A human mutation in STAT3 promotes type 1 diabetes through a defect in CD8+ T cell tolerance

A human STAT3 gain-of-function variant drives local Th17 dysregulation and skin inflammation in mice

Germline gain-of-function (GOF) variants in STAT3 cause an inborn error of immunity associated with early-onset poly-autoimmunity and immune dysregulation. To study tissue-specific immune dysregulation, we used a mouse model carrying a missense variant (p.G421R) that causes human disease. We observed spontaneous and imiquimod (IMQ)-induced skin inflammation associated with cell-intrinsic local Th17 responses in STAT3 GOF mice. CD4+ T cells were sufficient to drive skin inflammation and showed increased Il22 expression in expanded clones. Certain aspects of disease, including increased epidermal thickness, also required the presence of STAT3 GOF in epithelial cells. Treatment with a JAK inhibitor improved skin disease without affecting local Th17 recruitment and cytokine production. These findings collectively support the involvement of Th17 responses in the development of organ-specific immune dysregulation in STAT3 GOF and suggest that the presence of STAT3 GOF in tissues is important for disease and can be targeted with JAK inhibition.

STAT3 gain of function: Too much of a good thing in the skin!

Germline activating mutations in STAT3 cause a multi-systemic autoimmune and autoinflammatory condition. By studying a mouse model, Toth et al. (https://doi.org/10.1084/jem.20232091) propose a role for dysregulated IL-22 production by Th17 cells in causing some aspects of immune-mediated skin inflammation in human STAT3 GOF syndrome.

Autoimmune CD8+ T cells in type 1 diabetes: from single-cell RNA sequencing to T-cell receptor redirection

Type 1 diabetes (T1D) is an organ-specific autoimmune disease caused by pancreatic β cell destruction and mediated primarily by autoreactive CD8+ T cells. It has been shown that only a small number of stem cell-like β cell-specific CD8+ T cells are needed to convert normal mice into T1D mice; thus, it is likely that T1D can be cured or significantly improved by modulating or altering self-reactive CD8+ T cells. However, stem cell-type, effector and exhausted CD8+ T cells play intricate and important roles in T1D. The highly diverse T-cell receptors (TCRs) also make precise and stable targeted therapy more difficult. Therefore, this review will investigate the mechanisms of autoimmune CD8+ T cells and TCRs in T1D, as well as the related single-cell RNA sequencing (ScRNA-Seq), CRISPR/Cas9, chimeric antigen receptor T-cell (CAR-T) and T-cell receptor-gene engineered T cells (TCR-T), for a detailed and clear overview. This review highlights that targeting CD8+ T cells and their TCRs may be a potential strategy for predicting or treating T1D.

STAT5B SH2 variants disrupt mammary enhancers and the stability of genetic programs during pregnancy

During pregnancy, mammary tissue undergoes expansion and differentiation, leading to lactation, a process regulated by the hormone prolactin through the JAK2-STAT5 pathway. STAT5 activation is key to successful lactation making the mammary gland an ideal experimental system to investigate the impact of human missense mutations on mammary tissue homeostasis. Here, we investigated the effects of two human variants in the STAT5B SH2 domain, which convert tyrosine 665 to either phenylalanine (Y665F) or histidine (Y665H), both shown to activate STAT5B in cell culture. We ported these mutations into the mouse genome and found distinct and divergent functions. Homozygous Stat5bY665H mice failed to form functional mammary tissue, leading to lactation failure, with impaired alveolar development and greatly reduced expression of key differentiation genes. STAT5BY665H failed to recognize mammary enhancers and impeded STAT5A binding. In contrast, mice carrying the Stat5bY665F mutation exhibited abnormal precocious development, accompanied by an early activation of the mammary transcription program and the induction of otherwise silent genetic programs. Physiological adaptation was observed in Stat5bY665H mice as continued exposure to pregnancy hormones led to lactation. In summary, our findings highlight that human STAT5B variants can modulate their response to cytokines and thereby impact mammary homeostasis and lactation.

Activation of gp130 signaling in T cells drives TH17-mediated multi-organ autoimmunity

The IL-6-gp130-STAT3 signaling axis is a major regulator of inflammation. Activating mutations in the gene encoding gp130 and germline gain-of-function mutations in STAT3 (STAT3GOF) are associated with multi-organ autoimmunity, severe morbidity, and adverse prognosis. To dissect crucial cellular subsets and disease biology involved in activated gp130 signaling, the gp130-JAK-STAT3 axis was constitutively activated using a transgene, L-gp130, specifically targeted to T cells. Activating gp130 signaling in T cells in vivo resulted in fatal, early onset, multi-organ autoimmunity in mice that resembled human STAT3GOF disease. Female mice had more rapid disease progression than male mice. On a cellular level, gp130 signaling induced the activation and effector cell differentiation of T cells, promoted the expansion of T helper type 17 (TH17) cells, and impaired the activity of regulatory T cells. Transcriptomic profiling of CD4+ and CD8+ T cells from these mice revealed commonly dysregulated genes and a gene signature that, when applied to human transcriptomic data, improved the segregation of patients with transcriptionally diverse STAT3GOF mutations from healthy controls. The findings demonstrate that increased gp130-STAT3 signaling leads to TH17-driven autoimmunity that phenotypically resembles human STAT3GOF disease.

