ICOS mediates the development of insulin-dependent diabetes mellitus in nonobese diabetic mice

Abatacept for Delay of Type 1 Diabetes Progression in Stage 1 Relatives at Risk: A Randomized, Double-Masked, Controlled Trial

OBJECTIVE

Previous studies showed that inhibiting lymphocyte costimulation reduces declining β-cell function in individuals newly diagnosed with type 1 diabetes. We tested whether abatacept would delay or prevent progression of type 1 diabetes from normal glucose tolerance (NGT) to abnormal glucose tolerance (AGT) or to diabetes and the effects of treatment on immune and metabolic responses.

RESEARCH DESIGN AND METHODS

We conducted a phase 2, randomized, placebo-controlled, double-masked trial of abatacept in antibody-positive participants with NGT who received monthly abatacept/placebo infusions for 12 months. The end point was AGT or diabetes, assessed by oral glucose tolerance tests.

RESULTS

A total of 101 participants received abatacept and 111 placebo. Of these, 81 (35 abatacept and 46 placebo) met the end point of AGT or type 1 diabetes diagnosis (hazard ratio 0.702; 95% CI 0.452, 1.09; P = 0.11) The C-peptide responses to oral glucose tolerance tests were higher in the abatacept arm (P < 0.03). Abatacept reduced the frequency of inducible T-cell costimulatory (ICOS)+ PD1+ T-follicular helper (Tfh) cells during treatment (P < 0.0001), increased naive CD4+ T cells, and also reduced the frequency of CD4+ regulatory T cells (Tregs) from the baseline (P = 0.0067). Twelve months after treatment, the frequency of ICOS+ Tfh, naive CD4+ T cells, and Tregs returned to baseline.

CONCLUSIONS

Although abatacept treatment for 1 year did not significantly delay progression to glucose intolerance in at-risk individuals, it impacted immune cell subsets and preserved insulin secretion, suggesting that costimulation blockade may modify progression of type 1 diabetes.

ICOS-Deficient Regulatory T Cells Can Prevent Spontaneous Autoimmunity but Are Impaired in Controlling Acute Inflammation

ICOS is induced in activated T cells and its main role is to boost differentiation and function of effector T cells. ICOS is also constitutively expressed in a subpopulation of Foxp3⁺ regulatory T cells under steady-state condition. Studies using ICOS germline knockout mice or ICOS-blocking reagents suggested that ICOS has supportive roles in regulatory T (Treg) cell homeostasis, migration, and function. To avoid any compounding effects that may arise from ICOS-deficient non-Treg cells, we generated a conditional knockout system in which ICOS expression is selectively abrogated in Foxp3-expressing cells (ICOS FC mice). Compared to Foxp3-Cre control mice, ICOS FC mice showed a minor numerical deficit of steady-state Treg cells but did not show any signs of spontaneous autoimmunity, indicating that tissue-protective Treg populations do not heavily rely on ICOS costimulation. However, ICOS FC mice showed more severe inflammation in oxazolone-induced contact hypersensitivity, a model of atopic dermatitis. This correlated with elevated numbers of inflammatory T cells expressing IFN-γ and/or TNF-α in ICOS FC mice compared with the control group. In contrast, elimination of ICOS in all T cell compartments negated the differences, confirming that ICOS has a dual positive role in effector and Treg cells. Single-cell transcriptome analysis suggested that ICOS-deficient Treg cells fail to mature into T-bet⁺CXCR3⁺ "Th1-Treg" cells in the draining lymph node. Our results suggest that regimens that preferentially stimulate ICOS pathways in Treg cells might be beneficial for the treatment of Th1-driven inflammation.

The ICOS-ICOSL pathway tunes thymic selection

Negative selection of developing T cells plays a significant role in T cell tolerance to self-antigen. This process relies on thymic antigen presenting cells which express both self-antigens as well as co-signaling molecules. Inducible T cell costimulator (ICOS) belongs to the CD28 family of co-signaling molecules and binds to ICOS ligand (ICOSL). The ICOS signaling pathway plays important roles in shaping the immune response to infections, but its role in central tolerance is less well understood. Here we show that ICOSL is expressed by subsets of thymic dendritic cells and medullary thymic epithelial cells as well as thymic B cells. ICOS expression is upregulated as T cells mature in the thymus and correlates with T cell receptor signal strength during thymic selection. We also provide evidence of a role for ICOS signaling in mediating negative selection. Our findings suggest that ICOS may fine-tune T cell receptor signals during thymic selection contributing to the generation of a tolerant T cell population.

Epigenetic Alterations Are Associated With Gastric Emptying Disturbances in Diabetes Mellitus

Epigenetic modifications have been implicated to mediate several complications of diabetes mellitus (DM), especially nephropathy and retinopathy. Our aim was to ascertain whether epigenetic alterations in whole blood discriminate among patients with DM with normal, delayed, and rapid gastric emptying (GE).

Vitamin D Supplementation Modulates ICOS+ and ICOS- Regulatory T Cell in Siblings of Children With Type 1 Diabetes

OBJECTIVES

Vitamin D plays an immunoregulatory activity. The aim of this study was to assess the correlation between blood serum 25(OH)D levels and Th17 and Treg circulating subsets, mainly Treg/inducible costimulatory-positive (ICOS+), which seems to have a protective role in autoimmunity, in children with type 1 diabetes mellitus (T1D) and their healthy siblings (S). The secondary aim was to evaluate the impact of vitamin D supplementation on these subsets.

