Type 1 diabetes in BioBreeding rats is critically linked to an imbalance between Th17 and regulatory T cells and an altered TCR repertoire

The Future Exploring of Gut Microbiome-Immunity Interactions: From In Vivo/Vitro Models to In Silico Innovations

Investigating the complex interactions between microbiota and immunity is crucial for a fruitful understanding progress of human health and disease. This review assesses animal models, next-generation in vitro models, and in silico approaches that are used to decipher the microbiome-immunity axis, evaluating their strengths and limitations. While animal models provide a comprehensive biological context, they also raise ethical and practical concerns. Conversely, modern in vitro models reduce animal involvement but require specific costs and materials. When considering the environmental impact of these models, in silico approaches emerge as promising for resource reduction, but they require robust experimental validation and ongoing refinement. Their potential is significant, paving the way for a more sustainable and ethical future in microbiome-immunity research.

Type 1 Diabetes Mellitus: A Review on Advances and Challenges in Creating Insulin Producing Devices

Type 1 diabetes mellitus (T1DM) is the most common autoimmune chronic disease in young patients. It is caused by the destruction of pancreatic endocrine β-cells that produce insulin in specific areas of the pancreas, known as islets of Langerhans. As a result, the body becomes insulin deficient and hyperglycemic. Complications associated with diabetes are life-threatening and the current standard of care for T1DM consists still of insulin injections. Lifesaving, exogenous insulin replacement is a chronic and costly burden of care for diabetic patients. Alternative therapeutic options have been the focus in these fields. Advances in molecular biology technologies and in microfabrication have enabled promising new therapeutic options. For example, islet transplantation has emerged as an effective treatment to restore the normal regulation of blood glucose in patients with T1DM. However, this technique has been hampered by obstacles, such as limited islet availability, extensive islet apoptosis, and poor islet vascular engraftment. Many of these unsolved issues need to be addressed before a potential cure for T1DM can be a possibility. New technologies like organ-on-a-chip platforms (OoC), multiplexed assessment tools and emergent stem cell approaches promise to enhance therapeutic outcomes. This review will introduce the disorder of type 1 diabetes mellitus, an overview of advances and challenges in the areas of microfluidic devices, monitoring tools, and prominent use of stem cells, and how they can be linked together to create a viable model for the T1DM treatment. Microfluidic devices like OoC platforms can establish a crucial platform for pathophysiological and pharmacological studies as they recreate the pancreatic environment. Stem cell use opens the possibility to hypothetically generate a limitless number of functional pancreatic cells. Additionally, the integration of stem cells into OoC models may allow personalized or patient-specific therapies.

Modulation of gut microbiota in healthy rats after exposure to nutritional supplements

INTRODUCTION

Rats are experimental animals, frequently used as model organisms in the biomedical studies, and increasingly used to study the gut microbiota. Specifically, the aim of latter studies is either the elucidation of relationship between intestinal dysbiosis and diseases or the determination of nutrients or pharmaceutical agents which can cause the modulation in the presence or abundance of gut microbiota.

AIM

Herein, the research studies conducted on the gut microbiota of healthy rats are presented in a summarized and concise overview. The focus is on studies aimed to reveal the shifts in microbial composition and functional changes after exposure to various types of nutritional supplements.

METHODS

We performed the search of PubMed database using the term "rat gut microbiome microbiota" and examined studies aimed to assess the composition of gut microbiota in physiological homeostasis as well as the effect of various nutritional supplements on the gut microbiota of healthy rats.

The promise of CD4+FoxP3+ regulatory T-cell manipulation in vivo: applications for allogeneic hematopoietic stem cell transplantation

CD4⁺FoxP3⁺ regulatory T cells (Tregs) are a non-redundant population critical for the maintenance of self-tolerance. Over the past decade, the use of these cells for therapeutic purposes in transplantation and autoimmune disease has emerged based on their capacity to inhibit immune activation. Basic science discoveries have led to identifying key receptors on Tregs that can regulate their proliferation and function. Notably, the understanding that IL-2 signaling is crucial for Treg homeostasis promoted the hypothesis that in vivo IL-2 treatment could provide a strategy to control the compartment. The use of low-dose IL-2 in vivo was shown to selectively expand Tregs versus other immune cells. Interestingly, a number of other Treg cell surface proteins, including CD28, CD45, IL-33R and TNFRSF members, have been identified which can also induce activation and proliferation of this population. Pre-clinical studies have exploited these observations to prevent and treat mice developing autoimmune diseases and graft-versus-host disease post-allogeneic hematopoietic stem cell transplantation. These findings support the development of translational strategies to expand Tregs in patients. Excitingly, the use of low-dose IL-2 for patients suffering from graft-versus-host disease and autoimmune disease has demonstrated increased Treg levels together with beneficial outcomes. To date, promising pre-clinical and clinical studies have directly targeted Tregs and clearly established the ability to increase their levels and augment their function in vivo. Here we review the evolving field of in vivo Treg manipulation and its application to allogeneic hematopoietic stem cell transplantation.

