Induction Of Peripheral Tolerance Research Articles

Anergy-derived Foxp3+ T regulatory cell differentiation in the neonatal mouse

Abstract The neonatal period is a natural scenario to study the effects of peripheral self-antigen (Ag) recognition by autoreactive conventional CD4+ T cells under conditions of low Foxp3+ T regulatory cell (Treg) numbers and function. Moreover, the neonatal environment is an interesting scenario to study the relationship between the induction of CD4+ T cell anergy and the peripheral generation of anergy-derived Tregs, given that anergy induction relies on normal Treg function whereas anergy-derived Treg generation is optimal in the setting of Treg cell deficiency. We have hypothesized that the neonatal period is both necessary and sufficient to allow for the induction of anergy as well as the peripheral differentiation of anergy-derived Foxp3+ Tregs from naive conventional CD4+ T cells during self-Ag recognition. To test our hypotheses we developed a system of neonatal peripheral tolerance induction. Neonatal pups engineered to express the experimental “self” peptide Ag chicken ovalbumin (OVAp) were given OVAp/I-Ab–specific OT-II CD4+ T cells, and the pups were later examined for anergy induction, Treg differentiation, and development of autoimmunity. Our data demonstrate that in the neonatal period: 1) previously naive CD4+ T cells express markers of anergy following exposure to self-Ag, and a small fraction of these cells can be seen to differentiate to a Foxp3+ Treg phenotype, and 2) previously anergic CD4+ T cells typically retain their anergic phenotype but also give rise to a substantial fraction of Foxp3+ Tregs, and 3) animals remain free of autoimmune disease. These findings suggest that during the neonatal period peripheral Foxp3+ Treg cell differentiation may proceed through a conventional anergic CD4+ T cell intermediate.

OP09 Immunomodulatory mechanisms of faecal microbiota transplantation are associated with clinical response in ulcerative colitis: early results from STOP-Colitis

Abstract Background Studies of faecal microbiota transplantation (FMT) for treating ulcerative colitis (UC) have shown promising results. Mechanisms by which FMT modulates inflammation, however, remain unexplored. Through a prospective, open-label pilot of FMT in UC (STOP-Colitis) we conducted a sub-study to explore changes in host colonic mucosal immune cell subsets and gene expression following FMT. Methods Patients in this study received eight infusions of FMT over an 8-week period. Colon biopsies and blood were obtained at baseline and at the end of the study. Immunophenotyping of colonic lamina propria mononuclear cells (LPMC) and peripheral blood mononuclear cells (PBMC) was conducted. RNA sequencing was performed on colon biopsies for differential gene expression analysis followed by multi-omic integration. Results Seventeen patients were recruited to this sub-study; of which, 12 completed 8 weeks of FMT per protocol. Response (reduction in MAYO score) was seen in 67% (8/12) of patients. Analysis of colonic LPMC populations revealed a significant increase in regulatory T cells (Tregs, CD4+CD25+CD127lowFoxP3+; Δ 5.02%; p < 0.01), especially effector memory Treg subset (CD4+CD25+CD127-CCR7-CD45RA-; Δ 12%; p < 0.001), gut homing Tregs (CD4+CD25+CD127-CCR7-CD45RA-α4+; Δ 18.55%; p < 0.01) and IL-10 producing CD4 cells (Δ 2.16%; p = 0.04) in responders following FMT. Along with this, there was a significant reduction in mucosal Th17 cell (CD4+CD161+CCR6+; Δ −7.61%; p = 0.017), IL-17 producing CD4 cell (Δ −7.69%; p = 0.05) and CD8 cell (Δ -5.18%; p = 0.04) populations in FMT responders. Colonic mucosal gene expression and pathway analysis demonstrated that response to FMT was associated with significant downregulation of host antimicrobial defence response mainly REG and defensin family of anti-microbial peptides, pathogen-associated molecular pattern binding receptors, proteases, multiple MHC class II genes associated with antigen presentation and proinflammatory immune pathways. There was a significant upregulation of butanoate and propionate metabolic pathways in FMT responders. Analysis of PBMC revealed a significant increase in IL-10 producing CD4 cells suggesting that induction of peripheral immune tolerance is preferentially compartmentalised to the gut mucosa. Conclusion Response to FMT is associated with a significant increase in mucosal gut homing Tregs and butanoate metabolism along with a reduction in Th17 cells and multiple anti-microbial defence and proinflammatory pathways. FMT induces change in immune balance in local milieu which leads to clinical response in UC. Exploring microbial mediators in FMT which influence immunometabolism is now under investigation to underpin novel biotherapeutic approaches.

