of different combinations of IL-2, TGF-β1, atRA and RAPA. The resulting cells were characterized by the expression of FOXP3, activation, surface and homing markers. Methylation of the Conserved Non-coding Sequence 2 was also evaluated. Functional comparison of the different culture conditions was performed by suppression assays in vitro. Culturing naive human T cells with IL-2/TGFβ1 resulted in the generation of 54.2% of Treg cells (CD4+CD25+FOXP3+) whereas the addition of 100 nM atRA increased the yield of Treg cells to 66% (p = 0.0088). The addition of RAPA did not increase the number of Treg cells in any of these settings. Treg cells generated in the presence of atRA had an increased expression of the β7 integrin to nearly 100% of the generated Treg cells, while RAPA treated cells showed enhanced expression of CXCR4. The differential expression of homing molecules highlights the possibility of inducing Treg cells with differential organ-specific homing properties. Neither atRA nor RAPA had an effect on the highly methylated CNS2 sites, supporting reports that their contribution to the lineage stability of Treg cells is not mediated by methylation changes in this locus. Treg cells generated in the presence of RAPA show the most potent suppression effect on the proliferation of effector cells.

Regulatory T cells in multiple sclerosis and myasthenia gravis

Multiple sclerosis (MS) is a chronic debilitating disease of the central nervous system primarily mediated by T lymphocytes with specificity to neuronal antigens in genetically susceptible individuals. On the other hand, myasthenia gravis (MG) primarily involves destruction of the neuromuscular junction by antibodies specific to the acetylcholine receptor. Both autoimmune diseases are thought to result from loss of self-tolerance, which allows for the development and function of autoreactive lymphocytes. Although the mechanisms underlying compromised self-tolerance in these and other autoimmune diseases have not been fully elucidated, one possibility is numerical, functional, and/or migratory deficits in T regulatory cells (Tregs). Tregs are thought to play a critical role in the maintenance of peripheral immune tolerance. It is believed that Tregs function by suppressing the effector CD4+ T cell subsets that mediate autoimmune responses. Dysregulation of suppressive and migratory markers on Tregs have been linked to the pathogenesis of both MS and MG. For example, genetic abnormalities have been found in Treg suppressive markers CTLA-4 and CD25, while others have shown a decreased expression of FoxP3 and IL-10. Furthermore, elevated levels of pro-inflammatory cytokines such as IL-6, IL-17, and IFN-γ secreted by T effectors have been noted in MS and MG patients. This review provides several strategies of treatment which have been shown to be effective or are proposed as potential therapies to restore the function of various Treg subsets including Tr1, iTr35, nTregs, and iTregs. Strategies focusing on enhancing the Treg function find importance in cytokines TGF-β, IDO, interleukins 10, 27, and 35, and ligands Jagged-1 and OX40L. Likewise, strategies which affect Treg migration involve chemokines CCL17 and CXCL11. In pre-clinical animal models of experimental autoimmune encephalomyelitis (EAE) and experimental autoimmune myasthenia gravis (EAMG), several strategies have been shown to ameliorate the disease and thus appear promising for treating patients with MS or MG.

Myeloid-derived suppressor cells-a new therapeutic target to overcome resistance to cancer immunotherapy

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature myeloid cells that accumulate during pathologic conditions, such as cancer. Patients diagnosed with advanced metastatic cancers have an average survival of 12-24 mo, a survival time that hasn't changed significantly in the past 30 yr. Despite some encouraging improvements in response rates and overall survival in patients receiving immunotherapies, such as immune checkpoint inhibitors, most patients will ultimately progress. MDSCs contribute to immunotherapeutic resistance by actively inhibiting antitumor T cell proliferation and cytotoxic activity as well as by promoting expansion of protumorigenic T regulatory cells, thereby, dampening the host immune responses against the tumor. In addition, MDSCs promote angiogenesis, tumor invasion, and metastasis. Thus, MDSCs are potential therapeutic targets in cases of multiple cancers. This review focuses on the phenotypic and functional characteristics of MDSCs and provides an overview of the mono- and combinatorial-therapeutic strategies that target MDSCs with an objective of enhancing the efficacy of cancer immunotherapies.