Loss of GTPase of immunity-associated protein 5 (Gimap5) promotes pathogenic CD4+ T-cell development and allergic airway disease

BACKGROUND

GTPase of immunity-associated protein 5 (GIMAP5) is essential for lymphocyte homeostasis and survival. Recently, human GIMAP5 single nucleotide polymorphisms have been linked to an increased risk for asthma, whereas loss of Gimap5 in mice has been associated with severe CD4+ T cell-driven immune pathology.

OBJECTIVE

We sought to identify the molecular and cellular mechanisms by which Gimap5 deficiency predisposes to allergic airway disease.

METHODS

CD4+ T-cell polarization and development of pathogenic CD4+ T cells were assessed in Gimap5-deficient mice and a human patient with a GIMAP5 loss-of-function (LOF) mutation. House dust mite-induced airway inflammation was assessed by using a complete Gimap5 LOF (Gimap5sph/sph) and conditional Gimap5fl/flCd4Cre/ert2 mice.

RESULTS

GIMAP5 LOF mutations in both mice and human subjects are associated with spontaneous polarization toward pathogenic TH17 and TH2 cells in vivo. Mechanistic studies in vitro reveal that impairment of Gimap5-deficient TH cell differentiation is associated with increased DNA damage, particularly during TH1-polarizing conditions. DNA damage in Gimap5-deficient CD4+ T cells could be controlled by TGF-β, thereby promoting TH17 polarization. When challenged with house dust mite in vivo, Gimap5-deficient mice displayed an exacerbated asthma phenotype (inflammation and airway hyperresponsiveness), with increased development of TH2, TH17, and pathogenic TH17/TH2 cells.

CONCLUSION

Activation of Gimap5-deficient CD4+ T cells is associated with increased DNA damage and reduced survival that can be overcome by TGF-β. This leads to selective survival of pathogenic TH17 cells but also TH2 cells in human subjects and mice, ultimately promoting allergic airway disease.

Self-Recognition Sensitizes Mouse and Human Regulatory T Cells to Low-Dose CD28 Superagonist Stimulation

In rodents, low doses of CD28-specific superagonistic monoclonal antibodies (CD28 superagonists, CD28SA) selectively activate regulatory T cells (Treg). This observation has recently been extended to humans, suggesting an option for the treatment of autoimmune and inflammatory diseases. However, a mechanistic explanation for this phenomenon is still lacking. Given that CD28SA amplify T cell receptor (TCR) signals, we tested the hypothesis that the weak tonic TCR signals received by conventional CD4⁺ T cells (Tconv) in the absence of cognate antigen require more CD28 signaling input for full activation than the stronger TCR signals received by self-reactive Treg. We report that in vitro, the response of mouse Treg and Tconv to CD28SA strongly depends on MHC class II expression by antigen-presenting cells. To separate the effect of tonic TCR signals from self-peptide recognition, we compared the response of wild-type Treg and Tconv to low and high CD28SA doses upon transfer into wild-type or H-2M knockout mice, which lack a self-peptide repertoire. We found that the superior response of Treg to low CD28SA doses was lost in the absence of self-peptide presentation. We also tested if potentially pathogenic autoreactive Tconv would benefit from self-recognition-induced sensitivity to CD28SA stimulation by transferring TCR transgenic OVA-specific Tconv into OVA-expressing mice and found that low-dose CD28SA application inhibited, rather than supported, their expansion, presumably due to the massive concomitant activation of Treg. Finally, we report that also in the in vitro response of human peripheral blood mononuclear cells to CD28SA, HLA II blockade interferes with the expansion of Treg by low-dose CD28SA stimulation. These results provide a rational basis for the further development of low-dose CD28SA therapy for the improvement of Treg activity.

Gimap5-dependent inactivation of GSK3β is required for CD4+ T cell homeostasis and prevention of immune pathology

GTPase of immunity-associated protein 5 (Gimap5) is linked with lymphocyte survival, autoimmunity, and colitis, but its mechanisms of action are unclear. Here, we show that Gimap5 is essential for the inactivation of glycogen synthase kinase-3β (GSK3β) following T cell activation. In the absence of Gimap5, constitutive GSK3β activity constrains c-Myc induction and NFATc1 nuclear import, thereby limiting productive CD4⁺ T cell proliferation. Additionally, Gimap5 facilitates Ser389 phosphorylation and nuclear translocation of GSK3β, thereby limiting DNA damage in CD4⁺ T cells. Importantly, pharmacological inhibition and genetic targeting of GSK3β can override Gimap5 deficiency in CD4⁺ T cells and ameliorates immunopathology in mice. Finally, we show that a human patient with a GIMAP5 loss-of-function mutation has lymphopenia and impaired T cell proliferation in vitro that can be rescued with GSK3 inhibitors. Given that the expression of Gimap5 is lymphocyte-restricted, we propose that its control of GSK3β is an important checkpoint in lymphocyte proliferation.