Annexin-coated particles induce antigen-specific immunosuppression

Apoptotic cells mediate the development of tolerogenic dendritic cells (DC) and thus facilitate induction and maintenance of peripheral tolerance. Following the identification of the evolutionary conserved annexin core domain (Anx) as a specific signal on apoptotic cells which antagonises Toll-like receptor (TLR) signalling, we examined whether the tolerogenic capacity of Anx can be exploited to downregulate antigen-specific immune responses. The treatment of bone marrow-derived dendritic cells (BMDC) with particles harbouring Anx as well as the model antigen ovalbumin (OVA) attenuated the response of OVA-specific OT-II T cells. The co-culture of Anx-particle-treated DC and T cells resulted in an anergy-like phenotype characterized by reduced proliferation and cytokine secretion. Here we demonstrate that the anti-inflammatory effects of Anx which are mediated through DC can be used as a tool to generate a particle-based antigen delivery system that promotes antigen-specific immunosuppression. Such Anx-particles may be a new therapeutic approach for the treatment of autoimmune diseases.

Regulation of lung immunity by dendritic cells: Implications for asthma, chronic obstructive pulmonary disease and infectious disease.

Since the first description of dendritic cells by Steinman and Cohn in 1973, this important cell type has gained increasing attention. Over 4000 papers have been published on this topic annually during the last few years. At the beginning, dendritic cells were recognized for their immune stimulatory properties and their importance in initiating an adaptive immune response. Later, it was found that dendritic cells do not only initiate but also regulate immune responses. This attribute makes the so-called regulatory dendritic cells highly important for the prevention of exaggerated immune responses. Immune cells make contact with different Ags every day and must be tightly controlled to prevent excessive inflammation and subsequent organ destruction, particularly in organs such as the gut and lungs. Here, we give a brief overview of our current knowledge on how immune responses are controlled by dendritic cells, highlighting how they are involved in the induction of peripheral tolerance. We focus on what is known about these processes in the lung, with a closer look at their role in the induction and control of diseases such as bronchial asthma, chronic obstructive pulmonary disease and lung infections. Finally, we summarize some current approaches to modulate the behavior of dendritic cells that may hopefully lead to future therapeutics to control exaggerated immune responses.

Past, Present, and Future of Regulatory T Cell Therapy in Transplantation and Autoimmunity.

Regulatory T cells (Tregs) are important for the induction and maintenance of peripheral tolerance therefore, they are key in preventing excessive immune responses and autoimmunity. In the last decades, several reports have been focussed on understanding the biology of Tregs and their mechanisms of action. Preclinical studies have demonstrated the ability of Tregs to delay/prevent graft rejection and to control autoimmune responses following adoptive transfer in vivo. Due to these promising results, Tregs have been extensively studied as a potential new tool for the prevention of graft rejection and/or the treatment of autoimmune diseases. Currently, solid organ transplantation remains the treatment of choice for end-stage organ failure. However, chronic rejection and the ensuing side effects of immunosuppressants represent the main limiting factors for organ acceptance and patient survival. Autoimmune disorders are chronic diseases caused by the breakdown of tolerance against self-antigens. This is triggered either by a numerical or functional Treg defect, or by the resistance of effector T cells to suppression. In this scenario, patients receiving high doses of immunosuppressant are left susceptible to life-threatening opportunistic infections and have increased risk of malignancies. In the last 10 years, a few phase I clinical trials aiming to investigate safety and feasibility of Treg-based therapy have been completed and published, whilst an increasing numbers of trials are still ongoing. The first results showed safety and feasibility of Treg therapy and phase II clinical trials are already enrolling. In this review, we describe our understanding of Tregs focussing primarily on their ontogenesis, mechanisms of action and methods used in the clinic for isolation and expansion. Furthermore, we will describe the ongoing studies and the results from the first clinical trials with Tregs in the setting of solid organ transplantation and autoimmune disorders. Finally, we will discuss strategies to further improve the success of Treg therapy.