Signal Transducer and Activator of Transcription Proteins at the Nexus of Immunodeficiency, Autoimmunity and Cancer

The signal transducer and activator of transcription (STAT) family of proteins has been demonstrated to perform pivotal roles downstream of a myriad of cytokines, particularly those that control immune cell production and function. This is highlighted by both gain-of-function (GOF) and loss-of-function (LOF) mutations being implicated in various diseases impacting cells of the immune system. These mutations are typically inherited, although somatic GOF mutations are commonly observed in certain immune cell malignancies. This review details the growing appreciation of STAT proteins as a key node linking immunodeficiency, autoimmunity and cancer.

Baricitinib and β-Cell Function in Patients with New-Onset Type 1 Diabetes

BACKGROUND

Janus kinase (JAK) inhibitors, including baricitinib, block cytokine signaling and are effective disease-modifying treatments for several autoimmune diseases. Whether baricitinib preserves β-cell function in type 1 diabetes is unclear.

METHODS

In this phase 2, double-blind, randomized, placebo-controlled trial, we assigned patients with type 1 diabetes diagnosed during the previous 100 days to receive baricitinib (4 mg once per day) or matched placebo orally for 48 weeks. The primary outcome was the mean C-peptide level, determined from the area under the concentration-time curve, during a 2-hour mixed-meal tolerance test at week 48. Secondary outcomes included the change from baseline in the glycated hemoglobin level, the daily insulin dose, and measures of glycemic control assessed with the use of continuous glucose monitoring.

RESULTS

A total of 91 patients received baricitinib (60 patients) or placebo (31 patients). The median of the mixed-meal-stimulated mean C-peptide level at week 48 was 0.65 nmol per liter per minute (interquartile range, 0.31 to 0.82) in the baricitinib group and 0.43 nmol per liter per minute (interquartile range, 0.13 to 0.63) in the placebo group (P = 0.001). The mean daily insulin dose at 48 weeks was 0.41 U per kilogram of body weight per day (95% confidence interval [CI], 0.35 to 0.48) in the baricitinib group and 0.52 U per kilogram per day (95% CI, 0.44 to 0.60) in the placebo group. The levels of glycated hemoglobin were similar in the two trial groups. However, the mean coefficient of variation of the glucose level at 48 weeks, as measured by continuous glucose monitoring, was 29.6% (95% CI, 27.8 to 31.3) in the baricitinib group and 33.8% (95% CI, 31.5 to 36.2) in the placebo group. The frequency and severity of adverse events were similar in the two trial groups, and no serious adverse events were attributed to baricitinib or placebo.

CONCLUSIONS

In patients with type 1 diabetes of recent onset, daily treatment with baricitinib over 48 weeks appeared to preserve β-cell function as estimated by the mixed-meal-stimulated mean C-peptide level. (Funded by JDRF International and others; BANDIT Australian New Zealand Clinical Trials Registry number, ACTRN12620000239965.).

Deletion of Vβ3+CD4+ T cells by endogenous mouse mammary tumor virus 3 prevents type 1 diabetes induction by autoreactive CD8+ T cells

In both humans and NOD mice, type 1 diabetes (T1D) develops from the autoimmune destruction of pancreatic beta cells by T cells. Interactions between both helper CD4+ and cytotoxic CD8+ T cells are essential for T1D development in NOD mice. Previous work has indicated that pathogenic T cells arise from deleterious interactions between relatively common genes which regulate aspects of T cell activation/effector function (Ctla4, Tnfrsf9, Il2/Il21), peptide presentation (H2-A g7, B2m), and T cell receptor (TCR) signaling (Ptpn22). Here, we used a combination of subcongenic mapping and a CRISPR/Cas9 screen to identify the NOD-encoded mammary tumor virus (Mtv)3 provirus as a genetic element affecting CD4+/CD8+ T cell interactions through an additional mechanism, altering the TCR repertoire. Mtv3 encodes a superantigen (SAg) that deletes the majority of Vβ3+ thymocytes in NOD mice. Ablating Mtv3 and restoring Vβ3+ T cells has no effect on spontaneous T1D development in NOD mice. However, transferring Mtv3 to C57BL/6 (B6) mice congenic for the NOD H2 g7 MHC haplotype (B6.H2 g7) completely blocks their normal susceptibility to T1D mediated by transferred CD8+ T cells transgenically expressing AI4 or NY8.3 TCRs. The entire genetic effect is manifested by Vβ3+CD4+ T cells, which unless deleted by Mtv3, accumulate in insulitic lesions triggering in B6 background mice the pathogenic activation of diabetogenic CD8+ T cells. Our findings provide evidence that endogenous Mtv SAgs can influence autoimmune responses. Furthermore, since most common mouse strains have gaps in their TCR Vβ repertoire due to Mtvs, it raises questions about the role of Mtvs in other mouse models designed to reflect human immune disorders.

