The soluble CTLA-4 splice variant protects from type 1 diabetes and potentiates regulatory T-cell function

Soluble CTLA-4 regulates immune homeostasis and promotes resolution of inflammation by suppressing type 1 but allowing type 2 immunity

Cytotoxic T-lymphocyte-associated antigen -4 (CTLA-4) is a co-inhibitory receptor that restricts T cell activation. CTLA-4 exists as membrane (mCTLA-4) and soluble (sCTLA-4) forms, but the key producers, kinetics, and functions of sCTLA-4 are unclear. Here, we investigated the roles of sCTLA-4 in immune regulation under non-inflammatory and inflammatory conditions. Effector regulatory T (Treg) cells were the most active sCTLA-4 producers in basal and inflammatory states, with distinct kinetics upon T cell receptor (TCR) stimulation. We generated mice specifically deficient in sCTLA-4 production, which exhibited spontaneous activation of type 1 immune cells and heightened autoantibody/immunoglobulin E (IgE) production. Conversely, mCTLA-4-deficient mice developed severe type 2-skewed autoimmunity. sCTLA-4 blockade of CD80/86 on antigen-presenting cells inhibited T helper (Th)1, but not Th2, differentiation in vitro. In vivo, Treg-produced sCTLA-4, suppressed Th1-mediated experimental colitis, and enhanced wound healing but hampered tumor immunity. Thus, sCTLA-4 is essential for immune homeostasis and controlling type 1 immunity while allowing type 2 immunity to facilitate resolution in inflammatory conditions.

Risk Allele rs117026326-Mediated Alternative Splicing of GTF2I Promotes B Cell Proliferation in Primary Sjögren's Syndrome

Objectives: Primary Sjögren's syndrome (pSS) is associated with a risk allele T of rs117026326 located at a potential splicing enhancer within the intronic region of general transcription factor II-I (GTF2I). This study aimed to explore the rs117026326-regulated alternative splicing of GTF2I and its role in B cell overactivation in pSS. Methods: GTF2I isoform expressions and rs117026326 genotypes of pSS peripheral blood mononuclear cells (PBMCs) were examined using quantitative PCR and Sanger sequencing, respectively. GTF2IΔ was overexpressed in B cells, T cells, and macrophages using plasmid transfection. Proliferation of B cells and T cells was determined using Cell Counting Kit-8 (CCK8) assay. CD4+ T cell differentiation was inspected using flow cytometry. Proinflammatory cytokine production of macrophages was investigated using quantitative PCR. c-FOS expression in GTF2IΔ-transfected B cells was tested by quantitative PCR, and proliferation of GTF2IΔ-transfected B cells treated with c-FOS siRNA or c-FOS inhibitor was interrogated using CCK8 assay. Results: pSS patients with risk allele of rs117026326 expressed higher levels of GTF2IΔ and GTF2Iζ isoforms. GTF2IΔ expression was correlated with serum immunoglobulin G (IgG). GTF2IΔ promoted B cell proliferation and upregulated c-FOS expression. Knocking down or inhibition of c-FOS reversed B cell proliferation driven by GTF2IΔ. Conclusion: pSS risk allele of rs117026326 modulates alternative splicing of GTF2I and upregulates GTF2IΔ isoform, which promotes B cell proliferation through enhancing binding and transcription of c-FOS.

Association between Cytotoxic T-Lymphocyte-Associated Antigen 4 (CTLA-4) Locus and Early-Onset Anti-acetylcholine Receptor-Positive Myasthenia Gravis in Serbian Patients

Genome-wide association studies (GWAS) have provided strong evidence that early- and late-onset MG have different genetic backgrounds. Recent in silico analysis based on GWAS results revealed rs231735 and rs231770 variants within CTLA-4 locus as possible MG causative genetic factors. We aimed to explore the association of rs231735 and rs231770 with MG in a representative cohort of Serbian patients. We conducted an age-, sex-, and ethnicity-matched case-control study. Using TaqMan allele discrimination assays, the frequency of rs231735 and rs231770 genetic variants was examined in 447 AChR-MG patients and 447 matched controls. There was no significant association of rs231735 and rs231770 with the entire MG cohort (P > 0.05). Nevertheless, when stratifying patients into early-onset (n = 183) and late-onset MG (n = 264), we found early-onset patients had a significantly lower frequency of the rs231735 allele T compared to controls (OR = 0.734, 95% CI = 0.575-0.938, p10e6 permutation < 0.05), and rs231735 genotype TT and rs231770 genotype TT had a protective effect on early-onset MG (OR = 0.548, 95% CI = 0.339-0.888, and OR = 0.563, 95% CI = 0.314-1.011, p10e6 permutation < 0.05). Consequently, we found that individuals with the rs231735-rs231770 haplotype GC had a higher risk for developing early-onset MG (OR = 1.360, P = 0.027, p10e6 permutation < 0.05). Our results suggest that CTLA-4 rs231735 and rs231770 may be risk factors only for patients with early-onset MG in Serbian population.

Mini-Review: Tregs as a Tool for Therapy-Obvious and Non-Obvious Challenges and Solutions

Tregs have the potential to be utilized as a novel therapeutic agent for the treatment of various chronic diseases, including diabetes, Alzheimer's disease, asthma, and rheumatoid arthritis. One of the challenges associated with developing a therapeutic product based on Tregs is the non-selectivity of polyclonal cells. A potential solution to this issue is a generation of antigen-specific CAR-Tregs. Other challenges associated with developing a therapeutic product based on Tregs include the phenotypic instability of these cells in an inflammatory microenvironment, discrepancies between engineered Treg-like cells and natural Tregs, and the expression of dysfunctional isoforms of Treg marker genes. This review presents a summary of proposed strategies for addressing these challenges.

Advancing Animal Models of Human Type 1 Diabetes

Multiple rodent models have been developed to study the basis of type 1 diabetes (T1D). However, nonobese diabetic (NOD) mice and derivative strains still provide the gold standard for dissecting the basis of the autoimmune responses underlying T1D. Here, we review the developmental origins of NOD mice, and how they and derivative strains have been used over the past several decades to dissect the genetic and immunopathogenic basis of T1D. Also discussed are ways in which the immunopathogenic basis of T1D in NOD mice and humans are similar or differ. Additionally reviewed are efforts to "humanize" NOD mice and derivative strains to provide improved models to study autoimmune responses contributing to T1D in human patients.

Decoding the genetic influence of CT60 non-coding polymorphism in CTLA-4 gene and sCTLA-4 biomarker with rheumatoid arthritis in the Indian population

BACKGROUND

Cytoplasmic T Lymphocyte Antigen - 4 (CTLA-4) gene encodes an immunoregulatory receptor expressed on surface of activated T-cells to mediate peripheral tolerance against self-antigen. It suppresses auto-reactive T-cell proliferation either by inactivation or apoptosis of T-cells. The CTLA-4 mRNA undergoes alternative splicing to synthesize a native soluble form of CTLA-4 (sCTLA-4) protein, which lacks exon 3 that encodes for transmembrane region. As a result, sCTLA-4 circulates as a soluble serum protein and acts as an immunoregulator molecule to maintain homeostasis in the blood.

MATERIALS AND RESULTS

Techniques coupled with quantitative Polymerase Chain Reaction (qPCR) and High-Resolution Melting Analysis (HRMA) were used to screen CTLA-4 3'Untranslated Region (UTR) CT60 (A/G) rs3087243 Single Nucleotide Polymorphism (SNP) and their association with Rheumatoid Arthritis (RA) in the Indian population. In addition, we also evaluated the concentration of sCTLA-4 serum protein in RA patients carrying rs3087243 SNP with different genotypes (A/A, G/A, and G/G). Statistical analysis of Odds Ratio (OR), Confidence Interval (C.I), and Relative Risk (RR) have shown that frequency of CTLA-4 rs3087243 SNP G/G genotype was significantly associated with RA in the Indian population (OR 1.7140; CI = 1.0765 to 2.7290; RR = 1.5434; p = 0.0232). The sCTLA-4 concentration was also significantly lower in RA patients carrying rs3087243 SNP G/G genotype than control group (p < 0.001).

