Boosting regulatory T cell function for the treatment of autoimmune diseases – That’s only half the battle!

Regulatory T cells (Treg) represent a subset of specialized T cells that are essential for the regulation of immune responses and maintenance of peripheral tolerance. Once activated, Treg exert powerful immunosuppressive properties, for example by inhibiting T cell-mediated immune responses against self-antigens, thereby protecting our body from autoimmunity. Autoimmune diseases such as multiple sclerosis, rheumatoid arthritis or systemic lupus erythematosus, exhibit an immunological imbalance mainly characterized by a reduced frequency and impaired function of Treg. In addition, there has been increasing evidence that – besides Treg dysfunction – immunoregulatory mechanisms fail to control autoreactive T cells due to a reduced responsiveness of T effector cells (Teff) for the suppressive properties of Treg, a process termed Treg resistance. In order to efficiently treat autoimmune diseases and thus fully induce immunological tolerance, a combined therapy aimed at both enhancing Treg function and restoring Teff responsiveness could most likely be beneficial. This review provides an overview of immunomodulating drugs that are currently used to treat various autoimmune diseases in the clinic and have been shown to increase Treg frequency as well as Teff sensitivity to Treg-mediated suppression. Furthermore, we discuss strategies on how to boost Treg activity and function, and their potential use in the treatment of autoimmunity. Finally, we present a humanized mouse model for the preclinical testing of Treg-activating substances in vivo.

Gut microbiota and cardiovascular disease: opportunities and challenges

Coronary artery disease (CAD) is the most common health problem worldwide and remains the leading cause of morbidity and mortality. Over the past decade, it has become clear that the inhabitants of our gut, the gut microbiota, play a vital role in human metabolism, immunity, and reactions to diseases, including CAD. Although correlations have been shown between CAD and the gut microbiota, demonstration of potential causal relationships is much more complex and challenging. In this review, we will discuss the potential direct and indirect causal roots between gut microbiota and CAD development via microbial metabolites and interaction with the immune system. Uncovering the causal relationship of gut microbiota and CAD development can lead to novel microbiome-based preventative and therapeutic interventions. However, an interdisciplinary approach is required to shed light on gut bacterial-mediated mechanisms (e.g., using advanced nanomedicine technologies and incorporation of demographic factors such as age, sex, and ethnicity) to enable efficacious and high-precision preventative and therapeutic strategies for CAD.

Western Diet and the Immune System: An Inflammatory Connection

The consumption of Western-type calorically rich diets combined with chronic overnutrition and a sedentary lifestyle in Western societies evokes a state of chronic metabolic inflammation, termed metaflammation. Metaflammation contributes to the development of many prevalent non-communicable diseases (NCDs), and these lifestyle-associated pathologies represent a rising public health problem with global epidemic dimensions. A better understanding of how modern lifestyle and Western diet (WD) activate immune cells is essential for the development of efficient preventive and therapeutic strategies for common NCDs. Here, we review the current mechanistic understanding of how the Western lifestyle can induce metaflammation, and we discuss how this knowledge can be translated to protect the public from the health burden associated with their selected lifestyle.

Autoimmune Cytopenias in Chronic Lymphocytic Leukemia: Focus on Molecular Aspects

Autoimmune cytopenias, particularly autoimmune hemolytic anemia (AIHA) and immune thrombocytopenia (ITP), complicate up to 25% of chronic lymphocytic leukemia (CLL) cases. Their occurrence correlates with a more aggressive disease with unmutated VHIG status and unfavorable cytogenetics (17p and 11q deletions). CLL lymphocytes are thought to be responsible of a number of pathogenic mechanisms, including aberrant antigen presentation and cytokine production. Moreover, pathogenic B-cell lymphocytes may induce T-cell subsets imbalance that favors the emergence of autoreactive B-cells producing anti-red blood cells and anti-platelets autoantibodies. In the last 15 years, molecular insights into the pathogenesis of both primary and secondary AIHA/ITP has shown that autoreactive B-cells often display stereotyped B-cell receptor and that the autoantibodies themselves have restricted phenotypes. Moreover, a skewed T-cell repertoire and clonal T cells (mainly CD8+) may be present. In addition, an imbalance of T regulatory-/T helper 17-cells ratio has been involved in AIHA and ITP development, and correlates with various cytokine genes polymorphisms. Finally, altered miRNA and lnRNA profiles have been found in autoimmune cytopenias and seem to correlate with disease phase. Genomic studies are limited in these forms, except for recurrent mutations of KMT2D and CARD11 in cold agglutinin disease, which is considered a clonal B-cell lymphoproliferative disorder resulting in AIHA. In this manuscript, we review the most recent literature on AIHA and ITP secondary to CLL, focusing on available molecular evidences of pathogenic, clinical, and prognostic relevance.