Th2 cell clonal expansion at diagnosis in human type 1 diabetes

Soon after diagnosis with type 1 diabetes (T1D), many patients experience a period of partial remission. A longer partial remission is associated with a better response to treatment, but the mechanism is not known. The frequency of CD4+CD25+CD127hi (127-hi) cells, a cell subset with an anti-inflammatory Th2 bias, correlates positively with length of partial remission. The purpose of this study was to further characterize the nature of the Th2 bias in 127-hi cells. Single cell RNA sequencing paired with TCR sequencing of sorted 127-hi memory cells identifies clonally expanded Th2 clusters in 127-hi cells from T1D, but not from healthy donors. The Th2 clusters express GATA3, GATA3-AS1, PTGDR2, IL17RB, IL4R and IL9R. The existence of 127-hi Th2 cell clonal expansion in T1D suggests that disease factors may induce clonal expansion of 127-hi Th2 cells that prolong partial remission and delay disease progression.

Novel STAT3 variant causing infantile-onset autoimmune disease

Signal transducer and activator of transcription 3 (STAT3) is a member of the STAT protein family implicated in the development of infantile-onset multisystem autoimmune disease. STAT3-related autoimmune disease is characterized by multiorgan autoimmunity, lymphoproliferative disease, and recurrent infections. The presentation is variable, with some patients also developing neonatal diabetes mellitus and interstitial lung disease. Gain-of-function variants in the Src homology 2 domain, leading to autophosphorylation and activation of STAT3, have been previously reported in patients with disease. Here, we report a patient with a novel missense variant, p.Glu616Ala, in STAT3 presenting with infantile-onset multisystem autoimmune disease.

Exploration of common genomic signatures of systemic juvenile rheumatoid arthritis and type 1 diabetes

To explore the genetic characteristics of systemic juvenile rheumatoid arthritis (sJRA) and type 1 diabetes mellitus (T1D). The microarray data of sJRA and T1D from Gene Expression Omnibus (GEO) were analyzed. The shared differentially expressed genes (SDEGs) were identified by the Meta-analysis, and genes of extracellular proteins were identified. Then, transcription factors (TFs) and their target genes in SDEGs were obtained by comparing databases from HumanTFDB, and hTFtarget. After that, functional enrichment analyses of the previously identified gene sets were performed by metascape tool. Finally, immune infiltration was analysed by CIBERSORT. We found 175 up-regulated and 245 down-regulated SDEGs, and by constructing a TFs-targeted SDEGs network, 3 key TFs (ARID3A, NEF2, RUNX3) were screened. Functional enrichment analyses and immune infiltration results suggested not only the adaptive immune system but also the innate immune system, and signaling pathways like JAK-STAT are important in the pathogenesis of sJRA and T1D, involving biological processes such as CD4 T cell functions and neutrophil degranulation. This work suggests that innate immune abnormalities also play important roles in sJRA and T1D, CD4 T cell functions, neutrophil degranulation and the JAK-STAT pathway may be involved. The regulatory roles of ARID3A, NEF2, and RUNX3 in this network need to be further investigated.

Pancreatic draining lymph nodes (PLNs) serve as a pathogenic hub contributing to the development of type 1 diabetes

Type 1 diabetes (T1D) is a chronic, progressive autoinflammatory disorder resulting from the breakdown of self-tolerance and unrestrained β cell-reactive immune response. Activation of immune cells is initiated in islet and amplified in lymphoid tissues, especially those pancreatic draining lymph nodes (PLNs). The knowledge of PLNs as the hub of aberrant immune response is continuously being replenished and renewed. Here we provide a PLN-centered view of T1D pathogenesis and emphasize that PLNs integrate signal inputs from the pancreas, gut, viral infection or peripheral circulation, undergo immune remodeling within the local microenvironment and export effector cell components into pancreas to affect T1D progression. In accordance, we suggest that T1D intervention can be implemented by three major ways: cutting off the signal inputs into PLNs (reduce inflammatory β cell damage, enhance gut integrity and control pathogenic viral infections), modulating the immune activation status of PLNs and blocking the outputs of PLNs towards pancreatic islets. Given the dynamic and complex nature of T1D etiology, the corresponding intervention strategy is thus required to be comprehensive to ensure optimal therapeutic efficacy.