CONCLUSION

Co-inheritance of CTLA-4 signal peptide and 3'UTR SNPs may activate RAPP pathway. Downregulation of CTLA-4 and sCTLA-4 serum protein by rs3087243 SNP can increase the hyperactivation of T-cells, which causes RA.

Cluster of differentiation molecules in the metabolic syndrome

Metabolic syndrome (MetS) represents a significant public health concern due to its association with an increased risk of cardiovascular disease, type 2 diabetes, and other serious health conditions. Despite extensive research, the underlying molecular mechanisms contributing to MetS pathogenesis remain elusive. This review aims to provide a comprehensive overview of the molecular mechanisms linking MetS and cluster of differentiation (CD) markers, which play critical roles in immune regulation and cellular signaling. Through an extensive literature review with a systematic approach, we examine the involvement of various CD markers in MetS development and progression, including their roles in adipose tissue inflammation, insulin resistance, dyslipidemia, and hypertension. Additionally, we discuss potential therapeutic strategies targeting CD markers for the management of MetS. By synthesizing current evidence, this review contributes to a deeper understanding of the complex interplay between immune dysregulation and metabolic dysfunction in MetS, paving the way for the development of novel therapeutic interventions.

Soluble form of immune checkpoints in autoimmune diseases

Immune checkpoints are essential regulators of immune responses, either by activating or suppressing them. Consequently, they are regarded as pivotal elements in the management of infections, cancer, and autoimmune disorders. In recent years, researchers have identified numerous soluble immune checkpoints that are produced through various mechanisms and demonstrated biological activity. These soluble immune checkpoints can be produced and distributed in the bloodstream and various tissues, with their roles in immune response dysregulation and autoimmunity extensively documented. This review aims to provide a thorough overview of the generation of various soluble immune checkpoints, such as sPD-1, sCTLA-4, sTim-3, s4-1BB, sBTLA, sLAG-3, sCD200, and the B7 family, and their importance as indicators for the diagnosis and prediction of autoimmune conditions. Furthermore, the review will investigate the potential pathological mechanisms of soluble immune checkpoints in autoimmune diseases, emphasizing their association with autoimmune diseases development, prognosis, and treatment.

Evaluation of genetic association between celiac disease and type 1 diabetes

Purpose

Celiac disease (CD) is a chronic autoimmune disorder with a common genetic pathogenesis with type 1 diabetes (T1D). This study aimed to investigate the immune regulation in patients with both CD and T1D.

Methods

A total of 29 CD patients, 29 T1D patients, and 16 patients with both CD and T1D, along with 30 healthy controls (HCs) were included. The mRNA expression levels of TNF-α, IL-6, IL-2, and CTLA4 were evaluated in peripheral blood samples.

Results

The results showed that in patients with CD, T1D and CD/T1D, TNF-α mRNA levels were significantly increased (P = 0.0009, 0.0001, and 0.008, respectively), while CTLA4 mRNA levels were significantly decreased in them compared to the control group (P = 0.0009, 0.0001, and 0.004, respectively). IL-2 mRNA expression levels were also significantly higher in CD (P = 0.01) and comorbid CD/T1D (P = 0.01) patients than in the control group. There was no significant difference in terms of IL-6 expression between studied groups (P > 0.05).

Conclusions

TNF-α mRNA exhibited potential diagnostic value for distinguishing CD, T1D, and comorbid CD/T1D patients from HCs. These findings contribute to our understanding of the shared genetic factors and potential mechanisms underlying CD and T1D, which can aid in improved diagnostic methods and treatment approaches for these conditions.

Deciphering the role of alternative splicing in neoplastic diseases for immune-oncological therapies

Alternative splicing (AS) is an important molecular biological mechanism regulated by complex mechanisms involving a plethora of cis and trans-acting elements. Furthermore, AS is tissue specific and altered in various pathologies, including infectious, inflammatory, and neoplastic diseases. Recently developed immuno-oncological therapies include monoclonal antibodies (mAbs) and chimeric antigen receptor (CAR) T cells targeting, among others, immune checkpoint (ICP) molecules. Despite therapeutic successes have been demonstrated, only a limited number of patients showed long-term benefit from these therapies with tumor entity-related differential response rates were observed. Interestingly, splice variants of common immunotherapeutic targets generated by AS are able to completely escape and/or reduce the efficacy of mAb- and/or CAR-based tumor immunotherapies. Therefore, the analyses of splicing patterns of targeted molecules in tumor specimens prior to therapy might help correct stratification, thereby increasing therapy success by antibody panel selection and antibody dosages. In addition, the expression of certain splicing factors has been linked with the patients' outcome, thereby highlighting their putative prognostic potential. Outstanding questions are addressed to translate the findings into clinical application. This review article provides an overview of the role of AS in (tumor) diseases, its molecular mechanisms, clinical relevance, and therapy response.

Spontaneous immunological activities in the target tissue of vitiligo-prone Smyth and vitiligo-susceptible Brown lines of chicken

Introduction

Vitiligo is an acquired de-pigmentation disorder characterized by the post-natal loss of epidermal melanocytes (pigment-producing cells) resulting in the appearance of white patches in the skin. The Smyth chicken is the only model for vitiligo that shares all the characteristics of the human condition including: spontaneous post-natal loss of epidermal melanocytes, interactions between genetic, environmental and immunological factors, and associations with other autoimmune diseases. In addition, an avian model for vitiligo has the added benefit of an easily accessible target tissue (a growing feather) that allows for the repeated sampling of an individual and thus the continuous monitoring of local immune responses over time.

Methods

Using a combination of flow cytometry and gene expression analyses, we sought to gain a comprehensive understanding of the initiating events leading to expression of vitiligo in growing feathers by monitoring the infiltration of leukocytes and concurrent immunological activities in the target tissue beginning prior to visual onset and continuing throughout disease development.

Results

Here, we document a sequence of immunologically significant events, including characteristic rises in infiltrating B and αβ T cells as well as evidence of active leukocyte recruitment and cell-mediated immune activities (CCL19, IFNG, GZMA) leading up to visual vitiligo onset. Examination of growing feathers from vitiligo-susceptible Brown line chickens revealed anti-inflammatory immune activities which may be responsible for preventing vitiligo (IL10, CTLA4, FOXP3). Furthermore, we detected positive correlations between infiltrating T cells and changes in their T cell receptor diversity supporting a T cell-specific immune response.

Conclusion

Collectively, these results further support the notion of cell-mediated immune destruction of epidermal melanocytes in the pulp of growing feathers and open new avenues of study in the vitiligo-prone Smyth and vitiligo-susceptible Brown line chickens.

Progression of type 1 diabetes is associated with high levels of soluble PD-1 in islet autoantibody-positive children

AIMS/HYPOTHESIS

Type 1 diabetes is an autoimmune disorder that is characterised by destruction of pancreatic beta cells by autoreactive T lymphocytes. Although islet autoantibodies (AAb) are an indicator of disease progression, specific immune biomarkers that can be used as target molecules to halt development of type 1 diabetes have not been discovered. Soluble immune checkpoint molecules (sICM) play a pivotal role in counteracting excessive lymphocyte responses, but their role in type 1 diabetes is unexplored. In this longitudinal study, we measured sICM levels in AAb-positive (AAb+) children to identify molecules related to type 1 diabetes progression.

METHODS

We measured the levels of 14 sICM in the sera of AAb+ children (n=57) compared to those with recent-onset type 1 diabetes (n=79) and healthy children (n=44), obtained from two cohorts. AAb+ children were followed up and divided based on their progression to type 1 diabetes (AAbP) or not (AAbNP) (if they lost islet autoimmunity and did not develop disease in subsequent years). sICM were also measured in the sample taken at the visit closest to disease onset in AAbP children.

