Differential IL-21 signaling in APCs leads to disparate Th17 differentiation in diabetes-susceptible NOD and diabetes-resistant NOD.Idd3 mice

A surge in serum mucosal cytokines associated with seroconversion in children at risk for type 1 diabetes

AIMS/INTRODUCTION

Autoantibodies to pancreatic islet antigens identify young children at high risk of type 1 diabetes. On a background of genetic susceptibility, islet autoimmunity is thought to be driven by environmental factors, of which enteric viruses are prime candidates. We sought evidence for enteric pathology in children genetically at-risk for type 1 diabetes followed from birth who had developed islet autoantibodies ("seroconverted"), by measuring mucosa-associated cytokines in their sera.

MATERIALS AND METHODS

Sera were collected 3 monthly from birth from children with a first-degree type 1 diabetes relative, in the Environmental Determinants of Islet Autoimmunity (ENDIA) study. Children who seroconverted were matched for sex, age, and sample availability with seronegative children. Luminex xMap technology was used to measure serum cytokines.

RESULTS

Of eight children who seroconverted, for whom serum samples were available at least 6 months before and after seroconversion, the serum concentrations of mucosa-associated cytokines IL-21, IL-22, IL-25, and IL-10, the Th17-related cytokines IL-17F and IL-23, as well as IL-33, IFN-γ, and IL-4, peaked from a low baseline in seven around the time of seroconversion and in one preceding seroconversion. These changes were not detected in eight sex- and age-matched seronegative controls, or in a separate cohort of 11 unmatched seronegative children.

CONCLUSIONS

In a cohort of children at risk for type 1 diabetes followed from birth, a transient, systemic increase in mucosa-associated cytokines around the time of seroconversion lends support to the view that mucosal infection, e.g., by an enteric virus, may drive the development of islet autoimmunity.

Low-dose IL-2 reduces IL-21+ T cell frequency and induces anti-inflammatory gene expression in type 1 diabetes

Despite early clinical successes, the mechanisms of action of low-dose interleukin-2 (LD-IL-2) immunotherapy remain only partly understood. Here we examine the effects of interval administration of low-dose recombinant IL-2 (iLD-IL-2) in type 1 diabetes using high-resolution single-cell multiomics and flow cytometry on longitudinally-collected peripheral blood samples. Our results confirm that iLD-IL-2 selectively expands thymic-derived FOXP3⁺HELIOS⁺ regulatory T cells and CD56^bright NK cells, and show that the treatment reduces the frequency of IL-21-producing CD4⁺ T cells and of two innate-like mucosal-associated invariant T and V_γ9V_δ2 CD8⁺ T cell subsets. The cellular changes induced by iLD-IL-2 associate with an anti-inflammatory gene expression signature, which remains detectable in all T and NK cell subsets analysed one month after treatment. These findings warrant investigations into the potential longer-term clinical benefits of iLD-IL-2 in immunotherapy.

Aqueous extract of Passiflora alata leaves modulates in vitro the indoleamine 2,3-dioxygenase (IDO) and CD86 expression in bone marrow-derived professional antigen-presenting cells polarizing NOD mice T cells to a Treg profile

Dendritic cells (DCs) and macrophages are professional antigen-presenting cells (pAPCs), numerous in the pancreas of nonobese diabetic (NOD) mice and playing an essential role in the autoimmune response of type 1 diabetes. The expression of the enzyme indoleamine 2,3-dioxygenase (IDO) is a critical factor for the tolerogenic activity of pAPCs, acting in the catabolism of tryptophan, providing metabolites that suppress the T cell effectors and induce T regulatory cells differentiation. Here we investigated the in vitro mechanisms of lyophilized aqueous extract from Passiflora alata leaves (LAEPAL) that modulates bone marrow-derived professional antigen-presenting cells (BM-pAPCs), affecting their ability to polarize T cells. A cell culture model was defined using mixed cultures of BM-pAPCs and T lymphocytes NOD mice with stressed MIN-6 cells as a source of pancreatic β cells antigens. We showed that the treatment with 300 µg/mL of LAEPAL induces a significant decrease in the CD4 and CD8 T effector lymphocytes proliferation from diabetic but not in non-diabetic mice, followed by a reduction of the IL-6 and IFN-γ cytokines release in the cell cultures supernatants. Moreover, we observed an increase of CD4⁺CD25⁺FoxP3⁺ Tregs in the cell cultures from diabetic mice. These results could be partially explained by the LAEPAL modulatory effects in BM-pAPCs, downregulating the CD86 co-stimulatory molecule expression, and increasing IDO-1 expression in F4/80+ BM-pAPCs. These results contribute to a better understanding of the polyphenols' immunomodulatory properties, meaning they could induce tolerogenic antigen-presenting cells, which could polarize T cells to a Treg profile and decrease the activity of CD4+ and CD8+ T effector cells.

Circadian clock genes as promising therapeutic targets for autoimmune diseases

Circadian rhythm is a natural, endogenous process whose physiological functions are controlled by a set of clock genes. Disturbance of the clock genes have detrimental effects on both innate and adaptive immunity, which significantly enhance pro-inflammatory responses and susceptibility to autoimmune diseases via strictly controlling the individual cellular components of the immune system that initiate and perpetuate the inflammation pathways. Autoimmune diseases, especially rheumatoid arthritis (RA), often exhibit substantial circadian oscillations, and circadian rhythm is involved in the onset and progression of autoimmune diseases. Mounting evidence indicate that the synthetic ligands of circadian clock genes have the property of reducing the susceptibility and clinical severity of subjects. This review supplies an overview of the roles of circadian clock genes in the pathology of autoimmune diseases, including BMAL1, CLOCK, PER, CRY, REV-ERBα, and ROR. Furthermore, summarized some circadian clock genes as candidate genes for autoimmune diseases and current advancement on therapy of autoimmune diseases with synthetic ligands of circadian clock genes. The existing body of knowledge demonstrates that circadian clock genes are inextricably linked to autoimmune diseases. Future research should pay attention to improve the quality of life of patients with autoimmune diseases and reduce the effects of drug preparation on the normal circadian rhythms.

