Common ground: shared risk factors for type 1 diabetes and celiac disease.

Risk factors for most autoimmune diseases are multifactorial genetic variants modified by environmental risk factors. Type 1 diabetes and celiac disease share high-risk HLA haplotypes, and the prevalence of both diseases has increased in many regions during the past half century. Unknown environmental factors are suspected to have increased the disease penetrance. Celiac disease depends on immune responses to dietary gluten, whereas the environmental risk factors for type 1 diabetes are not yet clear. Here, we consider the shared heritable genetic factors and review evidence of the dietary and microbial exposures, particularly in early life, that might influence the pathogenesis of one or both diseases. A deeper mechanistic understanding of the environmental factors responsible for increased risk of these diseases should provide opportunities to manipulate exposure in children carrying defined risk markers and thus prevent and attenuate disease, as well as to identify new therapeutic strategies for patients.

Cracking the type 1 diabetes code: Genes, microbes, immunity, and the early life environment.

Type 1 diabetes (T1D) results from a complex interplay of genetic predisposition, immunological dysregulation, and environmental triggers, that culminate in the destruction of insulin-secreting pancreatic ß cells. This review provides a comprehensive examination of the multiple factors underpinning T1D pathogenesis, to elucidate key mechanisms and potential therapeutic targets. Beginning with an exploration of genetic risk factors, we dissect the roles of human leukocyte antigen (HLA) haplotypes and non-HLA gene variants associated with T1D susceptibility. Mechanistic insights gleaned from the NOD mouse model provide valuable parallels to the human disease, particularly immunological intricacies underlying ß cell-directed autoimmunity. Immunological drivers of T1D pathogenesis are examined, highlighting the pivotal contributions of both effector and regulatory T cells and the multiple functions of B cells and autoantibodies in ß-cell destruction. Furthermore, the impact of environmental risk factors, notably modulation of host immune development by the intestinal microbiome, is examined. Lastly, the review probes human longitudinal studies, unveiling the dynamic interplay between mucosal immunity, systemic antimicrobial antibody responses, and the trajectories of T1D development. Insights garnered from these interconnected factors pave the way for targeted interventions and the identification of biomarkers to enhance T1D management and prevention strategies.

SLAMF7 is critical for phagocytosis of haematopoietic tumour cells via Mac-1 integrin.

Cancer cells elude anti-tumour immunity through multiple mechanisms, including upregulated expression of ligands for inhibitory immune checkpoint receptors. Phagocytosis by macrophages plays a critical role in cancer control. Therapeutic blockade of signal regulatory protein (SIRP)-α, an inhibitory receptor on macrophages, or of its ligand CD47 expressed on tumour cells, improves tumour cell elimination in vitro and in vivo, suggesting that blockade of the SIRPα-CD47 checkpoint could be useful in treating human cancer. However, the pro-phagocytic receptor(s) responsible for tumour cell phagocytosis is(are) largely unknown. Here we find that macrophages are much more efficient at phagocytosis of haematopoietic tumour cells, compared with non-haematopoietic tumour cells, in response to SIRPα-CD47 blockade. Using a mouse lacking the signalling lymphocytic activation molecule (SLAM) family of homotypic haematopoietic cell-specific receptors, we determined that phagocytosis of haematopoietic tumour cells during SIRPα-CD47 blockade was strictly dependent on SLAM family receptors in vitro and in vivo. In both mouse and human cells, this function required a single SLAM family member, SLAMF7 (also known as CRACC, CS1, CD319), expressed on macrophages and tumour cell targets. In contrast to most SLAM receptor functions, SLAMF7-mediated phagocytosis was independent of signalling lymphocyte activation molecule-associated protein (SAP) adaptors. Instead, it depended on the ability of SLAMF7 to interact with integrin Mac-1 (refs 18, 19, 20) and utilize signals involving immunoreceptor tyrosine-based activation motifs. These findings elucidate the mechanism by which macrophages engulf and destroy haematopoietic tumour cells. They also reveal a novel SAP adaptor-independent function for a SLAM receptor. Lastly, they suggest that patients with tumours expressing SLAMF7 are more likely to respond to SIRPα-CD47 blockade therapy.

