Critical evaluation of regulatory T cells in autoimmunity: are the most potent regulatory specificities being ignored?

Autophagy dysregulation plays a crucial role in regulatory T-cell loss and neuroinflammation in amyotrophic lateral sclerosis (ALS)

OBJECTIVE

Neuroinflammation is the hallmark of amyotrophic lateral sclerosis (ALS) disease. Regulatory T cells (Tregs) are essential in immune tolerance and neuroinflammation prevention. It has been shown that a significant decrease in Treg and FoxP3 protein expression is observed in ALS patients. The main reason for the FoxP3+ Treg loss in ALS is unknown. In this study, the role of autophagy dysregulation in FoxP3+ Tregs in ALS was investigated.

METHODS

Twenty-three ALS patients and 24 healthy controls were recruited for the study. Mononuclear cells (MNCs) were obtained from peripheral blood, and then Tregs were isolated. Isolated Tregs were stained with FoxP3 and LC3 antibodies and analyzed in flow cytometry to determine autophagy levels in FoxP3+ Tregs in patients and controls.

RESULTS

The mean of FoxP3+ LC3+ cells, were 0.47 and 0.45 in patients and controls, respectively. The mean of FoxP3+ LC3- cells was 0.15 in patients and 0.20 in controls, p = 0.030 (p < 0.05). There is no significant correlation between ALSFRS-R decay rate and autophagy level in patients. Also, there is no significant difference between autophagy levels in FoxP3+ Tregs in patients with rapidly progressing ALS and slow-progressing ALS.

CONCLUSION

Excessive autophagy levels in FoxP3+ Tregs in ALS patients can potentially be an explanation for an increased cell death and result in worsened neuroinflammation and disease onset. However, the disease progress is not attributable to autophagy levels in FoxP3+ Tregs.

The potential for Treg-enhancing therapies in transplantation

Since the discovery of regulatory T cells (Tregs) as crucial regulators of immune tolerance against self-antigens, these cells have become a promising tool for the induction of donor-specific tolerance in transplantation medicine. The therapeutic potential of increasing in vivoTreg numbers for a favorable Treg to Teff cell ratio has already been demonstrated in several sophisticated pre-clinical models and clinical pilot trials. In addition to improving cell quantity, enhancing Treg function utilizing engineering techniques led to encouraging results in models of autoimmunity and transplantation. Here we aim to discuss the most promising approaches for Treg-enhancing therapies, starting with adoptive transfer approaches and ex vivoexpansion cultures (polyclonal vs. antigen specific), followed by selective in vivostimulation methods. Furthermore, we address next generation concepts for Treg function enhancement (CARs, TRUCKs, BARs) as well as the advantages and caveats inherit to each approach. Finally, this review will discuss the clinical experience with Treg therapy in ongoing and already published clinical trials; however, data on long-term results and efficacy are still very limited and many questions that might complicate clinical translation remain open. Here, we discuss the hurdles for clinical translation and elaborate on current Treg-based therapeutic options as well as their potencies for improving long-term graft survival in transplantation.

Immune Checkpoint Ligand Bioengineered Schwann Cells as Antigen-Specific Therapy for Experimental Autoimmune Encephalomyelitis

Failure to establish immune tolerance leads to the development of autoimmune disease. The ability to regulate autoreactive T cells without inducing systemic immunosuppression represents a major challenge in the development of new strategies to treat autoimmune disease. Here, a translational method for bioengineering programmed death-ligand 1 (PD-L1)- and cluster of differentiation 86 (CD86)-functionalized mouse Schwann cells (SCs) to prevent and ameliorate multiple sclerosis (MS) in established mouse models of chronic and relapsing-remitting experimental autoimmune encephalomyelitis (EAE) is described. It is shown that the intravenous (i.v.) administration of immune checkpoint ligand functionalized mouse SCs modifies the course of disease and ameliorates EAE. Further, it is found that such bioengineered mouse SCs inhibit the differentiation of myelin-specific helper T cells into pathogenic T helper type-1 (Th 1) and type-17 (Th 17) cells, promote the development of tolerogenic myelin-specific regulatory T (Treg ) cells, and resolve inflammatory central nervous system microenvironments without inducing systemic immunosuppression.

Potential Diagnostic Approaches for Prediction of Therapeutic Responses in Immune Thrombocytopenia