TIPE2 in dendritic cells inhibits the induction of pTregs in the gut mucosa

Dendritic cells (DCs) are professional antigen-presenting cells. The main function of DCs is to process antigen and present it to the T cells to induce T cell immunity. In addition to their function as potent stimulators of adaptive immunity, DCs are also crucial for maintaining immunological tolerance through the induction of peripheral regulatory T cells. Tumor necrosis factor-α-induced protein 8-2 (Tumor necrosis factor-α induced protein-8-like 2, TNFAIP8L2 or TIPE2) was expressed primarily by immune cells and maintains immune tolerance through the negative regulation of innate and adaptive immune responses. Previous studies indicate that TIPE2 in DCs may inhibit the innate immune response to RNA. However, the role of TIPE2 in DCs in the induction of peripheral tolerance remains unknown. Our current study showed that Tipe2-deficient DCs are more immature under homeostatic condition and consequently promote the induction of peripheral Tregs in the gut mucosa. Mechanistic studies revealed that TIPE2 promotes the expression of DC maturation markers CD80 and CD86 through the activation of PI3K-PKCδ-MAPK signaling pathway during the differentiation of DCs. Taken together, these results indicate that, in addition to acting as a negative regulator of pathogen-induced immune response, TIPE2 in DCs is also capable of promoting immune response under homeostatic condition through the suppression of peripheral tolerance.

Anergy into T regulatory cells: an integration of metabolic cues and epigenetic changes at the Foxp3 conserved non-coding sequence 2.

Peripheral immune self-tolerance relies on protective mechanisms to control autoreactive T cells that escape deletion in the thymus. Suppression of autoreactive lymphocytes is necessary to avoid autoimmunity and immune cell–mediated damage of healthy tissues. An intriguing relationship has emerged between two mechanisms of peripheral tolerance—induction of anergy and Foxp3 + regulatory T (Treg) cells—and is not yet well understood. A subpopulation of autoreactive anergic CD4 T cells is a precursor of Treg cells. We now hypothesize that phenotypic and mechanistic features of Treg cells can provide insights to understand the mechanisms behind anergy-derived Treg cell differentiation. In this short review, we will highlight several inherent similarities between the anergic state in conventional CD4 T cells as compared with fully differentiated natural Foxp3 + Treg cells and then propose a model whereby modulations in metabolic programming lead to changes in DNA methylation at the Foxp3 locus to allow Foxp3 expression following the reversal of anergy.

Intravenous Administration of Recombinant Factor VIII Induces Immune Tolerance to Subcutaneous Turoctocog Alfa Pegol (SC N8-GP) in Humanized Hemophilia A Mice

IntroductionTuroctocog alfa pegol (N8-GP) is a glycoPEGylated recombinant factor VIII (rFVIII) under development for treatment of hemophilia A (HA). Patients with severe HA receiving intravenous (IV) replacement therapy have 20-40% risk of developing inhibitory FVIII antibodies. It is unclear whether the absence of inhibitors in some patients is due to lack of response or due to peripheral tolerance. Induction of peripheral tolerance may be dependent on regulatory T-cells (Tregs) since they are suggested to be involved in regulation of the anti-FVIII antibody response.In this study, tolerance induction following IV rFVIII administration was assessed in humanized HA mice, described as a suitable model for tolerance induction as only a fraction produce anti-FVIII antibodies after IV FVIII exposure (Steinitz KN, et al. Blood 2012;119(17):4073-4082).AimsTo explore whether IV exposure to rFVIII induces peripheral tolerance to subcutaneous N8-GP (SC N8-GP) exposure in humanized HA mice, and whether Tregs play a role in tolerance induction.MethodsHLA-DR transgenic FVIII-deficient mice lacking murine MHC class II were treated with rFVIII IV once per week for 8 weeks, then challenged with SC N8-GP once a week for 8 weeks. The role of CD25+ Tregs was studied by treating one group of mice with depleting anti-CD25 antibodies during the IV exposure period.The presence of anti-FVIII antibodies was measured prior to IV and SC dosing, and at study end. Mice with anti-FVIII antibodies after IV rFVIII exposure were excluded from the analysis.ResultsNo anti-FVIII antibodies were detected after challenge with SC N8-GP in mice pretreated with IV rFVIII. Depletion of CD25+ Tregs (confirmed by flow cytometry) during the IV exposure did not significantly affect the anti-FVIII antibody response.ConclusionIt was demonstrated that peripheral tolerance to SC N8-GP was induced in humanized HA mice not responding to IV rFVIII exposure. Depletion of CD25+ Tregs during IV exposure was insufficient to abolish the induction of tolerance. DisclosuresReedtz-Runge:Novo Nordisk A/S: Employment. Weldingh:Novo Nordisk A/S: Employment. Schiøler Schultz:Novo Nordisk A/S: Employment. Holm Millner:Novo Nordisk A/S: Employment. Rode:Novo Nordisk A/S: Employment. Wiinberg:Novo Nordisk A/S: Employment. Kjelgaard-Hansen:Novo Nordisk A/S: Employment.