MuLV-related endogenous retroviral elements and Flt3 participate in aberrant end-joining events that promote B-cell leukemogenesis.

During V(D)J recombination of immunoglobulin genes, p53 and nonhomologous end-joining (NHEJ) suppress aberrant rejoining of DNA double-strand breaks induced by recombinase-activating genes (Rags)-1/2, thus maintaining genomic stability and limiting malignant transformation during B-cell development. However, Rag deficiency does not prevent B-cell leukemogenesis in p53/NHEJ mutant mice, revealing that p53 and NHEJ also suppress Rag-independent mechanisms of B-cell leukemogenesis. Using several cytogenomic approaches, we identified a novel class of activating mutations in Fms-like tyrosine kinase 3 (Flt3), a receptor tyrosine kinase important for normal hematopoiesis in Rag/p53/NHEJ triple-mutant (TM) B-cell leukemias. These mutant Flt3 alleles were created by complex genomic rearrangements with Moloney leukemia virus (MuLV)-related endogenous retroviral (ERV) elements, generating ERV-Flt3 fusion genes encoding an N-terminally truncated mutant form of Flt3 (trFlt3) that was transcribed from ERV long terminal repeats. trFlt3 protein lacked most of the Flt3 extracellular domain and induced ligand-independent STAT5 phosphorylation and proliferation of hematopoietic progenitor cells. Furthermore, expression of trFlt3 in p53/NHEJ mutant hematopoietic progenitor cells promoted development of clinically aggressive B-cell leukemia. Thus, repetitive MuLV-related ERV sequences can participate in aberrant end-joining events that promote development of aggressive B-cell leukemia.

Polymorphism in Sirpa modulates engraftment of human hematopoietic stem cells.

Graft failure in the transplantation of hematopoietic stem cells occurs despite donor-host genetic identity of human leukocyte antigens, suggesting that additional factors modulate engraftment. With the nobese diabetic (NOD)-severe combined immunodeficiency (SCID) xenotransplantation model, we found that the NOD background allowed better hematopoietic engraftment than did other strains with equivalent immunodeficiency-related mutations. We used positional genetics to characterize the molecular basis for this strain specificity and found that the NOD Sirpa allele conferred support for human hematopoiesis. NOD SIRP-alpha showed enhanced binding to the human CD47 ligand, and its expression on mouse macrophages was required for support of human hematopoiesis. Thus, we have identified Sirpa polymorphism as a potent genetic determinant of the engraftment of human hematopoietic stem cells.

The Influence of the Microbiome on Type 1 Diabetes.

Type 1 diabetes (T1D) is characterized by the autoimmune destruction of pancreatic ß cells. The rapid rise in T1D incidence during the past 50 y suggests environmental factors contribute to the disease. The trillion symbiotic microorganisms inhabiting the mammalian gastrointestinal tract (i.e., the microbiota) influence numerous aspects of host physiology. In this study we review the evidence linking perturbations of the gut microbiome to pancreatic autoimmunity. We discuss data from rodent models demonstrating the essential role of the gut microbiota on the development and function of the host's mucosal and systemic immune systems. Furthermore, we review findings from human longitudinal cohort studies examining the influence of environmental and lifestyle factors on microbiota composition and pancreatic autoimmunity. Taken together, these data underscore the requirement for mechanistic studies to identify bacterial components and metabolites interacting with the innate and adaptive immune system, which would set the basis for preventative or therapeutic strategies in T1D.

Identification of the inflammasome Nlrp1b as the candidate gene conferring diabetes risk at the Idd4.1 locus in the nonobese diabetic mouse.