Immune thrombocytopenia (ITP) is an autoimmune bleeding disorder in which, via unresolved mechanisms, platelets and megakaryocytes (MKs) are targeted by autoantibodies and/or T cells resulting in increased platelet destruction and impairment of MK function. Over the years, several therapeutic modalities have become available for ITP, however, therapeutic management has proven to be very challenging in several cases. Patients refractory to treatment can develop a clinically worsening disease course, treatment-induced toxicities and are predisposed to development of potentially life-endangering bleedings. It is therefore of critical importance to timely identify potential refractory patients, for which novel diagnostic approaches are urgently needed in order to monitor and predict specific therapeutic responses. In this paper, we propose promising diagnostic investigations into immune functions and characteristics in ITP, which may potentially be exploited to help predict platelet count responses and thereby distinguish therapeutic responders from non-responders. This importantly includes analysis of T cell homeostasis, which generally appears to be disturbed in ITP due to decreased and/or dysfunctional T regulatory cells (Tregs) leading to loss of immune tolerance and initiation/perpetuation of ITP, and this may be normalized by several therapeutic modalities. Additional avenues to explore in possible prediction of therapeutic responses include examination of platelet surface sialic acids, platelet apoptosis, monocyte surface markers, B regulatory cells and platelet microparticles. Initial studies have started evaluating these markers in relation to response to various treatments including glucocorticosteroids (GCs), intravenous immunoglobulins (IVIg) and/or thrombopoietin receptor agonists (TPO-RA), however, further studies are highly warranted. The systematic molecular analysis of a broad panel of immune functions may ultimately help guide and improve personalized therapeutic management in ITP.

Cross-Talk of the CNS With Immune Cells and Functions in Health and Disease

The immune system's role is much more than merely recognizing self vs. non-self and involves maintaining homeostasis and integrity of the organism starting from early development to ensure proper organ function later in life. Unlike other systems, the central nervous system (CNS) is separated from the peripheral immune machinery that, for decades, has been envisioned almost entirely as detrimental to the nervous system. New research changes this view and shows that blood-borne immune cells (both adaptive and innate) can provide homeostatic support to the CNS via neuroimmune communication. Neurodegeneration is mostly viewed through the lens of the resident brain immune populations with little attention to peripheral circulation. For example, cognition declines with impairment of peripheral adaptive immunity but not with the removal of microglia. Therapeutic failures of agents targeting the neuroinflammation framework (inhibiting immune response), especially in neurodegenerative disorders, call for a reconsideration of immune response contributions. It is crucial to understand cross-talk between the CNS and the immune system in health and disease to decipher neurodestructive and neuroprotective immune mechanisms for more efficient therapeutic strategies.

Regulatory T Cell-Derived TRAIL Is Not Required for Peripheral Tolerance

TRAIL (Tnfsf10/TRAIL/CD253/Apo2L) is an important immune molecule that mediates apoptosis. TRAIL can play key roles in regulating cell death in the tumor and autoimmune microenvironments. However, dissecting TRAIL function remains difficult because of the lack of optimal models. We have now generated a conditional knockout (Tnfsf10 L/L) for cell type-specific analysis of TRAIL function on C57BL/6, BALB/c, and NOD backgrounds. Previous studies have suggested a role for TRAIL in regulatory T cell (Treg)-mediated suppression. We generated mice with a Treg-restricted Tnfsf10 deletion and surprisingly found no impact on tumor growth in C57BL/6 and BALB/c tumor models. Furthermore, we found no difference in the suppressive capacity of Tnfsf10-deficient Tregs and no change in function or proliferation of T cells in tumors. We also assessed the role of TRAIL on Tregs in two autoimmune mouse models: the NOD mouse model of autoimmune diabetes and the myelin oligodendrocyte glycoprotein (MOG) C57BL/6 model of experimental autoimmune encephalomyelitis. We found that deletion of Tnfsf10 on Tregs had no effect on disease progression in either model. We conclude that Tregs do not appear to be dependent on TRAIL exclusively as a mechanism of suppression in both the tumor and autoimmune microenvironments, although it remains possible that TRAIL may contribute in combination with other mechanisms and/or in different disease settings. Our Tnfsf10 conditional knockout mouse should prove to be a useful tool for the dissection of TRAIL function on different cell populations in multiple mouse models of human disease.

Adoptive transfer of Tregs: A novel strategy for cell-based immunotherapy in spontaneous abortion: Lessons from experimental models

Since half of the genes are inherited from the paternal side, the maternal immune system has to tolerate the presence of foreign paternal antigens. Regulatory T cells facilitate the development and maintenance of peripheral tissue tolerance of the fetus during pregnancy. Reduction in regulatory T cells is associated with complications of pregnancy, including spontaneous abortion. Recent studies in mouse models have shown that the adoptive transfer of Tregs can prevent spontaneous abortion in mouse models through improving maternal tolerance. Thus, adoptive cell therapy using autologous Tregs could potentially be a novel therapeutic approach for cell-based immunotherapy in women with unexplained spontaneous abortion. Besides, strategies for activating and expanding antigen-specific Tregs ex vivo and in vivo based on pharmacological agents can pave the foundation for an approach incorporating immunotherapy and pharmacotherapy. This review aims to elaborate on the current understanding of the therapeutic potential of the adoptive transfer of Tregs in the treatment of spontaneous abortion disease.

T cell receptor sequencing in autoimmunity

T cells are an integral component of the adaptive immune response via the recognition of peptides by the cell surface-expressed T cell receptor (TCR). Rearrangement of the TCR genes results in a highly polymorphic repertoire on the T cells within a given individual. Although the diverse repertoire is beneficial for immune responses to foreign pathogens, recognition of self-peptides by T cells can contribute to the development of autoimmune disorders. Increasing evidence supports a pathogenic role for T cells in autoimmune pathology, and it is of interest to determine the TCR repertoires involved in autoimmune disease development. In this review, we summarize methodologies and advancements in the TCR sequencing field and discuss recent studies focused on TCR sequencing in a variety of autoimmune conditions. The rapidly evolving methodology of TCR sequencing has the potential to allow for a better understanding of autoimmune disease pathogenesis, identify disease-specific biomarkers, and aid in developing therapies to prevent and treat a number of these disorders.