PATIENTS AND METHODS

22 T1D and 33 S were enrolled. Glucose, hemoglobin A1c, 25 OH vitamin D (25[OH]D), T helper type 17 (Th17; CD4+CCR6+), regulatory T cells (Treg; CD4+CD25+Foxp3+), and Treg/ICOS+ cells were evaluated. According to human leukocyte antigen (HLA) haplotypes, subjects were classified as "at risk" (HLA+), "protective haplotypes" (HLA-; "nested controls"), and "undetermined" (HLAUND). T1D and S subjects were supplemented with cholecalciferol 1000 IU/die and evaluated after 6 months.

RESULTS

Vitamin D insufficiency (74.4%) and deficiency (43%) were frequent. S subjects with 25(OH)D levels <25 nmol/L had Th17, Treg (p < 0.01), and Treg/ICOS+ (P < 0.05) percentages higher than subjects with 25(OH)D >75 nmol/L. Treg/ICOS+ percentages (P < 0.05) were higher in HLA- S subjects compared to percentages observed in S with T1D. At baseline, in S subjects, a decreasing trend in Th17 and Treg/ICOS+ values (P < 0.05) from vitamin D deficiency to sufficiency was observed; 25(OH)D levels were negative predictors of Treg/ICOS+ (R2 = 0.301) and Th17 percentages (R2 = 0.138). After 6 months, supplemented S subjects showed higher 25(OH)D levels (P < 0.0001), and lower Th17 (P < 0.0001) and Treg/ICOS+ (P < 0.05) percentages than at baseline; supplemented T1D patients only had a decrease in Th17 levels (P < 0.05).

CONCLUSION

Serum 25(OH)D levels seem to affect Th17 and Treg cell subsets in S subjects, consistent with its immunomodulating role. HLA role should be investigated in a larger population.

Natural and Induced Tolerogenic Dendritic Cells

Dendritic cells (DCs) are highly susceptible to extrinsic signals that modify the functions of these crucial APCs. Maturation of DCs induced by diverse proinflammatory conditions promotes immune responses, but certain signals also induce tolerogenic functions in DCs. These "induced tolerogenic DCs" help to moderate immune responses such as those to commensals present at specific anatomical locations. However, also under steady-state conditions, some DCs are characterized by inherent tolerogenic properties. The immunomodulatory mechanisms constitutively present in such "natural tolerogenic DCs" help to promote tolerance to peripheral Ags. By extending tolerance initially established in the thymus, these functions of DCs help to regulate autoimmune and other immune responses. In this review we will discuss the mechanisms and functions of natural and induced tolerogenic DCs and offer further insight into how their possible manipulations may ultimately lead to more precise treatments for various immune-mediated conditions and diseases.

Role of Co-stimulatory Molecules in T Helper Cell Differentiation

CD4⁺ T cells play a central role in orchestrating the immune response to a variety of pathogens but also regulate autoimmune responses, asthma, allergic responses, as well as tumor immunity. To cover this broad spectrum of responses, naïve CD4⁺ T cells differentiate into one of several lineages of T helper cells, including Th1, Th2, Th17, and T_FH, as defined by their cytokine pattern and function. The fate decision of T helper cell differentiation integrates signals delivered through the T cell receptor, cytokine receptors, and the pattern of co-stimulatory signals received. In this review, we summarize the contribution of co-stimulatory and co-inhibitory receptors to the differentiation and maintenance of T helper cell responses.

Immunomodulatory Bonds of the Partnership between Dendritic Cells and T Cells

By acquiring, processing, and presenting both foreign and self-antigens, dendritic cells (DCs) initiate T cell activation that is shaped through the immunomodulatory functions of a variety of cell-membrane-bound molecules including BTLA-HVEM, CD40-CD40L, CTLA-4-CD80/CD86, CD70-CD27, ICOS-ICOS-L, OX40-OX40L, and PD-L1-PD-1, as well as several key cytokines and enzymes such as interleukin-6 (IL-6), IL-12, IL-23, IL-27, transforming growth factor-beta 1 (TGF-β1), retinaldehyde dehydrogenase (Raldh), and indoleamine 2,3-dioxygenase (IDO). Some of these distinct immunomodulatory signals are mediated by specific subsets of DCs, therefore contributing to the functional specialization of DCs in the priming and regulation of immune responses. In addition to responding to the DC-mediated signals, T cells can reciprocally modulate the immunomodulatory capacities of DCs, further refining immune responses. Here, we review recent studies, particularly in experimental mouse systems, that have delineated the integrated mechanisms of crucial immunomodulatory pathways that enable specific populations of DCs and T cells to work intimately together as single functional units that are indispensable for the maintenance of immune homeostasis.

Cutting Edge: ICOS-Deficient Regulatory T Cells Display Normal Induction of Il10 but Readily Downregulate Expression of Foxp3

The ICOS pathway has been implicated in the development and functions of regulatory T (Treg) cells, including those producing IL-10. Treg cell-derived IL-10 is indispensable for the establishment and maintenance of intestinal immune homeostasis. We examined the possible involvement of the ICOS pathway in the accumulation of murine colonic Foxp3- and/or IL-10-expressing cells. We show that ICOS deficiency does not impair induction of IL-10 by intestinal CD4 T cells but, instead, triggers substantial reductions in gut-resident and peripherally derived Foxp3⁺ Treg cells. ICOS deficiency is associated with reduced demethylation of Foxp3 CNS2 and enhanced loss of Foxp3. This instability significantly limits the ability of ICOS-deficient Treg cells to reverse ongoing inflammation. Collectively, our results identify a novel role for ICOS costimulation in imprinting the functional stability of Foxp3 that is required for the retention of full Treg cell function in the periphery.