Amelioration of regulatory T cells by Lactobacillus delbrueckii and Lactobacillus rhamnosus in pristane-induced lupus mice model.

Regulatory T cells (Tregs) play an indispensable role in the control of immune responses and induction of peripheral tolerance. Dysregulation of Tregs is involved in the pathogenesis of systemic lupus erythematosus (SLE). Tolerogenic probiotics have shown beneficial effects in the control of autoimmune diseases. We evaluated the prophylactic and therapeutic effects of Lactobacillus delbrueckii and Lactobacillus rhamnosus on Tregs and their related molecules in pristane-induced lupus mice model. Fifty-four female BALB/c mice (3-5 weeks) were randomly divided into nine groups. Lupus was induced in all groups using pristane. Prophylactic groups were treated from Day 0 (at the time of pristane injection) and treatment groups were treated 2 months later with L. rhamnosus, L. delbrueckii, mix of both probiotics, and prednisolone. One group was considered as SLE-induced control group without any treatment. Presence of antinuclear antibodies (ANA), antidouble-stranded DNA (anti-dsDNA), antiribonucleoprotein (anti-RNP), proteinuria, and serum level of creatinine, urea, the expression of forkhead box P3 (Foxp3), interleukin 6 (IL-6), IL-10,transforming growth factor β, and the number of Tregs were determined. SLE induction by pristane led to the formation of lipogranuloma, presence of ANA, anti-dsDNA, and anti-RNP. Probiotics consumption decreased the level of lipogranuloma, ANA, and anti-dsDNA. In addition, in probiotics receiving groups, Tregs and the expression level of Foxp3 increased, while IL-6 decreased. The effect of probiotics in the prophylactic group was more prominent. The results may indicate the effectiveness of L. delbrueckii and L. rhamnosus in the enhancement of Tregs and the decrease of inflammatory cytokines and disease severity in SLE-induced mice.

Neoantigen Vaccine Delivery for Personalized Anticancer Immunotherapy.

Cancer neoantigens derived from random somatic mutations in tumor tissue represent an attractive type of targets for the cancer immunotherapies including cancer vaccine. Vaccination against the tumor-specific neoantigens minimizes the potential induction of central and peripheral tolerance as well as the risk of autoimmunity. Neoantigen-based cancer vaccines have recently showed marked therapeutic potential in both preclinical and early-phase clinical studies. However, significant challenges remain in the effective and faithful identification of immunogenic neoepitopes and the efficient and safe delivery of the subunit vaccine components for eliciting potent and robust anticancer T cell responses. In this mini review, we provide a brief overview of the recent advances in the development of neoantigen-based cancer vaccines focusing on various vaccine delivery strategies for targeting and modulating antigen-presenting cells. We discuss current delivery approaches, including direct injection, ex vivo-pulsed dendritic cell vaccination, and biomaterial-assisted vaccination for enhancing the efficiency of neoantigen vaccines and present a perspective on future directions.