RESULTS

We found that AAb+ children had a distinct sICM profile compared with healthy children and those with recent-onset type 1 diabetes. In addition, AAb+ children who progressed to type 1 diabetes (AAbP) had higher sICM concentrations than non-progressors (AAbNP). Further, sICM levels decreased in AAbP children close to disease onset. Application of Cox regression models highlighted that high concentrations of soluble programmed cell death protein 1 (sPD-1) are associated with type 1 diabetes progression (HR 1.71; 95% CI 1.16, 2.51; p=0.007).

CONCLUSIONS/INTERPRETATION

This study reveals an sICM profile that is dysregulated during the preclinical stage of type 1 diabetes, and identifies sPD-1 as a pathophysiologically-relevant molecule that is associated with disease progression, offering a potential target for early interventions in autoimmune diabetes.

Theoretical Studies of DNA Microarray Present Potential Molecular and Cellular Interconnectivity of Signaling Pathways in Immune System Dysregulation

Autoimmunity is defined as the inability to regulate immunological activities in the body, especially in response to external triggers, leading to the attack of the tissues and organs of the host. Outcomes include the onset of autoimmune diseases whose effects are primarily due to dysregulated immune responses. In past years, there have been cases that show an increased susceptibility to other autoimmune disorders in patients who are already experiencing the same type of disease. Research in this field has started analyzing the potential molecular and cellular causes of this interconnectedness, bearing in mind the possibility of advancing drugs and therapies for the treatment of autoimmunity. With that, this study aimed to determine the correlation of four autoimmune diseases, which are type 1 diabetes (T1D), psoriasis (PSR), systemic sclerosis (SSc), and systemic lupus erythematosus (SLE), by identifying highly preserved co-expressed genes among datasets using WGCNA. Functional annotation was then employed to characterize these sets of genes based on their systemic relationship as a whole to elucidate the biological processes, cellular components, and molecular functions of the pathways they are involved in. Lastly, drug repurposing analysis was performed to screen candidate drugs for repositioning that could regulate the abnormal expression of genes among the diseases. A total of thirteen modules were obtained from the analysis, the majority of which were associated with transcriptional, post-transcriptional, and post-translational modification processes. Also, the evaluation based on KEGG suggested the possible role of TH17 differentiation in the simultaneous onset of the four diseases. Furthermore, clomiphene was the top drug candidate for regulating overexpressed hub genes; meanwhile, prilocaine was the top drug for regulating under-expressed hub genes. This study was geared towards utilizing transcriptomics approaches for the assessment of microarray data, which is different from the use of traditional genomic analyses. Such a research design for investigating correlations among autoimmune diseases may be the first of its kind.

Role of RNA Alternative Splicing in T Cell Function and Disease

Alternative RNA splicing, a ubiquitous mechanism of gene regulation in eukaryotes, expands genome coding capacity and proteomic diversity. It has essential roles in all aspects of human physiology, including immunity. This review highlights the importance of RNA alternative splicing in regulating immune T cell function. We discuss how mutations that affect the alternative splicing of T cell factors can contribute to abnormal T cell function and ultimately lead to autoimmune diseases. We also explore the potential applications of strategies that target the alternative splicing changes of T cell factors. These strategies could help design therapeutic approaches to treat autoimmune disorders and improve immunotherapy.

Shifts in isoform usage underlie transcriptional differences in regulatory T cells in type 1 diabetes

Genome-wide association studies have identified numerous loci with allelic associations to Type 1 Diabetes (T1D) risk. Most disease-associated variants are enriched in regulatory sequences active in lymphoid cell types, suggesting that lymphocyte gene expression is altered in T1D. Here we assay gene expression between T1D cases and healthy controls in two autoimmunity-relevant lymphocyte cell types, memory CD4+/CD25+ regulatory T cells (Treg) and memory CD4+/CD25- T cells, using a splicing event-based approach to characterize tissue-specific transcriptomes. Limited differences in isoform usage between T1D cases and controls are observed in memory CD4+/CD25- T-cells. In Tregs, 402 genes demonstrate differences in isoform usage between cases and controls, particularly RNA recognition and splicing factor genes. Many of these genes are regulated by the variable inclusion of exons that can trigger nonsense mediated decay. Our results suggest that dysregulation of gene expression, through shifts in alternative splicing in Tregs, contributes to T1D pathophysiology.

Genome-wide aggregated trans-effects on risk of type 1 diabetes: A test of the "omnigenic" sparse effector hypothesis of complex trait genetics

The "omnigenic" hypothesis postulates that the polygenic effects of common SNPs on a typical complex trait are mediated through trans-effects on expression of a relatively sparse set of effector ("core") genes. We tested this hypothesis in a study of 4,964 cases of type 1 diabetes (T1D) and 7,497 controls by using summary statistics to calculate aggregated (excluding the HLA region) trans-scores for gene expression in blood. From associations of T1D with aggregated trans-scores, nine putative core genes were identified, of which three-STAT1, CTLA4 and FOXP3-are genes in which variants cause monogenic forms of autoimmune diabetes. Seven of these genes affect the activity of regulatory T cells, and two are involved in immune responses to microbial lipids. Four T1D-associated genomic regions could be identified as master regulators via trans-effects on gene expression. These results support the sparse effector hypothesis and reshape our understanding of the genetic architecture of T1D.

Gata3 is detrimental to regulatory T cell function in autoimmune diabetes

Regulatory T cells (Tregs) protect against autoimmunity. In type 1 diabetes (T1D), Tregs slow the progression of beta cell autoimmunity within pancreatic islets. Increasing the potency or frequency of Tregs can prevent diabetes, as evidenced by studies in the nonobese diabetic (NOD) mouse model for T1D. We report herein that a significant proportion of islets Tregs in NOD mice express Gata3. The expression of Gata3 was correlated with the presence of IL-33, a cytokine known to induce and expand Gata3+ Tregs. Despite significantly increasing the frequency of Tregs in the pancreas, exogenous IL-33 was not protective. Based on these data, we hypothesized that Gata3 is deleterious to Treg function in autoimmune diabetes. To test this notion, we generated NOD mice with a Treg-specific deletion of Gata3. We found that deleting Gata3 in Tregs strongly protected against diabetes. Disease protection was associated with a shift of islet Tregs toward a suppressive CXCR3+Foxp3+ population. Our results suggest that islet Gata3+ Tregs are maladaptive and that this Treg subpopulation compromises the regulation of islet autoimmunity, contributing to diabetes onset.

High levels of blood circulating immune checkpoint molecules in children with new-onset type 1 diabetes are associated with the risk of developing an additional autoimmune disease

AIMS/HYPOTHESIS

We assessed the levels of blood circulating immune checkpoint molecules (ICMs) at diagnosis of type 1 diabetes, and determined their association with the risk of developing an additional autoimmune disorder over time.

METHODS

Children with new-onset type 1 diabetes (n = 143), without biological and/or clinical signs of additional autoimmune disorders, and healthy children (n = 75) were enrolled, and blood circulating levels of 14 ICMs were measured. The children with type 1 diabetes were divided into two groups on the basis of the development of an additional autoimmune disease in the 5 years after diabetes onset. Differences in soluble ICM levels between the groups were assessed, and a Cox regression analysis was used to evaluate their association with the risk of development of an additional autoimmune disease over time. To validate the data, circulating ICMs were measured in an independent cohort of 60 children with new-onset type 1 diabetes stratified into two groups.

RESULTS

We found that the levels of circulating ICMs were significantly higher in children with new-onset diabetes compared with healthy children. Further, we observed that children with type 1 diabetes who developed a second autoimmune disease over time (T1D-AAD⁺ children) had higher levels of soluble ICMs than children with type 1 diabetes who did not (T1D-AAD^- children). Cox regression models revealed that high circulating levels of CD137/4-1BB and PD-1 molecules at diabetes diagnosis were associated with the risk of developing an additional autoimmune disease in both type 1 diabetes cohorts.

CONCLUSIONS/INTERPRETATION

Our findings suggest that soluble CD137/4-1BB and PD-1 molecules may be used as prognostic biomarkers in children with type 1 diabetes, and may pave the way for novel immunological screening at diabetes onset, allowing early identification of children at higher risk of developing other autoimmune conditions over time.

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.

