Type 1 diabetes and T regulatory cells

Exosomes as biomarkers and therapeutic delivery for autoimmune diseases: Opportunities and challenges

Exosomes are spherical lipid bilayer vesicles composed of lipids, proteins and nucleic acids that deliver signaling molecules through a vesicular transport system to regulate the function and morphology of target cells, thereby involving in a variety of biological processes, such as cell apoptosis or proliferation, and cytokine production. In the past decades, there are emerging evidence that exosomes play pivotal roles in the pathological mechanisms of several autoimmune diseases (ADs), including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), type 1 diabetes mellitus (T1DM), Sjogren's syndrome (SS), multiple sclerosis (MS), inflammatory bowel disease (IBD). systemic sclerosis (SSc), etc. Several publications have shown that exosomes are involved in the pathogenesis of ADs mainly through intercellular communication and by influencing the response of immune cells. The level of exosomes and the expression of nucleic acids can reflect the degree of disease progression and are excellent biomarkers for ADs. In addition, exosomes have the potential to be used as drug carriers thanks to their biocompatibility and stability. In this review, we briefly summarized the current researches regarding the biological functions of exosomes in ADs, and provided an insight into the potential of exosomes as biomarkers and therapeutic delivery for these diseases.

The role of cytokines and T-bet, GATA3, ROR-γt, and FOXP3 transcription factors of T cell subsets in the natural clinical progression of Type 1 Diabetes

Th cells play an important role in pathogenesis of type 1 diabetes (T1D). Peripheral blood mononuclear cells were isolated from peripheral blood samples from newly diagnosed (ND), 1-year (1YD), and 5-year T1D (5YD) patients (n:8 of each group), 8 healthy controls (HC), and cultured for 24 h under unstimulated (US) and stimulated conditions. Cell ratios of Th1, Th2, Th17, Treg, and intracellular levels of IFN-γ, TNF-α, IL-10, TGF-β, IL-5, IL-13, IL-17, and IL-21 cytokines were evaluated using the flow cytometry. mRNA expressions of transcription factors T-bet, GATA3, ROR-γt, and FOXP3 of these cells were determined by real-time PCR. Reduced CD4⁺CD25^high cell ratios were detected in ND. CD4⁺CD25^high cells were found to be reduced in ND and 1YD compared to HC under IL-2-stimulated conditions. Intracellular IFN-γ and TNF-α levels were low in all patients under US and IL-12-stimulated conditions. IL-17A and IL-21 were found to be high in patients with IL-6-stimulated conditions. Expressions of IL-10 and TGF-β have been observed to be reduced in patients. Th1/Th2, Th17/Treg, and Th1/Treg ratios were higher in patient groups. FOXP3 and GATA3 mRNA expressions were found to be low in patients, while RORγt and T-bet mRNA levels were higher than HC. Th1, Th17, and Treg cells and their cytokines have been shown to be associated with type 1 diabetes.

The long and winding road: From mouse linkage studies to a novel human therapeutic pathway in type 1 diabetes

Autoimmunity involves a loss of immune tolerance to self-proteins due to a combination of genetic susceptibility and environmental provocation, which generates autoreactive T and B cells. Genetic susceptibility affects lymphocyte autoreactivity at the level of central tolerance (e.g., defective, or incomplete MHC-mediated negative selection of self-reactive T cells) and peripheral tolerance (e.g., failure of mechanisms to control circulating self-reactive T cells). T regulatory cell (Treg) mediated suppression is essential for controlling peripheral autoreactive T cells. Understanding the genetic control of Treg development and function and Treg interaction with T effector and other immune cells is thus a key goal of autoimmunity research. Herein, we will review immunogenetic control of tolerance in one of the classic models of autoimmunity, the non-obese diabetic (NOD) mouse model of autoimmune Type 1 diabetes (T1D). We review the long (and still evolving) elucidation of how one susceptibility gene, Cd137, (identified originally via linkage studies) affects both the immune response and its regulation in a highly complex fashion. The CD137 (present in both membrane and soluble forms) and the CD137 ligand (CD137L) both signal into a variety of immune cells (bi-directional signaling). The overall outcome of these multitudinous effects (either tolerance or autoimmunity) depends upon the balance between the regulatory signals (predominantly mediated by soluble CD137 via the CD137L pathway) and the effector signals (mediated by both membrane-bound CD137 and CD137L). This immune balance/homeostasis can be decisively affected by genetic (susceptibility vs. resistant alleles) and environmental factors (stimulation of soluble CD137 production). The discovery of the homeostatic immune effect of soluble CD137 on the CD137-CD137L system makes it a promising candidate for immunotherapy to restore tolerance in autoimmune diseases.

The Emerging Role of m6A Modification in Regulating the Immune System and Autoimmune Diseases

Over the past several decades, RNA modifications have rapidly emerged as an indispensable topic in epitranscriptomics. N6-methyladenosine (m6A), namely, methylation at the sixth position of an adenine base in an RNA molecule, is the most prevalent RNA modification in both coding and noncoding RNAs. m6A has emerged as a crucial posttranscriptional regulator involved in both physiological and pathological processes. Based on accumulating evidence, m6A participates in the pathogenesis of immune-related diseases by regulating both innate and adaptive immune cells through various mechanisms. Autoimmune diseases are caused by a self-destructive immune response in the setting of genetic and environmental factors, and recent studies have discovered that m6A may play an essential role in the development of autoimmune diseases. In this review, we focus on the important role of m6A modification in biological functions and highlight its contributions to immune cells and the development of autoimmune diseases, thereby providing promising epitranscriptomic targets for preventing and treating autoimmune disorders.