Elevated histone H3 acetylation is associated with genes involved in T lymphocyte activation and glutamate decarboxylase antibody production in patients with type 1 diabetes

AIMS/INTRODUCTION

Genetic and epigenetic mechanisms have been implicated in the pathogenesis of type 1 diabetes, and histone acetylation is an epigenetic modification pattern that activates gene transcription. However, the genome-wide histone H3 acetylation in new-onset type 1 diabetes patients has not been well described. Accordingly, we aimed to unveil the genome-wide promoter acetylation profile in CD4+ T lymphocytes from type 1 diabetes patients, especially for those who are glutamate decarboxylase antibody-positive.

MATERIALS AND METHODS

A total of 12 patients with new-onset type 1 diabetes who were glutamate decarboxylase antibody-positive were enrolled, and 12 healthy individuals were recruited as controls. The global histone H3 acetylation level of CD4+ T lymphocytes from peripheral blood was detected by western blot, with chromatin immunoprecipitation linked to microarrays to characterize the promoter acetylation profile. Furthermore, we validated the results of particular genes from chromatin immunoprecipitation linked to microarrays by using chromatin immunoprecipitation quantitative polymerase chain reaction, and analyzed the transcription level by real-time quantitative polymerase chain reaction.

RESULTS

Elevated global histone H3 acetylation level was observed in type 1 diabetes patients, with 607 differentially acetylated genes identified between type 1 diabetes patients and controls by chromatin immunoprecipitation linked to microarrays. The hyperacetylated genes were enriched in biological processes involved in immune cell activation and inflammatory response. Gene-specific assessments showed that increased transcription of inducible T-cell costimulator was in concordance with the elevated acetylation in its gene promoter, along with positive correlation with glutamate decarboxylase antibody titer in type 1 diabetes patients.

CONCLUSIONS

The present study generates a genome-wide histone acetylation profile specific to CD4+ T lymphocytes in type 1 diabetes patients who are glutamic acid decarboxylase antibody-positive, which is instrumental in improving our understanding of the epigenetic involvement in autoimmune diabetes.

Dichotomous roles of co-stimulatory molecules in diabetes mellitus

Numerous studies have established the importance of immune dysfunction in the development of diabetes mellitus, including typ1 and typ2 diabetes, and it is worth noting that T cell activation acts a key role in the pathogenesis of loss of β cell mass, adipose inflammation and insulin resistance. Regarding as an important checkpoint in the process of T cell activation, co-stimulatory molecules interaction between antigen present cells and T cells have been identified the critical role in the development of diabetes mellitus. Thus, blockage of co-stimulatory dyads interaction between antigen present cells and T cells was supposed to a potential of therapeutic strategies. However, studies also showed that inhibition or deletion of some co-stimulatory molecules do not always reduce the development of diabetes, and even exacerbate the disease activity. Here, in this context, we highlight the dichotomous role of co-stimulatory molecules interaction in the pathogenesis of diabetes.

Development of interleukin-17-producing Vγ2+ γδ T cells is reduced by ICOS signaling in the thymus

Co-stimulation is an integral part of T cell signaling involved in almost all facets of T cell biology. While much is known about co-stimulation in differentiation and function of conventional αβ T cells, less is known about how co-stimulation affects the development and programming of γδ T cells. In this study, we have investigated the role of inducible T cell co-stimulator (ICOS) on the development of γδ T cells. We show that ICOS is expressed by a population of immature Vγ2⁺CD45RB^low γδ T cells predisposed to interleukin-17 (IL-17) production. We found that treatment with ICOS specific antibodies drastically reduces fetal development of IL-17-producing γδ T cells by agonistic actions, and that ICOS deficient mice have a significant increase in the population of IL-17-producing Vγ2⁺ γδ T cells in the thymus, spleen, lymph nodes and skin and exhibit exacerbated sensitization responses to 2,4-dinitrofluorobenzene. In conclusion, this study demonstrates that development of IL-17-producing Vγ2⁺ γδ T cells is reduced by ICOS signaling in the thymus.

Co-stimulatory and Co-inhibitory Pathways in Autoimmunity

The immune system is guided by a series of checks and balances, a major component of which is a large array of co-stimulatory and co-inhibitory pathways that modulate the host response. Although co-stimulation is essential for boosting and shaping the initial response following signaling through the antigen receptor, inhibitory pathways are also critical for modulating the immune response. Excessive co-stimulation and/or insufficient co-inhibition can lead to a breakdown of self-tolerance and thus to autoimmunity. In this review, we will focus on the role of co-stimulatory and co-inhibitory pathways in two systemic (systemic lupus erythematosus and rheumatoid arthritis) and two organ-specific (multiple sclerosis and type 1 diabetes) emblematic autoimmune diseases. We will also discuss how mechanistic analysis of these pathways has led to the identification of potential therapeutic targets and initiation of clinical trials for autoimmune diseases, as well as outline some of the challenges that lie ahead.

Development of the Nonobese Diabetic Mouse and Contribution of Animal Models for Understanding Type 1 Diabetes

In 1974, the discovery of a mouse and a rat that spontaneously developed hyperglycemia led to the development of 2 autoimmune diabetes models: nonobese diabetic (NOD) mouse and Bio-Breeding rat. These models have contributed to our understanding of autoimmune diabetes, provided tools to dissect autoimmune islet damage, and facilitated development of early detection, prevention, and treatment of type 1 diabetes. The genetic characterization, monoclonal antibodies, and congenic strains have made NOD mice especially useful.Although the establishment of the inbred NOD mouse strain was documented by Makino et al (Jikken Dobutsu. 1980;29:1-13), this review will focus on the not-as-well-known history leading to the discovery of a glycosuric female mouse by Yoshihiro Tochino. This discovery was spearheaded by years of effort by Japanese scientists from different disciplines and dedicated animal care personnel and by the support of the Shionogi Pharmaceutical Company, Osaka, Japan. The history is based on the early literature, mostly written in Japanese, and personal communications especially with Dr Tochino, who was involved in diabetes animal model development and who contributed to the release of NOD mice to the international scientific community. This article also reviews the scientific contributions made by the Bio-Breeding rat to autoimmune diabetes.