Functional Impact of Risk Gene Variants on the Autoimmune Responses in Type 1 Diabetes

Type 1 diabetes (T1D) is an autoimmune disease that develops in the interplay between genetic and environmental factors. A majority of individuals who develop T1D have a HLA make up, that accounts for 50% of the genetic risk of disease. Besides these HLA haplotypes and the insulin region that importantly contribute to the heritable component, genome-wide association studies have identified many polymorphisms in over 60 non-HLA gene regions that also contribute to T1D susceptibility.

Combining the risk genes in a score (T1D-GRS), significantly improved the prediction of disease progression in autoantibody positive individuals. Many of these minor-risk SNPs are associated with immune genes but how they influence the gene and protein expression and whether they cause functional changes on a cellular level remains a subject of investigation. A positive correlation between the genetic risk and the intensity of the peripheral autoimmune response was demonstrated both for HLA and non-HLA genetic risk variants. We also observed epigenetic and genetic modulation of several of these T1D susceptibility genes in dendritic cells (DCs) treated with vitamin D3 and dexamethasone to acquire tolerogenic properties as compared to immune activating DCs (mDC) illustrating the interaction between genes and environment that collectively determines risk for T1D. A notion that targeting such genes for therapeutic modulation could be compatible with correction of the impaired immune response, inspired us to review the current knowledge on the immune-related minor risk genes, their expression and function in immune cells, and how they may contribute to activation of autoreactive T cells, Treg function or β-cell apoptosis, thus contributing to development of the autoimmune disease.

Activation pathways that drive CD4+ T cells to break tolerance in autoimmune diseases. Immunol Rev 2022;307:161-190. [PMID: 35142369 PMCID: PMC9255211 DOI: 10.1111/imr.13071]

Autoimmune diseases are characterized by dysfunctional immune systems that misrecognize self as non-self and cause tissue destruction. Several cell types have been implicated in triggering and sustaining disease. Due to a strong association of major histocompatibility complex II (MHC-II) proteins with various autoimmune diseases, CD4+ T lymphocytes have been thoroughly investigated for their roles in dictating disease course. CD4+ T cell activation is a coordinated process that requires three distinct signals: Signal 1, which is mediated by antigen recognition on MHC-II molecules; Signal 2, which boosts signal 1 in a costimulatory manner; and Signal 3, which helps to differentiate the activated cells into functionally relevant subsets. These signals are disrupted during autoimmunity and prompt CD4+ T cells to break tolerance. Herein, we review our current understanding of how each of the three signals plays a role in three different autoimmune diseases and highlight the genetic polymorphisms that predispose individuals to autoimmunity. We also discuss the drawbacks of existing therapies and how they can be addressed to achieve lasting tolerance in patients.

Soluble B7-CD28 Family Inhibitory Immune Checkpoint Proteins and Anti-Cancer Immunotherapy

Co-inhibitory B7-CD28 family member proteins negatively regulate T cell responses and are extensively involved in tumor immune evasion. Blockade of classical CTLA-4 (cytotoxic T lymphocyte-associated antigen-4) and PD-1 (programmed cell death protein-1) checkpoint pathways have become the cornerstone of anti-cancer immunotherapy. New inhibitory checkpoint proteins such as B7-H3, B7-H4, and BTLA (B and T lymphocyte attenuator) are being discovered and investigated for their potential in anti-cancer immunotherapy. In addition, soluble forms of these molecules also exist in sera of healthy individuals and elevated levels are found in chronic infections, autoimmune diseases, and cancers. Soluble forms are generated by proteolytic shedding or alternative splicing. Elevated circulating levels of these inhibitory soluble checkpoint molecules in cancer have been correlated with advance stage, metastatic status, and prognosis which underscore their broader involvement in immune regulation. In addition to their potential as biomarker, understanding their mechanism of production, biological activity, and pathological interactions may also pave the way for their clinical use as a therapeutic target. Here we review these aspects of soluble checkpoint molecules and elucidate on their potential for anti-cancer immunotherapy.

Alternative Splicing: A New Cause and Potential Therapeutic Target in Autoimmune Disease

Alternative splicing (AS) is a complex coordinated transcriptional regulatory mechanism. It affects nearly 95% of all protein-coding genes and occurs in nearly all human organs. Aberrant alternative splicing can lead to various neurological diseases and cancers and is responsible for aging, infection, inflammation, immune and metabolic disorders, and so on. Though aberrant alternative splicing events and their regulatory mechanisms are widely recognized, the association between autoimmune disease and alternative splicing has not been extensively examined. Autoimmune diseases are characterized by the loss of tolerance of the immune system towards self-antigens and organ-specific or systemic inflammation and subsequent tissue damage. In the present review, we summarized the most recent reports on splicing events that occur in the immunopathogenesis of systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) and attempted to clarify the role that splicing events play in regulating autoimmune disease progression. We also identified the changes that occur in splicing factor expression. The foregoing information might improve our understanding of autoimmune diseases and help develop new diagnostic and therapeutic tools for them.

Impact of cytotoxic T-lymphocyte-associated protein 4 codon 17 variant and expression on vitiligo risk

BACKGROUND

Cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) is one of the essential brakes expressed on T cells that prevent T-cell hyperactivation-associated autoimmune disorders. Several CTLA4 polymorphisms were implicated in the regulation of gene expression. We aimed to explore the association of CTLA4 expression and rs231775 (c.49A>G) variant with vitiligo risk and severity of the disease in a sample of the Middle Eastern population.

METHODS

The CTLA4 gene expression and genotyping for rs231775 (A/G) variant were assessed in 161 vitiligo patients and 165 controls using a real-time polymerase chain reaction. Vitiligo Area Severity Index (VASI) and Vitiligo Disease Activity score (VIDA) were evaluated.

RESULTS

A higher frequency of rs231775 G allele was observed in vitiligo cases than controls (45% vs. 33%, p = 0.002). After adjustment of age, sex, family history of vitiligo, and CTLA expression level, using multivariate analysis, G/G carriers were associated with a higher risk of vitiligo under recessive (OR = 2.94, 95% CI = 1.61-5.35, p < 0.001), dominant (OR = 1.87, 95% CI = 1.14-3.06, p = 0.013), and homozygote comparison (OR = 3.34, 95% CI = 1.73-6.42, p = 0.001) models. Although the CTLA4 relative expression levels were comparable to that of controls, G/G carriers exhibited a significantly lower expression profile (median = 0.63, IQR = 0.34-1.75) than A/A (median = 1.43, IQR = 0.39-4.25, p = 0.018) and A/G carriers (median = 1.68, IQR = 0.49-3.92, p = 0.007). No significant associations of CTLA4 variant/expression with disease severity and/or activity were observed.

CONCLUSION

The CTLA4 rs231775 variant was associated with vitiligo susceptibility and gene expression; the risky genotype (GG) was associated with lower CTLA4 relative expression levels than the other genotypes. Further large-scale studies in different populations are warranted.

Single-cell differential splicing analysis reveals high heterogeneity of liver tumor-infiltrating T cells

Recent advances in single-cell RNA sequencing (scRNA-seq) have improved our understanding of the association between tumor-infiltrating lymphocyte (TILs) heterogeneity and cancer initiation and progression. However, studies investigating alternative splicing (AS) as an important regulatory factor of heterogeneity remain limited. Here, we developed a new computational tool, DESJ-detection, which accurately detects differentially expressed splicing junctions (DESJs) between cell groups at the single-cell level. We analyzed 5063 T cells of hepatocellular carcinoma (HCC) and identified 1176 DESJs across 11 T cell subtypes. Interestingly, DESJs were enriched in UTRs, and have putative effects on heterogeneity. Cell subtypes with a similar function closely clustered together at the AS level. Meanwhile, we identified a novel cell state, pre-activation with the isoform markers ARHGAP15-205. In summary, we present a comprehensive investigation of alternative splicing differences, which provided novel insights into T cell heterogeneity and can be applied to other full-length scRNA-seq datasets.

