Beta Cells Deficient for Renalase Counteract Autoimmunity by Shaping Natural Killer Cell Activity.

Type 1 diabetes (T1D) arises from autoimmune-mediated destruction of insulin-producing pancreatic beta cells. Recent advancements in the technology of generating pancreatic beta cells from human pluripotent stem cells (SC-beta cells) have facilitated the exploration of cell replacement therapies for treating T1D. However, the persistent threat of autoimmunity poses a significant challenge to the survival of transplanted SC-beta cells. Genetic engineering is a promising approach to enhance immune resistance of beta cells as we previously showed by inactivating of the Renalase (Rnls) gene. Here we demonstrate that Rnls loss-of-function in beta cells shape autoimmunity by mediating a regulatory Natural Killer (NK) cell phenotype important for the induction of tolerogenic antigen presenting cells. Rnls-deficient beta cells mediate cell-cell-contact-independent induction of hallmark anti-inflammatory cytokine Tgfß1 in NK cells. In addition, surface expression of key regulatory NK immune checkpoints CD47 and Ceacam1 are markedly elevated on beta cells deficient for Rnls. Enhanced glucose metabolism in Rnls mutant beta cells is responsible for upregulation of CD47 surface expression. These findings are crucial to a better understand how genetically engineered beta cells shape autoimmunity giving valuable insights for future therapeutic advancements to treat and cure T1D.

Protective Renalase Deficiency in ß-Cells Shapes Immune Metabolism and Function in Autoimmune Diabetes.

Type 1 diabetes (T1D) is caused by the immune-mediated loss of pancreatic ß-cells that produce insulin. The latest advances in stem cell (SC) ß-cell differentiation methods have made a cell replacement therapy for T1D feasible. However, recurring autoimmunity would rapidly destroy transplanted SC ß-cells. A promising strategy to overcome immune rejection is to genetically engineer SC ß-cells. We previously identified Renalase (Rnls) as a novel target for ß-cell protection. Here we show that Rnls deletion endows ß-cells with the capacity to modulate the metabolism and function of immune cells within the local graft microenvironment. We used flow cytometry and single-cell RNA sequencing to characterize ß-cell graft-infiltrating immune cells in a mouse model for T1D. Loss of Rnls within transplanted ß-cells affected both the composition and the transcriptional profile of infiltrating immune cells in favor of an anti-inflammatory profile with decreased antigen-presenting capacity. We propose that changes in ß-cell metabolism mediate local immune regulation and that this feature could be exploited for therapeutic goals. ARTICLE HIGHLIGHTS: Protective Renalase (Rnls) deficiency impacts ß-cell metabolism. Rnls-deficient ß-cell grafts do not exclude immune infiltration. Rnls deficiency in transplanted ß-cells broadly modifies local immune function. Immune cell in Rnls mutant ß-cell grafts adopt a noninflammatory phenotype.

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.

Bioluminescent Monitoring of Graft Survival in an Adoptive Transfer Model of Autoimmune Diabetes in Mice.

Type 1 diabetes is characterized by the autoimmune destruction of the insulin-producing beta cells of the pancreas. A promising treatment for this disease is the transplantation of stem cell-derived beta cells. Genetic modifications, however, may be necessary to protect the transplanted cells from persistent autoimmunity. Diabetic mouse models are a useful tool for the preliminary evaluation of strategies to protect transplanted cells from autoimmune attack. Described here is a minimally invasive method for transplanting and imaging cell grafts in an adoptive transfer model of diabetes in mice. In this protocol, cells from the murine pancreatic beta cell line NIT-1 expressing the firefly luciferase transgene luc2 are transplanted subcutaneously into immunodeficient non-obese diabetic (NOD)-severe combined immunodeficient (scid) mice. These mice are simultaneously injected intravenously with splenocytes from spontaneously diabetic NOD mice to transfer autoimmunity. The grafts are imaged at regular intervals via non-invasive bioluminescent imaging to monitor the cell survival. The survival of mutant cells is compared to that of control cells transplanted into the same mouse.

CD5 Controls Gut Immunity by Shaping the Cytokine Profile of Intestinal T Cells.

CD5 is constitutively expressed on all T cells and is a negative regulator of lymphocyte function. However, the full extent of CD5 function in immunity remains unclear. CD5 deficiency impacts thymic selection and extra-thymic regulatory T cell generation, yet CD5 knockout was reported to cause no immune pathology. Here we show that CD5 is a key modulator of gut immunity. We generated mice with inducible CD5 knockdown (KD) in the autoimmune-prone nonobese diabetic (NOD) background. CD5 deficiency caused T cell-dependent wasting disease driven by chronic gut immune dysregulation. CD5 inhibition also exacerbated acute experimental colitis. Mechanistically, loss of CD5 increased phospho-Stat3 levels, leading to elevated IL-17A secretion. Our data reveal a new facet of CD5 function in shaping the T cell cytokine profile.