Inflammation versus regulation: how interferon-gamma contributes to type 1 diabetes pathogenesis

Type 1 diabetes is an autoimmune disease with onset from early childhood. The insulin-producing pancreatic beta cells are destroyed by CD8⁺ cytotoxic T cells. The disease is challenging to study mechanistically in humans because it is not possible to biopsy the pancreatic islets and the disease is most active prior to the time of clinical diagnosis. The NOD mouse model, with many similarities to, but also some significant differences from human diabetes, provides an opportunity, in a single in-bred genotype, to explore pathogenic mechanisms in molecular detail. The pleiotropic cytokine IFN-γ is believed to contribute to pathogenesis of type 1 diabetes. Evidence of IFN-γ signaling in the islets, including activation of the JAK-STAT pathway and upregulation of MHC class I, are hallmarks of the disease. IFN-γ has a proinflammatory role that is important for homing of autoreactive T cells into islets and direct recognition of beta cells by CD8⁺ T cells. We recently showed that IFN-γ also controls proliferation of autoreactive T cells. Therefore, inhibition of IFN-γ does not prevent type 1 diabetes and is unlikely to be a good therapeutic target. In this manuscript we review the contrasting roles of IFN-γ in driving inflammation and regulating the number of antigen specific CD8⁺ T cells in type 1 diabetes. We also discuss the potential to use JAK inhibitors as therapy for type 1 diabetes, to inhibit both cytokine-mediated inflammation and proliferation of T cells.

Deficiencies and Dysregulation of STAT Pathways That Drive Inborn Errors of Immunity: Lessons from Patients and Mouse Models of Disease

The STAT family proteins provide critical signals for immune cell development, differentiation, and proinflammatory and anti-inflammatory responses. Inborn errors of immunity (IEIs) are caused by single gene defects leading to immune deficiency and/or dysregulation, and they have provided opportunities to identify genes important for regulating the human immune response. Studies of patients with IEIs due to altered STAT signaling, and mouse models of these diseases, have helped to shape current understanding of the mechanisms whereby STAT signaling and protein interactions regulate immunity. Although many STAT signaling pathways are shared, clinical and immune phenotypes in patients with monogenic defects of STAT signaling highlight both redundant and nonredundant pathways. In this review, we provide an overview of the shared and unique signaling pathways used by STATs, phenotypes of IEIs with altered STAT signaling, and recent discoveries that have provided insight into the human immune response and treatment of disease.

The ups and downs of STAT3 function: too much, too little and human immune dysregulation

The STAT3 story has almost 30 years of evolving history. First identified in 1994 as a pro-inflammatory transcription factor, Signal Transducer and Activator of Transcription 3 (STAT3) has continued to be revealed as a quintessential pleiotropic signalling module spanning fields including infectious diseases, autoimmunity, vaccine responses, metabolism, and malignancy. In 2007, germline heterozygous dominant-negative loss-of-function variants in STAT3 were discovered as the most common cause for a triad of eczematoid dermatitis with recurrent skin and pulmonary infections, first described in 1966. This finding established that STAT3 plays a critical non-redundant role in immunity against some pathogens, as well as in the connective tissue, dental and musculoskeletal systems. Several years later, in 2014, heterozygous activating gain of function germline STAT3 variants were found to be causal for cases of early-onset multiorgan autoimmunity, thereby underpinning the notion that STAT3 function needed to be regulated to maintain immune homeostasis. As we and others continue to interrogate biochemical and cellular perturbations due to inborn errors in STAT3, we will review our current understanding of STAT3 function, mechanisms of disease pathogenesis, and future directions in this dynamic field.

Microbiota-dependent proteolysis of gluten subverts diet-mediated protection against type 1 diabetes

Diet and commensals can affect the development of autoimmune diseases like type 1 diabetes (T1D). However, whether dietary interventions are microbe-mediated was unclear. We found that a diet based on hydrolyzed casein (HC) as a protein source protects non-obese diabetic (NOD) mice in conventional and germ-free (GF) conditions via improvement in the physiology of insulin-producing cells to reduce autoimmune activation. The addition of gluten (a cereal protein complex associated with celiac disease) facilitates autoimmunity dependent on microbial proteolysis of gluten: T1D develops in GF animals monocolonized with Enterococcus faecalis harboring secreted gluten-digesting proteases but not in mice colonized with protease deficient bacteria. Gluten digestion by E. faecalis generates T cell-activating peptides and promotes innate immunity by enhancing macrophage reactivity to lipopolysaccharide (LPS). Gnotobiotic NOD Toll4-negative mice monocolonized with E. faecalis on an HC + gluten diet are resistant to T1D. These findings provide insights into strategies to develop dietary interventions to help protect humans against autoimmunity.