Serum sCTLA-4 level is not associated with type 1 diabetes or the coexistence of autoantibodies in children and adolescent patients from the southern region of Saudi Arabia

Background

The soluble form of CTLA-4 (sCTLA-4) is associated with several autoimmune diseases. The aim of the study is to measure the serum sCTLA-4 levels in type I diabetic (T1DM) patients and to assess the presence of autoantibodies for a possible association.

Methods

One hundred forty-two T1DM patients were enrolled in the study. Fifty of them were serologically positive for co-existing autoantibodies. One hundred and five subjects were enrolled in the study, as non-diabetic controls (1–17 years of age; median age—10 years). The serum samples of all the subjects were analyzed with ELISA to detect the concentration of sCTLA-4 and anti-GAD/IA2 IgG. Standard statistical analysis was conducted as required.

Results

Ninety-four (66%) subjects of T1DM patients and five (4.7%) subjects of the non-diabetic group had antibodies positive for anti-GAD/IA2. Serum sCTLA-4 was low in most of the subjects of both the diabetic and control groups (p = 0.18). In the control group, nine individuals (8.6%) were positive for sCTLA-4. Similarly, only seven patients (4.9%) in the T1DM group had high levels of sCTLA-4, of which two were found to be double positive for anti-thyroid peroxidase and anti-thyroglobulin antibodies. In addition, among the T1DM patients, no significant relationships were observed between sCTLA-4 levels and age of onset (p = 0.43), disease duration (p = 0.09), or glycemic control (p = 0.32).

Conclusion

Despite the previous findings of high sCTLA-4 levels in autoimmune diseases, serum levels of sCTLA-4 are not significantly different between T1DM patients and non-diabetic adolescents. Furthermore, we did not observe any association with autoantibody presence, glycemic control, or disease duration.

Gut Microbiota Regulation of T Cells During Inflammation and Autoimmunity

The intestinal microbiota plays a crucial role in influencing the development of host immunity, and in turn the immune system also acts to regulate the microbiota through intestinal barrier maintenance and immune exclusion. Normally, these interactions are homeostatic, tightly controlled, and organized by both innate and adaptive immune responses. However, a combination of environmental exposures and genetic defects can result in a break in tolerance and intestinal homeostasis. The outcomes of these interactions at the mucosal interface have broad, systemic effects on host immunity and the development of chronic inflammatory or autoimmune disease. The underlying mechanisms and pathways the microbiota can utilize to regulate these diseases are just starting to emerge. Here, we discuss the recent evidence in this area describing the impact of microbiota-immune interactions during inflammation and autoimmunity, with a focus on barrier function and CD4⁺ T cell regulation.

Immune checkpoint inhibitors and type 1 diabetes mellitus: a case report and systematic review

OBJECTIVE

To better define the rare adverse event (AE) of diabetes mellitus associated with immune checkpoint inhibitors (ICIs).

DESIGN AND METHODS

We report the case of a lung cancer patient with diabetic ketoacidosis (DKA) and autoimmune thyroiditis during pembrolizumab treatment. We provide a systematic review of all published cases (PubMed/Web of Science/Cochrane, through November 2018) of autoimmune diabetes mellitus related to blockade of the cytotoxic T-lymphocyte antigen 4 (CTLA-4)-, programmed cell death 1 (PD-1) receptor or its ligand (PD-L1) or combination (ICI) therapy.

RESULTS

Our literature search identified 90 patient cases (our case excluded). Most patients were treated with anti-PD-1 or anti-PD-L1 as monotherapy (79%) or in combination with CTLA-4 blockade (15%). On average, diabetes mellitus was diagnosed after 4.5 cycles; earlier for combination ICI at 2.7 cycles. Early-onset diabetes mellitus (after one or two cycles) was observed during all treatment regimens. Diabetic ketoacidosis was present in 71%, while elevated lipase levels were detected in 52% (13/25). Islet autoantibodies were positive in 53% of patients with a predominance of glutamic acid decarboxylase antibodies. Susceptible HLA genotypes were present in 65% (mostly DR4). Thyroid dysfunction was the most frequent other endocrine AE at 24% incidence in this patient population.

CONCLUSION

ICI-related diabetes mellitus is a rare but often life-threatening metabolic urgency of which health-care professionals and patients should be aware. Close monitoring of blood glucose and prompt endocrine investigation in case of hyperglycemia is advisable. Predisposing factors such as HLA genotype might explain why some individuals are at risk.

RGMB enhances the suppressive activity of the monomeric secreted form of CTLA-4

The immunoregulatory molecule CTLA-4 plays a crucial role in the maintenance of immune homeostasis. CTLA-4-neutralizing antibodies are now approved for the treatment of advanced melanoma, and are in development for treating other cancers as well. However, a thorough understanding of CTLA-4 function at the molecular level is necessary in order to develop strategies to prevent the unintended autoimmunity that is frequently associated with systemic blockade of CTLA-4 activity. Here, we describe an extracellular molecule, repulsive guidance molecule B (RGMB) as a novel binding partner of CTLA-4. RGMB expression was detected at high levels in dendritic cell subsets that have been suggested to have tolerogenic capabilities. RGMB binds an extracellular domain of CTLA-4, and specifically strengthens the binding of the monomeric, soluble form of CTLA-4 (sCTLA-4) to CD80, enhancing CTLA-4's suppressive effect on co-stimulation. Examination of expression data from tumor tissues revealed a negative correlation between RGMB expression and immune activation status in the majority of non-hematologic tumor tissues. These findings advance our understanding of CTLA-4 activity, as well as identify the RGMB/CTLA-4 binding interface as a potential target for the development of novel immune checkpoint blockade therapies.

Assessment of soluble cytotoxic T lymphocyte-associated antigen-4, transforming growth factor β1, and platelet-derived microparticles during dasatinib therapy for patients with chronic myelogenous leukemia

BACKGROUND

The outcome for chronic myelogenous leukemia (CML) patients presented in the chronic phase has changed dramatically since the introduction of tyrosine kinase inhibitor (TKI) therapy. Notably, an increased incidence of large granular lymphocytes (LGLs), which is related to immunological conditions, appears to be predictive of a favorable outcome for dasatinib therapy. We therefore examined the immunological characteristics of CML patients during dasatinib therapy by determining the plasma concentrations of five different biomarkers.

METHODS

The plasma levels of biomarkers, specifically interleukin-6, platelet-derived microparticles (PDMPs), soluble vascular cell adhesion molecule 1 (sVCAM-1), transforming growth factor (TGF) β1, and soluble cytotoxic T lymphocyte-associated antigen-4 (sCTLA-4), were measured by ELISA at baseline and after 2 and 6 months of TKI treatment. The incidence of LGLs was estimated by microscopic examination.

RESULTS

The levels of PDMPs, sVCAM-1, and TGFβ1 were significantly elevated in patients with CML. Dasatinib treatment was associated with a significant reduction in the levels of these markers and with an increased incidence of LGLs compared with imatinib or nilotinib treatment. In addition, an increased incidence of LGLs was significantly correlated with a decreased sCTLA-4 level during dasatinib therapy.

CONCLUSION

The assessment of the levels of specific biomarkers may be beneficial to understand the immunological conditions of patients with CML during dasatinib treatment.

Soluble immune checkpoints in cancer: production, function and biological significance

Immune checkpoints play important roles in immune regulation, and blocking immune checkpoints on the cell membrane is a promising strategy in the treatment of cancer. Based on this, monoclonal antibodies are having much rapid development, such as those against CTLA-4 (cytotoxic T lymphocyte antigen 4) and PD-1 (programmed cell death protein 1).But the cost of preparation of monoclonal antibodies is too high and the therapeutic effect is still under restrictions. Recently, a series of soluble immune checkpoints have been found such as sCTLA-4 (soluble CTLA-4) and sPD-1 (soluble PD-1). They are functional parts of membrane immune checkpoints produced in different ways and can be secreted by immune cells. Moreover, these soluble checkpoints can diffuse in the serum. Much evidence has demonstrated that these soluble checkpoints are involved in positive or negative immune regulation and that changes in their plasma levels affect the development, prognosis and treatment of cancer. Since they are endogenous molecules, they will not induce immunological rejection in human beings, which might make up for the deficiencies of monoclonal antibodies and enhance the utility value of these molecules. Therefore, there is an increasing need for investigating novel soluble checkpoints and their functions, and it is promising to develop relevant therapies in the future. In this review, we describe the production mechanisms and functions of various soluble immune checkpoint receptors and ligands and discuss their biological significance in regard to biomarkers, potential candidate drugs, therapeutic targets, and other topics.