Loss of function GIMAP5 mutation is associated with lymphopenia, but how it mediates T cell homeostasis is unclear. Here the authors study Gimap5^−/− mice and a patient with GIMAP5 deficiency to show how this GTPAse negatively regulates GSK3β activity to prevent DNA damage and cell death.

The Insulin Receptor Plays a Critical Role in T Cell Function and Adaptive Immunity

T cell activation is an energy-demanding process fueled by increased glucose consumption and accompanied by upregulation of the insulin receptor (INSR). In this article, we report that silencing the INSR in inducible knockdown rats impairs selective T cell functions but not thymocyte development. Glucose transport and glycolysis in activated CD4⁺ T cells were compromised in the absence of the INSR, which was associated with alterations in intracellular signaling pathways. The observed metabolic defects coincided with reduced cytokine production, proliferation, and migration, as well as increased apoptosis of CD4⁺ T cells. The cytotoxicity of CD8⁺ T cells in response to alloantigens was also diminished under these conditions, whereas the frequency and suppressive capacity of regulatory T cells were unaffected. The observed impairments proved to be decisive in vivo because silencing of the INSR attenuated clinical symptoms in animal models of acute graft-versus-host disease and multiple sclerosis. Taken together, our results suggest that upregulation of the INSR on T cells following activation is required for efficient adaptive immunity.

Relationship between Immunological Abnormalities in Rat Models of Diabetes Mellitus and the Amplification Circuits for Diabetes

A better understanding of pathogenic mechanisms is required in order to treat diseases. However, the mechanisms of diabetes mellitus and diabetic complications are extremely complex. Immune reactions are involved in the pathogenesis of diabetes and its complications, while diabetes influences immune reactions. Furthermore, both diabetes and immune reactions are influenced by genetic and environmental factors. To address these issues, animal models are useful tools. So far, various animal models of diabetes have been developed in rats, which have advantages over mice models in terms of the larger volume of tissue samples and the variety of type 2 diabetes models. In this review, we introduce rat models of diabetes and summarize the immune reactions in diabetic rat models. Finally, we speculate on the relationship between immune reactions and diabetic episodes. For example, diabetes-prone Biobreeding rats, type 1 diabetes model rats, exhibit increased autoreactive cellular and inflammatory immune reactions, while Goto-Kakizaki rats, type 2 diabetes model rats, exhibit increased Th2 reactions and attenuation of phagocytic activity. Investigation of immunological abnormalities in various diabetic rat models is useful for elucidating complicated mechanisms in the pathophysiology of diabetes. Studying immunological alterations, such as predominance of Th1/17 or Th2 cells, humoral immunity, and innate immune reactions, may improve understanding the structure of amplification circuits for diabetes in future studies.

The rise and fall of the CD28 superagonist TGN1412 and its return as TAB08: a personal account

Two decades ago, we discovered 'superagonistic' monoclonal antibodies specific for the CD28 molecule which are able to polyclonally activate T cells, in particular regulatory T cells, and are therapeutically active in many rodent models of autoimmunity, inflammation, transplantation, and tissue repair. A phase I trial of the human CD28 superagonist TGN1412 failed in 2006 due to an unexpected cytokine release syndrome, but after it became clear that dose-reduction allows to preferentially address regulatory T cells also in humans, clinical development was resumed under the name TAB08. Here, I recount the story of CD28 superagonist development from a personal perspective with an emphasis on the dramatic events during and after the 2006 phase I trial, the reasons for the failure of preclinical research to warn of the impending cytokine storm, and on the research which allowed resumption of clinical development.

Induction of T regulatory cells by the superagonistic anti-CD28 antibody D665 leads to decreased pathogenic IgG autoantibodies against desmoglein 3 in a HLA-transgenic mouse model of pemphigus vulgaris

Pemphigus vulgaris (PV) is a potentially life-threatening autoimmune disease of the skin and mucous membranes. Its pathogenesis is based on IgG autoantibodies that target the desmosomal cadherins, desmoglein 3 (Dsg3) and desmoglein 1 (Dsg1) and induce intra-epidermal loss of adhesion. Although the PV pathogenesis is well-understood, therapeutic options are still limited to immunosuppressive drugs, particularly corticosteroids, which are associated with significant side effects. Dsg3-reactive T regulatory cells (Treg) have been previously identified in PV and healthy carriers of PV-associated HLA class II alleles. Ex vivo, Dsg3-specific Treg cells down-regulated the activation of pathogenic Dsg3-specific T-helper (Th) 2 cells. In this study, in a HLA-DRB1*04:02 transgenic mouse model of PV, peripheral Treg cells were modulated by the use of Treg-depleting or expanding monoclonal antibodies, respectively. Our findings show that, in vivo, although not statistically significant, Treg cells exert a clear down-regulatory effect on the Dsg3-driven T-cell response and, accordingly, the formation of Dsg3-specific IgG antibodies. These observations confirm the powerful immune regulatory functions of Treg cells and identify Treg cells as potential therapeutic modulators in PV.