Genetic Modifiers of Thymic Selection and Central Tolerance in Type 1 Diabetes.

Type 1 diabetes (T1D) is caused by the T cell-driven autoimmune destruction of insulin-producing cells in the pancreas. T1D served as the prototypical autoimmune disease for genome wide association studies (GWAS) after having already been the subject of many linkage and association studies prior to the development of GWAS technology. Of the many T1D-associated gene variants, a minority appear disease-specific, while most are shared with one or more other autoimmune condition. Shared disease variants suggest defects in fundamental aspects of immune tolerance. The first layer of protective tolerance induction is known as central tolerance and takes place during the thymic selection of T cells. In this article, we will review candidate genes for type 1 diabetes whose function implicates them in central tolerance. We will describe examples of gene variants that modify the function of T cells intrinsically and others that indirectly affect thymic selection. Overall, these insights will show that a significant component of the genetic risk for T1D - and autoimmunity in general - pertains to the earliest stages of tolerance induction, at a time when protective intervention may not be feasible.

Genome-scale in vivo CRISPR screen identifies RNLS as a target for beta cell protection in type 1 diabetes.

Type 1 diabetes (T1D) is caused by the autoimmune destruction of pancreatic beta cells. Pluripotent stem cells can now be differentiated into beta cells, thus raising the prospect of a cell replacement therapy for T1D. However, autoimmunity would rapidly destroy newly transplanted beta cells. Using a genome-scale CRISPR screen in a mouse model for T1D, we show that deleting RNLS, a genome-wide association study candidate gene for T1D, made beta cells resistant to autoimmune killing. Structure-based modelling identified the U.S. Food and Drug Administration-approved drug pargyline as a potential RNLS inhibitor. Oral pargyline treatment protected transplanted beta cells in diabetic mice, thus leading to disease reversal. Furthermore, pargyline prevented or delayed diabetes onset in several mouse models for T1D. Our results identify RNLS as a modifier of beta cell vulnerability and as a potential therapeutic target to avert beta cell loss in T1D.

The type 1 diabetes candidate gene Dexi does not affect disease risk in the nonobese diabetic mouse model.

Genome-wide association studies have implicated more than 50 genomic regions in type 1 diabetes (T1D). A T1D region at chromosome 16p13.13 includes the candidate genes CLEC16A and DEXI. Conclusive evidence as to which gene is causal for the disease association of this region is missing. We previously reported that Clec16a deficiency modified immune reactivity and protected against autoimmunity in the nonobese diabetic (NOD) mouse model for T1D. However, the diabetes-associated SNPs at 16p13.13 were described to also impact on DEXI expression and others have argued that DEXI is the causal gene in this disease locus. To help resolve whether DEXI affects disease, we generated Dexi knockout (KO) NOD mice. We found that Dexi deficiency had no effect on the frequency of diabetes. To test for possible interactions between Dexi and Clec16a, we intercrossed Dexi KO and Clec16a knockdown (KD) NOD mice. Dexi KO did not modify the disease protection afforded by Clec16a KD. We conclude that Dexi plays no role in autoimmune diabetes in the NOD model. Our data provide strongly suggestive evidence that CLEC16A, not DEXI, is causal for the T1D association of variants in the 16p13.13 region.

Collective cancer invasion forms an integrin-dependent radioresistant niche.

Cancer fatalities result from metastatic dissemination and therapy resistance, both processes that depend on signals from the tumor microenvironment. To identify how invasion and resistance programs cooperate, we used intravital microscopy of orthotopic sarcoma and melanoma xenografts. We demonstrate that these tumors invade collectively and that, specifically, cells within the invasion zone acquire increased resistance to radiotherapy, rapidly normalize DNA damage, and preferentially survive. Using a candidate-based approach to identify effectors of invasion-associated resistance, we targeted ß1 and αVß3/ß5 integrins, essential extracellular matrix receptors in mesenchymal tumors, which mediate cancer progression and resistance. Combining radiotherapy with ß1 or αV integrin monotargeting in invading tumors led to relapse and metastasis in 40-60% of the cohort, in line with recently failed clinical trials individually targeting integrins. However, when combined, anti-ß1/αV integrin dual targeting achieved relapse-free radiosensitization and prevented metastatic escape. Collectively, invading cancer cells thus withstand radiotherapy and DNA damage by ß1/αVß3/ß5 integrin cross-talk, but efficient radiosensitization can be achieved by multiple integrin targeting.