Regulation of microglia related neuroinflammation contributes to the protective effect of Gelsevirine on ischemic stroke

Stroke, especially ischemic stroke, is an important cause of neurological morbidity and mortality worldwide. Growing evidence suggests that the immune system plays an intricate function in the pathophysiology of stroke. Gelsevirine (Gs), an alkaloid from Gelsemium elegans, has been proven to decrease inflammation and neuralgia in osteoarthritis previously, but its role in stroke is unknown. In this study, the middle cerebral artery occlusion (MCAO) mice model was used to evaluate the protective effect of Gs on stroke, and the administration of Gs significantly improved infarct volume, Bederson score, neurobiological function, apoptosis of neurons, and inflammation state in vivo. According to the data in vivo and the conditioned medium (CM) stimulated model in vitro, the beneficial effect of Gs came from the downregulation of the over-activity of microglia, such as the generation of inflammatory factors, dysfunction of mitochondria, production of ROS and so on. By RNA-seq analysis and Western-blot analysis, the JAK-STAT signal pathway plays a critical role in the anti-inflammatory effect of Gs. According to the results of molecular docking, inhibition assay, and thermal shift assay, the binding of Gs on JAK2 inhibited the activity of JAK2 which inhibited the over-activity of JAK2 and downregulated the phosphorylation of STAT3. Over-expression of a gain-of-function STAT3 mutation (K392R) abolished the beneficial effects of Gs. So, the downregulation of JAK2-STAT3 signaling pathway by Gs contributed to its anti-inflammatory effect on microglia in stroke. Our study revealed that Gs was benefit to stroke treatment by decreasing neuroinflammation in stroke as a potential drug candidate regulating the JAK2-STAT3 signal pathway.

STAT3 gain-of-function mutations connect leukemia with autoimmune disease by pathological NKG2Dhi CD8+ T cell dysregulation and accumulation

The association between cancer and autoimmune disease is unexplained, exemplified by T cell large granular lymphocytic leukemia (T-LGL) where gain-of-function (GOF) somatic STAT3 mutations correlate with co-existing autoimmunity. To investigate whether these mutations are the cause or consequence of CD8⁺ T cell clonal expansions and autoimmunity, we analyzed patients and mice with germline STAT3 GOF mutations. STAT3 GOF mutations drove the accumulation of effector CD8⁺ T cell clones highly expressing NKG2D, the receptor for stress-induced MHC-class-I-related molecules. This subset also expressed genes for granzymes, perforin, interferon-γ, and Ccl5/Rantes and required NKG2D and the IL-15/IL-2 receptor IL2RB for maximal accumulation. Leukocyte-restricted STAT3 GOF was sufficient and CD8⁺ T cells were essential for lethal pathology in mice. These results demonstrate that STAT3 GOF mutations cause effector CD8⁺ T cell oligoclonal accumulation and that these rogue cells contribute to autoimmune pathology, supporting the hypothesis that somatic mutations in leukemia/lymphoma driver genes contribute to autoimmune disease.

Impact of interleukin-6 on T cells in kidney transplant recipients

Interleukin-6 (IL-6), a multifunctional proinflammatory cytokine, plays a key role in T cell activation, survival, and differentiation. Acting as a switch that induces the differentiation of naïve T cells into Th17 cells and inhibits their development into regulatory T cells, IL-6 promotes rejection and abrogates tolerance. Therapies that target IL-6 signaling include antibodies to IL-6 and the IL-6 receptor and inhibitors of janus kinases; several of these therapeutics have demonstrated robust clinical efficacy in autoimmune and inflammatory diseases. Clinical trials of IL-6 inhibition in kidney transplantation have focused primarily on its effects on B cells, plasma cells, and HLA antibodies. In this review, we summarize the impact of IL-6 on T cells in experimental models of transplant and describe the effects of IL-6 inhibition on the T cell compartment in kidney transplant recipients.

Research progress of single-cell transcriptome sequencing in autoimmune diseases and autoinflammatory disease: A review