Regulating the regulators: Is introduction of an antigen-specific approach in regulatory T cells the next step to treat autoimmunity?

In autoimmunity, the important and fragile balance between immunity and tolerance is disturbed, resulting in abnormal immune responses to the body's own tissues and cells. CD4⁺CD25^hiFoxP3⁺ regulatory T cells (Tregs) induce peripheral tolerance in vivo by means of direct cell-cell contact and release of soluble factors, or indirectly through antigen-presenting cells (APC), thereby controlling auto-reactive effector T cells. Based on these unique capacities of Tregs, preclinical studies delivered proof-of-principle for the clinical use of Tregs for the treatment of autoimmune diseases. To date, the first clinical trials using ex vivo expanded polyclonal Tregs have been completed. These pioneering studies demonstrate the feasibility of generating large numbers of polyclonal Tregs in a good manufacturing practices (GMP)-compliant manner, and that infusion of Tregs is well tolerated by patients with no evidence of general immunosuppression. Nonetheless, only modest clinical results were observed, arguing that a more antigen-specific approach might be needed to foster a durable patient-specific clinical cell therapy without the risk for general immunosuppression. In this review, we discuss current knowledge, applications and future goals of adoptive immune-modulatory Treg therapy for the treatment of autoimmune disease and transplant rejection. We describe the key advances and prospects of the potential use of T cell receptor (TCR)- and chimeric antigen receptor (CAR)-engineered Tregs in future clinical applications. These approaches could deliver the long-awaited breakthrough in stopping undesired autoimmune responses and transplant rejections.

The Next Frontier of Regulatory T Cells: Promising Immunotherapy for Autoimmune Diseases and Organ Transplantations

Regulatory T cells (Tregs) are crucial in maintaining tolerance. Hence, Treg immunotherapy is an attractive therapeutic option in autoimmune diseases and organ transplantations. Currently, autoimmune diseases do not have a curative treatment and transplant recipients require life-long immunosuppression to prevent graft rejection. There has been significant progress in understanding polyclonal and antigen-specific Treg biology over the last decade. Clinical trials with good manufacturing practice (GMP) Treg cells have demonstrated safety and early efficacy of Treg therapy. GMP Treg cells can also be tracked following infusion. In order to improve efficacy of Tregs immunotherapy, it is necessary that Tregs migrate, survive and function at the specific target tissue. Application of antigen specific Tregs and maintaining cells' suppressive function and survival with low dose interleukin-2 (IL-2) will enhance the efficacy and longevity of infused GMP-grade Tregs. Notably, stability of Tregs in the local tissue can be manipulated by understanding the microenvironment. With the recent advances in GMP-grade Tregs isolation and antigen-specific chimeric antigen receptor (CAR)-Tregs development will allow functionally superior cells to migrate to the target organ. Thus, Tregs immunotherapy may be a promising option for patients with autoimmune diseases and organ transplantations in near future.

The Future of Regulatory T Cell Therapy: Promises and Challenges of Implementing CAR Technology

Cell therapy with polyclonal regulatory T cells (Tregs) has been translated into the clinic and is currently being tested in transplant recipients and patients suffering from autoimmune diseases. Moreover, building on animal models, it has been widely reported that antigen-specific Tregs are functionally superior to polyclonal Tregs. Among various options to confer target specificity to Tregs, genetic engineering is a particularly timely one as has been demonstrated in the treatment of hematological malignancies where it is in routine clinical use. Genetic engineering can be exploited to express chimeric antigen receptors (CAR) in Tregs, and this has been successfully demonstrated to be robust in preclinical studies across various animal disease models. However, there are several caveats and a number of strategies should be considered to further improve on targeting, efficacy and to understand the in vivo distribution and fate of CAR-Tregs. Here, we review the differing approaches to confer antigen specificity to Tregs with emphasis on CAR-Tregs. This includes an overview and discussion of the various approaches to improve CAR-Treg specificity and therapeutic efficacy as well as addressing potential safety concerns. We also discuss different imaging approaches to understand the in vivo biodistribution of administered Tregs. Preclinical research as well as suitability of methodologies for clinical translation are discussed.