Stem cell-derived tissue-associated regulatory T cells suppress the activity of pathogenic cells in autoimmune diabetes

The autoantigen-specific Tregs from pluripotent stem cells (PSCs), i.e., PSC-Tregs, have the ability to suppress autoimmunity. PSC-Tregs can be programmed to be tissue associated and to infiltrate into local inflamed tissues to suppress autoimmune responses after adoptive transfer. Nevertheless, the mechanisms by which the autoantigen-specific PSC-Tregs suppress the autoimmune response remain to be fully elucidated. In this study, we generated functional autoantigen-specific Tregs from the induced PSC (iPSCs), i.e., iPSC-Tregs, and investigated the underlying mechanisms of autoimmunity suppression by these Tregs in a type 1 diabetes (T1D) murine model. A double-Tg mouse model of T1D was established in F1 mice, in which the first generation of RIP-mOVA Tg mice that were crossed with OT-I T cell receptor (TCR) Tg mice was challenged with vaccinia viruses expressing OVA (VACV-OVA). We show that adoptive transfer of OVA-specific iPSC-Tregs greatly suppressed autoimmunity in the animal model and prevented the insulin-secreting pancreatic β cells from destruction. Further, we demonstrate that the adoptive transfer significantly reduced the expression of ICAM-1 in the diabetic pancreas and inhibited the migration of pathogenic CD8+ T cells and the production of the proinflammatory IFN-γ in the pancreas. These results indicate that the stem cell-derived tissue-associated Tregs can robustly accumulate in the diabetic pancreas, and, through downregulating the expression of ICAM-1 in the local inflamed tissues and inhibiting the production of proinflammatory cytokine IFN-γ, suppress the migration and activity of the pathogenic immune cells that cause T1D.

Ex vivo induction of regulatory T cells from conventional CD4+ T cells is sensitive to substrate rigidity

The immune system maintains a balance between protection and tolerance. Regulatory T cells (Tregs) function as a vital tolerance mechanism in the immune system to suppress effector immune cells. Additionally, Tregs can be utilized as a form of immunotherapy for autoimmune disorders. As T cells have previously been shown to exhibit sensitivity to the rigidity of an activating substrate upon activation via IL-2 secretion, we herein explore the previously unknown effect of substrate rigidity on the induction of Tregs from conventional naïve mouse CD4+ T cells. Substrates with modulatable rigidities ranging from a hundred kilopascals to a few megapascals were fabricated via poly(dimethylsiloxane). We found that there was a significant increase in Treg induction at lower substrate rigidities (i.e., E ~ 100 kPa) compared to higher rigidity levels (i.e., E ~ 3 MPa). To confirm that this significant difference in induction rate was truly related to T-cell mechanosensing, we administered compound Y-27632 to inhibit myosin contractility. In the presence of Y-27632, the myosin-based contractility was disrupted and, as a result, the difference in Treg induction caused by the substrate rigidity was abrogated. This study demonstrates that mechanosensing is involved in Treg induction and raises questions about the underlying molecular mechanisms involved in this process. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 3001-3008, 2018.

Phase I Study of Random Healthy Donor-Derived Allogeneic Natural Killer Cell Therapy in Patients with Malignant Lymphoma or Advanced Solid Tumors