Autoimmunity refers to the phenomenon that the body's immune system produces antibodies or sensitized lymphocytes to its own tissues to cause an immune response. Immune disorders caused by autoimmunity can mediate autoimmune diseases. Autoimmune diseases have complicated pathogenesis due to the many types of cells involved, and the mechanism is still unclear. The emergence of single-cell research technology can solve the problem that ordinary transcriptome technology cannot be accurate to cell type. It provides unbiased results through independent analysis of cells in tissues and provides more mRNA information for identifying cell subpopulations, which provides a novel approach to study disruption of immune tolerance and disturbance of pro-inflammatory pathways on a cellular basis. It may fundamentally change the understanding of molecular pathways in the pathogenesis of autoimmune diseases and develop targeted drugs. Single-cell transcriptome sequencing (scRNA-seq) has been widely applied in autoimmune diseases, which provides a powerful tool for demonstrating the cellular heterogeneity of tissues involved in various immune inflammations, identifying pathogenic cell populations, and revealing the mechanism of disease occurrence and development. This review describes the principles of scRNA-seq, introduces common sequencing platforms and practical procedures, and focuses on the progress of scRNA-seq in 41 autoimmune diseases, which include 9 systemic autoimmune diseases and autoinflammatory diseases (rheumatoid arthritis, systemic lupus erythematosus, etc.) and 32 organ-specific autoimmune diseases (5 Skin diseases, 3 Nervous system diseases, 4 Eye diseases, 2 Respiratory system diseases, 2 Circulatory system diseases, 6 Liver, Gallbladder and Pancreas diseases, 2 Gastrointestinal system diseases, 3 Muscle, Bones and joint diseases, 3 Urinary system diseases, 2 Reproductive system diseases). This review also prospects the molecular mechanism targets of autoimmune diseases from the multi-molecular level and multi-dimensional analysis combined with single-cell multi-omics sequencing technology (such as scRNA-seq, Single cell ATAC-seq and single cell immune group library sequencing), which provides a reference for further exploring the pathogenesis and marker screening of autoimmune diseases and autoimmune inflammatory diseases in the future.

A human STAT3 gain-of-function variant confers T cell dysregulation without predominant Treg dysfunction in mice

Primary immune regulatory disorders (PIRD) represent a group of disorders characterized by immune dysregulation, presenting with a wide range of clinical disease, including autoimmunity, autoinflammation, or lymphoproliferation. Autosomal dominant germline gain-of-function (GOF) variants in STAT3 result in a PIRD with a broad clinical spectrum. Studies in patients have documented a decreased frequency of FOXP3+ Tregs and an increased frequency of Th17 cells in some patients with active disease. However, the mechanisms of disease pathogenesis in STAT3 GOF syndrome remain largely unknown, and treatment is challenging. We developed a knock-in mouse model harboring a de novo pathogenic human STAT3 variant (p.G421R) and found these mice developed T cell dysregulation, lymphoproliferation, and CD4+ Th1 cell skewing. Surprisingly, Treg numbers, phenotype, and function remained largely intact; however, mice had a selective deficiency in the generation of iTregs. In parallel, we performed single-cell RNA-Seq on T cells from STAT3 GOF patients. We demonstrate only minor changes in the Treg transcriptional signature and an expanded, effector CD8+ T cell population. Together, these findings suggest that Tregs are not the primary driver of disease and highlight the importance of preclinical models in the study of disease mechanisms in rare PIRD.

Cutting Edge: Systemic Autoimmunity in Murine STAT3 Gain-of-Function Syndrome Is Characterized by Effector T Cell Expansion in the Absence of Overt Regulatory T Cell Dysfunction

Germline gain-of-function mutations in the transcriptional factor STAT3 promote early-onset multisystemic autoimmunity. To investigate how increased STAT3 promotes systemic inflammation, we generated a transgenic knock-in strain expressing a pathogenic human mutation STAT3K392R within the endogenous murine locus. As predicted, STAT3K392R mice develop progressive lymphoid hyperplasia and systemic inflammation, mirroring the human disease. However, whereas the prevailing model holds that increased STAT3 activity drives human autoimmunity by dysregulating the balance between regulatory T cells and Th17 cell differentiation, we observed increased Th17 cells in the absence of major defects in regulatory T cell differentiation or function. In addition, STAT3K392R animals exhibited a prominent accumulation of IFN-γ-producing CD4+ and CD8+ T cells. Together, these data provide new insights into this complex human genetic syndrome and highlight the diverse cellular mechanisms by which dysregulated STAT3 activity promotes breaks in immune tolerance.

Defining and targeting patterns of T cell dysfunction in inborn errors of immunity

Inborn errors of immunity (IEIs) are a group of more than 450 monogenic disorders that impair immune development and function. A subset of IEIs blend increased susceptibility to infection, autoimmunity, and malignancy and are known collectively as primary immune regulatory disorders (PIRDs). While many aspects of immune function are altered in PIRDs, one key impact is on T-cell function. By their nature, PIRDs provide unique insights into human T-cell signaling; alterations in individual signaling molecules tune downstream signaling pathways and effector function. Quantifying T-cell dysfunction in PIRDs and the underlying causative mechanisms is critical to identifying existing therapies and potential novel therapeutic targets to treat our rare patients and gain deeper insight into the basic mechanisms of T-cell function. Though there are many types of T-cell dysfunction, here we will focus on T-cell exhaustion, a key pathophysiological state. Exhaustion has been described in both human and mouse models of disease, where the chronic presence of antigen and inflammation (e.g., chronic infection or malignancy) induces a state of altered immune profile, transcriptional and epigenetic states, as well as impaired T-cell function. Since a subset of PIRDs amplify T-cell receptor (TCR) signaling and/or inflammatory cytokine signaling cascades, it is possible that they could induce T-cell exhaustion by genetically mimicking chronic infection. Here, we review the fundamentals of T-cell exhaustion and its possible role in IEIs in which genetic mutations mimic prolonged or amplified T-cell receptor and/or cytokine signaling. Given the potential insight from the many forms of PIRDs in understanding T-cell function and the challenges in obtaining primary cells from these rare disorders, we also discuss advances in CRISPR-Cas9 genome-editing technologies and potential applications to edit healthy donor T cells that could facilitate further study of mechanisms of immune dysfunctions in PIRDs. Editing T cells to match PIRD patient genetic variants will allow investigations into the mechanisms underpinning states of dysregulated T-cell function, including T-cell exhaustion.