CD137 Plays Both Pathogenic and Protective Roles in Type 1 Diabetes Development in NOD Mice

We previously reported that CD137 (encoded by Tnfrsf9) deficiency suppressed type 1 diabetes (T1D) progression in NOD mice. We also demonstrated that soluble CD137 produced by regulatory T cells contributed to their autoimmune-suppressive function in this model. These results suggest that CD137 can either promote or suppress T1D development in NOD mice depending on where it is expressed. In this study, we show that NOD.Tnfrsf9^-/- CD8 T cells had significantly reduced diabetogenic capacity, whereas absence of CD137 in non-T and non-B cells had a limited impact on T1D progression. In contrast, NOD.Tnfrsf9^-/- CD4 T cells highly promoted T1D development. We further demonstrated that CD137 was important for the accumulation of β cell-autoreactive CD8 T cells but was dispensable for their activation in pancreatic lymph nodes. The frequency of islet-infiltrating CD8 T cells was reduced in NOD.Tnfrsf9^-/- mice in part because of their decreased proliferation. Furthermore, CD137 deficiency did not suppress T1D development in NOD mice expressing the transgenic NY8.3 CD8 TCR. This suggests that increased precursor frequency of β cell-autoreactive CD8 T cells in NY8.3 mice obviated a role for CD137 in diabetogenesis. Finally, blocking CD137-CD137 ligand interaction significantly delayed T1D onset in NOD mice. Collectively, our results indicate that one important diabetogenic function of CD137 is to promote the expansion and accumulation of β cell-autoreactive CD8 T cells, and in the absence of CD137 or its interaction with CD137 ligand, T1D progression is suppressed.

The Spontaneous Autoimmune Neuromyopathy in ICOSL-/- NOD Mice Is CD4+ T-Cell and Interferon-γ Dependent

Abrogation of ICOS/ICOS ligand (ICOSL) costimulation prevents the onset of diabetes in the non-obese diabetic (NOD) mouse but, remarkably, yields to the development of a spontaneous autoimmune neuromyopathy. At the pathological level, ICOSL^−/− NOD mice show stronger protection from insulitis than their ICOS^−/− counterparts. Also, the ICOSL^−/− NOD model carries a limited C57BL/6 region containing the Icosl nul mutation, but, in contrast to ICOS^−/− NOD mice, no gene variant previously reported as associated to NOD diabetes. Therefore, we aimed at providing a detailed characterization of the ICOSL^−/− NOD model. The phenotype observed in ICOSL^−/− NOD mice is globally similar to that observed in ICOS^−/− and ICOS^−/−ICOSL^−/− double-knockout NOD mice, manifested by a progressive locomotor disability first affecting the front paws as observed by catwalk analysis and a decrease in grip test performance. The pathology remains limited to peripheral nerve and striated muscle. The muscle disease is characterized by myofiber necrosis/regeneration and an inflammatory infiltrate composed of CD4⁺ T-cells, CD8⁺ T-cells, and myeloid cells, resembling human myositis. Autoimmune neuromyopathy can be transferred to NOD.scid recipients by CD4⁺ but not by CD8⁺ T-cells isolated from 40-week-old female ICOSL^−/− NOD mice. The predominant role of CD4⁺ T-cells is further demonstrated by the observation that neuromyopathy does not develop in CIITA^−/−ICOSL^−/− NOD in contrast to β2microglobulin^−/−ICOSL^−/− NOD mice. Also, the cytokine profile of CD4⁺ T-cells infiltrating muscle and nerve of ICOSL^−/− NOD mice is biased toward a Th1 pattern. Finally, adoptive transfer experiments show that diabetes development requires expression of ICOSL, in contrast to neuromyopathy. Altogether, the deviation of autoimmunity from the pancreas to skeletal muscles in the absence of ICOS/ICOSL signaling in NOD mice is strictly dependent on CD4⁺ T-cells, leads to myofiber necrosis and regeneration. It provides the first mouse model of spontaneous autoimmune myopathy akin to human myositis.

Cellular and Molecular Mechanisms of Autoimmunity and Lupus Nephritis

Autoimmunity involves immune responses directed against self, which are a result of defective self/foreign distinction of the immune system, leading to proliferation of self-reactive lymphocytes, and is characterized by systemic, as well as tissue-specific, inflammation. Numerous mechanisms operate to ensure the immune tolerance to self-antigens. However, monogenetic defects or genetic variants that weaken immune tolerance render susceptibility to the loss of immune tolerance, which is further triggered by environmental factors. In this review, we discuss the phenomenon of immune tolerance, genetic and environmental factors that influence the immune tolerance, factors that induce autoimmunity such as epigenetic and transcription factors, neutrophil extracellular trap formation, extracellular vesicles, ion channels, and lipid mediators, as well as costimulatory or coinhibitory molecules that contribute to an autoimmune response. Further, we discuss the cellular and molecular mechanisms of autoimmune tissue injury and inflammation during systemic lupus erythematosus and lupus nephritis.