Association of CD28 and CTLA4 haplotypes with susceptibility to primary Sjögren's syndrome in Mexican population

BACKGROUND

Primary Sjögren's syndrome (pSS) is an autoimmune disease characterized by destruction of exocrine glands as a result of T and B cells infiltrated in glandular tissue. CD28 and CTLA-4 play a crucial role in T cell activation and inhibition. The aim of this study was to associate CD28 and CTLA4 haplotypes with susceptibility to pSS in patients from western Mexico.

METHODS

Polymerase chain reaction and restriction fragment length polymorphism were performed to identify CD28 and CTLA4 genotypes in 111 patients with pSS and 138 control subjects (CS). Haplotype analysis was carried out by SHEsis program. Soluble serum levels of CD28 (sCD28) and CTLA-4 (sCTLA-4) were quantified by ELISA kit.

RESULTS

The CD28 GC haplotype was associated with low risk to pSS (2.5-folds, P < 0.001). CTLA4 CAG and CGA were identified as genetic risk factor (P < 0.001;OR = 3.82[CI95%:2.022-7.296] and P < 0.001; OR = 11.38[CI95%:3.282-37.69] respectively). No difference in sCD28 and sCTLA-4 were found between patients and CS. However, pSS patients carriers of CD28 IVS3 + 17TC genotype showed high sCD28 (P = 0.039 vs TT carriers in CS). In regard to sCTLA-4, patient who carry CTLA4-319C>T, +49 A>G, and +6230 G>A, or their haplotypes did not show any difference.

CONCLUSION

Our findings suggest that CD28 GC, CTLA4 CAG, and CGA haplotypes are associated with susceptibility to pSS in patients from western Mexico. It seems that genetic control of CD28 and CTLA4 as well as local immune response in glandular tissue may regulate the impact of the gene expression in pSS. It is necessary to confirm this hypothesis in an integrative study.

The Role of NOD Mice in Type 1 Diabetes Research: Lessons from the Past and Recommendations for the Future

For more than 35 years, the NOD mouse has been the primary animal model for studying autoimmune diabetes. During this time, striking similarities to the human disease have been uncovered. In both species, unusual polymorphisms in a major histocompatibility complex (MHC) class II molecule confer the most disease risk, disease is caused by perturbations by the same genes or different genes in the same biological pathways and that diabetes onset is preceded by the presence of circulating autoreactive T cells and autoantibodies that recognize many of the same islet antigens. However, the relevance of the NOD model is frequently challenged due to past failures translating therapies from NOD mice to humans and because the appearance of insulitis in mice and some patients is different. Nevertheless, the NOD mouse remains a pillar of autoimmune diabetes research for its usefulness as a preclinical model and because it provides access to invasive procedures as well as tissues that are rarely procured from patients or controls. The current article is focused on approaches to improve the NOD mouse by addressing reasons why immune therapies have failed to translate from mice to humans. We also propose new strategies for mixing and editing the NOD genome to improve the model in ways that will better advance our understanding of human diabetes. As proof of concept, we report that diabetes is completely suppressed in a knock-in NOD strain with a serine to aspartic acid substitution at position 57 in the MHC class II Aβ. This supports that similar non-aspartic acid substitutions at residue 57 of variants of the human class II HLA-DQβ homolog confer diabetes risk.

Disease-specific biases in alternative splicing and tissue-specific dysregulation revealed by multitissue profiling of lymphocyte gene expression in type 1 diabetes

Genome-wide association studies (GWAS) have identified multiple, shared allelic associations with many autoimmune diseases. However, the pathogenic contributions of variants residing in risk loci remain unresolved. The location of the majority of shared disease-associated variants in noncoding regions suggests they contribute to risk of autoimmunity through effects on gene expression in the immune system. In the current study, we test this hypothesis by applying RNA sequencing to CD4+, CD8+, and CD19+ lymphocyte populations isolated from 81 subjects with type 1 diabetes (T1D). We characterize and compare the expression patterns across these cell types for three gene sets: all genes, the set of genes implicated in autoimmune disease risk by GWAS, and the subset of these genes specifically implicated in T1D. We performed RNA sequencing and aligned the reads to both the human reference genome and a catalog of all possible splicing events developed from the genome, thereby providing a comprehensive evaluation of the roles of gene expression and alternative splicing (AS) in autoimmunity. Autoimmune candidate genes displayed greater expression specificity in the three lymphocyte populations relative to other genes, with significantly increased levels of splicing events, particularly those predicted to have substantial effects on protein isoform structure and function (e.g., intron retention, exon skipping). The majority of single-nucleotide polymorphisms within T1D-associated loci were also associated with one or more cis-expression quantitative trait loci (cis-eQTLs) and/or splicing eQTLs. Our findings highlight a substantial, and previously underrecognized, role for AS in the pathogenesis of autoimmune disorders and particularly for T1D.

Coinhibitory Pathways in the B7-CD28 Ligand-Receptor Family

Immune responses need to be controlled for optimal protective immunity and tolerance. Coinhibitory pathways in the B7-CD28 family provide critical inhibitory signals that regulate immune homeostasis and defense and protect tissue integrity. These coinhibitory signals limit the strength and duration of immune responses, thereby curbing immune-mediated tissue damage, regulating resolution of inflammation, and maintaining tolerance to prevent autoimmunity. Tumors and microbes that cause chronic infections can exploit these coinhibitory pathways to establish an immunosuppressive microenvironment, hindering their eradication. Advances in understanding T cell coinhibitory pathways have stimulated a new era of immunotherapy with effective drugs to treat cancer, autoimmune and infectious diseases, and transplant rejection. In this review we discuss the current knowledge of the mechanisms underlying the coinhibitory functions of pathways in the B7-CD28 family, the diverse functional consequences of these inhibitory signals on immune responses, and the overlapping and unique functions of these key immunoregulatory pathways.

Check point inhibitors as therapies for infectious diseases

The recent successes of immune check point targeting therapies in treating cancer patients has driven a resurgence of interest in targeting these pathways in chronically infected patients. While still in early stages, basic and clinical data suggest that blockade of CTLA-4 and PD-1 can be beneficial in the treatment of chronic HIV, HBV, and HCV infection, as well as other chronic maladies. Furthermore, novel inhibitory receptors such as Tim-3, LAG-3, and TIGIT are the potential next wave of check points that can be manipulated for the treatment of chronic infection. Blockade of these pathways influences more than simply T cell responses, and may provide new therapeutic options for chronically infected patients.

Abnormalities in alternative splicing in diabetes: therapeutic targets

Diabetes mellitus (DM) is a non-communicable, metabolic disorder that affects 416 million individuals worldwide. Type 2 diabetes contributes to a vast 85-90% of the diabetes incidences while 10-15% of patients suffer from type 1 diabetes. These two predominant forms of DM cause a significant loss of functional pancreatic β-cell mass causing different degrees of insulin deficiency, most likely, due to increased β-cell apoptosis. Treatment options involve the use of insulin sensitisers, α-glucosidase inhibitors, and β-cell secretagogues which are often expensive, limited in efficacy and carry detrimental adverse effects. Cost-effective options for treatment exists in the form of herbal drugs, however, scientific validations of these widely used medicinal plants are still underway. Alternative splicing (AS) is a co-ordinated post-transcriptional process in which a single gene generates multiple mRNA transcripts which results in increased amounts of functionally different protein isoforms and in some cases aberrant splicing leads to metabolic disease. In this review, we explore the association of AS with metabolic alterations in DM and the biological significance of the abnormal splicing of some pathogenic diabetes-related genes. An understanding of the molecular mechanism behind abnormally spliced transcripts will aid in the development of new diagnostic, prognostic and therapeutic tools.