Distinct roles of T-cell lymphopenia and the microbial flora for gastrointestinal and CNS autoimmunity

T-cell lymphopenia is a major risk factor for autoimmunity. Here we describe congenic Lewis (LEW) rats with a loss-of-function mutation in the Gimap5 gene, leading to a 92% reduction in peripheral T-cell numbers. Gimap5-deficient LEW rats developed eosinophilic autoimmune gastroenteritis accompanied by a 40-fold increase in IgE serum levels. This phenotype was ameliorated by antibiotic treatment, indicating a critical role of the microbial flora in the development of inflammatory bowel disease. Interestingly, Gimap5-deficient LEW rats showed strongly aggravated experimental autoimmune encephalomyelitis (EAE) after immunization with guinea pig myelin basic protein. This phenotype, however, persisted after antibiosis, confirming that the enhanced CNS autoimmune response in T-cell lymphopenic Gimap5-deficient LEW rats was unrelated to the composition of the microbial flora. Rather, it seems that it was caused by the 7-fold increase in the percentage of activated T cells producing IL-17 and IFN-γ, and the skewed T-cell receptor (TCR) repertoire, both of which were the result of T-cell lymphopenia and not affected by antibiosis. This notion was supported by the observation that adoptive T-cell transfer corrected the TCR repertoire and improved EAE. Collectively, our findings confirm a critical albeit differential role of T-cell lymphopenia in the susceptibility to organ-specific autoimmune responses.-Fischer, H. J., Witte, A.-K., Walter, L., Gröne, H.-J., van den Brandt, J., Reichardt, H. M. Distinct roles of T-cell lymphopenia and the microbial flora for gastrointestinal and CNS autoimmunity.

GIMAP5 Deficiency Is Associated with Increased AKT Activity in T Lymphocytes

Long-term survival of T lymphocytes in quiescent state is essential to maintain their cell numbers in secondary lymphoid organs. In mice and in rats, the loss of functional GTPase of the immune associated nucleotide binding protein 5 (GIMAP5) causes peripheral T lymphopenia due to spontaneous death of T cells. The underlying mechanism responsible for the disruption of quiescence in Gimap5 deficient T cells remains largely unknown. In this study, we show that loss of functional Gimap5 results in increased basal activation of mammalian target of rapamycin (mTOR), independent of protein phosphatase 2A (PP2A) or AMP-activated protein kinase (AMPK). Our results suggest that the constitutive activation of the phosphoinositide 3-kinase (PI3K) pathway may be one of the consequences of the absence of functional GIMAP5.

Role of the gastrointestinal ecosystem in the development of type 1 diabetes

A new emphasis has been put on the role of the gastrointestinal (GI) ecosystem in autoimmune diseases; however, there is limited knowledge about its role in type 1 diabetes (T1D). Distinct differences have been observed in intestinal permeability, epithelial barrier function, commensal microbiota, and mucosal innate and adaptive immunity of patients and animals with T1D, when compared with healthy controls. The non-obese diabetic (NOD) mouse and the BioBreeding diabetes prone (BBdp) rat are the most commonly used models to study T1D pathogenesis. With the increasing awareness of the importance of the GI ecosystem in systemic disease, it is critical to understand the basics, as well as the similarities and differences between rat and mouse models and human patients. This review examines the current knowledge of the role of the GI ecosystem in T1D and indicates the extensive opportunities for further investigation that could lead to biomarkers and therapeutic interventions for disease prevention and/or modulation.

Depletion of Foxp3+ Regulatory T Cells Promotes Profibrogenic Milieu of Cholestasis-Induced Liver Injury

BACKGROUND

Accumulating evidence suggests that Foxp3+ regulatory T (Treg) cells act as inhibitory mediators of inflammation; however, the in vivo mechanism underlying this protection remains elusive in liver diseases.

AIMS

To clarify the in vivo role of Foxp3+ Treg cells in liver fibrosis, we used the DEREG mouse, which expresses the diphtheria toxin receptor under control of the Foxp3 promoter, allowing for specific deletion of Foxp3+ Treg cells.

METHODS

Bile duct ligation-induced liver injury and fibrosis were assessed by histopathology, fibrogenic gene expression, and measurement of cytokine and chemokine levels.