Substance P blocks ovariectomy-induced bone loss by modulating inflammation and potentiating stem cell function

Osteoporosis is an age-related disease caused by imbalanced bone remodeling resulting from excessive bone resorption. Osteoporosis is tightly linked with induction of chronic inflammation, which activates osteoclasts and impairs osteoprogenitor in bone marrow. T helper 17 (Th17) cells have been recently recognized as one of major inducers in the pathophysiology of bone loss by secreting IL-17. Thus, modulation of Th17 development is anticipated to affect the progression of osteoporosis.

Substance P (SP) is reported to provide anti-inflammatory effects by controlling immune cell profile and also, promote restoration of damaged stem cell niches—the bone marrow—by repopulating BMSCs or potentiating its paracrine ability. This study aimed to explore the therapeutic effects of systemically injected SP on ovariectomy (OVX)-induced osteoporosis.

Resultantly, SP injection obviously blocked OVX-induced impairment of bone microarchitecture and reduction of the mineral density. In osteoporotic condition, SP could ameliorate chronic inflammation by promoting Treg cell polarization and inhibiting the development of osteoclastogenic Th17 cells. Moreover, SP could rejuvenate stem cell and enable stem cells to repopulate and differentiate into osteoblast.

Collectively, our study strongly suggests that SP treatment can block osteoporosis and furthermore, SP treatment provides therapeutic effect on chronic disease with inflammation and stem cell dysfunction.

IL-17F induces inflammation, dysfunction and cell death in mouse islets

Type 17 immune responses, typified by the production of the cytokines IL-17A and IL-17F, have been implicated in the development of type 1 diabetes in animal models and human patients, however the underlying pathogenic mechanisms have not been clearly elucidated. While previous studies show that IL-17A enhances inflammatory gene expression and cell death in mouse β-cells and human islets, the function of IL-17F in pancreatic β-cells is completely untested to date. Here we show that IL-17F exhibits potent pathogenic effects in mouse β-cell lines and islets. IL-17F signals via the IL-17RA and -RC subunits in β-cells and in combination with other inflammatory cytokines induces expression of chemokine transcripts, suppresses the expression of β-cell identity genes and impairs glucose stimulated insulin secretion. Further IL-17F induces cell death in primary mouse islets. This occurs via Jnk, p38 and NF-κB dependent induction of Nos2 and is completely ablated in the presence of an inducible nitric oxide synthase (iNOS) inhibitor. Together these data indicate that IL-17F possesses similar pathogenic activities to IL-17A in mouse β-cell lines and islets and is likely to be a type 17 associated pathogenic factor in type 1 diabetes.

Cytokines in type 1 diabetes: mechanisms of action and immunotherapeutic targets

Cytokines play crucial roles in orchestrating complex multicellular interactions between pancreatic β cells and immune cells in the development of type 1 diabetes (T1D) and are thus potential immunotherapeutic targets for this disorder. Cytokines that can induce regulatory functions-for example, IL-10, TGF-β and IL-33-are thought to restore immune tolerance and prevent β-cell damage. By contrast, cytokines such as IL-6, IL-17, IL-21 and TNF, which promote the differentiation and function of diabetogenic immune cells, are thought to lead to T1D onset and progression. However, targeting these dysregulated cytokine networks does not always result in consistent effects because anti-inflammatory or proinflammatory functions of cytokines, responsible for β-cell destruction, are context dependent. In this review, we summarise the current knowledge on the involvement of well-known cytokines in both the initiation and destruction phases of T1D and discuss advances in recently discovered roles of cytokines. Additionally, we emphasise the complexity and implications of cytokine modulation therapy and discuss the ways in which this strategy has been translated into clinical trials.

Significant body mass increase by oral administration of a cascade of shIL21-MSTN yeast-based DNA vaccine in mice

Base on the practical of MSTN-specific yeast-based protein vaccine in mice as described previously, this research was designed for developing a better DNA vaccine (a cascade of shIL21-MSTN yeast-based DNA vaccine) than solely MSTN yeast-based DNA vaccine to block the endogenous MSTN in the murine model. We first constructed the target vectors, including CMV-driven MSTN expression vector and a combined shIL21-MSTN vector which containing MSTN expression cassette and shIL21 (short hairpin RNA-IL21) expression cassette. After necessary validation, recombinant yeast vaccines harboring different vectors were well prepared. Subsequently, after 2-month administration, the MSTN-specific immune response was detected with western blots. The commercial ELISA assays indicated that the production of IL21 and IL6 were decreased compared with control groups. More importantly, the MSTN-specific antibody titer was much higher in the shIL21-MSTN group than MSTN group, which was consistent with the western blots result. The most important finding was significant body mass increased after oral administration of these yeast-based DNA vaccines, in which the shIL21-MSTN vaccine is slightly higher than the sole MSTN vaccine in mice. In this study, we confirmed the role of different MSTN-specific yeast-based DNA vaccines on increasing body mass in mice, to provide a good inspiration for livestock breeding through the new type of immunoregulatory method. On the other hand, we also detected the possible modulating role of shIL21 on the dendritic cell-mediated immune function which needs more practical application and deeper exploration.