NKT Cells in the Liver are Important for Peripheral Tolerance Induction

NKT Cells in the Liver are Important for Peripheral Tolerance Induction

Role of E3 ubiquitin ligase GRAIL in B cell activation and tolerance

Abstract To date, B cells are believed to play a central role in pathogenesis of various autoimmune diseases as loss of B-cell tolerance with emergence of autoreactive B cells and pathogenic autoantibodies are the hallmark features of autoimmune disorders; however the intrinsic mechanisms that underlie initial breaks in B cell tolerance have not been completely defined. GRAIL, gene related to anergy in lymphocytes (encoded by Rnf128) is an E3 ubiquitin ligase associated with CD4+ and CD8+ T cell tolerance. Our data for first time show GRAIL expression in both mouse and human B cells, with higher expression in anergic B cells and that GRAIL deficiency in B cells leads to impaired B cell peripheral tolerance induction and greater susceptibility to autoimmune diseases. GRAIL deficient B cells exhibited hyperresponsivness in terms of proliferation and antibody production upon antigen stimulation in vitro and in vivo. Concomitantly, GRAIL-deficient B cells were less efficient in downregulation of IgM after B cell receptor (BCR) crosslinking and exhibited increased CD79a expression and activation leading to elevated activation of proximal BCR-signaling components and Ca2+mobilization; GRAIL expression promoted CD79a ubiquitination and degradation. Interestingly, GRAIL expression is also essential to control antigen-presenting property of B cells towards T helper 1 (Th1), Th2, Th17 and follicular helper T (Tfh) cells; since GRAIL deficiency in B cells leads to augmented development and function of Th1, Th2, Th17 and Tfh cells in vitro and in vivo. Thus, our results indicate that GRAIL is a crucial intrinsic factor controlling B cell activation and tolerance by targeting of BCR component CD79a for degradation.

NKG2D: A Master Regulator of Immune Cell Responsiveness

NKG2D is an activating receptor that is mostly expressed on cells of the cytotoxic arm of the immune system. Ligands of NKG2D are normally of low abundance, but can be induced in virtually any cell in response to stressors, such as infection and oncogenic transformation. Engagement of NKG2D stimulates the production of cytokines and cytotoxic molecules and traditionally this receptor is, therefore, viewed as a molecule that mediates direct responses against cellular threats. However, accumulating evidence indicates that this classical view is too narrow. During NK cell development, engagement of NKG2D has a long-term impact on the expression of NK cell receptors and their responsiveness to extracellular cues, suggesting a role in NK cell education. Upon chronic NKG2D engagement, both NK and T cells show reduced responsiveness of a number of activating receptors, demonstrating a role of NKG2D in induction of peripheral tolerance. The image that emerges is that NKG2D can mediate both inhibitory and activating signals, which depends on the intensity and duration of ligand engagement. In this review, we provide an overview of the impact of NKG2D stimulation during hematopoietic development and during acute and chronic stimulation in the periphery on responsiveness of other receptors than NKG2D. We propose that NKG2D interprets the context of the immunological environment through detection of cellular cues and in response sets the appropriate activation threshold for a large number of immune receptors. This perspective is of particular importance for future therapies that aim to exploit NKG2D signaling to fight tumors or infection.

Antigen presenting cell-targeted proinsulin expression converts insulin-specific CD8+ T-cell priming to tolerance in autoimmune-prone NOD mice.

Type 1 diabetes (T1D) results from autoimmune destruction of insulin-producing pancreatic β cells. Therapies need to incorporate strategies to overcome the genetic defects that impair induction or maintenance of peripheral T-cell tolerance and contribute to disease development. We tested whether the enforced expression of an islet autoantigen in antigen-presenting cells (APC) counteracted peripheral T-cell tolerance defects in autoimmune-prone NOD mice. We observed that insulin-specific CD8+ T cells transferred to mice in which proinsulin was transgenically expressed in APCs underwent several rounds of division and the majority were deleted. Residual insulin-specific CD8+ T cells were rendered unresponsive and this was associated with TCR downregulation, loss of tetramer binding and expression of a range of co-inhibitory molecules. Notably, accumulation and effector differentiation of insulin-specific CD8+ T cells in pancreatic lymph nodes was prominent in non-transgenic recipients but blocked by transgenic proinsulin expression. This shift from T-cell priming to T-cell tolerance exemplifies the tolerogenic capacity of autoantigen expression by APC and the capacity to overcome genetic tolerance defects.

Splenocyte Infusion and Whole-Body Irradiation for Induction of Peripheral Tolerance in Porcine Lung Transplantation: Modifications of the Preconditioning Regime for Improved Clinical Feasibility.