Restoring Regulatory T Cells in Type 1 Diabetes

Genetic and cellular studies of type 1 diabetes in patients and in the nonobese diabetic mouse model of type 1 diabetes point to an imbalance between effector T cells and regulatory T cells (Tregs) as a driver of the disease. The imbalance may arise as a consequence of genetically encoded defects in thymic deletion of islet antigen-specific T cells, induction of islet antigen-specific thymic Tregs, unfavorable tissue environment for peripheral Treg induction, and failure of islet antigen-specific Tregs to survive in the inflamed islets secondary to insufficient IL-2 signals. These understandings are the foundation for rationalized design of new therapeutic interventions to restore the balance by selectively targeting effector T cells and boosting Tregs.

Modulation of Phenotype and Function of Human CD4+CD25+ T Regulatory Lymphocytes Mediated by cAMP-Elevating Agents

We have shown that cholera toxin (CT) and other cyclic AMP (cAMP)-elevating agents induce upregulation of the inhibitory molecule CTLA-4 in human resting CD4⁺ T lymphocytes, which following the treatment acquired suppressive functions. In this study, we evaluated the effect of cAMP-elevating agents on human CD4⁺CD25⁺ T cells, which include the T regulatory cells (Tregs) that play a pivotal role in the maintenance of immunological tolerance. We found that cAMP-elevating agents induce upregulation of CTLA-4 in CD4⁺CD25⁻ and further enhance its expression in CD4⁺CD25⁺ T cells. We observed an increase of two isoforms of mRNA coding for the membrane and the soluble CTLA-4 molecules, suggesting that the regulation of CTLA-4 expression by cAMP is at the transcriptional level. In addition, we found that the increase of cAMP in CD4⁺CD25⁺ T cells converts the CD4⁺CD25⁺Foxp3⁻ T cells in CD4⁺CD25⁺Foxp3⁺ T cells, whereas the increase of cAMP in CD4⁺CD25⁻ T cells did not upregulate Foxp3 in the absence of activation stimuli. To investigate the function of these cells, we performed an in vitro suppression assay by culturing CD4⁺CD25⁺ T cells untreated or pre-treated with CT with anti-CD3 mAbs-stimulated autologous peripheral blood mononuclear cell. We found that CT enhances the inhibitory function of CD4⁺CD25⁺ T cells, CD4⁺, and CD8⁺ T cell proliferation and IFNγ production are strongly inhibited by CD4⁺CD25⁺ T cells pre-treated with cAMP-elevating agents. Furthermore, we found that CD4⁺CD25⁺ T lymphocytes pre-treated with cAMP-elevating agents induce the upregulation of CD80 and CD86 co-stimulatory molecules on immature dendritic cells (DCs) in the absence of antigenic stimulation, however without leading to full DC maturation. These data show that the increase of intracellular cAMP modulates the phenotype and function of human CD4⁺CD25⁺ T cells.

In vitro Treg expansion favors the full-length splicing isoform of CTLA4

AIM

We compared fresh and in vitro expanded human Tregs for their CTLA4 splicing isoform expression.

METHODS

The CD4(+)CD25(+)CD127(low/-)phenotype was used for sorting Tregs and mRNA levels were measured with relative qRT-PCR.

RESULTS

In fresh Tregs the level of soluble CTLA4 (sCTLA4) was half of that of full-length CTLA4, whereas in expanded cells sCTLA4 level was tenfold lower. The most striking change took place early on: sCTLA4 expression decreased significantly when cells were simply kept in culture.

CONCLUSION

In the in vitro expanded Tregs, the splicing of CTLA4 is affected. Our findings can be significant for clinical cell manufacturing. First, even minimal processing of cells may impact the functional molecules. Second, Treg expansion yields more potent CTLA4 receptor bearing cells.

MECHANISMS IN ENDOCRINOLOGY: Alternative splicing: the new frontier in diabetes research

Type 1 diabetes (T1D) is a chronic autoimmune disease in which pancreatic β cells are killed by infiltrating immune cells and by cytokines released by these cells. This takes place in the context of a dysregulated dialogue between invading immune cells and target β cells, but the intracellular signals that decide β cell fate remain to be clarified. Alternative splicing (AS) is a complex post-transcriptional regulatory mechanism affecting gene expression. It regulates the inclusion/exclusion of exons into mature mRNAs, allowing individual genes to produce multiple protein isoforms that expand the proteome diversity. Functionally related transcript populations are co-ordinately spliced by master splicing factors, defining regulatory networks that allow cells to rapidly adapt their transcriptome in response to intra and extracellular cues. There is a growing interest in the role of AS in autoimmune diseases, but little is known regarding its role in T1D. In this review, we discuss recent findings suggesting that splicing events occurring in both immune and pancreatic β cells contribute to the pathogenesis of T1D. Splicing switches in T cells and in lymph node stromal cells are involved in the modulation of the immune response against β cells, while β cells exposed to pro-inflammatory cytokines activate complex splicing networks that modulate β cell viability, expression of neoantigens and susceptibility to immune-induced stress. Unveiling the role of AS in β cell functional loss and death will increase our understanding of T1D pathogenesis and may open new avenues for disease prevention and therapy.

Association of Cytotoxic T-Lymphocyte Antigen 4 (CTLA4) and Thyroglobulin (TG) Genetic Variants with Autoimmune Hypothyroidism

Autoimmune hypothyroidism is known to be caused by immune responses related to the thyroid gland and its immunological feature includes presence of autoimmune antibodies. Therefore the aim was to analyze presence of anti-TPO antibodies in hypothyroidism patients in Gujarat. Cytotoxic T-Lymphocyte Antigen 4 (CTLA4) is one of the susceptibility genes for various autoimmune diseases. Hence, exon1 +49A/G and 3’UTR CT60A/G single nucleotide polymorphisms (SNPs) in CTLA4 and its mRNA expression levels were investigated in autoimmune hypothyroidism patients. Thyroglobulin (TG) is known to be associated with autoimmune thyroid disorders and thus exon 33 (E33) SNP in TG was investigated. We analyzed the presence of anti-TPO antibodies in the plasma samples of 84 hypothyroidism patients and 62 controls by ELISA. PCR-RFLP technique was used for genotyping of polymorphisms. sCTLA4 and flCTLA4 mRNA expression levels were assessed by real time PCR. 59.52% of hypothyroid patients had anti-TPO antibodies in their circulation. The genotype and allele frequencies differed significantly for +49A/G (p = 0.0004 for +49AG, p = 0.0019 for +49GG & p = 0.0004 for allele), CT60 (p = 0.0110 for CT60AG, p = 0.0005 for CT60GG & p<0.0001 for allele) and TG E33 (p = 0.0003 for E33TC p<0.0001 for E33CC& p<0.0001 for allele) SNPs between patients and controls. Patients had significantly decreased mRNA levels of both sCTLA4 (p = 0.0017) and flCTLA4 (p<0.0001) compared to controls. +49A/G and CT60 polymorphisms of CTLA4 were in moderate linkage disequilibrium. Logistic regression analysis indicated significant association of CT49A/G, CT60A/G and TG exon 33 polymorphisms with susceptibility to autoimmune hypothyroidism when adjusted for age and gender. Our results suggest +49A/G and CT60 polymorphism of CTLA4 and E33 polymorphism of TG may be genetic risk factors for autoimmune hypothyroidism susceptibility and down regulation of both forms of CTLA4 advocates the crucial role of CTLA4 in pathogenesis of autoimmune hypothyroidism.

Alternative Splicing in CKD

Alternative splicing (AS) has emerged in the postgenomic era as one of the main drivers of proteome diversity, with ≥94% of multiexon genes alternatively spliced in humans. AS is therefore one of the main control mechanisms for cell phenotype, and is a process deregulated in disease. Numerous reports describe pathogenic mutations in splice factors, splice sites, or regulatory sequences. Additionally, compared with the physiologic state, disease often associates with an abnormal proportion of splice isoforms (or novel isoforms), without an apparent driver mutation. It is therefore essential to study how AS is regulated in physiology, how it contributes to pathogenesis, and whether we can manipulate faulty splicing for therapeutic advantage. Although the disease most commonly linked to deregulation of AS in several genes is cancer, many reports detail pathogenic splice variants in diseases ranging from neuromuscular disorders to diabetes or cardiomyopathies. A plethora of splice variants have been implicated in CKDs as well. In this review, we describe examples of these CKD-associated splice variants and ideas on how to manipulate them for therapeutic benefit.