CD122 blockade restores immunological tolerance in autoimmune type 1 diabetes via multiple mechanisms

Signaling through IL-2/IL-15Rβ (CD122) is essential for the differentiation and function of T cells and NK cells. A mAb against CD122 has been implicated to suppress autoimmune type 1 diabetes (T1D) development in animal models. However, the mechanisms remain poorly understood. We find that in vivo administration of an anti-CD122 mAb (CD122 blockade) restores immune tolerance in nonobese diabetic (NOD) mice via multiple mechanisms. First, CD122 blockade selectively ablates pathogenic NK cells and memory phenotype CD8+ T cells from pancreatic islets. In contrast, islet CD4+Foxp3+ Tregs are only mildly affected. Second, CD122 blockade suppresses IFN-γ production in islet immune cells. Third, CD122 blockade inhibits the conversion of islet Th17 cells into diabetogenic Th1 cells. Furthermore, a combination of anti-CD122 mAb and Treg-trophic cytokines (IL-2 or IL-33) enhances the abundance and function of islet Tregs. In summary, these data provide crucial mechanistic insights into CD122 blockade-mediated immunoregulation and support therapeutic benefits of this combinational treatment in T1D.

Interactions Between the Neuroendocrine System and T Lymphocytes in Diabetes

It is well established that there is a fine-tuned bidirectional communication between the immune and neuroendocrine tissues in maintaining homeostasis. Several types of immune cells, hormones, and neurotransmitters of different chemical nature are involved as communicators between organs. Apart of being key players of the adaptive arm of the immune system, it has been recently described that T lymphocytes are involved in the modulation of metabolism of several tissues in health and disease. Diabetes may result mainly from lack of insulin production (type 1 diabetes) or insufficient insulin and insulin resistance (type 2 diabetes), both influenced by genetic and environmental components. Herein, we discuss accumulating data regarding the role of the adaptive arm of the immune system in the pathogenesis of diabetes; including the action of several hormones and neurotransmitters influencing on central and peripheral T lymphocytes development and maturation, particularly under the metabolic burden triggered by diabetes. In addition, we comment on the role of T-effector lymphocytes in adipose and liver tissues during diabetes, which together enhances pancreatic β-cell stress aggravating the disease.

Role of IL-21 in HTLV-1 infections with emphasis on HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP)

Interleukin-21 (IL-21) enhances the survival and cytotoxic properties of cytotoxic T cells (CTLs) and exhibits essential roles in controlling chronic viral infections. HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a chronic progressive inflammatory disease of the nervous system. The main determinant of disease progression is efficiency of the CTL response to Human T lymphotropic virus types I (HTLV-1). In this study, the expression of host IL-21 and HTLV-I Tax and proviral load (PVL) was evaluated to understand the role and mechanism of IL-21 in HTLV-1 infections and the subsequent development of HAM/TSP. A cross-sectional study was carried out on 20 HAM/TSP patients, 20 asymptomatic HTLV-1 carriers (ACs) and 20 healthy controls (HCs) to evaluate the expression of IL-21 and Tax and PVL in non-activated and phorbol myristate acetate (PMA)-ionomycin-activated peripheral blood mononuclear cells (PBMCs). The mean mRNA expression of IL-21 in the non-activated and activated PBMCs was higher (by 5-13 times) in the HAM/TSP patients than in ACs and HCs (p < 0.05); however, there was no significant difference between ACs and HCs. In contrast to the IL-21 mRNA expression, the serum level of the IL-21 protein was significantly lower in the HAM/TSP patients than in ACs and HCs (p < 0.05). Furthermore, higher expression of Tax and PVL was observed in the HAM/TSP subjects than ACs (p < 0.05). In addition, Tax gene expression was positively correlated with PVL (R = 0.595, p = 0.000) and IL-21 gene expression (R = 0.395, p = 0.021) in the HTLV-1-infected subjects. In conclusion, the increase in IL-21 mRNA expression may reflect the attempt of infected T cells to induce an appropriate antiviral response, and the decrease in IL-21 protein expression may reflect the inhibition of IL-21 mRNA translation by viral factors in favour of virus evasion and dissemination.

Type 1 diabetes genetic susceptibility and dendritic cell function: potential targets for treatment

Type 1 diabetes is an autoimmune disease that results from the defective induction or maintenance of T cell tolerance against islet β cell self-antigens. Under steady-state conditions, dendritic cells with tolerogenic properties are critical for peripheral immune tolerance. Tolerogenic dendritic cells can induce T cell anergy and deletion and, in some contexts, induce or expand regulatory T cells. Dendritic cells contribute to both immunomodulatory effects and triggering of pathogenesis in type 1 diabetes. This immune equilibrium is affected by both genetic and environmental factors that contribute to the development of type 1 diabetes. Genome-wide association studies and disease association studies have identified >50 polymorphic loci that lend susceptibility or resistance to insulin-dependent diabetes mellitus. In parallel, diabetes susceptibility regions known as insulin-dependent diabetes loci have been identified in the nonobese diabetic mouse, a model for human type 1 diabetes, providing a better understanding of potential immunomodulatory factors in type 1 diabetes risk. Most genetic candidates have annotated immune cell functions, but the focus has been on changes to T and B cells. However, it is likely that some of the genomic susceptibility in type 1 diabetes directly interrupts the tolerogenic potential of dendritic cells in the pathogenic context of ongoing autoimmunity. Here, we will review how gene polymorphisms associated with autoimmune diabetes may influence dendritic cell development and maturation processes that could lead to alterations in the tolerogenic function of dendritic cells. These insights into potential tolerogenic and pathogenic roles for dendritic cells have practical implications for the clinical manipulation of dendritic cells toward tolerance to prevent and treat type 1 diabetes.