The evolving role of TonEBP as an immunometabolic stress protein

Tonicity-responsive enhancer-binding protein (TonEBP), which is also known as nuclear factor of activated T cells 5 (NFAT5), was discovered 20 years ago as a transcriptional regulator of the cellular response to hypertonic (hyperosmotic salinity) stress in the renal medulla. Numerous studies since then have revealed that TonEBP is a pleiotropic stress protein that is involved in a range of immunometabolic diseases. Some of the single-nucleotide polymorphisms (SNPs) in TONEBP introns are cis-expression quantitative trait loci that affect TONEBP transcription. These SNPs are associated with increased risk of type 2 diabetes mellitus, diabetic nephropathy, inflammation, high blood pressure and abnormal plasma osmolality, indicating that variation in TONEBP expression might contribute to these phenotypes. In addition, functional studies have shown that TonEBP is involved in the pathogenesis of rheumatoid arthritis, atherosclerosis, diabetic nephropathy, acute kidney injury, hyperlipidaemia and insulin resistance, autoimmune diseases (including type 1 diabetes mellitus and multiple sclerosis), salt-sensitive hypertension and hepatocellular carcinoma. These pathological activities of TonEBP are in contrast to the protective actions of TonEBP in response to hypertonicity, bacterial infection and DNA damage induced by genotoxins. An emerging theme is that TonEBP is a stress protein that mediates the cellular response to a range of pathological insults, including excess caloric intake, inflammation and oxidative stress.

Characterization of proinsulin-specific regulatory T cells in type 1 diabetes at different ages of onset

BACKGROUND AND OBJECTIVES

Regulatory T cells (Tregs) play an important role in maintaining tolerance to self-antigens. Defects in the frequency and function of polyclonal Tregs have been reported in type 1 diabetes (T1D). However, characteristics of proinsulin (PI)-specific Tregs in human T1D have not yet been explored. Therefore, we aimed to characterize PI-specific Tregs in two distinct pathophysiological subtypes of T1D, juvenile-onset T1D (JOT1D) and adult-onset T1D (AOT1D), distinguished by the age of onset.

METHODS

Peripheral blood mononuclear cells of the recruited subjects were stimulated in vitro with PI-derived peptides. PI-specific Tregs were characterized by flow cytometry using the combination of markers CD25, CD137, FOXP3 and CD45RA.

RESULTS

Firstly, we observed similar frequencies of polyclonal Tregs in the T1D (n = 25) and healthy control (HC) (n = 20) subjects (P = 0.96), with a positive correlation between age and frequency of polyclonal Tregs (r = +0.35, P = 0.04). While the frequency of polyclonal Tregs was higher in AOT1D group (P = 0.02), both JOT1D (n = 14) and AOT1D groups (n = 11) had a comparable frequency of PI-specific Tregs in their peripheral blood. The frequency of PI-specific memory Tregs was significantly high in both the JOT1D (P = 0.02) and AOT1D (P = 0.009) groups compared to their respective HC groups (n = 10). Finally, we observed no significant difference in the expression of FOXP3 and IL-2 receptor in PI-specific Tregs in all the groups.

CONCLUSIONS

Unlike polyclonal Tregs, both T1D subtypes harbor comparable frequencies of PI-specific Tregs. Chronic antigen presentation results in a distinct memory-like phenotype of PI-specific Tregs in these subjects irrespective of the age of disease onset.

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.

The influence and impact of ageing and immunosenescence (ISC) on adaptive immunity during multiple sclerosis (MS) and the animal counterpart experimental autoimmune encephalomyelitis (EAE)

The human ageing process encompasses mechanisms that effect a decline in homeostasis with increased susceptibility to disease and the development of chronic life-threatening illness. Increasing age affects the immune system which undergoes a progressive loss of efficiency, termed immunosenescence (ISC), to impact on quantitative and functional aspects of innate and adaptive immunity. The human demyelinating disease multiple sclerosis (MS) and the corresponding animal model experimental autoimmune encephalomyelitis (EAE) are strongly governed by immunological events that primarily involve the adaptive arm of the immune response. MS and EAE are frequently characterised by a chronic pathology and a protracted disease course which thereby creates the potential for exposure to the inherent, on-going effects and consequences of ISC. Collective evidence is presented to confirm the occurrence of established and unendorsed biological markers of ISC during the development of both diseases. Moreover, results are discussed from studies during the course of MS and EAE that reveal a premature upregulation of ISC-related biomarkers which indicates untimely alterations to the adaptive immune system. The effects of ISC and a prematurely aged immune system on autoimmune-associated neurodegenerative conditions such as MS and EAE are largely unknown but current evaluation of data justifies and encourages further investigation.

Regulatory T cell-based therapies for autoimmunity

Autoimmune disorders are long-term diseases that adversely affect the quality of life for patients, and they are one of the top ten leading causes of death. While each autoimmune disorder is unique, they all are caused by a breakdown of tolerance against endogenous proteins. This leads to auto-inflammatory events that promote the destruction of organs in a humoral and cellular immune mediated manner. Treatment options for autoimmunity can involve the use of chemical and biologic agents that suppress inflammation. While these treatment options for patients have shown to be beneficial in autoimmunity, they can result in patients being vulnerable to opportunistic infections. Newer therapies aim to identify methods to specifically block auto-inflammatory immune cells while allowing for an intact immune response to other antigens. T regulatory (Treg) cells are a subtype of the adoptive immune cell that is capable of suppressing inflammatory events in an antigen-specific manner, but they are often poorly functioning within autoimmune patients. Treg cells have been well characterized for their immune modulating capabilities and preclinical and early clinical studies support their therapeutic potential for antigen-specific immune suppression. This review will examine the current understanding of Treg cell function and the therapeutic potential of enhancing Treg cells in patients with inflammatory disorders.

