Induction Of Anergy Research Articles

Revisiting Current Concepts on the Tolerogenicity of Steady-State Dendritic Cell Subsets and Their Maturation Stages

The original concept stated that immature dendritic cells (DC) act tolerogenically whereas mature DC behave strictly immunogenically. Meanwhile, it is also accepted that phenotypically mature stages of all conventional DC subsets can promote tolerance as steady-state migratory DC by transporting self-antigens to lymph nodes to exert unique functions on regulatory T cells. We propose that in vivo 1) there is little evidence for a tolerogenic function of immature DC during steady state such as CD4 T cell anergy induction, 2) all tolerance as steady-state migratory DC undergo common as well as subset-specific molecular changes, and 3) these changes differ by quantitative and qualitative markers from immunogenic DC, which allows one to clearly distinguish tolerogenic from immunogenic migratory DC.

Serial Stimulation of Invariant Natural Killer T Cells with Covalently Stabilized Bispecific T-cell Engagers Generates Antitumor Immunity While Avoiding Anergy.

CD1d-restricted invariant natural killer T cells (iNKT cells) mediate strong antitumor immunity when stimulated by glycolipid agonists. However, attempts to develop effective iNKT cell agonists for clinical applications have been thwarted by potential problems with dose-limiting toxicity and by activation-induced iNKT cell anergy, which limits the efficacy of repeated administration. To overcome these issues, we developed a unique bispecific T-cell engager (BiTE) based on covalent conjugates of soluble CD1d with photoreactive analogues of the glycolipid α-galactosylceramide. Here we characterize the in vivo activities of iNKT cell-specific BiTEs and assess their efficacy for cancer immunotherapy in mouse models using transplantable colorectal cancer or melanoma tumor lines engineered to express human Her2 as a tumor-associated antigen. Systemic administration of conjugated BiTEs stimulated multiple iNKT cell effector functions including cytokine release, secondary activation of NK cells, and induction of dendritic cell maturation and also initiated epitope spreading for tumor-specific CD8+ cytolytic T-cell responses. The antitumor effects of iNKT-cell activation with conjugated BiTEs were further enhanced by simultaneous checkpoint blockade with antibodies to CTLA-4, providing a potential approach for combination immunotherapy. Multiple injections of covalently stabilized iNKT cell-specific BiTEs activated iNKT cells without causing iNKT cell anergy or exhaustion, thus enabling repeated administration for effective and nontoxic cancer immunotherapy regimens. SIGNIFICANCE: Covalently stabilized conjugates that engage the antigen receptors of iNKT cells and target a tumor antigen activate potent antitumor immunity without induction of anergy or depletion of the responding iNKT cells.

Th2 cell infiltrations predict neoadjuvant chemotherapy response of estrogen receptor-positive breast cancer.

High infiltration of Th2 is linked to breast cancer progression and metastasis through the induction of cytokine release and T-cell anergy. The estrogen receptor (ER)-positive subtype, which accounts for 70% of breast cancer, is known to respond less to neoadjuvant chemotherapy (NAC) due to its low potential for proliferation. We hypothesized that Th2 high tumors are highly proliferative, and thus more likely to respond to NAC in ER-positive breast cancer. We obtained clinicopathological data and overall survival information on 1,069 breast cancer patients from The Cancer Genome Atlas (TCGA). Computational algorithms and CIBERSORT were used to estimate immune cell infiltration. Additionally, xCell was used for validation. Th2 high tumors did not consistently associate with an unfavorable immune cell composition and tumor immune microenvironment but were found to be significantly elevated in the cancer stage. Th2 high tumors also correlated with high Nottingham pathological grade, as well as with Ki-67 and proliferation score in ER-positive subtypes. High Th2 tumors achieved a pathological complete response (pCR) significantly higher in ER-positive breast cancer. In conclusion, high levels of Th2 are associated with aggressive features of breast cancer. Th2 levels may be a biomarker in patient selection for NAC in ER-positive breast cancer.

Redirecting iNKT Cell Antitumor Immunity with α-GalCer/CD1d-scFv Fusion Proteins.

Invariant natural killer T (iNKT) cells display important properties that could bridge the innate and adaptive immunity, and they have been shown to play key roles in cancer immunotherapy. However, administration of iNKT cell agonist αGalCer fails to induce sustained antitumor immunity due to the rapid anergy induction after an initial strong activation. To this end, we have designed a recombinant CD1d protein that is fused to an anti-TAA scFv, which is able to recruit iNKT cells to the tumor site and induce tumor regression. Importantly, recombinant CD1d fusion proteins loaded with α-GalCer demonstrated sustained activation of iNKT cells upon repeated injections and superior tumor control, as compared to α-GalCer treatment.