RESULTS

Depletion of Foxp3+ Treg cells enhanced Th17 cell response as demonstrated by the increase of IL-17+ cells and related gene expressions including Il17f, Il17ra, and Rorgt in the fibrotic livers of DEREG mice. Of note, infiltration of CD8+ T cells and Cd8 gene expression was significantly increased in the livers of DEREG mice. Consistent with increased IL-17+ and CD8+ T cell responses, DEREG mice generated higher levels of inflammatory cytokines (TNF-α, IL-6, and IL-12p70) and chemokines (MCP-1, MIP-1α, and RANTES). These results were concordant with severity of liver fibrosis and hepatic enzyme levels (ALT and ALP).

CONCLUSIONS

The present findings demonstrate that Foxp3+ Treg cells inhibit the profibrogenic inflammatory milieu through suppression of pro-fibrogenic CD8+ and IL-17+ T cells.

GIMAP GTPase family genes: potential modifiers in autoimmune diabetes, asthma, and allergy

GTPase of the immunity-associated protein (GIMAP) family members are differentially regulated during human Th cell differentiation and have been previously connected to immune-mediated disorders in animal studies. GIMAP4 is believed to contribute to the Th cell subtype-driven immunological balance via its role in T cell survival. GIMAP5 has a key role in BB-DR rat and NOD mouse lymphopenia. To elucidate GIMAP4 and GIMAP5 function and role in human immunity, we conducted a study combining genetic association in different immunological diseases and complementing functional analyses. Single nucleotide polymorphisms tagging the GIMAP haplotype variation were genotyped in Finnish type 1 diabetes (T1D) families and in a prospective Swedish asthma and allergic sensitization birth cohort. Initially, GIMAP5 rs6965571 was associated with risk for asthma and allergic sensitization (odds ratio [OR] 3.74, p = 0.00072, and OR 2.70, p = 0.0063, respectively) and protection from T1D (OR 0.64, p = 0.0058); GIMAP4 rs13222905 was associated with asthma (OR 1.28, p = 0.035) and allergic sensitization (OR 1.27, p = 0.0068). However, after false discovery rate correction for multiple testing, only the associations of GIMAP4 with allergic sensitization and GIMAP5 with asthma remained significant. In addition, transcription factor binding sites surrounding the associated loci were predicted. A gene-gene interaction in the T1D data were observed between the IL2RA rs2104286 and GIMAP4 rs9640279 (OR 1.52, p = 0.0064) and indicated between INS rs689 and GIMAP5 rs2286899. The follow-up functional analyses revealed lower IL-2RA expression upon GIMAP4 knockdown and an effect of GIMAP5 rs2286899 genotype on protein expression. Thus, the potential role of GIMAP4 and GIMAP5 as modifiers of immune-mediated diseases cannot be discarded.

Gut immune deficits in LEW.1AR1-iddm rats partially overcome by feeding a diabetes-protective diet

The gut immune system and its modification by diet have been implicated in the pathogenesis of type 1 diabetes (T1D). Therefore, we investigated gut immune status in non-diabetes-prone LEW.1AR1 and diabetes-prone LEW.1AR1-iddm rats and evaluated the effect of a low antigen, hydrolysed casein (HC)-based diet on gut immunity and T1D. Rats were weaned onto a cereal-based or HC-based diet and monitored for T1D. Strain and dietary effects on immune homeostasis were assessed in non-diabetic rats (50-60 days old) and rats with recent-onset diabetes using flow cytometry and immunohistochemistry. Immune gene expression was analysed in mesenteric lymph nodes (MLN) and jejunum using quantitative RT-PCR and PCR arrays. T1D was prevented in LEW.1AR1-iddm rats by feeding an HC diet. Diabetic LEW.1AR1-iddm rats had fewer lymphoid tissue T cells compared with LEW.1AR1 rats. The percentage of CD4(+)  Foxp3(+) regulatory T (Treg) cells was decreased in pancreatic lymph nodes (PLN) of diabetic rats. The jejunum of 50-day LEW.1AR1-iddm rats contained fewer CD3(+) T cells, CD163(+) M2 macrophages and Foxp3(+) Treg cells. Ifng expression was increased in MLN and Foxp3 expression was decreased in the jejunum of LEW.1AR1-iddm rats; Ifng/Il4 was decreased in jejunum of LEW.1AR1-iddm rats fed HC. PCR arrays revealed decreased expression of M2-associated macrophage factors in 50-day LEW.1AR1-iddm rats. Wheat peptides stimulated T-cell proliferation and activation in MLN and PLN cells from diabetic LEW.1AR1-iddm rats. LEW.1AR1-iddm rats displayed gut immune cell deficits and decreased immunoregulatory capacity, which were partially corrected in animals fed a low antigen, protective HC diet consistent with other models of T1D.