Regulation of B cell homeostasis by Ptpn22 contributes to type 1 diabetes in NOD mice.

PURPOSE: A coding variant in PTPN22 (C1858T) is one of the most important genetic risk factors in type 1 diabetes (T1D). The role of the PTPN22 risk allele in B cells is still incompletely understood and has not been investigated directly in T1D. This study aimed to explore the role of PTPN22 in the homeostasis of B cells and its influence in T1D. METHODS: Wild-type (WT) and Ptpn22 inducible knockdown (KD) NOD mice were treated with 200 µg/ml doxycycline at the age of 10 weeks for 1-2 months. B cell compositions in the bone marrow, peritoneal cavity and spleen were examined. The pathogenicity of Ptpn22 KD B cells was explored by adoptive cell transfer. RESULTS: Ptpn22 silencing increased the frequency of recirculating mature B cells in the bone marrow, decreased the frequency of B-1a cells in the peritoneal cavity and suppressed the formation of marginal zone B cells and plasma cells in the spleen. Changes in the composition of the peripheral B cell compartment caused by altered cell proliferation while rates of apoptosis were not affected. Significantly, co-transfer of Ptpn22 KD B cells with NY8.3 diabetogenic T cells diminished the frequency of diabetes in recipient NOD.scid mice compared with co-transfer of WT B cells. CONCLUSIONS: Our study constitutes the first functional study of Ptpn22 in B cells in NOD mice. Our findings suggest that Ptpn22 variation contributes to T1D by modifying the B cell compartment and support a gain-of-function for the PTPN22 disease variant.

Anti-CD3 Antibody for the Prevention of Type 1 Diabetes: A Story of Perseverance.

Type 1 diabetes (T1D) is an autoimmune disease characterized by an insulin deficiency. Ever since the discovery of insulin almost 100 years ago, patients with T1D have relied on multiple daily insulin injections to survive an otherwise deadly disease. Despite decades of research and clinical trials, no treatment exists yet to prevent or cure T1D. A recent prevention trial using the anti-CD3 antibody teplizumab in individuals at a high risk of developing T1D has provided the first piece of evidence that a safe and transient intervention may be able to delay disease. In this Perspective, we review the 40-year long history of anti-CD3 and discuss how this antibody became a candidate for the treatment of autoimmune diabetes. The path that leads to its use in this latest clinical trial for T1D has been winding and strewn with setbacks. The molecular actions of the anti-CD3 antibody that target T lymphocytes are well-understood, but its systemic effect on immune function has proven more difficult to unravel. Moreover, preclinical data suggested that the utility of anti-CD3 for the prevention of T1D may be limited. However, the latest clinical data are encouraging and exemplify how a basic discovery can, decades later and with much perseverance, become a promising therapeutic candidate.

Increased ß-cell proliferation before immune cell invasion prevents progression of type 1 diabetes.

Type 1 diabetes (T1D) is characterized by pancreatic islet infiltration by autoreactive immune cells and a near-total loss of ß-cells1. Restoration of insulin-producing ß-cells coupled with immunomodulation to suppress the autoimmune attack has emerged as a potential approach to counter T1D2-4. Here we report that enhancing ß-cell mass early in life, in two models of female NOD mice, results in immunomodulation of T-cells, reduced islet infiltration and lower ß-cell apoptosis, that together protect them from developing T1D. The animals displayed altered ß-cell antigens, and islet transplantation studies showed prolonged graft survival in the NOD-LIRKO model. Adoptive transfer of splenocytes from the NOD-LIRKOs prevented development of diabetes in pre-diabetic NOD mice. A significant increase in the splenic CD4+CD25+FoxP3+ regulatory T-cell (Treg) population was observed to underlie the protected phenotype since Treg depletion rendered NOD-LIRKO mice diabetic. The increase in Tregs coupled with activation of TGF-ß/SMAD3 signaling pathway in pathogenic T-cells favored reduced ability to kill ß-cells. These data support a previously unidentified observation that initiating ß-cell proliferation, alone, prior to islet infiltration by immune cells alters the identity of ß-cells, decreases pathologic self-reactivity of effector cells and increases Tregs to prevent progression of T1D.

Regulation of thymocyte trafficking by Tagap, a GAP domain protein linked to human autoimmunity.