Local triggering of the ICOS coreceptor by CD11c(+) myeloid cells drives organ inflammation in lupus

The inducible T cell costimulator (ICOS) is a potent promoter of organ inflammation in murine lupus. ICOS stimulates T follicular helper cell differentiation in lymphoid tissue, suggesting that it might drive autoimmunity by enhancing autoantibody production. Yet the pathogenic relevance of this mechanism remains unclear. It is also unknown whether other ICOS-induced processes might contribute to lupus pathology. Here we show that selective ablation of ICOS ligand (ICOSL) in CD11c(+) cells, but not in B cells, dramatically ameliorates kidney and lung inflammation in lupus-prone MRL.Fas(lpr) mice. Autoantibody formation was largely unaffected by ICOSL deficiency in CD11c(+) cells. However, ICOSL display by CD11c(+) cells in inflamed organs had a nonredundant role in protecting invading T cells from apoptosis by elevating activity of the PI3K-Akt signaling pathway, thereby facilitating T cell accrual. These findings reveal a mechanism that locally sustains organ inflammation in lupus.

Th17 down-regulation is involved in reduced progression of schistosomiasis fibrosis in ICOSL KO mice

Background

Granulomatous and fibrosing inflammation in response to parasite eggs is the main pathology that occurs during infection with Schistosoma spp. CD4+ T cells play critical roles in both host immune responses against parasitic infection and immunopathology in schistosomiasis,and coordinate many types of immune cells that contribute to fibrosis. ICOSL plays an important role in controlling specific aspects of T cell activation, differentiation, and function. Previous work has suggested that ICOS is essential for Th17 cell development. However, the immunopathogenesis of this pathway in schistosomiasis fibrosisis still unclear.

Methodology/Principal Findings

Using models of schistosomiasis in ICOSL KO and the C57BL/6 WT mice, we studied the role of the ICOSL/ICOS interaction in the mediation of the Th17 response in host granulomatous inflammation, particularly in liver fibrosis during S. japonicum infection, and investigated the immune responses and pathology of ICOSL KO mice in these models. The results showed that ICOSL KO mice exhibited improved survival, reduced liver granulomatous inflammation around parasite eggs, markedly inhibited hepatic fibrosis development, lower levels of Th17-related cytokines (IL-17/IL-21), Th2-related cytokines (IL-4/IL-6/IL-10), a pro-fibrotic cytokine (IL-13), and TGF-β1, but higher level of Th1-related cytokine (IFN-γ) compared to wild-type (WT) mice. The reduced progression of fibrogenesis was correlated with the down-regulation of Th17 and Th2 and the elimination of ICOSL/ICOS interactions.

Conclusions/Significance

Our findings suggest that IL-17-producing cells contribute to the hepatic granulomatous inflammation and subsequent fibrosis. Importantly, there was a clearly positive correlation between the presence of IL-17-producing cells and ICOS expression in ICOSL KO mice, and additional results indicated that Th17 was involved in the pathological tissue remodeling in liver fibrosis induced by schistosomiasis.

The full activation and differentiation of T cells into Th1, Th2 or Th17 cells requires costimulatory molecules and cytokines. ICOS has also been implicated in chronic inflammation and is critical for Th17 cell development. CD4⁺ IL-17-secreting T cells have been shown to contribute to pathology in some models of liver fibrosis. However, neither the significance nor the immunopathogenesis of this pathway have been elucidated in schistosomiasis fibrosis. The present study used the ICOSL KO mice to assess the role of the ICOSL/ICOS interaction in the mediation of the Th17 response in host granulomatous inflammation, particularly in liver fibrosis during S.japonicum infection. This study further clarifies the immune regulatory mechanism of fibrosis and sheds light on the understanding of the immunopathogenesis of Schistosoma-induced fibrosis. It might reveal new therapeutic targets that interfere with Th17 cell migration or differentiation in granulomas and the subsequent fibrosis following infection with S. japonicum.

Advances in our understanding of the pathophysiology of Type 1 diabetes: lessons from the NOD mouse

T1D (Type 1 diabetes) is an autoimmune disease caused by the immune-mediated destruction of pancreatic β-cells. Studies in T1D patients have been limited by the availability of pancreatic samples, a protracted pre-diabetic phase and limitations in markers that reflect β-cell mass and function. The NOD (non-obese diabetic) mouse is currently the best available animal model of T1D, since it develops disease spontaneously and shares many genetic and immunopathogenic features with human T1D. Consequently, the NOD mouse has been extensively studied and has made a tremendous contribution to our understanding of human T1D. The present review summarizes the key lessons from NOD mouse studies concerning the genetic susceptibility, aetiology and immunopathogenic mechanisms that contribute to autoimmune destruction of β-cells. Finally, we summarize the potential and limitations of immunotherapeutic strategies, successful in NOD mice, now being trialled in T1D patients and individuals at risk of developing T1D.

Expression of B7 and CD28 family genes in newly diagnosed type 1 diabetes

Type-1 diabetes (T1D) is caused by T-cell mediated autoimmune reaction directed against the insulin-secreting beta cells. We hypothesized that in addition to antigen/MHC recognition the co-stimulatory B7 and CD28 pathway is also strongly affected in T1D. CD80, CD86, CD28, CTLA4, ICOS and CD25 mRNA expression was characterized in 49 newly diagnosed young T1D patients (mean age 11 ± 5 years, 25 male/24 women) and 31 controls (mean age 14 ± 7 years, 14 male/17 women). In addition, polymorphisms in CTLA4 (rs231806, rs231775, rs3087243) were genotyped and soluble CTLA4 plasma levels measured by ELISA. T1D patients presented with higher peripheral blood expression levels of CD80 (Mann-Whitney U-test, p=0.0001) and lower ICOS levels compared to healthy controls (Glm adjusted for age, p=0.0004). CD80 expression in T1D patients correlated with expression of two CTLA4 splice variants (Spearman's rank correlation, rho=0.56, p=0.0002 for sCTLA4; rho=0.61, p<0.0001 for flCTLA4). In controls, CD80 expression correlated with CD25 expression (Spearman's rank correlation, rho=0.57, p=0.002). A strong correlation was observed between sCTLA4 and flCTLA4 (Spearman's rank correlation, rho=0.94, p<0.0001). We also found a tendency that the CTLA4 +49A/G polymorphism influenced sCTLA4 mRNA expression in T1D individuals and was lowest in individuals with the GG genotype (Mann-Whitney U-test, p=0.039). However, we could not identify associations between gene expression and plasma levels of sCTLA4. To summarize, we expect that newly diagnosed T1D among children and adolescents is associated with activation of CD80 and CTLA4 in peripheral blood. Additional studies will be needed to elucidate the role of CD80/CTLA4 signaling in T1D.