Mast cells contribute to autoimmune diabetes by releasing interleukin-6 and failing to acquire a tolerogenic IL-10+ phenotype

Mast cells (MCs) are innate immune cells that exert positive and negative immune modulatory functions capable to enhance or limit the intensity and/or duration of adaptive immune responses. Although MCs are crucial to regulate T cell immunity, their action in the pathogenesis of autoimmune diseases is still debated. Here we demonstrate that MCs play a crucial role in T1D pathogenesis so that their selective depletion in conditional MC knockout NOD mice protects them from the disease. MCs of diabetic NOD mice are overly inflammatory and secrete large amounts of IL-6 that favors differentiation of IL-17-secreting T cells at the site of autoimmunity. Moreover, while MCs of control mice acquire an IL-10+ phenotype upon interaction with FoxP3+ Treg cells, MCs of NOD mice do not undergo this tolerogenic differentiation. Our data indicate that overly inflammatory MCs unable to acquire a tolerogenic IL-10+ phenotype contribute to the pathogenesis of autoimmune T1D.

The Non-Obese Diabetic Mouse Strain as a Model to Study CD8(+) T Cell Function in Relapsing and Progressive Multiple Sclerosis

Multiple sclerosis (MS) is a neurodegenerative disease resulting from an autoimmune attack on central nervous system (CNS) myelin. Although CD4⁺ T cell function in MS pathology has been extensively studied, there is also strong evidence that CD8⁺ T lymphocytes play a key role. Intriguingly, CD8⁺ T cells accumulate in great numbers in the CNS in progressive MS, a form of the disease that is refractory to current disease-modifying therapies that target the CD4⁺ T cell response. Here, we discuss the function of CD8⁺ T cells in experimental autoimmune encephalomyelitis (EAE), a mouse model of MS. In particular, we describe EAE in non-obese diabetic (NOD) background mice, which develop a pattern of disease characterized by multiple attacks and remissions followed by a progressively worsening phase. This is highly reminiscent of the pattern of disease observed in nearly half of MS patients. Particular attention is paid to a newly described transgenic mouse strain (1C6) on the NOD background whose CD4⁺ and CD8⁺ T cells are directed against the encephalitogenic peptide MOG_[35–55]. Use of this model will give us a more complete picture of the role(s) played by distinct T cell subsets in CNS autoimmunity.

Organ-specific differences in achieving tolerance

PURPOSE OF REVIEW

When it comes to tolerance induction, kidney allografts behave differently from heart allografts that behave differently from lung allografts. Here, we examine how and why different organ allografts respond differently to the same tolerance induction protocol.

RECENT FINDINGS

Allograft tolerance has been achieved in experimental and clinical kidney transplantation. Inducing tolerance in experimental recipients of heart and lung allografts has, however, proven to be more challenging. New protocols being developed in nonhuman primates based on mixed chimerism and cotransplantation of tolerogenic organs may provide mechanistic insights to help overcome these challenges.

SUMMARY

Tolerance induction protocols that are successful in patients transplanted with 'tolerance-prone' organs such as kidneys and livers will most likely not succeed in recipients of 'tolerance-resistant' organs such as hearts and lungs. Separate clinical trials using more robust tolerance protocols will be required to achieve tolerance in heart and lung recipients.

IL-21R signaling is critical for induction of spontaneous experimental autoimmune encephalomyelitis

IL-17-producing CD4+ T cells (Th17 cells) have well-described pathogenic roles in tissue inflammation and autoimmune diseases, such as experimental autoimmune encephalomyelitis (EAE); however, the involvement of IL-21 in these processes has remained controversial. While IL-21 is an essential autocrine amplification factor for differentiation of Th17 cells, the loss of IL-21 or IL-21 receptor (IL-21R) does not protect mice from actively induced EAE. Here, we utilized a transgenic EAE mouse model, in which T and B cells overexpress receptors for myelin oligodendrocyte glycoprotein (MOG) (referred to as 2D2xTH mice), and demonstrated that IL-21 is critical for the development of a variant form of spontaneous EAE in these animals. Il21r deletion in 2D2xTH mice reduced the incidence and severity of spontaneous EAE, which was associated with a defect in Th17 cell generation. Moreover, IL-21R deficiency limited IL-23R expression on Th17 cells and inhibited expression of key molecules involved in the generation of pathogenic Th17 cells. Conversely, loss of IL-23R in 2D2xTH mice resulted in complete resistance to the development of spontaneous EAE. Our data identify a previously unappreciated role for IL-21 in EAE and reveal that IL-21-mediated signaling supports generation and stabilization of pathogenic Th17 cells and development of spontaneous autoimmunity.

The Presence and Preferential Activation of Regulatory T Cells Diminish Adoptive Transfer of Autoimmune Diabetes by Polyclonal Nonobese Diabetic (NOD) T Cell Effectors into NSG versus NOD-scid Mice

NOD-scid.Il2rg(null) (NSG) mice are currently being used as recipients to screen for pathogenic autoreactive T cells in type 1 diabetes (T1D) patients. We questioned whether the restriction of IL-2R γ-chain (Il-2rγ)-dependent cytokine signaling only to donor cells in NSG recipients differently influenced the activities of transferred diabetogenic T cells when they were introduced as a monoclonal/oligoclonal population versus being part of a polyclonal repertoire. Unexpectedly, a significantly decreased T1D transfer by splenocytes from prediabetic NOD donors was observed in Il-2rγ(null)-NSG versus Il-2rγ-intact standard NOD-scid recipients. In contrast, NOD-derived monoclonal/oligoclonal TCR transgenic β cell-autoreactive T cells in either the CD8 (AI4, NY8.3) or CD4 (BDC2.5) compartments transferred disease significantly more rapidly to NSG than to NOD-scid recipients. The reduced diabetes transfer efficiency by polyclonal T cells in NSG recipients was associated with enhanced activation of regulatory T cells (Tregs) mediated by NSG myeloid APC. This enhanced suppressor activity was associated with higher levels of Treg GITR expression in the presence of NSG than NOD-scid APC. These collective results indicate NSG recipients might be efficiently employed to test the activity of T1D patient-derived β cell-autoreactive T cell clones and lines, but, when screening for pathogenic effectors within polyclonal populations, Tregs should be removed from the transfer inoculum to avoid false-negative results.