Manipulating regulatory T cells: a promising strategy to treat autoimmunity

CD4(+)CD25(+)Foxp3(+)regulatory T cells (Treg cells) are extremely important in maintaining immune tolerance. Manipulation of Treg cells, especially autoantigen-specific Treg cells is a promising approach for treatments of autoimmune disease since Treg cells may provide the advantage of antigen specificity without overall immune suppression. However, the clinical application of Treg cells has long been limited due to low numbers of Treg cells and the difficulty in identifying their antigen specificity. In this review, we summarize studies that demonstrate regression of autoimmune diseases using Treg cells as therapeutics. We also discuss approaches to generate polyclonal and autoantigen-specific Treg cells in vitro and in vivo. We also discuss our recent study that describes a novel approach of generating autoantigen-specific Treg cells in vivo and restoring immune tolerance by two steps apoptosis-antigen therapy.

Continuum model of T-cell avidity: Understanding autoreactive and regulatory T-cell responses in type 1 diabetes

Type 1 diabetes (T1D) is an autoimmune disease that results from the destruction of insulin-secreting pancreatic β cells, leading to abolition of insulin secretion and onset of diabetes. Cytotoxic CD4(+) and CD8(+) T cells, activated by antigen presenting cells (APCs), are both implicated in disease onset and progression. Regulatory T cells (Tregs), on the other hand, play a leading role in regulating immunological tolerance and resistant homoeostasis in T1D by suppressing effector T cells (Teffs). Recent data indicates that after activation, conventional Teffs transiently produce interleukin IL-2, a cytokine that acts as a growth factor for both Teffs and Tregs. Tregs suppress Teffs through IL-2 deprivation, competition and Teff conversion into inducible Tregs (iTregs). To investigate the interactions of these components during T1D progression, a mathematical model of T-cell dynamics is developed as a predictor of β-cell loss, with the underlying hypothesis that avidity of Teffs and Tregs, i.e., the binding affinity of T-cell receptors to peptide-major histocompatibility complexes on host cells, is continuum. The model is used to infer a set of criteria that determines susceptibility to T1D in high risk subjects. Our findings show that diabetes onset is guided by the absence of Treg-to-Teff dominance at specific high avidities, rather than over the whole range of avidity, and that the lack of overall dominance of Teffs-to-Tregs over time is the underlying cause of the "honeymoon period", the remission phase observed in some T1D patients. The model also suggests that competition between Teffs and Tregs is more effective than Teff-induction into iTregs in suppressing Teffs, and that a prolonged full width at half maximum of IL-2 release is a necessary condition for curbing disease onset. Finally, the model provides a rationale for observing rapid and slow progressors of T1D based on modest heterogeneity in the kinetic parameters.

The immunobiology of apotransferrin in type 1 diabetes

The transferrin (Tf) family of iron binding proteins includes important endogenous modulators of the immune function that may modulate autoimmune diseases. To define more clearly the role of apotransferrin (apoTf) in type 1 diabetes we determined the impact of this protein on type 1 diabetes as investigated in islet cells, animal models and patient sera. First, we demonstrated that recombinant apoTf counteracts the cytokine-induced death of murine pancreatic islet cells. Secondly, human apoTf administration favourably influences the course of type 1 diabetes in animal models, resulting in protection against disease development that was associated with reduction of insulitis and reduced levels of proinflammatory cytokines. Finally, we confirmed that patients with newly diagnosed type 1 diabetes manifest significantly lower apoTf serum levels compared to healthy controls and patients with long-lasting disease. In conclusion, our data suggest the apoTf pivotal role in the perpetuation of type 1 diabetes pathology.

Thymic gene transfer of myelin oligodendrocyte glycoprotein ameliorates the onset but not the progression of autoimmune demyelination

Tolerance induction, and thus prevention of autoimmunity, is linked with the amount of self-antigen presented on thymic stroma. We describe that intrathymic (i.t.) delivery of the autoantigen, myelin oligodendrocyte glycoprotein (MOG), via a lentiviral vector (LV), led to tolerance induction and prevented mice from developing fulminant experimental autoimmune encephalomyelitis (EAE). This protective effect was associated with the long-term expression of antigen in transduced stromal cells, which resulted in the negative selection of MOG-specific T cells and the generation of regulatory T cells (Tregs). These selection events were effective at decreasing T-cell proliferative responses and reduced Th1 and Th17 cytokines. In vivo, this translated to a reduction in inflammation and demyelination with minimal, or no axonal loss in the spinal cords of treated animals. Significantly intrathymic delivery of MOG to mice during the priming phase of the disease failed to suppress clinical symptoms despite mice being previously treated with a clearing anti-CD4 antibody. These results indicate that targeting autoantigens to the thymic stroma might offer an alternative means to induce the de novo production of tolerant, antigen-specific T cells; however, methods that control the number and or the activation of residual autoreactive cells in the periphery are required to successfully treat autoimmune neuroinflammation.