Self and microbiota-derived epitopes induce CD4+ T cell anergy and conversion into CD4+Foxp3+ regulatory cells

The physiological role of T cell anergy induction as a key mechanism supporting self-tolerance remains undefined, and natural antigens that induce anergy are largely unknown. In this report, we used TCR sequencing to show that the recruitment of CD4+CD44+Foxp3−CD73+FR4+ anergic (Tan) cells expands the CD4+Foxp3+ (Tregs) repertoire. Next, we report that blockade in peripherally-induced Tregs (pTregs) formation due to mutation in CNS1 region of Foxp3 or chronic exposure to a selecting self-peptide result in an accumulation of Tan cells. Finally, we show that microbial antigens from Akkermansia muciniphila commensal bacteria can induce anergy and drive conversion of naive CD4+CD44-Foxp3− T (Tn) cells to the Treg lineage. Overall, data presented here suggest that Tan induction helps the Treg repertoire to become optimally balanced to provide tolerance toward ubiquitous and microbiome-derived epitopes, improving host ability to avert systemic autoimmunity and intestinal inflammation.

Nuclear Receptor Subfamily 4 Group A Member 1 Overexpression Prolongs Free Flap Allotransplant Graft Survival by Inducing T-Cell Anergy in the Rat

BackgroundNew strategies to inhibit acute rejection are needed for further applications of composite tissue allotransplantation. The nuclear receptor subfamily 4 group A member 1 (NR4A1) is considered a key controller of maintaining tolerance homeostasis. However, the effect of NR4A1 in suppressing rejection responses after allotransplantation remains unknown. MethodsBrown Norway rat groin flaps were transplanted into Lewis rat recipients. The recipients were administrated cytosporone B, an NR4A1 activator. NR4A1 expression and graft survival time were assessed. T helper type 1 and regulatory T cell populations in the second lymphoid organ were detected by flow cytometry. Furthermore, a retrovirus containing NR4A1 was constructed and transfected to T cells in vitro. After stimulation, interleukin 2 and interferon gamma secretions were detected in the T cells. ResultsAdministration of cytosporone B activated NR4A1 expression in allotransplant recipients and was associated with prolonged survival time of the vascularized free flap allograft. T helper type 1 cells in the recipient secondary lymphoid organs were decreased, whereas the population of regulatory T cells did not change. Interleukin 2 and interferon gamma were suppressed in vitro in the T cells overexpressing NR4A1. ConclusionsWe demonstrated that the overexpressed NR4A1 is associated with suppressed graft rejection response. The suppression effect may attribute to induction of T-cell anergy and blockade of key immunologic cytokines.

The two-faces of NK cells in oncolytic virotherapy

Oncolytic viruses (OVs) are immunotherapeutics capable of directly killing cancer cells and with potent immunostimulatory properties. OVs exert their antitumor effect, at least partially, by activating the antitumor immune response, of which NK cells are an important component. However, if on the one hand increasing evidence revealed that NK cells are important mediators of oncolytic virotherapy, on the other hand, NK cells have evolved to fight viral infections, and therefore they can have a detrimental effect for the efficacy of OVs. In this review, we will discuss the dichotomy between the antitumor and antiviral functions of NK cells related to oncolytic virotherapy. We will also review NK cell-based and OV-based therapies, engineered OVs aimed at enhancing immune stimulation, and combination therapies involving OVs and NK cells currently used in cancer immunotherapy.

Phase IIa study of marrow infiltrating lymphocytes (MILs), an adoptive T cell therapy, alone or in combination with nivolumab in non-small cell lung cancer (NSCLC).