Non-classical MHC I-E negatively regulates macrophage activation and Th17 cell development in NOD mice

Transgenic expression of I-E molecules prevents diabetes in NOD mice. So far, the precise role of these non-classical MHC II molecules remains elusive. Here, we showed that transgenic expression of I-E^k alpha 16 molecule in NOD mice selectively reduced Th17 cells in the thymus and pancreatic draining lymph nodes. The reduction in Th17 cells was associated with both attenuated IL-6 production and decreased activation of macrophages. Mechanistically, transgenic expression of the I-E molecule diminished expression of intracellular classical MHC II molecule and led to impaired TLR4-mediated signaling. In contrast to classical MHC II molecule, this non-classical MHC II molecule negatively regulates the inflammatory responses of macrophages. Altogether, our study reveals a novel regulatory role of I-E molecules in modulating inflammatory immune responses.

CD4 T cell differentiation in type 1 diabetes

Susceptibility to type 1 diabetes is associated strongly with human leucocyte antigen (HLA) genes, implicating T cells in disease pathogenesis. In humans, CD8 T cells predominantly infiltrate the islets, yet their activation and propagation probably requires CD4 T cell help. CD4 T cells can select from several differentiation fates following activation, and this choice has profound consequences for their subsequent cytokine production and migratory potential. In turn, these features dictate which other immune cell types T cells interact with and influence, thereby determining downstream effector functions. Obtaining an accurate picture of the type of CD4 T cell differentiation associated with a particular immune-mediated disease therefore constitutes an important clue when planning intervention strategies. Early models of T cell differentiation focused on the dichotomy between T helper type 1 (Th1) and Th2 responses, with type 1 diabetes (T1D) being viewed mainly as a Th1-mediated pathology. However, several additional fate choices have emerged in recent years, including Th17 cells and follicular helper T cells. Here we revisit the issue of T cell differentiation in autoimmune diabetes, highlighting new evidence from both mouse models and patient samples. We assess the strengths and the weaknesses of the Th1 paradigm, review the data on interleukin (IL)-17 production in type 1 diabetes and discuss emerging evidence for the roles of IL-21 and follicular helper T cells in this disease setting. A better understanding of the phenotype of CD4 T cells in T1D will undoubtedly inform biomarker development, improve patient stratification and potentially reveal new targets for therapeutic intervention.

ROR inverse agonist suppresses insulitis and prevents hyperglycemia in a mouse model of type 1 diabetes

Hyperglycemia associated with type 1 diabetes is a consequence of immune-mediated destruction of insulin producing pancreatic β-cells. Although it is apparent that both CD8(+) T cells and TH1 cells are key contributors to type 1 diabetes, the function of TH17 cells in disease onset and progression remains unclear. The nuclear receptors retinoic acid receptor-related orphan receptors-α and γt (RORα and RORγt) play critical roles in the development of TH17 cells and ROR-specific synthetic ligands have proven efficacy in several mouse models of autoimmunity. To investigate the roles and therapeutic potential for targeting the RORs in type 1 diabetes, we administered SR1001, a selective RORα/γ inverse agonist, to nonobese diabetic mice. SR1001 significantly reduced diabetes incidence and insulitis in the treated mice. Furthermore, SR1001 reduced proinflammatory cytokine expression, particularly TH17-mediated cytokines, reduced autoantibody production, and increased the frequency of CD4(+)Foxp3(+) T regulatory cells. These data suggest that TH17 cells may have a pathological role in the development of type 1 diabetes, and use of ROR-specific synthetic ligands targeting this cell type may prove utility as a novel treatment for type 1 diabetes.

A T cell extrinsic mechanism by which IL-2 dampens Th17 differentiation

Genetic variants in il2 and il2ra have been associated with autoimmune disease susceptibility in both genome-wide association studies (GWAS) in humans and in genetic linkage studies in experimental models of autoimmunity. Specifically, genetic variants resulting in a low IL-2 phenotype are susceptibility alleles while variants resulting in a high IL-2 phenotype are resistance alleles. The association of high IL-2 phenotypes with resistance has been attributed primarily to the T cell intrinsic promotion of regulatory T cell development, maintenance, and function; however, IL-2 can also act T cell intrinsically to dampen differentiation of pathogenic IL-17-producing Th17 cells. Here, we have uncovered a novel T cell extrinsic mechanism whereby IL-2 promotes both IFN-γ and IL-27 production from tissue resident macrophages which in turn dampen the differentiation of pathogenic Th17 cells.

Role of fractalkine in the pathogenesis of primary Sjögren syndrome: increased serum levels of fractalkine, its expression in labial salivary glands, and the association with clinical manifestations

OBJECTIVE

To investigate the expression of fractalkine and identify the clinical effects of fractalkine and its receptor (CX3CR1) in patients with primary Sjögren syndrome (pSS).