AIRE expressing marginal zone dendritic cells balances adaptive immunity and T-follicular helper cell recruitment

Autoimmune polyendocrine syndrome Type I (APS I) results in multiple endocrine organ destruction and is caused by mutations in the Autoimmune regulator gene (AIRE). In the thymic stroma, cells expressing the AIRE gene dictate T cell education and central tolerance. Although this function is the most studied, AIRE is also expressed in the periphery in DCs and stromal cells. Still, how AIRE regulated transcription modifies cell behaviour in the periphery is largely unknown. Here we show that AIRE is specifically expressed by 33D1(+) DCs and dictates the fate of antibody secreting cell movement within the spleen. We also found that AIRE expressing 33D1(+) DCs expresses self-antigens as exemplified by the hallmark gene insulin. Also, as evidence for a regulatory function, absence of Aire in 33D1(+) DCs led to reduced levels of the chemokine CXCL12 and increased co-stimulatory properties. This resulted in altered activation and recruitment of T-follicular helper cells and germinal centre B cells. The altered balance leads to a change of the early response to a T cell-dependent antigen in Aire(-/-) mice. These findings add to the understanding of how specific DC subtypes regulate the early responses during T cell-dependent antibody responses within the spleen and further define the role of AIRE in the periphery as regulator of self-antigen expression and lymphocyte migration.

B7h-expressing dendritic cells and plasma B cells mediate distinct outcomes of ICOS costimulation in T cell-dependent antibody responses

Background

The ICOS-B7h costimulatory receptor-ligand pair is required for germinal center formation, the production of isotype-switched antibodies, and antibody affinity maturation in response to T cell-dependent antigens. However, the potentially distinct roles of regulated B7h expression on B cells and dendritic cells in T cell-dependent antibody responses have not been defined.

Results

We generated transgenic mice with lineage-restricted B7h expression to assess the cell-type specific roles of B7h expression on B cells and dendritic cells in regulating T cell-dependent antibody responses. Our results show that endogenous B7h expression is reduced on B cells after activation in vitro and is also reduced in vivo on antibody-secreting plasma B cells in comparison to both naïve and germinal center B cells from which they are derived. Increasing the level of B7h expression on activated and plasma B cells in B-B7hTg mice led to an increase in the number of antibody-secreting plasma cells generated after immunization and a corresponding increase in the concentration of antigen-specific high affinity serum IgG antibodies of all isotypes, without affecting the number of responding germinal center B cells. In contrast, ICOS costimulation mediated by dendritic cells in DC-B7hTg mice contributed to germinal center formation and selectively increased IgG2a production without affecting the overall magnitude of antibody responses.

Conclusions

Using transgenic mice with lineage-restricted B7h expression, we have revealed distinct roles of ICOS costimulation mediated by dendritic cells and B cells in the regulation of T cell-dependent antibody responses.

CD28 family and chronic rejection: "to belatacept...And beyond!"

Kidneys are one of the most frequently transplanted human organs. Immunosuppressive agents may prevent or reverse most acute rejection episodes; however, the graft may still succumb to chronic rejection. The immunological response involved in the chronic rejection process depends on both innate and adaptive immune response. T lymphocytes have a pivotal role in chronic rejection in adaptive immune response. Meanwhile, we aim to present a general overview on the state-of-the-art knowledge of the strategies used for manipulating the lymphocyte activation mechanisms involved in allografts, with emphasis on T-lymphocyte costimulatory and coinhibitory molecules of the B7-CD28 superfamily. A deeper understanding of the structure and function of these molecules improves both the knowledge of the immune system itself and their potential action as rejection inducers or tolerance promoters. In this context, the central role played by CD28 family, especially the relationship between CD28 and CTLA-4, becomes an interesting target for the development of immune-based therapies aiming to increase the survival rate of allografts and to decrease autoimmune phenomena. Good results obtained by the recent development of abatacept and belatacept with potential clinical use aroused better expectations concerning the outcome of transplanted patients.

ICOS-dependent homeostasis and function of Foxp3+ regulatory T cells in islets of nonobese diabetic mice

A progressive waning in Foxp3(+) regulatory T cell (Treg) functions is thought to provoke autoimmunity in the NOD model of type 1 diabetes (T1D). A deficiency in IL-2 is one of the main triggers for the defective function of Tregs in islets. Notably, abrogation of the ICOS pathway in NOD neonates or BDC2.5-NOD (BDC2.5) mice exacerbates T1D, suggesting an important role for this costimulatory pathway in tolerance to islet Ags. Thus, we hypothesize that ICOS selectively promotes Foxp3(+) Treg functions in BDC2.5 mice. We show that ICOS expression discriminates effector Foxp3(-) T cells from Foxp3(+) Tregs and specifically designates a dominant subset of intra-islet Tregs, endowed with an increased potential to expand, secrete IL-10, and mediate suppressive activity in vitro and in vivo. Consistently, Ab-mediated blockade or genetic deficiency of ICOS selectively abrogates Treg-mediated functions and T1D protection and exacerbates disease in BDC2.5 mice. Moreover, T1D progression in BDC2.5 mice is associated with a decline in ICOS expression in and expansion and suppression by intra-islet Foxp3(+) Tregs. We further show that the ICOS(+) Tregs, in contrast to their ICOS(-) counterparts, are more sensitive to IL-2, a critical signal for their survival and functional stability. Lastly, the temporal loss in ICOS(+) Tregs is readily corrected by IL-2 therapy or protective Il2 gene variation. Overall, ICOS is critical for the homeostasis and functional stability of Foxp3(+) Tregs in prediabetic islets and maintenance of T1D protection.