Hierarchical transcriptional profile of urothelial cells development and differentiation

The urothelial lining of the lower urinary tract is the most efficient permeability barrier in animals, exhibiting a highly differentiated phenotype and a remarkable regenerative capacity upon wounding. During development and possibly during repair, cells undergo a sequence of hierarchical transcriptional events that mark the transition of these cells from the least differentiated urothelial phenotype characteristic of the basal cell layer, to the most differentiated cellular phenotype characteristic of the superficial cell layer. Unraveling normal urothelial differentiation program is essential to uncover the underlying causes of many congenital abnormalities and for the development of an appropriate differentiation niche for stem cells, for future use in urinary tract tissue engineering and organ reconstruction. Kruppel like factor-5 appears to be at the top of the hierarchy activating several downstream transcription factors, the most prominent of which is peroxisome proliferator activator receptor-γ. Eventually those lead to the activation of transcription factors that directly regulate the expression of uroplakin proteins along with other proteins that mediate the permeability function of the urothelium. In this review, we discuss the most recent findings in the area of urothelial cellular differentiation and transcriptional regulation, aiming for a comprehensive overview that aids in a refined understanding of this process.

Induced regulatory T cells are phenotypically unstable and do not protect mice from rapidly progressive glomerulonephritis

Regulatory T (Treg) cells are a suppressive CD4⁺ T-cell subset. We generated induced Treg (iTreg) cells and explored their therapeutic potential in a murine model of rapidly progressive glomerulonephritis. Polyclonal naive CD4⁺ T cells were cultured in vitro with interleukin-2 (IL-2), transforming growth factor-β1, all-trans-retinoic acid and monoclonal antibodies against interferon-γ and IL-4, generating Foxp3⁺ iTreg cells. To enhance their suppressive phenotype, iTreg cultures were modified with the addition of a monoclonal antibody against IL-12p40 or by using RORγt^-/- CD4⁺ T cells. Induced Treg cells were transferred into models of delayed-type hypersensitivity and experimental glomerulonephritis. The iTreg cells exhibited comparable surface receptor expression and in vitro suppressive ability to natural Treg cells, but did not regulate antigen-specific delayed-type hypersensitivity or systemic inflammatory immune responses, losing Foxp3 expression in vivo. In glomerulonephritis, transferred iTreg cells did not prevent renal injury or modulate systemic T helper type 1 immune responses. Induced Treg cells cultured with anti-IL-12p40 had an enhanced suppressive phenotype in vitro and regulated dermal delayed-type hypersensitivity in vivo, but were not protective against renal injury, losing Foxp3 expression, especially in the transferred cells recruited to the kidney. Use of RORγt^-/- CD4⁺ T cells or iTreg cells generated from sensitized CD4⁺ Foxp3^- cells did not regulate renal or systemic inflammatory responses in vivo. In conclusion, iTreg cells suppress T-cell proliferation in vitro, but do not regulate experimental glomerulonephritis, being unstable in this inflammatory milieu in vivo.

The dual nature of retinoic acid in pemphigus and its therapeutic potential: Special focus on all-trans Retinoic Acid

The efficient treatment of pemphigus with no certain side effect remained a controversial issue. Although there are various options for controlling disease severity, the majority of them may cause serious side effects. Retinoic acid (RA), an active metabolite converted from vitamin A, plays an active role in immune functions. Effects of RA, especially all-trans-Retinoic Acid (ATRA) on different types of cells involved in immune responses were analyzed in vitro and in vivo. RAs could affect the differentiation of T helper (Th) cells, B cells responses, stabilization of both natural regulatory T cells (nTregs) and regulatory B cells (Bregs) populations, and regulating the expression of critical genes in immune responses. The role of RA, based on major immune cells involved in pemphigus has not been addressed so far. In this study, we sought to determine the possible effects of RA, with a special focus on ATRA in pemphigus. All the evidences of ATRA effects on the immune system were collected and their association with the pemphigus was analyzed. According to the previous results, ATRA causes a decline in Th17 populations; increase in CD4+ induced regulatory T cells (iTregs), stabilization of nTregs, and promotion of suppressive B cells, which are critical in the improvement of pemphigus. Nevertheless, it also causes shifting of the Th1:Th2 balance toward Th2 cells, which is not favorable for pemphigus patients. In conclusion, ATRA acts via different ways in pemphigus. Due to increase in the suppressive function via iTregs, nTregs, and Bregs, it is suggested that patients with pemphigus may benefit from systemic ATRA therapy. To clarify this issue, further studies, such as clinical trials are needed.