Natural killer (NK) cells with mismatched killer cell immunoglobulin-like receptor-ligand pairs have shown efficacy and been proven safe in treatment of cancer patients. Ex vivo-expanded and highly activated NK cells (MG4101) had been generated under good manufacturing practice conditions, which demonstrated potent anticancer activity in vitro and in vivo in preclinical studies. The current phase I clinical trial was designed to evaluate safety and possible clinical efficacy of repetitive administrations of MG4101 derived from random unrelated healthy donors into patients with malignant lymphoma or advanced, recurrent solid tumors. The maximum dose (3 × 10(7) cells/kg, triple infusion) was tolerable without significant adverse events. Of 17 evaluable patients, 8 patients (47.1%) showed stable disease and 9 (52.9%) showed progressive disease. We also evaluated the capacity of MG4101 to influence host immune responses. Administration of MG4101 augmented NKG2D expression on CD8(+) T cells and upregulated chemokines that recruit T cells. In contrast, administration of MG4101 reduced regulatory T cells and myeloid-derived suppressor cells and suppressed TGFβ production. In conclusion, administration of a large number of MG4101 cells was not only safe and feasible, but also exhibited efficacy in maintaining the effector arm of the host immune response.

Role of Regulatory T Cells (Treg) and the Treg Effector Molecule Fibrinogen-like Protein 2 in Alloimmunity and Autoimmunity

CD4(+)CD25(+)Foxp3(+) regulatory T cells (Treg) are critical to the maintenance of immune tolerance. Treg are known to utilize a number of molecular pathways to control immune responses and maintain immune homeostasis. Fibrinogen-like protein 2 (FGL2) has been identified by a number of investigators as an important immunosuppressive effector of Treg, which exerts its immunoregulatory activity by binding to inhibitory FcγRIIB receptors expressed on antigen-presenting cells including dendritic cells, endothelial cells, and B cells. More recently, it has been suggested that FGL2 accounts for the immunosuppressive activity of a highly suppressive subset of Treg that express T cell immunoreceptor with Ig and ITIM domains (TIGIT). Here we discuss the important role of Treg and FGL2 in preventing alloimmune and autoimmune disease. The FGL2-FcγRIIB pathway is also known to be utilized by viruses and tumor cells to evade immune surveillance. Moving forward, therapies based on modulation of the FGL2-FcγRIIB pathway hold promise for the treatment of a wide variety of conditions ranging from autoimmunity to cancer.

Adoptive cell transfer in autoimmune hepatitis

Adoptive cell transfer is an intervention in which autologous immune cells that have been expanded ex vivo are re-introduced to mitigate a pathological process. Tregs, mesenchymal stromal cells, dendritic cells, macrophages and myeloid-derived suppressor cells have been transferred in diverse immune-mediated diseases, and Tregs have been the focus of investigations in autoimmune hepatitis. Transferred Tregs have improved histological findings in animal models of autoimmune hepatitis and autoimmune cholangitis. Key challenges relate to discrepant findings among studies, phenotypic instability of the transferred population, uncertain side effects and possible need for staged therapy involving anti-inflammatory drugs. Future investigations must resolve issues about the purification, durability and safety of these cells and consider alternative populations if necessary.

Killer B lymphocytes and their fas ligand positive exosomes as inducers of immune tolerance

Induction of immune tolerance is a key process by which the immune system is educated to modulate reactions against benign stimuli such as self-antigens and commensal microbes. Understanding and harnessing the natural mechanisms of immune tolerance may become an increasingly useful strategy for treating many types of allergic and autoimmune diseases, as well as for improving the acceptance of solid organ transplants. Our laboratory and others have been interested in the natural ability of some B lymphocytes to express the death-inducing molecule Fas ligand (FasL), and their ability to kill T helper (T_H) lymphocytes. We have recently shown that experimental transformation of human B cells by a non-replicative variant of Epstein-Barr virus (EBV) consistently resulted in high expression of functional FasL protein. The production and release of FasL⁺ exosomes that co-expressed major histocompatibility complex (MHC) class II molecules and had the capacity to kill antigen-specific T_H cells was also observed. Several lines of evidence indicate that FasL+ B cells and FasL⁺MHCII⁺ exosomes have important roles in natural immune tolerance and have a great deal of therapeutic potential. Taken together, these findings suggest that EBV-immortalized human B lymphoblastoid cell lines could be used as cellular factories for FasL⁺ exosomes, which would be employed to therapeutically establish and/or regain immune tolerance toward specific antigens. The goals of this review are to summarize current knowledge of the roles of FasL⁺ B cells and exosomes in immune regulation, and to suggest methods of manipulating killer B cells and FasL⁺ exosomes for clinical purposes.