Regulatory T cells play a role in T-cell receptor CDR2 peptide regulation of experimental autoimmune encephalomyelitis

Eliciting T-cell receptor (TCR) -specific responsiveness has been known to provide an effective autoregulatory mechanism for limiting inflammation mediated by T effector cells. Our previous use of TCR peptides derived from the CDR3 regions of a pathogenic TCR effectively reversed ongoing experimental autoimmune encephalomyelitis (EAE) in a humanized TCR transgenic model. In this study, we use the TCR BV8S2 CDR2 peptide in the non-transgenic C57BL/6 EAE model to down-regulate the heterogeneous TCR BV8S2(+)  MOG-35-55-specific pathogenic T-cell population and demonstrate successful treatment of EAE after disease onset. Suppression of disease was associated with reduced MOG-35-55-specific and non-specific T-cell production of interleukin-17a and interferon-γ in the central nervous system, as well as reduced numbers of CD4(+) and Foxp3(+) T cells in the central nervous system. With the use of Foxp3-GFP and Foxp3 conditional knockout mice, we demonstrate that the TCR CDR2 peptide treatment effect is dependent on the presence of Foxp3(+) regulatory T cells and that regulatory T cell numbers are significantly expanded in the periphery of treated mice. Hence, TCR CDR2 peptide therapy is effective in regulating heterogeneous, pathogenic T-cell populations through the activity of the Foxp3(+) regulatory T cell population.

Probiotic upregulation of peripheral IL-17 responses does not exacerbate neurological symptoms in experimental autoimmune encephalomyelitis mouse models

CONTEXT

It is of great importance to evaluate the safety of probiotics in dysregulated immune conditions, as probiotics can possibly modulate immune functions in the host.

OBJECTIVE

We tried to confirm the safety of using Lactobacillus casei strain Shirota (LcS) to help prevent autoimmunity in the central nervous system.

METHODS

We used two chronic experimental autoimmune encephalomyelitis (EAE) models, a relapse and remission type EAE model in SJL/J mice and a durable type model in C57BL/6 mice. LcS was administered from 1 week before antigen sensitization until the end of the experiments, and neurological symptoms and histopathological changes of the spinal cord were observed. Immunological parameters were also examined in the SJL/J mouse model.

RESULTS

LcS administration did not exacerbate neurological symptoms or histopathological changes of the spinal cord in either model but instead tended to improve neurological symptoms in the SJL/J mouse EAE model. LcS administration transiently upregulated IL-17 production by antigen-stimulated lymphocytes of draining lymph nodes 7 days after sensitization. Enhanced production of IL-10 and an increase in the percentage of CD4(+)CD25(+) T regulatory cells were also observed at the same sites. Strong expression of IL-17 mRNA was detected in the spinal cord of mice that displayed severe neurological symptoms on day 12, but this expression was not enhanced by LcS administration.

CONCLUSION

These results demonstrate that LcS does not exacerbate, but instead may improve EAE depending on the immunization conditions, and that IL-17 responses at peripheral sites may not always result in a worsening of autoimmune diseases.

Experimental autoimmune encephalomyelitis evolution was not modified by multiple infections with Strongyloides venezuelensis

According to the hygiene hypothesis, the increased incidence of allergic and autoimmune diseases in developed countries is mainly explained by the decreased contact between the human population and certain environmental agents as lactobacillus, mycobacteria and helminths. In this study, we evaluated the effect of multiple infections with Strongyloides venezuelensis on the development of experimental autoimmune encephalomyelitis (EAE) in Lewis rats. Multiple infections before EAE induction were not able to change the evolution of the disease. No alterations were observed in weight loss, clinical score and inflammation intensity at the central nervous system. The presence of significant levels of parasite-specific IgG1 but not IgG2b suggested a Th2 polarization. However, the percentage and absolute number of CD4+CD25+Foxp3+ T cells were not changed, being their levels in the spleen and lymph nodes of infected rats comparable to the ones found in normal animals. These results suggest that a Th2-polarized response without concomitant expansion of Foxp3+ regulatory T cells was not able to modify EAE progression. Even though these results do not threaten the hygiene hypothesis, they suggest that this paradigm might be an oversimplification. They also emphasize the need of a study to compare the immunoregulatory ability associated with different helminth spp.

Dendritic cell generation and CD4+ CD25high FOXP3+ regulatory t cells in human head and neck carcinoma during radio-chemotherapy

Background

Regulatory T cells (Treg) and dendritic cells (DC) play an important role in tumor immunity and immune escape. However, their interplay and the effects of anti-cancer therapy on the human immune system are largely unknown.

Methods

For DC generation, CD14⁺ monocytes were enriched by immunomagnetic selection from peripheral blood of advanced head and neck squamous cell carcinoma (HNSCC) patients and differentiated into immature DC using GM-SCF and IL-4. DC maturation was induced by addition of TNFα. The frequency of CD4⁺CD25^highF0XP3⁺ Treg in HNSCC patients was analyzed before and after radio-chemotherapy (RCT) by four-color flow cytometry.