B7-H4 as a protective shield for pancreatic islet beta cells

Auto- and alloreactive T cells are major culprits that damage β-cells in type 1 diabetes (T1D) and islet transplantation. Current immunosuppressive drugs can alleviate immune-mediated attacks on islets. T cell co-stimulation blockade has shown great promise in autoimmunity and transplantation as it solely targets activated T cells, and therefore avoids toxicity of current immunosuppressive drugs. An attractive approach is offered by the newly-identified negative T cell co-signaling molecule B7-H4 which is expressed in normal human islets, and its expression co-localizes with insulin. A concomitant decrease in B7-H4/insulin co-localization is observed in human type 1 diabetic islets. B7-H4 may play protective roles in the pancreatic islets, preserving their function and survival. In this review we outline the protective effect of B7-H4 in the contexts of T1D, islet cell transplantation, and potentially type 2 diabetes. Current evidence offers encouraging data regarding the role of B7-H4 in reversal of autoimmune diabetes and donor-specific islet allograft tolerance. Additionally, unique expression of B7-H4 may serve as a potential biomarker for the development of T1D. Future studies should continue to focus on the islet-specific effects of B7-H4 with emphasis on mechanistic pathways in order to promote B7-H4 as a potential therapy and cure for T1D.

Targeting the IL-17/IFN-γ axis as a potential new clinical therapy for type 1 diabetes

Type 1 diabetes (T1D) results from the autoimmune destruction of insulin-producing pancreatic beta cells. There is now mounting evidence that pro-inflammatory pathways, which are mediated by T cells that secrete IL-17 and IFN-γ, play a critical role in the loss of beta cells. These data suggest that blockade of T cells that secrete IL-17 and IFN-γ may halt or reverse disease in subjects with recent-onset T1D. Agents to facilitate this approach are currently in clinical use. Ustekinumab, a humanized monoclonal antibody that targets the shared p40 subunit of IL-12 and IL-23, has been used for the treatment of psoriasis, an indication for which it has proven to be safe and effective. In this review, we summarize the evidence that supports a combined pathogenic role of IL-17 and IFN-γ in the development of T1D, with the aim of providing a rationale for testing agents such as ustekinumab for the treatment of T1D.

Consumption of acidic water alters the gut microbiome and decreases the risk of diabetes in NOD mice

Infant formula and breastfeeding are environmental factors that influence the incidence of Type 1 Diabetes (T1D) as well as the acidity of newborn diets. To determine if altering the intestinal microbiome is one mechanism through which an acidic liquid plays a role in T1D, we placed non-obese diabetic (NOD)/ShiLtJt mice on neutral (N) or acidified H2O and monitored the impact on microbial composition and diabetes incidence. NOD-N mice showed an increased development of diabetes, while exhibiting a decrease in Firmicutes and an increase in Bacteroidetes, Actinobacteria, and Proteobacteria from as early as 2 weeks of age. NOD-N mice had a decrease in the levels of Foxp3 expression in CD4(+)Foxp3(+) cells, as well as decreased CD4(+)IL17(+) cells, and a lower ratio of IL17/IFNγ CD4+ T-cells. Our data clearly indicates that a change in the acidity of liquids consumed dramatically alters the intestinal microbiome, the presence of protective Th17 and Treg cells, and the incidence of diabetes. This data suggests that early dietary manipulation of intestinal microbiota may be a novel mechanism to delay T1D onset in genetically pre-disposed individuals.

Generation of Transgenic Rats Using Lentiviral Vectors

Transgenesis is a valuable tool with which to study different aspects of gene function in the context of the intact organism. During the last two decades a tremendous number of transgenic animals have been generated, and the continuous improvement of technology and the development of new systems have fostered their widespread application in biomedical research. Generally, transgenic animals are generated by introducing foreign DNA into fertilized oocytes, which can be achieved either by injecting recombinant DNA into the pronucleus or by transferring lentiviral particles into the perivitelline space. While mice remain the favored species in many laboratories, there are a number of applications where the use of rats is advantageous. One such research area is multiple sclerosis. Here, several experimental models are available that are closely mimicking the human disease, and it is possible to induce neuroinflammation by transferring pathogenic T cells which can then be studied by flow cytometry and 2-photon live imaging. Unlike for mice, the development of transgenic rats has encountered some hurdles in the past, e.g., due to a complicated reproductive biology and the frailty of the fertilized oocytes in vitro. In this chapter we provide a protocol describing how we manipulate single cell embryos in our lab in order to efficiently generate transgenic rats in a variety of different strains using lentiviral gene transfer.