METHODS

Serum fractalkine levels were determined by ELISA. Immunohistochemical staining was done to compare the expression of fractalkine and CX3CR1 between salivary glands (SG) of patients with SS and controls. The cells to be merged with fractalkine were evaluated by confocal microscopy. Type of CX3CR1-expressing cells among infiltrating lymphocytes in SG was analyzed by confocal microscopy. Further, associations among fractalkine, proinflammatory cytokines, and clinical profiles were investigated.

RESULTS

Serum fractalkine levels in patients with pSS were higher than those in the control group (p = 0.026). SG expression of fractalkine and its receptor was upregulated in patients with pSS compared to that in the controls by immunohistochemistry. Higher histological grade was associated with more fractalkine-positive cells per total epithelial cells. Epithelial cells were the main fractalkine-expressing cell type in the SG. Serum fractalkine levels were significantly correlated with proinflammatory cytokines levels (interleukin 17: r = 0.685, p = 0.029; tumor necrosis factor-α: r = 0.444, p = 0.003), antinuclear antibody (r = 0.349, p = 0.022), and immunoglobulin G levels (r = 0.325, p = 0.044). Serum fractalkine levels in patients with extraglandular manifestations of pSS were significantly higher than in those without extraglandular manifestations (p = 0.026).

CONCLUSION

Fractalkine and CX3CR1 may play a role in the pathogenesis of pSS, including extraglandular manifestations.

Cellular factors targeting APCs to modulate adaptive T cell immunity

The fate of adaptive T cell immunity is determined by multiple cellular and molecular factors, among which the cytokine milieu plays the most important role in this process. Depending on the cytokines present during the initial T cell activation, T cells become effector cells that produce different effector molecules and execute adaptive immune functions. Studies thus far have primarily focused on defining how these factors control T cell differentiation by targeting T cells themselves. However, other non-T cells, particularly APCs, also express receptors for the factors and are capable of responding to them. In this review, we will discuss how APCs, by responding to those cytokines, influence T cell differentiation and adaptive immunity.

Expression of IL-2 in β cells by AAV8 gene transfer in pre-diabetic NOD mice prevents diabetes through activation of FoxP3-positive regulatory T cells

We previously demonstrated that intraperitoneal delivery of adeno-associated virus serotype 8 (AAV8) stably transduces the pancreas, including the β cells in the pancreatic islets. We further demonstrated the ability to deliver and express target genes specifically in β cells for at least 6 months using a murine insulin promoter in a double-stranded, self-complementary AAV vector. Recombinant interleukin (IL)-2 has been shown to induce CD4(+)CD25(+) regulatory T cells (Tregs) in several mouse models of autoimmune disease. Here we evaluated the effects of double-stranded adeno-associated virus serotype 8-mouse insulin promoter (dsAAV8-mIP)-mediated delivery of  2 to pancreatic β cells in non-obese diabetic (NOD) mice. AAV8-mIP-mediated gene expression of IL-2 to pancreatic β cells of 10-week-old NOD mice prevented the onset of hyperglycemia in NOD mice more in a dose-dependent manner with the lower dose of virus being more effective than a higher dose of AAV-mIP-IL-2 and IL-4. Moreover, the local β-cell expression of IL-2 increased the number of CD4(+)CD25(+)FoxP3(+) cells in the pancreatic lymph node (PLN) and SPL in both NOD and C57BL/6 mice. Taken together, these results demonstrate that local, low expression of mIL-2 in islets prevents progress of diabetes through the regulation of Tregs.

Heart transplantation: challenges facing the field

There has been significant progress in the field of heart transplantation over the last 45 years. The 1-yr survival rates following heart transplantation have improved from 30% in the 1970s to almost 90% in the 2000s. However, there has been little change in long-term outcomes. This is mainly due to chronic rejection, malignancy, and the detrimental side effects of chronic immunosuppression. In addition, over the last decade, new challenges have arisen such as increasingly complicated recipients and antibody-mediated rejection. Most, if not all, of these obstacles to long-term survival could be prevented or ameliorated by the induction of transplant tolerance wherein the recipient's immune system is persuaded not to mount a damaging immune response against donor antigens, thus eliminating the need for chronic immunosuppression. However, the heart, as opposed to other allografts like kidneys, appears to be a tolerance-resistant organ. Understanding why organs like kidneys and livers are prone to tolerance induction, whereas others like hearts and lungs are tolerance-resistant, could aid in our attempts to achieve long-term, immunosuppression-free survival in human heart transplant recipients. It could also advance the field of pig-to-human xenotransplantation, which, if successful, would eliminate the organ shortage problem. Of course, there are alternative futures to the field of heart transplantation that may include the application of total mechanical support, stem cells, or bioengineered whole organs. Which modality will be the first to reach the ultimate goal of achieving unlimited, long-term, circulatory support with minimal risk to longevity or lifestyle is unknown, but significant progress in being made in each of these areas.

Interleukin-21: a double-edged sword with therapeutic potential

Interleukin-21 is a cytokine with broad pleiotropic actions that affect the differentiation and function of lymphoid and myeloid cells. Since its discovery in 2000, a tremendous amount has been learned about its biological actions and the molecular mechanisms controlling IL-21-mediated cellular responses. IL-21 regulates both innate and adaptive immune responses, and it not only has key roles in antitumour and antiviral responses but also exerts major effects on inflammatory responses that promote the development of autoimmune diseases and inflammatory disorders. Numerous studies have shown that enhancing or inhibiting the action of IL-21 has therapeutic effects in animal models of a wide range of diseases, and various clinical trials are underway. The current challenge is to understand how to specifically modulate the actions of IL-21 in the context of each specific immune response or pathological situation. In this Review, we provide an overview of the basic biology of IL-21 and discuss how this information has been - and can be - exploited therapeutically.