All-trans retinoic acid favors the development and function of regulatory T cells from liver transplant patients

Graft-versus-host disease (GVHD) is an intractable complication in transplant patients. Regulatory T cells (Tregs) have the ability to prevent GVHD and consist of two subsets: natural Tregs (nTregs) and induced Tregs (iTregs). In comparison to nTregs, iTregs originate in the periphery under certain conditions and show improved proliferative and suppressive abilities in an inflammatory milieu. All-trans retinoic acid (atRA) favors Treg expansion and FoxP3 expression in human Tregs. However, whether atRA can affect the function of iTregs from transplant patients remains inconclusive. Therefore, we sorted naïve T cells from liver transplant patients and cultured them in vitro. Further analyses were performed to assess the suppressive function of iTregs in vitro and in vivo. atRA favored expansion and forkhead box P3 expression in iTregs from transplant patients. In comparison to iTregs from healthy donors, iTregs from transplant patients showed decent suppressive abilities in vitro and in vivo. Our findings suggest that atRA can potentially improve the development and function of iTregs from transplant patients. Furthermore, our results provide novel insights into Treg therapy in GVHD clinical trials.

Myeloid derived suppressor cells-An overview of combat strategies to increase immunotherapy efficacy

Myeloid-derived suppressor cells (MDSCs) contribute to tumor-mediated immune escape and negatively correlate with overall survival of cancer patients. Nowadays, a variety of methods to target MDSCs are being investigated. Based on the intervention stage of MDSCs, namely development, expansion and activation, function and turnover, these methods can be divided into: (I) prevention or differentiation to mature cells, (II) blockade of MDSC expansion and activation, (III) inhibition of MDSC suppressive activity or (IV) depletion of intratumoral MDSCs. This review describes effective mono- or multimodal-therapies that target MDSCs for the benefit of cancer treatment.

The role of all-trans retinoic acid in the biology of Foxp3+ regulatory T cells

Regulatory T (Treg) cells are necessary for immune system homeostasis and the prevention of autoimmune diseases. Foxp3 is specifically expressed in Treg cells and plays a key role in their differentiation and function. Foxp3(+) Treg cells are consisted of naturally occurring, thymus-derived Treg (nTreg) and peripheral-induced Treg (iTreg) cells that may have different functional characteristics or synergistic roles. All-trans retinoic acid (atRA), a vitamin A metabolite, regulates a wide range of biological processes, including cell differentiation and proliferation. Recent studies demonstrated that atRA also regulates the differentiation of T helper (Th) cells and Treg cells. Moreover, atRA also sustains nTreg stability under inflammatory conditions. In this review, we summarize the significant progress of our understanding of the role(s) and mechanisms of atRA in Treg biology.

Dual immune modulatory effect of vitamin A in human visceral leishmaniasis

Vitamin A supplementation has shown to prevent mortality by diarrheal and respiratory diseases in several countries. Nevertheless, there are few studies investigating the effect of vitamin A in visceral leishmaniasis (VL), although there are reports of its deficiency in children with symptomatic VL in Brazil and Bangladesh. This study analyzed the effect of vitamin A on a subset of Treg cells and monocytes isolated from symptomatic VL and from healthy children residing in an endemic area for VL in Northeast Brazil. Serum retinol concentrations correlated inversely with IL-10 and TGF-β productions in CD4(+)CD25(high)Foxp3(+) T cells isolated from children with VL stimulated with leishmanial antigens. All-trans retinoic acid in vitro induced IL-10 in CD4(+)CD25(high)Foxp3(+) T cells; IL-10 and TGF-β production in CD4(+)CD25-Foxp3- T cells, and IL-10 in monocytes isolated from healthy children. However, the use of all-trans retinoic acid together with leishmanial antigens in vitro prevented increases in IL-10 production in Treg cells and monocytes isolated from VL children. Strikingly, those results show a potential dual role of vitamin A in the immune system: improvement of a regulatory profile in cells from healthy children after leishmanial stimulation and down modulation of IL-10 in Treg cells and monocytes during symptomatic VL. Therefore, the use of vitamin A concomitant to VL therapy might be useful in improving recovery from disease status caused by Leishmania infantum infection and warrants additional study.

Epigenetics in the treatment of systemic lupus erythematosus: potential clinical application

The current treatments of systemic lupus erythematosus (SLE) have been based on the use of immunosuppressive drugs which are linked to serious side effects. The more effective therapeutic approaches with minimal or no side effects for SLE patients are hard to develop, mainly due to the complexity of the disease. The discovery of pharmacoepigenetics provides a new way to solve this problem. Epigenetic modifications can influence drug efficacy by altering gene expression via changing chromatin structure. Although still in early development, epigenetic studies in SLE are expected to reveal novel therapeutic targets and disease biomarkers in autoimmunity. For example, miRNAs, which have been identified to govern many genes including drug targets, are altered in disease development and after drug administration. This review aims to present an overview of current epigenetic mechanisms involved in the pathogenesis of SLE, and discuss their potential roles in clinical and pharmacological applications.