[Immunological disorders of diabetes mellitus in experimental rat models]

A comprehensive understanding of the pathogenic mechanism is the prerequisite for proper disease management. However, the mechanisms of diabetes mellitus and diabetic complication remain extremely complicated and unresolved. While immune reactions are involved in the pathogenesis of diabetes and diabetic complication, the diabetic condition itself can influence immune responses. Furthermore, both diabetes and immune reactions are regulated by genetic and environmental factors. As a result, animal models have evolved to be powerful research tools to elucidate the complicated mechanisms for the pathogenesis of diabetes. Recently, various animal models of diabetes have been developed in rats, which provide advantages over mouse models in the scale of tissue samples and variation in type 2 diabetes models. In this review, we introduced rat models of diabetes and summarized the immune reactions in diabetic rats to propose the relationship between immune reactions and diabetes. Type 1 diabetes is induced by self-reactive cellular immune reactions. On the other hand, type 2 diabetes in rat models is associated with augmentation of innate immune reactions and increased humoral immunity. For example, helper T (Th) 1/Th17 cells are prevalent in non-obese type 1 diabetes rats (diabetes-prone BioBreeding rats), while non-obese type 2 diabetes rats (Goto-Kakizaki rat) show higher levels of natural IgM and T cell ratios with elevated Th2 cells compared with Wister rats. The investigation of immunological disorders in various diabetic rat models is useful to elucidate complicated mechanisms for the pathophysiology of diabetes. In future studies, immunological experimentations altering Th1/Th17 or Th2 cell levels and natural immune reactions may lend support to understanding the causes of diabetes and predicting the pathological conditions in diabetes.

Promotion of autoimmune diabetes by cereal diet in the presence or absence of microbes associated with gut immune activation, regulatory imbalance, and altered cathelicidin antimicrobial Peptide

We are exposed to millions of microbial and dietary antigens via the gastrointestinal tract, which likely play a key role in type 1 diabetes (T1D). We differentiated the effects of these two major environmental factors on gut immunity and T1D. Diabetes-prone BioBreeding (BBdp) rats were housed in specific pathogen-free (SPF) or germ-free (GF) conditions and weaned onto diabetes-promoting cereal diets or a protective low-antigen hydrolyzed casein (HC) diet, and T1D incidence was monitored. Fecal microbiota 16S rRNA genes, immune cell distribution, and gene expression in the jejunum were analyzed. T1D was highest in cereal-SPF (65%) and cereal-GF rats (53%) but inhibited and delayed in HC-fed counterparts. Nearly all HC-GF rats remained diabetes-free, whereas HC-fed SPF rats were less protected (7 vs. 29%). Bacterial communities differed in SPF rats fed cereal compared with HC. Cereal-SPF rats displayed increased gut CD3(+) and CD8α(+) lymphocytes, ratio of Ifng to Il4 mRNA, and Lck expression, indicating T-cell activation. The ratio of CD3(+) T cells expressing the Treg marker Foxp3(+) was highest in HC-GF and lowest in cereal-SPF rats. Resident CD163(+) M2 macrophages were increased in HC-protected rats. The cathelicidin antimicrobial peptide (Camp) gene was upregulated in the jejunum of HC diet-protected rats, and CAMP(+) cells colocalized with CD163. A cereal diet was a stronger promoter of T1D than gut microbes in association with impaired gut immune homeostasis.

The BB rat as a model of human type 1 diabetes

The BB rat is an important rodent model of human type 1 diabetes (T1D) and has been used to study mechanisms of diabetes pathogenesis as well as to investigate potential intervention therapies for clinical trials. The Diabetes-Prone BB (BBDP) rat spontaneously develops autoimmune T1D between 50 and 90 days of age. The Diabetes-Resistant BB (BBDR) rat has similar diabetes-susceptible genes as the BBDP, but does not become diabetic in viral antibody-free conditions. However, the BBDR rat can be induced to develop T1D in response to certain treatments such as regulatory T cell (T(reg)) depletion, toll-like receptor ligation, or virus infection. These diabetes-inducible rats develop hyperglycemia under well-controlled circumstances and within a short, predictable time frame (14-21 days), thus facilitating their utility for investigations of specific stages of diabetes development. Therefore, these rat strains are invaluable models for studying autoimmune diabetes and the role of environmental factors in its development, of particular importance due to the influx of studies associating virus infection and human T1D.

Targeting regulatory T cells in the treatment of type 1 diabetes mellitus

Type 1 diabetes mellitus (T1DM) is a T cell-mediated autoimmune disease resulting in islet β cell destruction, hypoinsulinemia, and severely altered glucose homeostasis. T1DM has classically been attributed to the pathogenic actions of auto-reactive effector T cells(Teffs) on the β cell. Recent literature now suggests that a failure of a second T cell subtype, known as regulatory T cells (Tregs), plays a critical role in the development of T1DM. During immune homeostasis, Tregs counterbalance the actions of autoreactive Teff cells, thereby participating in peripheral tolerance. An imbalance in the activity between Teff and Tregs may be crucial in the breakdown of peripheral tolerance, leading to the development of T1DM. In this review, we summarize our current understanding of Treg function in health and in T1DM, and examine the effect of experimental therapies for T1DM on Treg cell number and function in both mice and humans.

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.

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.