Results

In HNSCC patients, the frequency of Treg (0.33 ± 0.06%) was significantly (p = 0.001) increased compared to healthy controls (0.11 ± 0.02%), whereas RCT had variable effects on the Treg frequency inducing its increase in some patients and decrease in others. After six days in culture, monocytes of all patients had differentiated into immature DC. However, DC maturation indicated by CD83 up-regulation (70.7 ± 5.5%) was successful only in a subgroup of patients and correlated well with lower frequencies of peripheral blood Treg in those patients.

Conclusion

The frequency of regulatory T cells is elevated in HNSCC patients and may be modulated by RCT. Monocyte-derived DC in HNSCC patients show a maturation deficiency ex vivo. Those preliminary data may have an impact on multimodality clinical trials integrating cellular immune modulation in patients with advanced HNSCC.

HE3286, an orally bioavailable synthetic analogue of an active DHEA metabolite suppresses spontaneous autoimmune diabetes in the non-obese diabetic (NOD) mouse

5-Androstene-3β,7β,17β-triol (AET) is a naturally occurring anti-inflammatory adrenal steroid that limits acute and chronic inflammation. HE3286 (17α-ethynyl-5-androstene-3β,7β,17β-triol) is a synthetic derivative of AET with improved pharmaceutical properties and efficacy in some animal models of autoimmunity. Here, daily oral doses of HE3286 led to a suppression of spontaneous autoimmune diabetes in the non-obese diabetic mouse model of type 1 diabetes mellitus when administered either shortly before or after the first incidence of disease onset. Efficacy was associated with reduced insulitis and a suppression of the pathogenic T helper cell type 1 and type 17 phenotypes in peripheral lymphoid organs. These results demonstrate that daily oral treatment with HE3286 administrated relatively late in the destructive autoimmune process led to a suppression of type 1 diabetes mellitus onset and of the pathological inflammatory status, supporting its clinical evaluation in type 1 diabetes mellitus subjects.

Adenosine deaminase potentiates the generation of effector, memory, and regulatory CD4+ T cells

By interacting with CD26 on the CD4+ T cell surface and with the AdoR A(₂B) on the DC surface, ADA triggers a costimulatory signal for human T cells. The aim of this study was to know whether ADA-mediated costimulation plays a role in the differentiation of T cells. The results show that irrespective of its enzymatic activity and dependent on TNF-α, IFN-γ, and IL-6 action, ADA enhanced the differentiation of CD4+CD45RA+CD45RO⁻ naïve T cells toward CD4+CD25+CD45RO+ Teffs and CD4+CD45RA⁻CD45RO+ memory T cells. Furthermore, ADA potentiated generation of CD4+CD25(high)Foxp3+ Tregs by a mechanism that seems to be mainly dependent on the enzymatic activity of ADA. Interestingly, an ADA-mediated increase on Teff, memory T cell, and Treg generation occurred, not only in cocultures from healthy individuals but also from HIV-infected patients. These data suggest that ADA is a relevant modulator of CD4+ T cell differentiation, even in cells from immunologically compromised individuals.

Naturally occurring CD4+CD25+ regulatory T cells prevent but do not improve experimental myasthenia gravis

In the current study, we investigated whether naturally occurring CD4(+)CD25(+) T cells, separated by immunomagnetic anti-CD4 and anti-CD25 Abs from naive animals, are able to protect from experimental autoimmune myasthenia gravis (EAMG) and modify the progression of ongoing disease when administered to Torpedo californica acetylcholine receptor (AChR)-immunized Lewis rats. Even though CD4(+)CD25(+) and CD4(+)CD25(high) T cell frequencies were similar in the spleens and lymph nodes of EAMG and healthy rats, we observed that CD4(+)CD25(+) T cells isolated from the spleens of naive animals inhibited in vitro the Ag-induced proliferation of T cell lines specific to the self-peptide 97-116 of the anti-AChR subunit (R97-116), an immunodominant and myasthenogenic T cell epitope, whereas CD4(+)CD25(+) T cells purified from the spleens of EAMG rats were less effective. CD4(+)CD25(+) T cells from EAMG rats expressed less forkhead box transcription factor P3 but more CTLA-4 mRNA than healthy rats. Naive CD4(+)CD25(+) T cells, obtained from naive rats and administered to T. californica AChR-immunized animals according to a preventive schedule of treatment, reduced the severity of EAMG, whereas their administration 4 wk postinduction of the disease, corresponding to the onset of clinical symptoms (therapeutic treatment), was not effective. We think that the exogenous administration of CD4(+)CD25(+) naive T cells prevents the early events underlying the induction of EAMG, events linked to the T cell compartment (Ag recognition, epitope spreading, and T cell expansion), but fails to ameliorate ongoing EAMG, when the IgG-mediated complement attack to the AChR at the neuromuscular junction has already taken place.

Role of regulatory T cells in rheumatoid arthritis: facts and hypothesis

Regulatory T cells (Treg) are a CD4⁺ lymphocyte subset involved in self-tolerance and autoimmunity prevention. There is evidence for a phenotypic and/or functional impairment of this cell subset during the natural history of several chronic autoimmune/inflammatory diseases, including rheumatoid arthritis (RA). Although the intracellular transcription factor FoxP3 is thought to be the master regulator of Treg cell function, a number of other molecules expressed on the cell surface have been proposed for the identification of Treg cells. This is important in order to favour their possible selective isolation and in the development of new therapeutic strategies. In the present paper, available data on phenotypic and functional characterization of Treg cells in both peripheral blood and synovial fluid from RA patients are reviewed and their possible pathogenic role in triggering and perpetuating rheumatoid joint inflammation is discussed.