Blockade of the programmed death-1 (PD1) pathway undermines potent genetic protection from type 1 diabetes

Aims/Hypothesis

Inhibition of PD1-PDL1 signaling in NOD mice accelerates onset of type 1 diabetes implicating this pathway in suppressing the emergence of pancreatic beta cell reactive T-cells. However, the molecular mechanism by which PD1 signaling protects from type 1 diabetes is not clear. We hypothesized that differential susceptibility of Idd mouse strains to type 1 diabetes when challenged with anti PDL1 will identify genomic loci that collaborate with PD1 signaling in suppressing type 1 diabetes.

Methods

Anti PDL1 was administered to NOD and various Idd mouse strains at 10 weeks of age and onset of disease was monitored by measuring blood glucose levels. Additionally, histological evaluation of the pancreas was performed to determine degree of insulitis. Statistical analysis of the data was performed using Log-Rank and Student's t-test.

Results

Blockade of PDL1 rapidly precipitated type 1 diabetes in nearly all NOD Idd congenic strains tested, despite the fact that all are moderately (Idd5, Idd3 and Idd10/18) or highly (Idd3/10/18 and Idd9) protected from spontaneous type 1 diabetes by virtue of their protective Idd genes. Only the Idd3/5 strain, which is nearly 100% protected from spontaneous disease, remained normoglycemic following PDL1 blockade.

Conclusions

These results indicate that multiple Idd loci collaborate with PD1 signaling. Anti PDL1 treatment undermines a large portion of the genetic protection mediated by Idd genes in the NOD model of type 1 diabetes. Basal insulitis correlated with higher susceptibility to type 1 diabetes. These findings have important implications since the PD1 pathway is a target for immunotherapy.

Double deficiency in IL-17 and IFN-γ signalling significantly suppresses the development of diabetes in the NOD mouse

AIMS/HYPOTHESIS

T helper type (Th) 17 cells have been shown to play important roles in mouse models of several autoimmune diseases that have been classified as Th1 diseases. In the NOD mouse, the relevance of Th1 and Th17 is controversial, because single-cytokine-deficient NOD mice develop diabetes similarly to wild-type NOD mice.

METHODS

We studied the impact of IL-17/IFN-γ receptor double deficiency in NOD mice on the development of insulitis/diabetes compared with IL-17 single-deficient mice and wild-type mice by monitoring diabetes-related phenotypes. The lymphocyte phenotypes were determined by flow cytometric analysis.

RESULTS

IL-17 single-deficient NOD mice showed delayed onset of diabetes and reduced severity of insulitis, but the cumulative incidence of longstanding diabetes in the IL-17-deficient mice was similar to that in wild-type mice. The IL-17/IFN-γ receptor double-deficient NOD mice showed an apparent decline in longstanding diabetes onset, but not in insulitis compared with that in the IL-17 single-deficient mice. We also found that double-deficient NOD mice had a severe lymphopenic phenotype and preferential increase in regulatory T cells among CD4(+) T cells compared with the IL-17 single-deficient mice and wild-type NOD mice. An adoptive transfer study with CD4(+)CD25(-) T cells from young non-diabetic IL-17 single-deficient NOD mice, but not those from older mice, showed significantly delayed disease onset in immune-deficient hosts compared with the corresponding wild-type mice.

CONCLUSIONS/INTERPRETATION

These results indicate that IL-17/Th17 participates in the development of insulitis and that both IL-17 and IFN-γ signalling may synergistically contribute to the development of diabetes in NOD mice.

Interleukin-21 in chronic inflammatory diseases

Interleukin-21 (IL-21), a cytokine produced by various subsets of activated CD4+ T cells, regulates multiple innate and adaptive immune responses. Indeed, IL-21 controls the proliferation and function of CD4+ and CD8+ T lymphocytes, drives the differentiation of B cells into memory cells and Ig-secreting plasma cells, enhances the activity of natural killer cells and negatively regulates the differentiation and activity of regulatory T cells. Moroever, IL-21 can stimulate nonimmune cells to synthesize various inflammatory molecules. Excessive production of IL-21 has been described in many human chronic inflammatory disorders and there is evidence that blockade of IL-21 helps attenuate detrimental responses in mouse models of immune-mediated diseases. In this article we briefly review data supporting the pathogenic role of IL-21 in immune-inflammatory pathologies and discuss the benefits and risks of IL-21 neutralization in patients with such diseases.

Genetic interactions among Idd3, Idd5.1, Idd5.2, and Idd5.3 protective loci in the nonobese diabetic mouse model of type 1 diabetes

In the NOD mouse model of type 1 diabetes, insulin-dependent diabetes (Idd) loci control the development of insulitis and diabetes. Independently, protective alleles of Idd3/Il2 or Idd5 are able to partially protect congenic NOD mice from insulitis and diabetes, and to partially tolerize islet-specific CD8(+) T cells. However, when the two regions are combined, mice are almost completely protected, strongly suggesting the existence of genetic interactions between the two loci. Idd5 contains at least three protective subregions/causative gene candidates, Idd5.1/Ctla4, Idd5.2/Slc11a1, and Idd5.3/Acadl, yet it is unknown which of them interacts with Idd3/Il2. Through the use of a series of novel congenic strains containing the Idd3/Il2 region and different combinations of Idd5 subregion(s), we defined these genetic interactions. The combination of Idd3/Il2 and Idd5.3/Acadl was able to provide nearly complete protection from type 1 diabetes, but all three Idd5 subregions were required to protect from insulitis and fully restore self-tolerance. By backcrossing a Slc11a1 knockout allele onto the NOD genetic background, we have demonstrated that Slc11a1 is responsible for the diabetes protection resulting from Idd5.2. We also used Slc11a1 knockout-SCID and Idd5.2-SCID mice to show that both loss-of-function alleles provide protection from insulitis when expressed on the SCID host alone. These results lend further support to the hypothesis that Slc11a1 is Idd5.2.