Type 1 diabetes in the NOD mouse model has been linked to >30 insulin-dependent diabetes (Idd) susceptibility loci. Idd4 on chromosome 11 consists of two subloci, Idd4.1 and Idd4.2. Using congenic analysis of alleles in NOD and NOD-resistant (NOR) mice, we previously defined Idd4.1 as an interval containing >50 genes that controlled expression of genes in the type 1 IFN pathway. In this study, we report refined mapping of Idd4.1 to a 1.1-Mb chromosomal region and provide genomic sequence analysis and mechanistic evidence supporting its role in innate immune regulation of islet-directed autoimmunity. Genetic variation at Idd4.1 was mediated by radiation-sensitive hematopoietic cells, and type 1 diabetes protection conferred by the NOR allele was abrogated in mice treated with exogenous type 1 IFN-ß. Next generation sequence analysis of the full Idd4.1 genomic interval in NOD and NOR strains supported Nlrp1b as a strong candidate gene for Idd4.1. Nlrp1b belongs to the Nod-like receptor (NLR) gene family and contributes to inflammasome assembly, caspase-1 recruitment, and release of IL-1ß. The Nlrp1b of NOR was expressed as an alternative spliced isoform that skips exon 9, resulting in a premature stop codon predicted to encode a truncated protein. Functional analysis of the truncated NOR Nlrp1b protein demonstrated that it was unable to recruit caspase-1 and process IL-1ß. Our data suggest that Idd4.1-dependent protection from islet autoimmunity is mediated by differences in type 1 IFN- and IL-1ß-dependent immune responses resulting from genetic variation in Nlrp1b.

Sex Effects at the Ramparts: Nutrient- and Microbe-Mediated Regulation of the Immune-Metabolic Interface.

The relationships between dietary compounds, derivative metabolites, and host metabolism and immunity are controlled by diverse molecular mechanisms. Essential contributions to these dynamics come from the community of microbes (the microbiome) inhabiting the human digestive tract. The composition and function of the microbiome are shaped by available nutrients, and reciprocally, these organisms produce an as yet poorly defined repertoire of molecules that communicate with the epithelial barrier and the mucosal immune system. We present evidence that diet-derived vitamins and lipids regulate immunity and metabolic function and highlight the diverse mechanisms through which these effects are impacted by sex. We discuss exciting new data emerging from studies using high-throughput sequencing technology, specialized mouse models, and bio-specimens, and clinical data from human subjects that have begun to reveal the complexity of these interactions. Also profiled in this chapter are the striking sex differences in pathways by which dietary nutrients and gut microbes modify metabolism, immunity, and immune- and inflammation-mediated diseases. Although the incidence, severity, and therapeutic responses of many autoimmune diseases differ by sex, the molecular mechanisms of these effects remain poorly understood.

Immune recognition and response to the intestinal microbiome in type 1 diabetes.

Type 1 diabetes (T1D) is an autoimmune disease resulting from T cell-mediated destruction of the insulin-secreting pancreatic beta cells. During the past 50 years T1D incidence has increased dramatically in many countries accompanied by an earlier age of onset especially in persons with lower genetic risk. These observations have prompted investigations of dynamic environmental factors that may contributor to risk for anti-pancreatic immunity. The gut and pancreas are anatomically and biochemically linked through the enteroinsular axis, a system in which gut-derived immune and metabolic signals have the potential to evoke effects in the pancreas. The gut microbiome (i.e. the 100 trillion symbiotic microorganisms which inhabit the mammalian gastrointestinal tract) influences numerous aspects of host metabolism, development and immunity. Here we examine recent evidence linking gut microbiome composition and function to pancreatic autoimmunity. Studies in children with genetic risk factors for T1D and analyses of the microbiome in rodent models have begun to associations between an altered microbiome composition potentially favoring a pro-inflammatory intestinal metabolic milieu and T1D. We discuss how environmental factors during critical developmental windows - gestation, birth, weaning and puberty may contribute to T1D risk. For example mode of delivery (vaginal or C-section) and exposure to antibiotics (pre- or post-natally) are two factors that modulate the maternal and/or offspring microbiome and can impact T1D development. Taken together, these emerging data underscore the requirement for longitudinal studies and mechanistic investigations in human subjects and rodent models to identify the basis for microbiome modulation of T1D and to identify biomarkers and therapeutics to improve the delayed onset and prevention of the disease.

Modulation of type 1 and type 2 diabetes risk by the intestinal microbiome.