Multiple autoimmune pathologies are associated with single-nucleotide polymorphisms of the human gene TAGAP, which encodes TAGAP, a guanosine triphosphatase (GTPase)-activating protein. We showed in mice that Tagap-mediated signaling by the sema3E/plexin-D1 ligand-receptor complex attenuates thymocytes' adhesion to the cortex through their ß1-containing integrins. By promoting thymocyte detachment within the cortex of the thymus, Tagap-mediated signaling enabled their translocation to the medulla, which is required for continued thymic selection. Tagap physically interacted with the cytoplasmic domain of plexin-D1 and directly stimulated the activity and signaling of the GTPase RhoA. In addition, Tagap indirectly mediated the activation of Cdc42 in response to the binding of sema3E to plexin-D1. Both RhoA and Cdc42 are key mediators of cytoskeletal and integrin dynamics in thymocytes. Knockdown of Tagap in mice suppressed the sema3E- and plexin-D1-mediated release of thymocytes that adhered within the cortex through ß1-containing integrins. This suppression led to the impaired translocation of thymocytes from the cortex to the medulla and resulted in the formation of ectopic medullary structures within the thymic cortex. Our results suggest that TAGAP variation modulates the risk of autoimmunity by altering thymocyte migration during thymic selection.

Peripherally induced regulatory T cells contribute to the control of autoimmune diabetes in the NOD mouse model.

Type 1 diabetes (T1D) results from the autoimmune destruction of pancreatic beta cells and is partly caused by deficiencies in the Foxp3+ regulatory T-cell (Treg) compartment. Conversely, therapies that increase Treg function can prevent autoimmune diabetes in animal models. The majority of Tregs develop in the thymus (tTregs), but a proportion of Foxp3+ Tregs is generated in the periphery (pTregs) from Foxp3- CD4+ T-cell precursors. Whether pTregs play a distinct role in T1D has not yet been explored. We report here that pTregs are a key modifier of disease in the nonobese diabetic (NOD) mouse model for T1D. We generated NOD mice deficient for the Foxp3 enhancer CNS1 involved in pTreg induction. We show that CNS1 knockout decreased the frequency of pTregs and increased the risk of diabetes. Our results show that pTregs fulfill an important non-redundant function in the prevention of beta cell autoimmunity that causes T1D.

In Vivo Enrichment of Diabetogenic T Cells.

Dysfunctional T cells can mediate autoimmunity, but the inaccessibility of autoimmune tissues and the rarity of autoimmune T cells in the blood hinder their study. We describe a method to enrich and harvest autoimmune T cells in vivo by using a biomaterial scaffold loaded with protein antigens. In model antigen systems, we found that antigen-specific T cells become enriched within scaffolds containing their cognate antigens. When scaffolds containing lysates from an insulin-producing ß-cell line were implanted subcutaneously in autoimmune diabetes-prone NOD mice, ß-cell-reactive T cells homed to these scaffolds and became enriched. These T cells induced diabetes after adoptive transfer, indicating their pathogenicity. Furthermore, T-cell receptor (TCR) sequencing identified many expanded TCRs within the ß-cell scaffolds that were also expanded within the pancreata of NOD mice. These data demonstrate the utility of biomaterial scaffolds loaded with disease-specific antigens to identify and study rare, therapeutically important T cells.

Ptpn22 Modifies Regulatory T Cell Homeostasis via GITR Upregulation.

PTPN22 gene variation associates with multiple autoimmune diseases, including type 1 diabetes and rheumatoid arthritis. Loss of function studies have demonstrated that PTPN22 impinges on the homeostatic behavior of regulatory T (Treg) cells, a lineage critical for immune tolerance. The frequency and absolute number of Treg cells is increased in Ptpn22-deficient mice, but the mechanism driving this increase is unknown. In this study, we show that Ptpn22 knockdown (KD) promoted the expansion of the Treg cell compartment by upregulating the glucocorticoid-induced TNFR family-related protein (GITR) and increasing GITR signaling. Ptpn22 KD did not accelerate cell division but instead prolonged Treg cell survival, as measured by a decrease in the frequency of apoptotic Treg cells. Loss of Ptpn22 caused a concomitant increase in the proportion of CD44(hi)CD62L(lo) effector Treg cells, at the expense of CD44(lo)CD62L(hi) central Treg cells. The increase in Treg cell numbers, but not their differentiation toward an effector phenotype, was dependent on GITR signaling, because blockade of GITR ligand prevented Treg cell expansion caused by Ptpn22 KD. These findings indicate that GITR plays a key role in regulating the overall size of the Treg cell pool. Our results suggest that the size and composition of the Treg cell compartment are independently controlled and have implications for the design of immunotherapies that seek to improve Treg cell function.