Early treatment of NOD mice with B7-H4 reduces the incidence of autoimmune diabetes

OBJECTIVE

Autoimmune diabetes is a T cell-mediated disease in which insulin-producing β-cells are destroyed. Autoreactive T cells play a central role in mediating β-cell destruction. B7-H4 is a negative cosignaling molecule that downregulates T-cell responses. In this study, we aim to determine the role of B7-H4 on regulation of β-cell-specific autoimmune responses.

RESEARCH DESIGN AND METHODS

Prediabetic (aged 3 weeks) female NOD mice (group 1, n = 21) were treated with intraperitoneal injections of B7-H4.Ig at 7.5 mg/kg, with the same amount of mouse IgG (group 2, n = 24), or with no protein injections (group 3, n = 24), every 3 days for 12 weeks.

RESULTS

B7-H4.Ig reduced the incidence of autoimmune diabetes, compared with the control groups (diabetic mice 28.6% of group 1, 66.7% of group 2 [P = 0.0081], and 70.8% of group 3 [group 1 vs. 3, P = 0.0035]). Histological analysis revealed that B7-H4 treatment did not block islet infiltration but rather suppressed further infiltrates after 9 weeks of treatment (group 1 vs. 2, P = 0.0003). B7-H4 treatment also reduced T-cell proliferation in response to GAD65 stimulation ex vivo. The reduction of diabetes is not due to inhibition of activated T cells in the periphery but rather to a transient increase of Foxp3(+) CD4(+) T-cell population at one week posttreatment (12.88 ± 1.29 vs. 11.58 ± 1.46%; n = 8; P = 0.03).

CONCLUSIONS

Our data demonstrate the protective role of B7-H4 in the development of autoimmune diabetes, suggesting a potential means of preventing type 1 diabetes by targeting the B7-H4 pathway.

The ICOS/ICOSL pathway is required for optimal antitumor responses mediated by anti-CTLA-4 therapy

The anti-CTL-associated antigen 4 (anti-CTLA-4) antibody ipilimumab is the first agent to show improved survival in a randomized phase III trial that enrolled patients with metastatic melanoma. Studies are ongoing to identify mechanisms that elicit clinical benefit in the setting of anti-CTLA-4 therapy. We previously reported that treated patients had an increase in the frequency of T cells expressing the inducible costimulator (ICOS) molecule, a T-cell-specific molecule that belongs to the CD28/CTLA-4/B7 immunoglobulin superfamily. ICOS and its ligand (ICOSL) have been shown to play diverse roles in T-cell responses such as mediating autoimmunity as well as enhancing the development/activity of regulatory T cells. These seemingly opposing roles have made it difficult to determine whether the ICOS/ICOSL pathway is necessary for antitumor responses. To determine whether the ICOS/ICOSL pathway might play a causal role in the antitumor effects mediated by anti-CTLA-4, we conducted studies in ICOS-sufficient and ICOS-deficient mice bearing B16/BL6 melanoma. We show that ICOS(+) T cells comprised a population of Th1 cytokine producing and tumor antigen-specific effector cells. Furthermore, in the absence of ICOS, antitumor T-cell responses elicited by anti-CTLA-4 are significantly diminished, thereby impairing tumor rejection. Our findings establish that the ICOS/ICOSL pathway is necessary for the optimal therapeutic effect of anti-CTLA-4, thus implicating this pathway as a target for future combinatorial strategies to improve the efficacy of anti-CTLA-4 therapy.

A subset of interleukin-21+ chemokine receptor CCR9+ T helper cells target accessory organs of the digestive system in autoimmunity

This study describes a CD4+ T helper (Th) cell subset marked by coexpression of the cytokine interleukin 21 (IL-21) and the gut-homing chemokine receptor CCR9. Although CCR9+ Th cells were observed in healthy mice and humans, they were enriched in the inflamed pancreas and salivary glands of NOD mice and in the circulation of Sjögren's syndrome patients. CCR9+ Th cells expressed large amounts of IL-21, inducible T cell costimulator (ICOS), and the transcription factors Bcl6 and Maf, and also supported antibody production from B cells, thereby resembling T follicular B helper (Tfh) cells. However, in contrast to Tfh cells, CCR9+ Th cells displayed limited expression of CXCR5 and the targets of CCR9+ Th cells were CD8+ T cells whose responsiveness to IL-21 was necessary for the development of diabetes. Thus, CCR9+ Th cells are a subset of IL-21-producing T helper cells that influence regional specification of autoimmune diseases that affect accessory organs of the digestive system.

An update on the use of NOD mice to study autoimmune (Type 1) diabetes

The widely used nonobese diabetic (NOD) mouse model of autoimmune (Type 1) diabetes mellitus shares multiple characteristics with the human disease, and studies employing this model continue to yield clinically relevant and important information. Here, we review some of the recent key findings obtained from NOD mouse investigations that have both advanced our understanding of disease pathogenesis and suggested new therapeutic targets and approaches. Areas discussed include antigen discovery, identification of genes and pathways contributing to disease susceptibility, development of strategies to image islet inflammation and the testing of therapeutics. We also review recent technical advances that, combined with an improved understanding of the NOD mouse model's limitations, should work to ensure its popularity, utility and relevance in the years ahead.