Genetic and epigenetic variation in the lineage specification of regulatory T cells

Regulatory T (Treg) cells, which suppress autoimmunity and other inflammatory states, are characterized by a distinct set of genetic elements controlling their gene expression. However, the extent of genetic and associated epigenetic variation in the Treg cell lineage and its possible relation to disease states in humans remain unknown. We explored evolutionary conservation of regulatory elements and natural human inter-individual epigenetic variation in Treg cells to identify the core transcriptional control program of lineage specification. Analysis of single nucleotide polymorphisms in core lineage-specific enhancers revealed disease associations, which were further corroborated by high-resolution genotyping to fine map causal polymorphisms in lineage-specific enhancers. Our findings suggest that a small set of regulatory elements specify the Treg lineage and that genetic variation in Treg cell-specific enhancers may alter Treg cell function contributing to polygenic disease.

DOI:http://dx.doi.org/10.7554/eLife.07571.001

The immune system protects the body from infection. Key to this protection is the ability to mount an immune response that is sufficient to deal with the threat, but is not so large that the damage it causes to the body exceeds its immediate benefit. Immune cells called regulatory T cells (or Treg cells for short) help to shut down the immune response after a threat has been successfully destroyed. They also prevent the immune system from attacking the body's own cells, a phenomenon known as autoimmunity.

All cells in the body carry the same set of genes, but the activity of these genes varies between cell types to enable the cells to perform their different jobs. This is possible because our DNA contains regions called regulatory elements that can control the expression of particular genes. These regions can be activated in specific types of cells, which results in specific chemical modifications to DNA that only affect gene activity in those cells.

The DNA sequences of these regulatory elements vary between individuals. This ‘genetic variation’ can lead to differences in the chemical modifications that occur to DNA, which is known as epigenetic variation. This means that Treg cells in one person may work in a different way to those in another individual, which could make some individuals more susceptible to autoimmune diseases than others. However, it was not clear how much genetic and epigenetic variation exists in Treg cells.

Here, Arvey et al. examined Treg and other immune cells from human and mouse donors. The experiments show that some of the epigenetic modifications present in many individuals only in Treg cells, which indicates that they may be important for the activity of the Treg cells. Unexpectedly, most of the epigenetic modifications were specific to either mice or humans, but Arvey et al. identified a core set of genes that had been modified only in Treg cells in both species. In the human cells, Arvey et al. also identified genetic differences in regulatory elements that are associated with autoimmune diseases.

Arvey et al.'s findings suggest that a small set of regulatory elements are crucial to the role of Treg cells in the immune system. Furthermore, genetic variation in these elements can lead to epigenetic changes in Treg cells that contribute to autoimmune diseases in humans. Further study may lead to the development of new treatments for these diseases.

DOI:http://dx.doi.org/10.7554/eLife.07571.002

Selective Treg reconstitution during lymphopenia normalizes DC costimulation and prevents graft-versus-host disease

Regulatory T cells (Tregs) have been shown to enhance immune reconstitution and prevent graft-versus-host disease (GVHD) after hematopoietic stem cell transplantation; however, it is unclear how Tregs mediate these effects. Here, we developed a model to examine the mechanism of Treg-dependent regulation of immune reconstitution. Lymphopenic mice were selectively reconstituted with Tregs prior to transfer of conventional CD4+ T cells. Full Treg reconstitution prevented the rapid oligoclonal proliferation that gives rise to pathogenic CD4 effector T cells, while preserving the slow homeostatic form of lymphopenia-induced peripheral expansion that repopulates a diverse peripheral T cell pool. Treg-mediated CTLA-4-dependent downregulation of CD80/CD86 on DCs was critical for inhibition of rapid proliferation and was a function of the Treg/DC ratio achieved by reconstitution. In an allogeneic BM transplant model, selective Treg reconstitution before T cell transfer also normalized DC costimulation and provided complete protection against GVHD. In contrast, cotransfer of Tregs was not protective. Our results indicate that achieving optimal recovery from lymphopenia should aim to improve early Treg reconstitution in order to increase the relative number of Tregs to DCs and thereby inhibit spontaneous oligoclonal T cell proliferation.

Interleukin 2 Topical Cream for Treatment of Diabetic Foot Ulcer: Experiment Protocol

Background

It is estimated there are 2.9 million diabetic patients in the United Kingdom, and around 5%-7% of patients have diabetic ulcers. This number will continue to increase globally. Diabetic ulcers are a major economic burden on the healthcare system. More than £650 million is spent on foot ulcers or amputations each year, and up to 100 people a week have a limb amputated due to diabetes. In T1DM, the level of IL-2 is reduced, and hence, wound healing is in a prolonged inflammatory phase. It is not known if IL-2 topical cream can shorten the healing process in T1DM patients.

Objective

The objective of this study is to understand the pathophysiology in type 1 diabetes (T1DM) and investigate possible future treatment based on its clinical features. The hypothesis is that IL-2 cream can speed up wound healing in NOD mice and that this can be demonstrated in a ten-week study. An experiment protocol is designed in a mouse model for others to conduct the experiment. The discussion is purely based on diabetic conditions; lifestyle influences like smoking and drinking are not considered.

Methods

Skin incisions will be created on 20 nonobese diabetic (NOD) mice, and IL-2 topical cream will be applied in a 10-week study to prove the hypothesis. Mice will be randomly and equally divide into two groups with one being the control group.

Results

T1DM patients have a decreased number of T regulatory (Treg) cells and interleukin 2 (IL-2). These are the keys to the disease progression and delay in wound healing. Diabetic ulcer is a chronic wound and characterized by a prolonged inflammatory phase.

Conclusions

If the experiment is successful, T1DM patients will have an alternative, noninvasive treatment of foot ulcers. In theory, patients with other autoimmune diseases could also use IL-2 topical cream for treatment.

Association analysis of PTPN22, CTLA4 and IFIH1 genes with type 1 diabetes in Colombian families

BACKGROUND

Protein tyrosine phosphatase, non-receptor type 22 (lymphoid) (PTPN22), cytotoxic T-lymphocyte-associated protein 4 (CTLA4), and interferon induced with helicase C domain 1 (IFIH1) are among the confirmed type 1 diabetes (T1D) susceptibility genes in several populations. The aim of this study was to evaluate the role of PTPN22, CTLA4, and IFIH1 gene variants in the development of T1D in a Colombian population.

METHODS

Associations of PTPN22, CTLA4, and IFIH1 variants with T1D were investigated in a sample of 197 nuclear families, including 205 affected children, in the Colombian population. Three to four single nucleotide polymorphisms (SNPs) were analyzed per gene: rs2476600, rs2476601, rs1217418, and rs2488457 for PTPN22; rs1990760, rs3747517, and rs10930046 for IFIH1; and rs231775, rs3087243, and rs231779 for CTLA4. A transmission disequilibrium test was performed for the global sample, in addition to stratified analysis considering autoimmunity, age at onset, and parent of origin. Haplotypes per gene were also analyzed.

RESULTS

There was no significant transmission distortion for CTLA4. Conversely, SNPs rs10930046 (IFIH1) and rs2476601 (PTPN222) exhibited significant transmission distortion of the C and T alleles, respectively, from parents to affected children (odds ratio [OR] 0.57 and 1.83, respectively). In addition, decreased transmission of the C allele for rs10930046 occurred preferentially from mothers. Stratification analysis revealed that this association was maintained in individuals who were positive for autoantibodies and in those with an age of diagnosis <5 years.

CONCLUSION

The results show that IFIH1 and PTPN22 are associated with T1D in Colombian families.