TPS9630 Background: Primary or secondary resistance to anti-PD-1 may be due to loss of T cell function. Persistent antigen stimulation can lead to impaired CD8+ T cell function, which often results in acquired resistance to PD-1 inhibition. It is unclear whether reinvigoration of tumor infiltrating cells or recruitment of novel T cells impart the activity of anti-PD-1 therapy. The bone marrow is a reservoir for antigen experienced memory T cells. We have previously shown that MILs can be generated for patients with hematologic malignancies and solid tumors including patients with NSCLC. MILs are the product of the activation and expansion of bone marrow T cells with a polyantigenic memory phenotype that recognize tumor antigens, are cytotoxic to autologous tumor and are able to persist over a long period of time. In a pre-clinical study of NSCLC, MILs were able to be expanded in all patients tested. Furthermore, all of the NSCLC products tested showed specificity to shared NSCLC antigens. The combination of adoptive cell therapy (ACT) with checkpoint inhibitors (CPIs) has distinctive positive effects on CD8 and CD4 T cell subsets, with the possibility for complete tumor control. We hypothesize that patients with NSCLC who have relapsed on anti-PD-1 treatment could benefit from an infusion of non-exhausted, central memory-enhanced, antigen specific T cells i.e. MILs which can delay the induction of tumor-associated anergy and augment the overall effectiveness of immunotherapy. Methods: Patients with advanced NSCLC who have progressed following prior anti-PD-1 therapy, with sufficient bone marrow reserve and an ECOG 0-1 are eligible. In eligible patients, bone marrow (200 mL) will be harvested and processed. Patients will undergo lymphodepletion (fludarabine 300 mg/m2/day and cyclophosphamide 30 mg/m2/day on days -5,-4,-3) followed by infusion of MILs on day 0. In Part 1, up to 6 patients will be administered MILs alone on day 0. In Part 2, approximately 20 subjects will be administered MILs on day 0 followed by NIVO 480 mg Q4W starting on day 1. The objectives of the study are to assess safety of MILs alone and in combination with NIVO, as well as efficacy. The first patient was treated in December 2019. Clinical trial information: NCT04069936 .

Epigenomics of T Cell Activation and Memory

Abstract A characteristic feature of adaptive immunity is the rapid recall response of memory T cells, the ability of memory T cells to produce cytokines in response to pathogen much more rapidly than naïve T cells. We have recently found that this rapid recall ability is associated with epigenetic gene poising. Here, we aim to uncover the mechanism that underlie chromatin remodeling during initial activation of T cells and, thus, contribute to the establishment of memory phenotype. Upon encountering an antigen, naïve T helper cells become activated, differentiate into several lineages and contribute to immune response. Activation of T cells is dependent on organized and timely opening and closing of chromatin. Herein, we identify AP-1 as the transcription factor that directs most of this remodeling. Chromatin accessibility profiling showed quick opening of closed chromatin in naïve T cells within hours of activation. These newly open regions were strongly enriched for the AP-1 motif, and indeed, ChIP-Seq demonstrated AP-1 binding at more than 70% of them. Broad inhibition of AP-1 activity prevented chromatin opening at AP-1 sites and reduced expression of nearby genes. Similarly, induction of anergy in the absence of co-stimulation during activation, was associated with reduced induction of AP-1 and a failure of proper chromatin remodeling. The translational relevance of these findings was highlighted by the substantial overlap of AP-1–dependent elements with risk loci for multiple immune diseases, most notably multiple sclerosis, IBD and allergy. Our findings define AP-1 as the key link between T cell activation and chromatin remodeling.

Anergy-derived Foxp3+ T regulatory cell differentiation in the neonatal mouse

Abstract The neonatal period is a natural scenario to study the effects of peripheral self-antigen (Ag) recognition by autoreactive conventional CD4+ T cells under conditions of low Foxp3+ T regulatory cell (Treg) numbers and function. Moreover, the neonatal environment is an interesting scenario to study the relationship between the induction of CD4+ T cell anergy and the peripheral generation of anergy-derived Tregs, given that anergy induction relies on normal Treg function whereas anergy-derived Treg generation is optimal in the setting of Treg cell deficiency. We have hypothesized that the neonatal period is both necessary and sufficient to allow for the induction of anergy as well as the peripheral differentiation of anergy-derived Foxp3+ Tregs from naive conventional CD4+ T cells during self-Ag recognition. To test our hypotheses we developed a system of neonatal peripheral tolerance induction. Neonatal pups engineered to express the experimental “self” peptide Ag chicken ovalbumin (OVAp) were given OVAp/I-Ab–specific OT-II CD4+ T cells, and the pups were later examined for anergy induction, Treg differentiation, and development of autoimmunity. Our data demonstrate that in the neonatal period: 1) previously naive CD4+ T cells express markers of anergy following exposure to self-Ag, and a small fraction of these cells can be seen to differentiate to a Foxp3+ Treg phenotype, and 2) previously anergic CD4+ T cells typically retain their anergic phenotype but also give rise to a substantial fraction of Foxp3+ Tregs, and 3) animals remain free of autoimmune disease. These findings suggest that during the neonatal period peripheral Foxp3+ Treg cell differentiation may proceed through a conventional anergic CD4+ T cell intermediate.

An Integrative Network Modeling Approach to T CD4 Cell Activation.