Polygenic autoimmune disease risk alleles impacting B cell tolerance act in concert across shared molecular networks in mouse and in humans

Most B cells produced in the bone marrow have some level of autoreactivity. Despite efforts of central tolerance to eliminate these cells, many escape to periphery, where in healthy individuals, they are rendered functionally non-responsive to restimulation through their antigen receptor via a process termed anergy. Broad repertoire autoreactivity may reflect the chances of generating autoreactivity by stochastic use of germline immunoglobulin gene segments or active mechanisms may select autoreactive cells during egress to the naïve peripheral B cell pool. Likewise, it is unclear why in some individuals autoreactive B cell clones become activated and drive pathophysiologic changes in autoimmune diseases. Both of these remain central questions in the study of the immune system(s). In most individuals, autoimmune diseases arise from complex interplay of genetic risk factors and environmental influences. Advances in genome sequencing and increased statistical power from large autoimmune disease cohorts has led to identification of more than 200 autoimmune disease risk loci. It has been observed that autoantibodies are detectable in the serum years to decades prior to the diagnosis of autoimmune disease. Thus, current models hold that genetic defects in the pathways that control autoreactive B cell tolerance set genetic liability thresholds across multiple autoimmune diseases. Despite the fact these seminal concepts were developed in animal (especially murine) models of autoimmune disease, some perceive a disconnect between human risk alleles and those identified in murine models of autoimmune disease. Here, we synthesize the current state of the art in our understanding of human risk alleles in two prototypical autoimmune diseases – systemic lupus erythematosus (SLE) and type 1 diabetes (T1D) along with spontaneous murine disease models. We compare these risk networks to those reported in murine models of these diseases, focusing on pathways relevant to anergy and central tolerance. We highlight some differences between murine and human environmental and genetic factors that may impact autoimmune disease development and expression and may, in turn, explain some of this discrepancy. Finally, we show that there is substantial overlap between the molecular networks that define these disease states across species. Our synthesis and analysis of the current state of the field are consistent with the idea that the same molecular networks are perturbed in murine and human autoimmune disease. Based on these analyses, we anticipate that murine autoimmune disease models will continue to yield novel insights into how best to diagnose, prognose, prevent and treat human autoimmune diseases.

Research progress on application of single-cell TCR/BCR sequencing technology to the tumor immune microenvironment, autoimmune diseases, and infectious diseases

Single-cell omics is the profiling of individual cells through sequencing and other technologies including high-throughput analysis for single-cell resolution, cell classification, and identification as well as time series analyses. Unlike multicellular studies, single-cell omics overcomes the problem of cellular heterogeneity. It provides new methods and perspectives for in-depth analyses of the behavior and mechanism of individual cells in the cell population and their relationship with the body, and plays an important role in basic research and precision medicine. Single-cell sequencing technologies mainly include single-cell transcriptome sequencing, single-cell assay for transposase accessible chromatin with high-throughput sequencing, single-cell immune profiling (single-cell T-cell receptor [TCR]/B-cell receptor [BCR] sequencing), and single-cell transcriptomics. Single-cell TCR/BCR sequencing can be used to obtain a large amount of single-cell gene expression and immunomics data at one time, and combined with transcriptome sequencing and TCR/BCR diversity data, can resolve immune cell heterogeneity. This paper summarizes the progress in applying single-cell TCR/BCR sequencing technology to the tumor immune microenvironment, autoimmune diseases, infectious diseases, immunotherapy, and chronic inflammatory diseases, and discusses its shortcomings and prospects for future application.

The Impact of STAT3 rs1053005 Variation on Type 1 Diabetes Mellitus Susceptibility: Association Study and in Silico Analysis

AIMS

Type 1 diabetes (T1DM) is an autoimmune disorder with multiple genetic and environmental risk factors that are still poorly understood. The signal transducer and activator of transcription (STAT) proteins play a pivotal role in immune-cell genesis and regulation. This study aimed to determine the effect of rs1053005 single nucleotide polymorphism (SNP) in 3'-UTR of STAT3 mRNA on the susceptibility to T1DM in an Iranian population.