Autoimmune cytopenias in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is frequently complicated by secondary autoimmune cytopenias (AIC) represented by autoimmune hemolytic anemia (AIHA), immune thrombocytopenia (ITP), pure red cell aplasia, and autoimmune granulocytopenia. The distinction of immune cytopenias from cytopenias due to bone marrow infiltration, usually associated with a worse outcome and often requiring a different treatment, is mandatory. AIHA and ITP are more frequently found in patients with unfavorable biological risk factors for CLL. AIC secondary to CLL respond less favorably to standard treatments than their primary forms, and treating the underlying CLL with chemotherapy or monoclonal antibodies may ultimately be necessary.

Fast food fever: reviewing the impacts of the Western diet on immunity

While numerous changes in human lifestyle constitute modern life, our diet has been gaining attention as a potential contributor to the increase in immune-mediated diseases. The Western diet is characterized by an over consumption and reduced variety of refined sugars, salt, and saturated fat. Herein our objective is to detail the mechanisms for the Western diet's impact on immune function. The manuscript reviews the impacts and mechanisms of harm for our over-indulgence in sugar, salt, and fat, as well as the data outlining the impacts of artificial sweeteners, gluten, and genetically modified foods; attention is given to revealing where the literature on the immune impacts of macronutrients is limited to either animal or in vitro models versus where human trials exist. Detailed attention is given to the dietary impact on the gut microbiome and the mechanisms by which our poor dietary choices are encoded into our gut, our genes, and are passed to our offspring. While today's modern diet may provide beneficial protection from micro- and macronutrient deficiencies, our over abundance of calories and the macronutrients that compose our diet may all lead to increased inflammation, reduced control of infection, increased rates of cancer, and increased risk for allergic and auto-inflammatory disease.

Effects of parental omega-3 fatty acid intake on offspring microbiome and immunity

The "Western diet" is characterized by increased intake of saturated and omega-6 (n-6) fatty acids with a relative reduction in omega-3 (n-3) consumption. These fatty acids can directly and indirectly modulate the gut microbiome, resulting in altered host immunity. Omega-3 fatty acids can also directly modulate immunity through alterations in the phospholipid membranes of immune cells, inhibition of n-6 induced inflammation, down-regulation of inflammatory transcription factors, and by serving as pre-cursors to anti-inflammatory lipid mediators such as resolvins and protectins. We have previously shown that consumption by breeder mice of diets high in saturated and n-6 fatty acids have inflammatory and immune-modulating effects on offspring that are at least partially driven by vertical transmission of altered gut microbiota. To determine if parental diets high in n-3 fatty acids could also affect offspring microbiome and immunity, we fed breeding mice an n-3-rich diet with 40% calories from fat and measured immune outcomes in their offspring. We found offspring from mice fed diets high in n-3 had altered gut microbiomes and modestly enhanced anti-inflammatory IL-10 from both colonic and splenic tissue. Omega-3 pups were protected during peanut oral allergy challenge with small but measurable alterations in peanut-related serologies. However, n-3 pups displayed a tendency toward worsened responses during E. coli sepsis and had significantly worse outcomes during Staphylococcus aureus skin infection. Our results indicate excess parental n-3 fatty acid intake alters microbiome and immune response in offspring.

The effect of autoimmune arthritis treatment strategies on regulatory T-cell dynamics

PURPOSE OF REVIEW

Since their discovery over 15 years ago, intensive research has focused on the presence, phenotype and function of FOXP3(+) regulatory T cells (Treg) in autoimmune diseases such as rheumatoid arthritis (RA). The questions of whether Treg deficiencies underlie autoimmune pathology and whether or how Treg-related therapeutic approaches might be successful are still a subject of a vivid debate. In this review we give an overview of how current therapies influence Treg numbers and function in RA and juvenile idiopathic arthritis (JIA) and discuss these findings in the light of new Treg-based intervention strategies for autoimmune arthritis.

RECENT FINDINGS

The attempt to relate rheumatic diseases like rheumatoid arthritis and juvenile idiopathic arthritis to Treg has led to somewhat heterogeneous observations. So far, no clear defects in Treg numbers or function have been identified in autoimmune arthritis. The current standard therapies, that is methotrexate and biologicals, are generally effective, but the exact mechanism of action and their effect on Treg is not fully known. Nevertheless, the majority of in-vitro and ex-vivo data point towards a positive influence of these treatments on Treg number and function. These observations are not all consistent, however, and it is not known whether the observed effects on Treg are primary or secondary effects. To safely conduct targeted regulatory T-cell therapy in rheumatic diseases more knowledge about regulatory T-cell function in an inflammatory environment is needed that coincides with the initiative to elucidate the exact mechanism of current therapies.