Th17 cells in type 1 diabetes

T1D is an autoimmune disorder, which involves the CD4(+) as well as CD8(+) T-cell-mediated destruction of β cells. Recently, another population of T cells (Th17) is found to be involved in T1D pathology. This review will discuss the characteristics of Th17 cells and the mechanism of Th17-mediated T1D development. Th17 cell expansion is unstrained under T1D condition. Certain Treg cells are defective in T1D and lose the control of Th17 expansion. In addition, the altered function of APCs and a subset of monocytes which spontaneously secrete IL-1β and IL-6 in T1D determine the abnormal expansion of Th17 as well. The pathogenic Th17 cells can cause the imbalance between Teff and Treg cells. Conversion from Th17 to Th1 phenotype and Th17 stimulated CTL responses may play an accessory role in T1D as well. Due to the effects of Th17 on T1D, therapeutic strategies designed to inhibit these cells are applicable and the positive effects are obvious. Taken together, Th17 may exert essential effects on the development of T1D. Identification of the underlying mechanism may inspire new viewpoints for the therapy of this disease.

Aiolos promotes TH17 differentiation by directly silencing Il2 expression

CD4(+) interleukin 17 (IL-17)-producing helper T cells (T(H)17 cells) are instrumental in the immune response to pathogens. However, an overactive T(H)17 response results in tissue inflammation and autoimmunity, and therefore it is important to identify the molecular mechanisms that control the development of T(H)17 cells. IL-2 suppresses such development, but how IL-2 production is actively suppressed during T(H)7 differentiation is not understood. Here we report that under T(H)17-polarizing conditions, the transcription factors STAT3 and AhR upregulated the expression of Aiolos, a member of the Ikaros family of transcription factors. Using Aiolos-deficient mice, we demonstrated that Aiolos silenced the Il2 locus, promoting T(H)17 differentiation in vitro and in vivo. Thus, we have identified a module in the transcriptional program of T(H)17 cells that actively limits IL-2 production and promotes their differentiation.

TH17 Cells in Autoimmunity and Immunodeficiency: Protective or Pathogenic?

In 2005 a newly discovered T helper cell subset that secreted interleukin (IL)-17 became the center of attention in immunology. Initial studies painted Th17 cells as the culprit for destruction in many different autoimmune and auto-inflammatory diseases. Subsequently, the discovery of patients with primary immunodeficiencies in the IL-17 pathway taught us that Th17 cells have a critical role in defense against certain fungal and bacterial infections. Moreover, the paradoxical exacerbation of Crohn's disease in the clinical trials of a Secukinumab (AIN457), a fully human neutralizing antibody to IL-17A, has cast into doubt a universal pro-inflammatory and harmful role for Th17 cells. Evidence now suggests that depending on the environment Th17 cells can alter their differentiation program, ultimately giving rise to either protective or pro-inflammatory cells. In this review we will summarize the evidence from patients with immunodeficiencies, autoimmune, or auto-inflammatory diseases that teaches us how the pro-inflammatory versus protective function of Th17 cells varies within the context of different human diseases.

A defect in cell death of macrophages is a conserved feature of nonobese diabetic mouse

Impaired apoptosis in immune effector cells such as macrophages has been implicated in the development of autoimmune disease by promoting the breakdown of self-tolerance and the sustained production of cytotoxic molecules. Macrophages from nonobese diabetic (NOD) mouse, an animal model of human autoimmune diabetes, exhibit several defects that are causally linked to the onset and progression of the disease. In this context, we investigated whether NOD macrophages have a defect in a cell death pathway, and if that is the case, the mechanism underlying such dysregulation of cell death. We found that NOD macrophages were resistant to treatment with a broad spectrum of cell death stimuli, triggering both apoptotic and non-apoptotic death. Through analysis of intracellular signaling pathways along with the expression of apoptosis-related proteins, we found that atypical resistance to cell death was associated with an elevated expression of anti-apoptotic Bcl-X(L) but not the NF-κB signaling pathway in NOD macrophages. Further, ABT-737, which can inhibit Bcl-X(L) function, sensitized NOD macrophages to apoptosis induced by diverse apoptotic stimuli, thus restoring sensitivity to cell death. Taken together, our results suggest a macrophage-intrinsic defect in cell death as a potential mechanism that promotes an immune attack towards pancreatic β-cells and the development of autoimmune diabetes in NOD mice.

Essential roles of insulin expression in Aire+ tolerogenic dendritic cells in maintaining peripheral self-tolerance of islet β-cells

Anti-insulin autoimmunity is one of the primary forces in initiating and progressing β-cell destruction in type 1 diabetes. While insulin expression in thymic medullary epithelial cells has been shown to be essential for establishing β-cell central tolerance, the function of insulin expression in antigen-presenting cells (APCs) of hematopoietic lineage remains elusive. With a Cre-lox reporter approach, we labeled Aire-expressing cells with enhanced yellow fluorescent proteins, and found that insulin expression in the spleen was restricted predominantly to a population of Aire(+)CD11c(int)B220(+) dendritic cells (DCs). Targeted insulin deletion in APCs failed to induce anti-islet autoimmunity in B6 mice. In contrast, elevated levels of T cell infiltration into islets were observed in B6(g7) congenic mice when insulin was specifically deleted in their CD11c-expressing DCs (B6(g7)·CD11c-ΔIns mice). Thus, insulin expression in BM-derived, Aire(+) tolerogenic DCs may play an essential role to prevent the activation and expansion of insulin-reactive T cells in the periphery.