METHODS

PCR-RFLP was conducted on 250 T1DM patients and 250 control cases to assess STAT3 rs1053005 polymorphism. Moreover, several bioinformatics tools were employed to identify the candidate miRNAs targeting the STAT3 mRNA region under study as well as the effect of rs1053005 on their binding site.

RESULTS

Significant variations in the distribution of genotypes and alleles were seen between cases and controls. The comparison results of the frequency of AA, AG, and GG genotypes between T1DM patients and control groups were 49.2% versus 64.8%, 39.2 versus 30%, and 11.6 versus 5.2%, respectively. Individuals who carried GG genotype were at 2.93-fold increased risk of developing T1DM and the G allele was associated with 1.79-fold higher T1DM risk. Bioinformatics analysis demonstrated that due to rs1053005, the interaction of 3 miRNAs were broken, 3 were weakened, 2 were reinforced, and 4 binding sites were created.

CONCLUSION

The result of this study indicates an association between STAT3 rs1053005 and T1DM susceptibility which may be due to interference of the SNP with native-binding site of some predicted miRNAs.

Sera Protein Signatures of Endometrial Cancer Lymph Node Metastases

The presence of lymph node metastases in endometrial cancer patients is a critical factor guiding treatment decisions; however, surgical and imaging methods for their detection are limited by morbidity and inaccuracy. To determine if sera can predict the presence of positive lymph nodes, sera collected from endometrial cancer patients with or without lymph node metastases, and benign gynecology surgical patients (N = 20 per group) were subjected to electron spray ionization mass spectrometry (ES-MS). Peaks that were significantly different among the groups were evaluated by leave one out cross validation (LOOCV) for their ability to differentiation between the groups. Proteins in the peaks were identified by MS/MS of five specimens in each group. Ingenuity Pathway Analysis was used to predict pathways regulated by the protein profiles. LOOCV of sera protein discriminated between each of the group comparisons and predicted positive lymph nodes. Pathways implicated in metastases included loss of PTEN activation and PI3K, AKT and PKA activation, leading to calcium signaling, oxidative phosphorylation and estrogen receptor-induced transcription, leading to platelet activation, epithelial-to-mesenchymal transition and senescence. Upstream activators implicated in these events included neurostimulation and inflammation, activation of G-Protein-Coupled Receptor Gβγ, loss of HER-2 activation and upregulation of the insulin receptor.

STAT3 Role in T-Cell Memory Formation

Along with the clinical success of immuno-oncology drugs and cellular therapies, T-cell biology has attracted considerable attention in the immunology community. Long-term immunity, traditionally analyzed in the context of infection, is increasingly studied in cancer. Many signaling pathways, transcription factors, and metabolic regulators have been shown to participate in the formation of memory T cells. There is increasing evidence that the signal transducer and activator of transcription-3 (STAT3) signaling pathway is crucial for the formation of long-term T-cell immunity capable of efficient recall responses. In this review, we summarize what is currently known about STAT3 role in the context of memory T-cell formation and antitumor immunity.

STAT3 gain-of-function syndrome

STAT3 gain-of-function (GOF) syndrome is a multi-organ primary immune regulatory disorder characterized by early onset autoimmunity. Patients present early in life, most commonly with lymphoproliferation, autoimmune cytopenias, and growth delay. However, disease is often progressive and can encompass a wide range of clinical manifestations such as: enteropathy, skin disease, pulmonary disease, endocrinopathy, arthritis, autoimmune hepatitis, and rarely neurologic disease, vasculopathy, and malignancy. Treatment of the autoimmune and immune dysregulatory features of STAT3-GOF patients relies heavily on immunosuppression and is often challenging and fraught with complications including severe infections. Defects in the T cell compartment leading to effector T cell accumulation and decreased T regulatory cells may contribute to autoimmunity. While T cell exhaustion and apoptosis defects likely contribute to the lymphoproliferative phenotype, no conclusive correlations are yet established. Here we review the known mechanistic and clinical characteristics of this heterogenous PIRD.

AMULET: a novel read count-based method for effective multiplet detection from single nucleus ATAC-seq data

Detecting multiplets in single nucleus (sn)ATAC-seq data is challenging due to data sparsity and limited dynamic range. AMULET (ATAC-seq MULtiplet Estimation Tool) enumerates regions with greater than two uniquely aligned reads across the genome to effectively detect multiplets. We evaluate the method by generating snATAC-seq data in the human blood and pancreatic islet samples. AMULET has high precision, estimated via donor-based multiplexing, and high recall, estimated via simulated multiplets, compared to alternatives and identifies multiplets most effectively when a certain read depth of 25K median valid reads per nucleus is achieved.