The prevalence of type 1 and type 2 diabetes have both risen dramatically over the last 50 years. Recent findings point towards the gut microbiota as a potential contributor to these trends. The hundred trillion bacteria residing in the mammalian gut have established a symbiotic relation with their host and influence many aspects of host metabolism, physiology, and immunity. In this review, we examine recent data linking gut microbiome composition and function to anti-pancreatic immunity, insulin-resistance, and obesity. Studies in rodents and human longitudinal studies suggest that an altered gut microbiome characterized by lower diversity and resilience is associated with type 1 and type 2 diabetes. Through its metabolites and enzymatic arsenal, the microbiota shape host metabolism, energy extracted from the diet and contribute to the normal development of the immune system and to tissue inflammation. Increasing evidence underscores the importance of the maternal microbiome, the gestational environment and the conditions of newborn delivery in establishing the gut microbiota of the offspring. Perturbations of the maternal microbiome during gestation, or that of the offspring during early infant development may promote a pro-inflammatory environment conducive to the development of autoimmunity and metabolic disturbance. Collectively the findings reviewed herein underscore the need for mechanistic investigations in rodent models and in human studies to better define the relationships between microbial and host inflammatory activity in diabetes, and to evaluate the potential of microbe-derived therapeutics in the prevention and treatment of both forms of diabetes.

Polymorphism in the innate immune receptor SIRPα controls CD47 binding and autoimmunity in the nonobese diabetic mouse.

The signal regulatory protein (SIRP) locus encodes a family of paired receptors that mediate both activating and inhibitory signals and is associated with type 1 diabetes (T1D) risk. The NOD mouse model recapitulates multiple features of human T1D and enables mechanistic analysis of the impact of genetic variations on disease. In this study, we identify Sirpa encoding an inhibitory receptor on myeloid cells as a gene in the insulin-dependent diabetes locus 13.2 (Idd13.2) that drives islet inflammation and T1D. Compared to T1D-resistant strains, the NOD variant of SIRPα displayed greater binding to its ligand CD47, as well as enhanced T cell proliferation and diabetogenic potency. Myeloid cell-restricted expression of a Sirpa transgene accelerated disease in a dose-dependent manner and displayed genetic and functional interaction with the Idd5 locus to potentiate insulitis progression. Our study demonstrates that variations in both SIRPα sequence and expression level modulate T1D immunopathogenesis. Thus, we identify Sirpa as a T1D risk gene and provide insight into the complex mechanisms by which disease-associated variants act in concert to drive defined stages in disease progression.

γδ T cells are essential effectors of type 1 diabetes in the nonobese diabetic mouse model.

γδ T cells, a lineage of innate-like lymphocytes, are distinguished from conventional αß T cells in their Ag recognition, cell activation requirements, and effector functions. γδ T cells have been implicated in the pathology of several human autoimmune and inflammatory diseases and their corresponding mouse models, but their specific roles in these diseases have not been elucidated. We report that γδ TCR(+) cells, including both the CD27(-)CD44(hi) and CD27(+)CD44(lo) subsets, infiltrate islets of prediabetic NOD mice. Moreover, NOD CD27(-)CD44(hi) and CD27(+)CD44(lo) γδ T cells were preprogrammed to secrete IL-17, or IFN-γ upon activation. Adoptive transfer of type 1 diabetes (T1D) to T and B lymphocyte-deficient NOD recipients was greatly potentiated when γδ T cells, and specifically the CD27(-) γδ T cell subset, were included compared with transfer of αß T cells alone. Ab-mediated blockade of IL-17 prevented T1D transfer in this setting. Moreover, introgression of genetic Tcrd deficiency onto the NOD background provided robust T1D protection, supporting a nonredundant, pathogenic role of γδ T cells in this model. The potent contributions of CD27(-) γδ T cells and IL-17 to islet inflammation and diabetes reported in this study suggest that these mechanisms may also underlie human T1D.

Gut Microbiome Alterations Accompany Metabolic Normalization Following Bariatric Surgery in ROHHAD Syndrome.