Preculture of PBMCs at high cell density increases sensitivity of T-cell responses, revealing cytokine release by CD28 superagonist TGN1412

Human volunteers receiving TGN1412, a humanized CD28-specific monoclonal antibody, experienced a life-threatening cytokine release syndrome during a recent trial. Preclinical tests using human PBMCs had failed to announce the rapid release of TNF, IFN-γ, and other toxic cytokines in response to this CD28 “superagonist” (CD28SA). CD28SA activate T-lymphocytes by ligating CD28 without overt engagement of the TCR. They do, however, depend on “tonic” TCR signals, which they amplify. Here we show that short-term preculture of PBMCs at high, but not at low, cell density results in massive cytokine release during subsequent stimulation with soluble TGN1412. Restoration of reactivity was cell-contact dependent, involved functional maturation of both monocytes and T cells, was sensitive to blockade by HLA-specific mAb, and was associated with TCR polarization and tyrosine phosphorylation. CD4 effector memory T cells were identified as the main source of proinflammatory cytokines. Importantly, responses to other T-cell activating agents, including microbial antigens, were also enhanced if PBMCs were first allowed to interact under tissue-like conditions. We provide a protocol, which strongly improves reactivity of circulating T cells to soluble stimulants, thereby allowing for more reliable preclinical testing of both activating and inhibitory immunomodulatory drugs.

CD4 T cells and their antigens in the pathogenesis of autoimmune diabetes

Pathogenesis of type 1 diabetes (T1D) is mediated by effector T cells and CD4 Th1 and Th17T cells have important roles in this process. While effector function of Th1 cells is well established, because of their inherent plasticity Th17 cells have been more controversial. Th17 cells contribute to pathogenicity, but several studies indicate that Th17 cells transfer disease through conversion to Th1 cells in vivo. CD4T cells are attracted to islets by β-cell antigens which include insulin and the two new autoantigens, chromogranin A and islet amyloid polypeptide, all proteins of the secretory granule. Peptides of insulin and ChgA bind to the NOD class II molecule in an unconventional manner and since autoantigenic peptides may typically bind to MHC with low affinity, it is postulated that post-translational modifications of β-cell peptides could contribute to the interaction between peptides, MHC, and the autoreactive TCR.

Loss of immunological tolerance in Gimap5-deficient mice is associated with loss of Foxo in CD4+ T cells

Previously, we reported the abrogation of quiescence and reduced survival in lymphocytes from Gimap5(sph/sph) mice, an ENU germline mutant with a missense mutation in the GTPase of immunity-associated protein 5 (Gimap5). These mice showed a progressive loss of peripheral lymphocyte populations and developed spontaneous colitis, resulting in early mortality. In this study, we identify the molecular pathways that contribute to the onset of colitis in Gimap5(sph/sph) mice. We show that CD4(+) T cells become Th1/Th17 polarized and are critically important for the development of colitis. Concomitantly, regulatory T cells become reduced in frequency in the peripheral tissues, and their immunosuppressive capacity becomes impaired. Most importantly, these progressive changes in CD4(+) T cells are associated with the loss of Forkheadbox group O (Foxo)1, Foxo3, and Foxo4 expression. Our data establish a novel link between Gimap5 and Foxo expression and provide evidence for a regulatory mechanism that controls Foxo protein expression and may help to maintain immunological tolerance.

Expansion of Th17 cells and functional defects in T regulatory cells are key features of the pancreatic lymph nodes in patients with type 1 diabetes

OBJECTIVE

Autoimmune diseases, including type 1 diabetes, are thought to have a Th17-cell bias and/or a T-regulatory cell (Treg) defect. Understanding whether this is a hallmark of patients with type 1 diabetes is a crucial question that is still unsolved, largely due to the difficulties of accessing tissues targeted by the disease.

RESEARCH DESIGN AND METHODS

We phenotypically and functionally characterized Th17 cells and Tregs residing in the pancreatic-draining lymph nodes (PLNs) of 19 patients with type 1 diabetes and 63 nondiabetic donors and those circulating in the peripheral blood of 14 type 1 diabetic patients and 11 healthy subjects.

RESULTS

We found upregulation of Th17 immunity and functional defects in CD4(+)CD25(bright) Tregs in the PLNs of type 1 diabetic subjects but not in their peripheral blood. In addition, the proinsulin-specific Treg-mediated control was altered in the PLNs of diabetic patients. The dysfunctional Tregs isolated from diabetic subjects did not contain contaminant effector T cells and were all epigenetically imprinted to be suppressive, as defined by analysis of the Treg-specific demethylated region within the forkhead box P3 (FOXP3) locus.

CONCLUSIONS

These data provide evidence for an unbalanced immune status in the PLNs of type 1 diabetic subjects, and treatments restoring the immune homeostasis in the target organ of these patients represent a potential therapeutic strategy.