BackgroundPreoperative low-dose whole-body irradiation (IRR) with 1.5 and 7 Gy thymic IRR of the recipient, combined with a perioperative donor splenocyte infusion lead to reliable donor specific peripheral tolerance in our allogeneic porcine lung transplantation model. To reduce the toxicity of this preconditioning regime, modifications of the IRR protocol and their impact on allograft survival were assessed.MethodsLeft-sided single lung transplantation from major histocompatibility complex and sex mismatched donors was performed in 14 adult female minipigs. Recipient animals were exposed to 3 different protocols of nonmyeloablative IRR within 12 hours before transplantation. All animals were administered a donor splenocyte infusion on the day of lung transplantation. Intravenous pharmacologic immunosuppression was withdrawn after 28 postoperative days. Allograft survival was monitored by chest radiographs and bronchoscopy.ResultsIRR prolonged transplant survival in a dose- and field-dependent manner. Shielding of the bone marrow from IRR (total lymphoid IRR at 1.5 and 7 Gy thymic IRR) significantly reduced protocol toxicity defined as thrombocytopenia and consecutive increased bleeding propensity, but had a less effective impact on graft survival. Whole-body IRR at 0.5 and 7 Gy thymic IRR proved to be ineffective for reliable tolerance induction. Eventually, high levels of circulating CD4+CD25high regulatory T cells were present in long-term survivors.ConclusionsThese data show that the infusion of donor-specific alloantigen in combination with IRR is efficient once a threshold dose is exceeded.

Short-course rapamycin treatment enables engraftment of immunogenic gene-engineered bone marrow under low-dose irradiation to permit long-term immunological tolerance

BackgroundApplication of genetically modified hematopoietic stem cells is increasingly mooted as a clinically relevant approach to protein replacement therapy, immune tolerance induction or conditions where both outcomes may be helpful. Hematopoietic stem and progenitor cell (HSPC)-mediated gene therapy often requires highly toxic pretransfer recipient conditioning to provide a ‘niche’ so that transferred HSPCs can engraft effectively and to prevent immune rejection of neoantigen-expressing engineered HSPCs. For widespread clinical application, reducing conditioning toxicity is an important requirement, but reduced conditioning can render neoantigen-expressing bone marrow (BM) and HSC susceptible to immune rejection if immunity is retained.MethodsBM or HSPC-expressing OVA ubiquitously (actin.OVA) or targeted to MHC II+ cells was transferred using low-dose (300 cGy) total body irradiation. Recipients were administered rapamycin, cyclosporine or vehicle for 3 weeks commencing at BM transfer. Engraftment was determined using CD45 congenic donors and recipients. Induction of T-cell tolerance was tested by immunising recipients and analysing in-vivo cytotoxic T-lymphocyte (CTL) activity. The effect of rapamycin on transient effector function during tolerance induction was tested using an established model of tolerance induction where antigen is targeted to dendritic cells.ResultsImmune rejection of neoantigen-expressing BM and HSPCs after low-dose irradiation was prevented by a short course of rapamycin, but not cyclosporine, treatment. Whereas transient T-cell tolerance developed in recipients of OVA-expressing BM administered vehicle, only when engraftment of neoantigen-expressing BM was facilitated with rapamycin treatment did stable, long-lasting T-cell tolerance develop. Rapamycin inhibited transient effector function development during tolerance induction and inhibited development of CTL activity in recipients of OVA-expressing BM.ConclusionsRapamycin acts to suppress acquisition of transient T-cell effector function during peripheral tolerance induction elicited by HSPC-encoded antigen. By facilitating engraftment, short-course rapamycin permits development of long-term stable T-cell tolerance.

Overview of LAG-3-Expressing, IL-10-Producing Regulatory T Cells.

Regulatory T cells (Treg cells) play crucial roles in the induction of peripheral tolerance to self- and foreign-antigens. IL-10-producing regulatory T cells (IL-10-producing Treg cells) constitute a Treg cell subset characterized by the production of high amounts of IL-10, cytokine-mediated immunosuppressive capabilities, and independence of Foxp3 expression for their suppressive activity. In the past decade, identifying naturally occurring IL-10-producing Treg cells was difficult due to the lack of suitable surface markers. More recently, lymphocyte activation gene 3 (LAG-3) is a CD4 homologue that has been identified as a marker for IL-10-producing Treg cells. CD4+CD25-LAG3+ T cells produce large amounts of IL-10 and suppress colitis in a mouse model. These CD4+CD25-LAG3+ Treg cells also exhibit suppressive activity in murine models of lupus and humoral immunity in a TGF-β3-dependent manner. Moreover, the combined expression of LAG-3 and CD49b identifies IL-10-producing Treg cells in mice and humans more specifically. Recently, LAG-3 has gained more attention in the context of immune checkpoints because it believed to be related to T cell tolerance and exhausted T cells that infiltrate the tumor microenvironment. Tumors and the tumor microenvironment promote development of IL-10-producing Treg cells and fostertumorgrowth. This response might interfere with protective immune responses. Understanding LAG-3-expressing IL-10-producing Treg cells may contribute to the development of novel therapeutic strategies in immune-mediated diseases.