Rapid onset obesity with hypoventilation, hypothalamic, and autonomic dysregulation (ROHHAD) syndrome in childhood is characterized by abrupt onset weight gain and dysautonomia with variable neuroendocrine involvement. In the absence of definitive disease-modifying therapies, the primary management strategy remains symptom control. This case report describes the first successful correction of obesity, dysautonomia, and metabolic derangement in a patient with ROHHAD following Roux-en-Y gastric bypass. Anthropometrics, metabolic profiling, and stool microbiome composition were assessed in a longitudinal fashion. In the 48-month period following surgery, the patient body mass index (BMI) reduced by 9.5 kg/m2 and metabolic status improved, evidenced in weaning of insulin, and improved glycated hemoglobin, lipid profile, and hepatic enzymes. Chronic diarrhea resolved after surgery and prior to significant weight loss. Evaluation of stool bacterial composition and biomass demonstrated shifts in absolute abundance and taxonomic composition in longitudinal samples following surgery. This case demonstrates the potential efficacy of bariatric surgery in correcting the metabolic disruption of ROHHAD syndrome, producing long-term changes in gut microbiome composition and biomass.

Chromosomal reinsertion of broken RSS ends during T cell development.

The V(D)J recombinase catalyzes DNA transposition and translocation both in vitro and in vivo. Because lymphoid malignancies contain chromosomal translocations involving antigen receptor and protooncogene loci, it is critical to understand the types of "mistakes" made by the recombinase. Using a newly devised assay, we characterized 48 unique TCRbeta recombination signal sequence (RSS) end insertions in murine thymocyte and splenocyte genomic DNA samples. Nearly half of these events targeted "cryptic" RSS-like elements. In no instance did we detect target-site duplications, which is a hallmark of recombinase-mediated transposition in vitro. Rather, these insertions were most likely caused by either V(D)J recombination between a bona fide RSS and a cryptic RSS or the insertion of signal circles into chromosomal loci via a V(D)J recombination-like mechanism. Although wild-type, p53, p53 x scid, H2Ax, and ATM mutant thymocytes all showed similar levels of RSS end insertions, core-RAG2 mutant thymocytes showed a sevenfold greater frequency of such events. Thus, the noncore domain of RAG2 serves to limit the extent to which the integrity of the genome is threatened by mistargeting of V(D)J recombination.

Lunatic Fringe prolongs Delta/Notch-induced self-renewal of committed αß T-cell progenitors.

Lunatic Fringe (Lfng) enhances Notch1 activation by Delta-like 4 (DL4) to promote Notch1-dependent T-lineage commitment of thymus-seeding progenitors. Subsequently, Notch1 and T-cell receptor-ß (TCRß)-containing pre-TCR complexes signal CD4/CD8 double-negative 3 (DN3) committed T-cell progenitors to survive, proliferate, and differentiate into CD4/CD8 double-positive (DP) αß T-cell precursors. Few DP thymocytes develop without Notch1 or pre-TCR signals, whereas ectopic Notch1 activation causes T-cell leukemia. However, mechanisms of a Notch-pre-TCR collaboration during this "ß-selection" process are poorly understood. We genetically manipulated Lfng to attenuate or enhance Notch1 activation in DN3 thymocytes without inducing leukemogenesis. We show that Lfng temporally sustains DL-induced Notch1 signaling to prolong proliferative self-renewal of pre-DP thymocytes. Pre-TCR signaling greatly augmented Notch trophic functions to promote robust proliferation of pre-DP progenitors. In contrast, in the absence of DL/Notch signaling, pre-TCR-expressing progenitors rapidly atrophied and differentiated into DP thymocytes. Thus, Lfng prolongs Notch1 signaling to promote self-renewal more than differentiation during the early stages of ß-selection. Our data provide novel insights into the Notch-pre-TCR collaboration, and suggest that decreasing Lfng expression during the DN3-DP transition minimizes the potent leukemogenic potential of Notch1 signaling.

Immune responses to gut bacteria associated with time to diagnosis and clinical response to T cell-directed therapy for type 1 diabetes prevention.