The adaptive immune response is initiated by the interaction of the T cell antigen receptor/CD3 complex (TCR) with a cognate peptide bound to a MHC molecule. This interaction, along with the activity of co-stimulatory molecules and cytokines in the microenvironment, enables cells to proliferate and produce soluble factors that stimulate other branches of the immune response for inactivation of infectious agents. The intracellular activation signals are reinforced, amplified and diversified by a complex network of biochemical interactions, and includes the activity of molecules that modulate the activation process and stimulate the metabolic changes necessary for fulfilling the cell energy demands. We present an approach to the analysis of the main early signaling events of T cell activation by proposing a concise 46-node hybrid Boolean model of the main steps of TCR and CD28 downstream signaling, encompassing the activity of the anergy factor Ndrg1, modulation of activation by CTLA-4, and the activity of the nutrient sensor AMPK as intrinsic players of the activation process. The model generates stable states that reflect the overcoming of activation signals and induction of anergy by the expression of Ndrg1 in the absence of co-stimulation. The model also includes the induction of CTLA-4 upon activation and its competition with CD28 for binding to the co-stimulatory CD80/86 molecules, leading to stable states that reflect the activation arrest. Furthermore, the model integrates the activity of AMPK to the general pathways driving differentiation to functional cell subsets (Th1, Th2, Th17, and Treg). Thus, the network topology incorporates basic mechanism associated to activation, regulation and induction of effector cell phenotypes. The model puts forth a conceptual framework for the integration of functionally relevant processes in the analysis of the T CD4 cell function.

T-Cell Molecular Modulation Responses in Atherosclerosis Anergy.

Atherosclerosis continues to be a major cause of death in patients with cardiovascular diseases. The cooperative role of immunity has been recently considered in atherosclerotic plaque inflammation, especially adaptive immune response by T cells. In this review, we examine the possible role of T cells in atherosclerosis-mediated inflammation and conceivable therapeutic strategies that can ameliorate complications of atherosclerosis. The cytokines secreted by T-lymphocyte subsets, different pathophysiological profiles of microRNAs (miRs), and the growth factor/receptor axis have diverse effects on the inflammatory cycle of atherosclerosis. Manipulation of miRNA expression and prominent growth factor receptors involved in inflammatory cytokine secretion in atherosclerosis can be considered diagnostic biomarkers in the induction of anergy and blockade of atherosclerotic development. This manuscript reviews immunomodulation of T cells responses in atherosclerosis anergy.

Lactoferrin Induces Tolerogenic Bone Marrow-Derived Dendritic Cells.

Dendritic cells (DCs) are professional antigen-presenting cells (APCs) that initiate both T-cell responses and tolerance. Tolerogenic DCs (tDCs) are regulatory DCs that suppress immune responses through the induction of T-cell anergy and Tregs. Because lactoferrin (LF) was demonstrated to induce functional Tregs and has a protective effect against inflammatory bowel disease, we explored the tolerogenic effects of LF on mouse bone marrow-derived DCs (BMDCs). The expression of CD80/86 and MHC class II was diminished in LF-treated BMDCs (LF-BMDCs). LF facilitated BMDCs to suppress proliferation and elevate Foxp3+ induced Treg (iTreg) differentiation in ovalbumin-specific CD4+ T-cell culture. Foxp3 expression was further increased by blockade of the B7 molecule using CTLA4-Ig but was diminished by additional CD28 stimulation using anti-CD28 Ab. On the other hand, the levels of arginase-1 and indoleamine 2,3-dioxygenase-1 (known as key T-cell suppressive molecules) were increased in LF-BMDCs. Consistently, the suppressive activity of LF-BMDCs was partially restored by inhibitors of these molecules. Collectively, these results suggest that LF effectively causes DCs to be tolerogenic by both the suppression of T-cell proliferation and enhancement of iTreg differentiation. This tolerogenic effect of LF is due to the reduction of costimulatory molecules and enhancement of suppressive molecules.

The relationship of vitamin D status with the development and course of diabetes mellitus type 1

Type 1 diabetes mellitus (T1DM) is a chronic autoimmune disease that develops as a result of a genetic predisposition and environmental factors. Literature data indicate that the suboptimal status of vitamin D can be considered as a risk factor for the development of T1DM, especially at some stages of life. Adequate vitamin D supplementation in childhood may provide a protective effect and reduce the risk of developing T1DM at a later age. Pathogenesis of T1DM predisposes to abnormalities in the metabolism of vitamin D, including the development of vitamin D deficiency. Moreover, the immunomodulating effect of calcitriol (induction of immune tolerance and T-cell anergy, impaired B-cell activity and antibodies production) suggests the therapeutic potential of vitamin D in autoimmune diseases, including T1DM. A number of studies have demonstrated the positive clinical effects of various vitamin D preparations with respect to maintaining residual -cell function, improving glycemia control in patients with T1DM. Determining the optimal doses of vitamin D for patients with T1DM may contribute to disease control and prevention of complications.