PD-1/PDL-1 pathway in patients with endometriosis

Introduction: Programmed death-1 (PD-1) is one of the most important inhibitory co-receptors. Studies show that the PD-1/PD-L1 pathway regulates the induction and maintenance of peripheral tolerance and protects tissues from attack in physiological conditions. Several studies have shown association of PD-1/PD-L1 pathway with several diseases although, to date, no such studies have been performed for endometriosis. Aims: The aim of this study was to describe the frequencies of T and B lymphocytes expressing PD-1 and PD-L1 molecules in patients with endometriosis. Material and methods: The expression of PD-1 and PD-L1 was analyzed using flow cytometry on T and B lymphocytes collected from 20 adult women with newly diagnosed, untreated endometriosis. The control group consisted of 20 healthy age-matched women. Results: We observed high expression of PD-1 and PD-L1 on analyzed lymphocytes subpopulations of patients with endometriosis. Among T cells, the expression of PD-1 on protein level was higher on CD4+ cells in patients (mean: 31.54 ± 13.74%) than in healthy controls (mean: 5.35 ± 1.54%, p < 0.001). Moreover, higher frequencies of PD-1 + /CD8 + cells and PD-1 + /CD19 + cells in the study group than in healthy volunteers were observed (mean: 18.71 ± 10.37% vs. 3.6 ± 1.45%, p = 0.015 and 12.07 ± 4.34% vs. 1.67 ± 0.84%, p = 0.017, respectively). There was a positive correlation between PD-1 + and PD-L1 + CD19 + B cells (r = 0.43, p = 0.026). Conclusion: High expression of PD-1 and PD-L1 on T and B cells could represent the hallmark of immune system reaction to chronic antigenic exposition in patients with endometriosis.

Mesenchymal Stromal Cell Secretion of Programmed Death-1 Ligands Regulates T Cell Mediated Immunosuppression.

Mesenchymal stromal cells (MSCs) exert broad immunosuppressive potential, modulating the activity of cells of innate and adaptive immune systems. As MSCs become accepted as a therapeutic option for the treatment of immunological disorders such as Graft versus Host Disease, our need to understand the intricate details by which they exert their effects is crucial. Programmed death‐1 (PD‐1) is an important regulator in T cell activation and homeostatic control. It has been reported that this pathway may be important in contact‐dependent mediated immunomodulation by MSCs. The aim of this study was to establish whether MSCs, in addition to their cell‐surface expression, are able to secrete PD‐1 ligands (PD‐L1 and PD‐L2) and their potential importance in modulating contact‐independent mechanisms of MSC immunosuppression. Here we report that MSCs express and secrete PD‐L1 and PD‐L2 and that this is regulated by exposure to interferon γ and tumor necrosis factor α. MSCs, via their secretion of PD‐1 ligands, suppress the activation of CD4+ T cells, downregulate interleukin‐2 secretion and induce irreversible hyporesponsiveness and cell death. Suppressed T cells demonstrated a reduction in AKT phosphorylation at T308 and a subsequent increase in FOXO3 expression that could be reversed with blockade of PD‐L1. In conclusion, we demonstrate for the first time, that MSCs are able to secrete PD‐1 ligands, with this being the first known report of a biological role for PD‐L2 in MSCs. These soluble factors play an important role in modulating immunosuppressive effects of MSCs directly on T cell behavior and induction of peripheral tolerance. Stem Cells 2017;35:766–776

What's Hot, What's New From the 2016 American Transplant Congress.

From June 11-15, 2016 the American Transplant Congress, the joint meeting of the American Society of Transplantation and the American Society of Transplant Surgeons, held its annual meeting in Boston, MA. The meeting, attended by 5200 registrants, included pre-meeting conferences, focused topic sessions, and hundreds of high-quality presentations from the transplant field. This meeting report highlights key findings from specific basic science, translational, and clinical research presentations deemed to have notable impact in thematic areas. In particular, there were a number of transformative studies indicating important advances in the understanding of alloimmunity, chronic rejection, tolerance, and organ-specific outcomes. Many of these results are discussed in the context of the published literature to showcase rapid advances in the transplant field.