Parental dietary fat intake alters offspring microbiome and immunity

Mechanisms underlying modern increases in prevalence of human inflammatory diseases remain unclear. The hygiene hypothesis postulates that decreased microbial exposure has, in part, driven this immune dysregulation. However, dietary fatty acids also influence immunity, partially through modulation of responses to microbes. Prior reports have described the direct effects of high-fat diets on the gut microbiome and inflammation, and some have additionally shown metabolic consequences for offspring. Our study sought to expand on these previous observations to identify the effects of parental diet on offspring immunity using mouse models to provide insights into challenging aspects of human health. To test the hypothesis that parental dietary fat consumption during gestation and lactation influences offspring immunity, we compared pups of mice fed either a Western diet (WD) fatty acid profile or a standard low-fat diet. All pups were weaned onto the control diet to specifically test the effects of early developmental fat exposure on immune development. Pups from WD breeders were not obese or diabetic, but still had worse outcomes in models of infection, autoimmunity, and allergic sensitization. They had heightened colonic inflammatory responses, with increased circulating bacterial LPS and muted systemic LPS responsiveness. These deleterious impacts of the WD were associated with alterations of the offspring gut microbiome. These results indicate that parental fat consumption can leave a "lard legacy" impacting offspring immunity and suggest inheritable microbiota may contribute to the modern patterns of human health and disease.

Comparison of induced versus natural regulatory T cells of the same TCR specificity for induction of tolerance to an environmental antigen

Recent evidence shows that natural CD25(+)Foxp3(+) regulatory T cells (nTreg) and induced CD25(+)Foxp3(+) regulatory T cells (iTreg) both contribute to tolerance in mouse models of colitis and asthma, but there is little evidence regarding their relative contributions to this tolerance. We compared the abilities of nTreg and iTreg, both from OVA-TCR-transgenic OTII mice, to mediate tolerance in OVA-asthmatic C57BL/6 mice. The iTreg were differentiated from Th2 effector T cells by exposure to IL-10-differentiated dendritic cells (DC10) in vitro or in vivo, whereas we purified nTreg from allergen-naive mice and exposed them to DC10 before use. Each Treg population was subsequently repurified and tested for its therapeutic efficacy in vitro and in vivo. DC10 engaged the nTreg in a cognate fashion in Forster (or fluorescence) resonance energy transfer assays, and these nTreg reduced in vitro OVA-asthmatic Th2 effector T cell responses by 41-56%, whereas the comparator iTreg reduced these responses by 72-86%. Neutralization of IL-10, but not TGF-β, eliminated the suppressive activities of iTreg but not nTreg. Delivery of 5 × 10(5) purified nTreg reduced allergen challenge-induced airway IL-4 (p ≤ 0.03) and IL-5 (p ≤ 0.001) responses of asthmatic recipients by ≤ 23% but did not affect airway hyperresponsiveness or IgE levels, whereas equal numbers of iTreg of identical TCR specificity reduced all airway responses to allergen challenge by 82-96% (p ≤ 0.001) and fully normalized airway hyperresponsiveness. These data confirm that allergen-specific iTreg and nTreg have active roles in asthma tolerance and that iTreg are substantially more tolerogenic in this setting.

An exploratory study of the interplay between decreased concentration of tryptophan, accumulation of kynurenines, and inflammatory arthritis