Immune-targeted therapies have efficacy for treatment of autoinflammatory diseases. For example, treatment with the T cell-specific anti-CD3 antibody teplizumab delayed disease onset in participants at high risk for type 1 diabetes (T1D) in the TrialNet 10 (TN-10) trial. However, heterogeneity in therapeutic responses in TN-10 and other immunotherapy trials identifies gaps in understanding disease progression and treatment responses. The intestinal microbiome is a potential source of biomarkers associated with future T1D diagnosis and responses to immunotherapy. We previously reported that antibody responses to gut commensal bacteria were associated with T1D diagnosis, suggesting that certain antimicrobial immune responses may help predict disease onset. Here, we investigated anticommensal antibody (ACAb) responses against a panel of taxonomically diverse intestinal bacteria species in sera from TN-10 participants before and after teplizumab or placebo treatment. We identified IgG2 responses to three species that were associated with time to T1D diagnosis and with teplizumab treatment responses that delayed disease onset. These antibody responses link human intestinal bacteria with T1D progression, adding predictive value to known T1D risk factors. ACAb analysis provides a new approach to elucidate heterogeneity in responses to immunotherapy and identify individuals who may benefit from teplizumab, recently approved by the U.S. Food and Drug Administration for delaying T1D onset.

Postpartum defects in inflammatory response after gestational diabetes precede progression to type 2 diabetes: a nested case-control study within the SWIFT study.

BACKGROUND: Gestational diabetes (GDM) is a distinctive form of diabetes that first presents in pregnancy. While most women return to normoglycemia after delivery, they are nearly ten times more likely to develop type 2 diabetes than women with uncomplicated pregnancies. Current prevention strategies remain limited due to our incomplete understanding of the early underpinnings of progression. AIM: To comprehensively characterize the postpartum profiles of women shortly after a GDM pregnancy and identify key mechanisms responsible for the progression to overt type 2 diabetes using multi-dimensional approaches. METHODS: We conducted a nested case-control study of 200 women from the Study of Women, Infant Feeding and Type 2 Diabetes After GDM Pregnancy (SWIFT) to examine biochemical, proteomic, metabolomic, and lipidomic profiles at 6-9 weeks postpartum (baseline) after a GDM pregnancy. At baseline and annually up to two years, SWIFT administered research 2-hour 75-gram oral glucose tolerance tests. Women who developed incident type 2 diabetes within four years of delivery (incident case group, n = 100) were pair-matched by age, race, and pre-pregnancy body mass index to those who remained free of diabetes for at least 8 years (control group, n = 100). Correlation analyses were used to assess and integrate relationships across profiling platforms. RESULTS: At baseline, all 200 women were free of diabetes. The case group was more likely to present with dysglycemia (e.g., impaired fasting glucose levels, glucose tolerance, or both). We also detected differences between groups across all omic platforms. Notably, protein profiles revealed an underlying inflammatory response with perturbations in protease inhibitors, coagulation components, extracellular matrix components, and lipoproteins, whereas metabolite and lipid profiles implicated disturbances in amino acids and triglycerides at individual and class levels with future progression. We identified significant correlations between profile features and fasting plasma insulin levels, but not with fasting glucose levels. Additionally, specific cross-omic relationships, particularly among proteins and lipids, were accentuated or activated in the case group but not the control group. CONCLUSIONS: Overall, we applied orthogonal, complementary profiling techniques to uncover an inflammatory response linked to elevated triglyceride levels shortly after a GDM pregnancy, which is more pronounced in women who progress to overt diabetes.

Variation in the Cd3 zeta (Cd247) gene correlates with altered T cell activation and is associated with autoimmune diabetes.

Tuning of TCR-mediated activation was demonstrated to be critical for lineage fate in T cell development, as well as in the control of autoimmunity. In this study, we identify a novel diabetes susceptibility gene, Idd28, in the NOD mouse and provide evidence that Cd3zeta (Cd247) constitutes a prime candidate gene for this locus. Moreover, we show that the allele of the Cd3zeta gene expressed in NOD and DBA/2 mouse strains confers lower levels of T cell activation compared with the allele expressed by C57BL/6 (B6), BALB/c, and C3H/HeJ mice. These results support a model in which the development of autoimmune diabetes is dependent on a TCR signal mediated by a less-efficient NOD allele of the Cd3zeta gene.