Anti-tumor effects of adenovirus containing human growth hormone sequences in a mouse model of human ovarian cancer

Women with ovarian cancer have a low survival rate and develop resistance to chemotherapy, so new approaches to treatment are needed. We unexpectedly found administration of a replication-deficient adenovirus containing human growth hormone sequences (AdXGH) was beneficial in a mouse model of human ovarian cancer. Intraperitoneal injections of AdXGH prolonged median survival from a mean of 31 ± 1.2 to 40 ± 1.4 days in immunodeficient SCID mice given SKOV3.ip1 human ovarian cancer cells in the peritoneal cavity. Adenovirus containing human prolactin or del32-71growth hormone sequences had no effect. Repeated injection of growth hormone or implantation of tablets with sustained growth hormone release did not increase survival. Control mice had overlapping tumors throughout the peritoneal cavity and liver and frequent lung metastases 24 days after tumor cell injection. Mice that received two injections of AdXGH had no lung metastases. Mice that received four injections had no lung or liver metastases and peritoneal fibrosis. They did not survive longer than mice that received two injections, but they had enlarged livers with hepatocellular changes, indicating that a limitation of increasing the dose is liver toxicity.

The role of costimulation in antibody deficiencies: ICOS and common variable immunodeficiency

SUMMARY

The identification of mutations in the inducible costimulator (ICOS) gene in nine patients with common variable immunodeficiency (CVID) was a major breakthrough. CVID is a complex, highly heterogeneous primary immunodeficiency disease, and the discovery of these mutations revealed a molecular basis. ICOS belongs to the CD28 family of costimulatory molecules and is expressed exclusively on activated T cells. It has at least three critical functions: germinal center formation, isotype class switching, and the development of memory B cells. The discovery of human ICOS deficiency showed that a monogenic disorder could account for the full spectrum of manifestations seen in childhood and adulthood-onset CVID, including autoimmune, inflammatory, and malignant disease complications, as well as recurrent infections. Moreover, this discovery showed that a disorder which had previously been perceived as a B-cell disease might in fact have its genetic origin in human T cells. In this article, we review the role of ICOS in the mammalian immune system and human disease, as well as the discovery and characteristics of patients with ICOS deficiency. Finally, we also discuss how these 'human knockouts' have contributed to our understanding of ICOS functions and have suggested potential avenues for using therapeutic ICOS manipulation to treat other diseases.

Impaired CD4 and CD8 effector function and decreased memory T cell populations in ICOS-deficient patients

Interaction of ICOS with its ligand is essential for germinal center formation, T cell immune responses, and development of autoimmune diseases. Human ICOS deficiency has been identified worldwide in nine patients with identical ICOS mutations. In vitro studies of the patients to date have shown only mild T cell defect. In this study, we report an in-depth analysis of T cell function in two siblings with novel ICOS deficiency. The brother displayed mild skin infections and impaired Ig class switching, whereas the sister had more severe symptoms, including immunodeficiency, rheumatoid arthritis, inflammatory bowel disease, interstitial pneumonitis, and psoriasis. Despite normal CD3/CD28-induced proliferation and IL-2 production in vitro, peripheral blood T cells in both patients showed a decreased percentage of CD4 central and effector memory T cells and impaired production of Th1, Th2, and Th17 cytokines upon CD3/CD28 costimulation or PMA/ionophore stimulation. The defective polarization into effector cells was associated with impaired induction of T-bet, GATA3, MAF, and retinoic acid-related orphan nuclear hormone receptor (RORC). Reduced CTLA-4(+)CD45RO(+)FoxP3(+) regulatory T cells and diminished induction of inhibitory cell surface molecules, including CTLA-4, were also observed in the patients. T cell defect was not restricted to CD4 T cells because reduced memory T cells and impaired IFN-gamma production were also noted in CD8 T cells. Further analysis of the patients demonstrated increased induction of receptor activator of NF-kappaB ligand (RANKL), lack of IFN-gamma response, and loss of Itch expression upon activation in the female patient, who had autoimmunity. Our study suggests that extensive T cell dysfunction, decreased memory T cell compartment, and imbalance between effector and regulatory cells in ICOS-deficient patients may underlie their immunodeficiency and/or autoimmunity.

Gene gun-mediated DNA vaccination enhances antigen-specific immunotherapy at a late preclinical stage of type 1 diabetes in nonobese diabetic mice

Type 1 diabetes (T1D) is characterized by the T cell mediated destruction of the insulin-producing beta cells. Antigen-specific immunotherapies are used to selectively tolerize beta cell-specific pathogenic T cells either directly, or indirectly through the induction of immunoregulatory T cells. A key concern of antigen-specific immunotherapy is exacerbating autoimmunity. We compared the T cell reactivity and efficacy induced by plasmid DNA (pDNA) encoding glutamic acid decarboxylase 65 (GAD65) administered via intramuscular versus gene gun vaccination in NOD mice at a late preclinical stage of T1D. Whereas intramuscular injection of pGAD65 promoted a predominant type 1 CD4(+) T cell response and failed to suppress ongoing beta cell autoimmunity, gene gun vaccination preferentially induced IL-4 secreting CD4(+) T cells and significantly delayed the onset of diabetes. These findings demonstrate that gene gun delivery of autoantigen-encoding pDNA preferentially elicits immunoregulatory T cells and offers a safe, effective mode of pDNA vaccination for the treatment of T1D and other autoimmune diseases.