Tryptophan is an essential amino acid which influences a wide range of physiological processes, including mood, cognition, and immunity. In the autoimmune diseases, such as rheumatoid arthritis (RA), the induction of tryptophan catabolism may help to diminish exacerbated immune responses. In this study, using collagen-induced arthritis (CIA) in DBA/1 mice which is an animal model of RA, the endogenous activity of the kynurenine pathway in the immune system was monitored before and after onset of the disease. An increased rate of the initiation of tryptophan catabolism via the kynurenine pathway throughout CIA has been observed. However, decreased tryptophan concentration in the lymph nodes from pre-arthritic mice was not enough to prevent development of CIA. In contrast, resolution of inflammation coincided with the decreased concentration of tryptophan and accumulation of its catabolites: kynurenine, anthranilic acid, and 3-hydroxyanthranilic acid in lymph nodes but not in the spleen. In addition, the lack of the accumulation of kynurenine and its downstream metabolites in the pre-arthritic lymph nodes coincided with increased mRNA expression for genes involved in the catabolism of kynurenine (Kynureninase, kynurenine 3-monooxygenase, and 3-hydroxyanthranilate 3,4 dioxygenase). However, in the lymph nodes from mice with established CIA, mRNA expression for these genes was normalized. Hence, keeping in mind an exploratory character of the results, it can be postulated that an anti-inflammatory role of the kynurenine pathway reaches its full potential only when decreased concentration of tryptophan coincides with accumulation of kynurenines driven by metabolic regulation of gene expression on the kynurenine pathway.

Systemic metabolism of tryptophan and its catabolites, kynurenine and 3-HAA, in mice with inflammatory arthritis

Tryptophan is an essential amino acid. The liver is primary organ involved the oxidative catabolism of tryptophan. However, in the immune system, tryptophan and its catabolites, kynurenine and 3-hydroxyanthranilic acid (3-HAA), play an anti-inflammatory role. Rheumatoid arthritis (RA) is an autoimmune disease. Collagen induced arthritis (CIA) is an animal model of RA. Therefore, it was of interest to measure concentration of tryptophan, kynurenine and 3-HAA in mice with CIA. Concentration of tryptophan and 3-HAA was measured with HPLC methods. Concentration of kynurenine was measured with colorimetric test. mRNA expression for the kynurenine pathway genes was assessed using qRT-PCR. It has been found that in sera from diseased mice concentration of tryptophan was not changed. Concentration of kynurenine and 3-HAA was decreased. Moreover, in the livers from mice with CIA, concentration of tryptophan and kynurenine was decreased. These observations coincided with decreased mRNA expression for Ido2 and Afm and increased mRNA expression for Kynureninase in the liver. It has been also shown that in CIA the concentration of 3-HAA was increased in the kidneys.

Regulatory T-cells in chronic lymphocytic leukemia and autoimmune diseases

Regulatory T-cells (Tregs) constitute a small subset of cells that are actively involved in maintaining self-tolerance, in immune homeostasis and in antitumor immunity. They are thought to play a significant role in the progression of cancer and are generally increased in patient with chronic lymphocytic leukemia (CLL). Their number correlates with more aggressive disease status and is predictive of the time to treatment, as well. Moreover, it is now clear that dysregulation in Tregs cell frequency and/or function may result in a plethora of autoimmune diseases, including multiple sclerosis, type 1 diabetes mellitus, myasthenia gravis, systemic lupus erythematosus, autoimmune lymphoproliferative disorders, rheumatoid arthritis, and psoriasis. Efforts are made aiming to develop approaches to deplete Tregs or inhibit their function in cancer and autoimmune disorders, as well.

Preserved function of regulatory T cells in chronic HIV-1 infection despite decreased numbers in blood and tissue

Regulatory T cells (Tregs) are potent immune modulators, but their role in human immunodeficiency virus type 1 (HIV-1) pathogenesis remains poorly understood. We performed a detailed analysis of the frequency and function of Tregs in a large cohort of HIV-1-infected individuals and HIV-1 negative controls. While HIV "elite controllers" and uninfected individuals had similar Treg numbers and frequencies, the absolute numbers of Tregs declined in blood and gut-associated lymphoid tissue in patients with chronic progressive HIV-1 infection. Despite quantitative changes in Tregs, HIV-1 infection was not associated with an impairment of ex vivo suppressive function of flow-sorted Tregs in both HIV controllers and untreated chronic progressors.

Therapeutic potential of Tregs to treat rheumatoid arthritis

There is accumulating evidence for regulatory T cell defects in rheumatoid arthritis and that some biologic interventions, in particular anti-TNF, can target this population. Despite the challenges in defining regulatory T cells in patients, there are a number of approaches currently being developed to utilise their potent immunosuppressive properties. Through genetic manipulation Tregs can be generated ex vivo or in vivo that target antigens present in the inflamed joint. Here we discuss these approaches, their refinement to restore tolerance in patients with rheumatoid arthritis, and strategies to prevent their conversion towards a Th17 phenotype.