The Many Faces of CD4+ T Cells: Immunological and Structural Characteristics

As a major arm of the cellular immune response, CD4⁺ T cells are important in the control and clearance of infections. Primarily described as helpers, CD4⁺ T cells play an integral role in the development and activation of B cells and CD8⁺ T cells. CD4⁺ T cells are incredibly heterogeneous, and can be divided into six main lineages based on distinct profiles, namely T helper 1, 2, 17 and 22 (Th1, Th2, Th17, Th22), regulatory T cells (Treg) and T follicular helper cells (Tfh). Recent advances in structural biology have allowed for a detailed characterisation of the molecular mechanisms that drive CD4⁺ T cell recognition. In this review, we discuss the defining features of the main human CD4⁺ T cell lineages and their role in immunity, as well as their structural characteristics underlying their detection of pathogens.

Regulatory T Cell Plasticity and Stability and Autoimmune Diseases

CD4⁺CD25⁺ regulatory T cells (Tregs) are a class of CD4⁺ T cells with immunosuppressive functions that play a critical role in maintaining immune homeostasis. However, in certain disease settings, Tregs demonstrate plastic differentiation, and the stability of these Tregs, which is characterized by the stable expression or protective epigenetic modifications of the transcription factor Foxp3, becomes abnormal. Plastic Tregs have some features of helper T (Th) cells, such as the secretion of Th-related cytokines and the expression of specific transcription factors in Th cells, but also still retain the expression of Foxp3, a feature of Tregs. Although such Th-like Tregs can secrete pro-inflammatory cytokines, they still possess a strong ability to inhibit specific Th cell responses. Therefore, the plastic differentiation of Tregs not only increases the complexity of the immune circumstances under pathological conditions, especially autoimmune diseases, but also shows an association with changes in the stability of Tregs. The plastic differentiation and stability change of Tregs play vital roles in the progression of diseases. This review focuses on the phenotypic characteristics, functions, and formation conditions of several plastic Tregs and also summarizes the changes of Treg stability and their effects on inhibitory function. Additionally, the effects of Treg plasticity and stability on disease prognosis for several autoimmune diseases were also investigated in order to better understand the relationship between Tregs and autoimmune diseases.

Agent-Based Modeling of Immune Response to Study the Effects of Regulatory T Cells in Type 1 Diabetes

Regulatory T cells (Tregs) have an important role in self-tolerance. Understanding the functions of Tregs is important for preventing or slowing the progress of Type 1 Diabetes. We use a two-dimensional (2D) agent-based model to simulate immune response in mice and test the effects of Tregs in tissue protection. We compared the immune response with and without Tregs, and also tested the effects of Tregs from different sources or with different functions. The results show that Tregs can inhibit the proliferation of effector T cells by inhibiting antigens presenting via dendritic cells (DCs). Although the number and function of Tregs affect the inhibition, a small number of Tregs compared to CD4+ T cells can effectively protect islets in pancreatic tissue. Finally, we added Tregs to the system in the middle phase of the immune response. The simulation results show that Tregs can inhibit the production of effector CD8+ T cells and maintain a good environment for β cell regeneration.

Singular role for T-BET+CXCR3+ regulatory T cells in protection from autoimmune diabetes

Foxp3⁺ regulatory T (Treg) cells are crucial for restraining inflammation in a variety of autoimmune diseases, including type 1 diabetes (T1D). However, the transcriptional and functional phenotypes of Treg cells within the pancreatic lesion remain poorly understood. Here we characterized pancreas-infiltrating Treg cells in the NOD mouse model of T1D and uncovered a substantial enrichment of the Treg subpopulation expressing the chemokine receptor CXCR3. Accumulation of CXCR3⁺ Treg cells within pancreatic islets was dependent on the transcription factor T-BET, and genetic ablation of T-BET increased the onset and penetrance of disease, abrogating the sex bias normally seen in the NOD model. Both male and female mice lacking T-BET⁺ Treg cells showed a more aggressive insulitic infiltrate, reflected most prominently by elevated production of type 1 cytokines. Our results suggest the possibility of fine therapeutic targeting of Treg cells, in a tissue- and cell-subset-specific fashion, as a more focused immunotherapy for T1D.

Th1/Th2 cytokines in Type 1 diabetes: Relation to duration of disease and gender

BACKGROUND

T-cells are important in the pathogenesis of Type 1 diabetes (T1D). However, the exact role of T-cell subpopulations in this pathway remains unknown. The purpose of this study was to assess the expression pattern of T helper 1 (Th1) interferon-gamma (IFN-γ) and Th2 interleukin-4 (IL-4) cytokines and their relationship with sex and disease duration in T1D patients.

MATERIALS AND METHODS

This study was conducted on 21 T1D patients and 22 healthy subjects. Gene expression analysis of peripheral blood mononuclear cells (PBMCs) was performed using real-time reverse transcriptase polymerase chain reaction.

RESULTS

IFN-γ gene expression was significantly lower in T1D patients compared with controls (P < 0.05). Conversely, IL-4 mRNAs were significantly increased in the PBMCs from patients as compared to controls (P < 0.05). There was no significant difference in the expression of IL-4 and IFN-γ between men and women with T1D (P > 0.05) while IL-4 mRNA expression in male patients was about 1.9 folds higher than female patients. Moreover, IFN-γ mRNA expression in female patients was about 1.8 folds lower than male patients. Patients were divided into two groups regarding their disease duration: <10 years and >10 years. A significant increase in the IL-4 expression was observed between two groups of patients compared to controls (P < 0.0001). Conversely, there was a significant difference in the expression of IFN-γ only between patients with more than 10 years of disease duration (P = 0.02).

CONCLUSION

These data propose supplementary implications for the role of Th1/Th2 imbalance in T1D immunopathogenesis. Moreover, factors such as sex and disease duration may have some influence on cytokine mRNA expression.