Deficiency of HIF1α in Antigen-Presenting Cells Aggravates Atherosclerosis and Type 1 T-Helper Cell Responses in Mice.

OBJECTIVE: Although immune responses drive the pathogenesis of atherosclerosis, mechanisms that control antigen-presenting cell (APC)-mediated immune activation in atherosclerosis remain elusive. We here investigated the function of hypoxia-inducible factor (HIF)-1α in APCs in atherosclerosis. APPROACH AND RESULTS: We found upregulated HIF1α expression in CD11c(+) APCs within atherosclerotic plaques of low-density lipoprotein receptor-deficient (Ldlr(-/-)) mice. Conditional deletion of Hif1a in CD11c(+) APCs in high-fat diet-fed Ldlr(-/-) mice accelerated atherosclerotic plaque formation and increased lesional T-cell infiltrates, revealing a protective role of this transcription factor. HIF1α directly controls Signal Transducers and Activators of Transcription 3 (Stat3), and a reduced STAT3 expression was found in HIF1α-deficient APCs and aortic tissue, together with an upregulated interleukin-12 expression and expansion of type 1 T-helper (Th1) cells. Overexpression of STAT3 in Hif1a-deficient APCs in bone marrow reversed enhanced atherosclerotic lesion formation and reduced Th1 cell expansion in chimeric Ldlr(-/-) mice. Notably, deletion of Hif1a in LysM(+) bone marrow cells in Ldlr(-/-) mice did not affect lesion formation or T-cell activation. In human atherosclerotic lesions, HIF1α, STAT3, and interleukin-12 protein were found to colocalize with APCs. CONCLUSIONS: Our findings identify HIF1α to antagonize APC activation and Th1 T cell polarization during atherogenesis in Ldlr(-/-) mice and to attenuate the progression of atherosclerosis. These data substantiate the critical role of APCs in controlling immune mechanisms that drive atherosclerotic lesion development.

The Autoimmunity-Associated Gene CLEC16A Modulates Thymic Epithelial Cell Autophagy and Alters T Cell Selection.

CLEC16A variation has been associated with multiple immune-mediated diseases, including type 1 diabetes, multiple sclerosis, systemic lupus erythematosus, celiac disease, Crohn's disease, Addison's disease, primary biliary cirrhosis, rheumatoid arthritis, juvenile idiopathic arthritis, and alopecia areata. Despite strong genetic evidence implicating CLEC16A in autoimmunity, this gene's broad association with disease remains unexplained. We generated Clec16a knock-down (KD) mice in the nonobese diabetic (NOD) model for type 1 diabetes and found that Clec16a silencing protected against autoimmunity. Disease protection was attributable to T cell hyporeactivity, which was secondary to changes in thymic epithelial cell (TEC) stimuli that drive thymocyte selection. Our data indicate that T cell selection and reactivity were impacted by Clec16a variation in thymic epithelium owing to Clec16a's role in TEC autophagy. These findings provide a functional link between human CLEC16A variation and the immune dysregulation that underlies the risk of autoimmunity.

PTPN22 silencing in the NOD model indicates the type 1 diabetes-associated allele is not a loss-of-function variant.

PTPN22 encodes the lymphoid tyrosine phosphatase (LYP) and is the second strongest non-HLA genetic risk factor for type 1 diabetes. The PTPN22 susceptibility allele generates an LYP variant with an arginine-to-tryptophan substitution at position 620 (R620W) that has been reported by several studies to impart a gain of function. However, a recent report investigating both human cells and a knockin mouse model containing the R620W homolog suggested that this variation causes faster protein degradation. Whether LYP R620W is a gain- or loss-of-function variant, therefore, remains controversial. To address this issue, we generated transgenic NOD mice (nonobese diabetic) in which Ptpn22 can be inducibly silenced by RNA interference. We found that Ptpn22 silencing in the NOD model replicated many of the phenotypes observed in C57BL/6 Ptpn22 knockout mice, including an increase in regulatory T cells. Notably, loss of Ptpn22 led to phenotypic changes in B cells opposite to those reported for the human susceptibility allele. Furthermore, Ptpn22 knockdown did not increase the risk of autoimmune diabetes but, rather, conferred protection from disease. Overall, to our knowledge, this is the first functional study of Ptpn22 within a model of type 1 diabetes, and the data do not support a loss of function for the PTPN22 disease variant.