The biology of FoxP3: a key player in immune suppression during infections, autoimmune diseases and cancer

The Transcription factor FoxP3 belongs to the forkhead/winged-helix family of transcriptional regulators and shares general structural features with other FoxP family members. FoxP3 functions as a master of transcription for the development of regulatory T-cells (Treg cells) both in humans and in mice. Natural genetic mutations ofFoxP3 that disrupt its function in humans result in an autoimmune syndrome called Immune Polyendocrinopathy, Enteropathy, X-linked (IPEX) and in mice, its deletion causes the Scurfy phenotype, with similar pathology. The finding that FoxP3 is required for the development and function of Tregs has led to an explosion of research in determining its regulation and function in the immune system. Understanding the biological properties of FoxP3 has a wide range of implications for immune tolerance, autoimmune disorders, inflammation and immune response to infectious diseases and cancer.

Prevention and treatment of experimental autoimmune encephalomyelitis with clonotypic CDR3 peptides: CD4(+) Foxp3(+) T-regulatory cells suppress interleukin-2-dependent expansion of myelin basic protein-specific T cells

T-cell receptor (TCR)-derived peptides are recognized by the immune system and are capable of modulating autoimmune responses. Using the myelin basic protein (MBP) TCR 1501 transgenic mouse model, we demonstrated that TCR CDR3 peptides from the transgenic TCR can provide a protective effect when therapy is initiated before the induction of experimental autoimmune encephalomyelitis (EAE). More importantly, TCR CDR3 peptide therapy can ameliorate the disease when administered after EAE onset. Concurrent with the therapeutic effects, we observed reduced T-cell proliferation and reduced interleukin-2 (IL-2) levels in response to stimulation with MBP-85-99 peptide in splenocyte cultures from mice receiving TCR CDR3 peptides compared with that of control mice. Moreover, we found that Foxp3(+) CD4 T cells from mice protected with TCR CDR3 peptide are preferentially expanded in the presence of IL-2. This is supportive of a proposed mechanism where Foxp3(+) T-regulatory cells induced by therapy with MBP-85-99 TCR CDR3 peptides limit expansion and the encephalitogenic activity of MBP-85-99-specific T cells by regulating the levels of secreted IL-2.

Regulatory T cells and autoimmunity

PURPOSE OF REVIEW

The identification of regulatory T cells (Tregs) as regulators of immunological self-tolerance has stimulated tremendous interest in the field. Over the past 12 months, new studies have added greatly to our understanding of the role of Tregs in autoimmune disease, details of which are presented here.

RECENT FINDINGS

In this review, the mechanism of action of Tregs, their antigen specificity and their frequency and function in different autoimmune diseases is explored. Currently available data on the role of transforming growth factor-beta, the reciprocal relationship between Tregs and Th17 cells, Treg markers, and current therapeutic approaches are evaluated. Other regulatory cells, which have been recently identified to play a significant role in autoimmunity, are described.

SUMMARY

Increasing insights into understanding the complex mechanisms of action of Tregs have already led to exciting therapeutic advances. This review provides an in-depth analysis of recent advances in the field of Tregs in autoimmunity. It highlights targets for future immunomodulatory therapy that may treat and potentially cure autoimmune disease, and it identifies areas for future research.

Self-peptides prolong survival in murine autoimmunity via reduced IL-2/IL-7-mediated STAT5 signaling, CD8 coreceptor, and V alpha 2 down-regulation

Although the pathogenic role of B cells and CD4 T cells has been studied extensively, less is known about the role of CD8 T cells in autoimmunity and self-tolerance. To evaluate the role of CD8 T cells in autoimmunity and its modulation using self-peptides, we used mice expressing soluble OVA (sOVA) under control of the keratin-14 promoter. Spontaneous autoimmunity occurred when sOVA mice were crossed with OT-I mice, whose CD8 T cells carry a Valpha2/Vbeta5-transgenic TCR with specificity for the OVA(257-264) peptide. Eighty-three percent of OVA/OT-I mice died during the first 2 wk of life due to multiple organ inflammation. In contrast, preventive or therapeutic OVA(257-264) peptide injections induced a dose-dependent increase in survival. Healthy survivors exhibited reductions in peripheral CD8 T cells, CD8 coreceptor, and Valpha2 expression. Furthermore, CD8 T cells from healthy mice were anergic and could not be activated by exogenous IL-2. A block in IL-2/IL-7 signaling via the STAT5 pathway provided the basis for low surface expression of the CD8 coreceptor and failure of IL-2 to break CD8 T cell anergy. Thus, the soluble TCR ligand triggered multiple tolerance mechanisms in these sOVA/OT-I mice, making this treatment approach a potential paradigm for modulating human autoimmune diseases.