AP-1 activity induced by co-stimulation is required for chromatin opening during T cell activation.

Activation of T cells is dependent on the organized and timely opening and closing of chromatin. Herein, we identify AP-1 as the transcription factor that directs most of this remodeling. Chromatin accessibility profiling showed quick opening of closed chromatin in naive T cells within 5 h of activation. These newly opened regions were strongly enriched for the AP-1 motif, and indeed, ChIP-seq demonstrated AP-1 binding at >70% of them. Broad inhibition of AP-1 activity prevented chromatin opening at AP-1 sites and reduced the expression of nearby genes. Similarly, induction of anergy in the absence of co-stimulation during activation was associated with reduced induction of AP-1 and a failure of proper chromatin remodeling. The translational relevance of these findings was highlighted by the substantial overlap of AP-1-dependent elements with risk loci for multiple immune diseases, including multiple sclerosis, inflammatory bowel disease, and allergic disease. Our findings define AP-1 as the key link between T cell activation and chromatin remodeling.

Nanoparticles Containing an Insulin-ChgA Hybrid Peptide Protect from Transfer of Autoimmune Diabetes by Shifting the Balance between Effector T Cells and Regulatory T Cells.

CD4 T cells play a critical role in promoting the development of autoimmunity in type 1 diabetes. The diabetogenic CD4 T cell clone BDC-2.5, originally isolated from a NOD mouse, has been widely used to study the contribution of autoreactive CD4 T cells and relevant Ags to autoimmune diabetes. Recent work from our laboratory has shown that the Ag for BDC-2.5 T cells is a hybrid insulin peptide (2.5HIP) consisting of an insulin C-peptide fragment fused to a peptide from chromogranin A (ChgA) and that endogenous 2.5HIP-reactive T cells are major contributors to autoimmune pathology in NOD mice. The objective of this study was to determine if poly(lactide-co-glycolide) (PLG) nanoparticles (NPs) loaded with the 2.5HIP Ag (2.5HIP-coupled PLG NPs) can tolerize BDC-2.5 T cells. Infusion of 2.5HIP-coupled PLG NPs was found to prevent diabetes in an adoptive transfer model by impairing the ability of BDC-2.5 T cells to produce proinflammatory cytokines through induction of anergy, leading to an increase in the ratio of Foxp3+ regulatory T cells to IFN-γ+ effector T cells. To our knowledge, this work is the first to use a hybrid insulin peptide, or any neoepitope, to re-educate diabetogenic T cells and may have significant implications for the development of an Ag-specific therapy for type 1 diabetes patients.

Attenuated Listeria vaccine for cancer immunotherapy expands Vγ2Vδ2 T cells in rhesus monkeys that retain their central memory phenotype and HMBPP responsiveness

Abstract Human γδ T cells expressing Vγ2Vδ2 TCRs monitor foreign- and self-isoprenoid metabolites to mediate immunity to microbes and tumors. Bisphosphonate treatment of tumors increases isopentenyl pyrophosphate that is sensed by butyrophilin 3A1, allowing Vγ2Vδ2 cells to kill tumors independent of MHC expression or tumor mutational burden. In clinical trials, adoptive immunotherapy with Vγ2Vδ2 cells has few side effects but has resulted in only a few partial and complete remissions. Direct immunization of cancer patients with either a bisphosphonate or bromohydrin pyrophosphate and IL-2, expands Vγ2Vδ2 cells but they rapidly contract, terminally differentiate, and lose responsiveness. Monkeys immunized with zoledronic acid also lost responsiveness. We sought to develop a live bacterial vaccine for Vγ2Vδ2 cells. Listeria monocytogenes (Lm) were attenuated by actA deletion with a mutant PrfA protein (G155S) that increased their virulence. Immunization with attenuated Lm expanded Vγ2Vδ2 cells on secondary immunization that persisted after a third immunization. Vγ2Vδ2 cells retained central memory phenotypes, expressed inflammatory chemokine receptors, and produced IFN-γ without induction of anergy. Expression of PrfA (G155S) was critical because immunization with ΔactA Lm with wild-type PrfA resulted in minimal Vγ2Vδ2 T cell expansions. Similarly, despite high HMBPP levels, immunization with ΔlytB ΔactA prfAwt Lm also resulted in minimal expansions. Thus, Lm stimulation of Vγ2Vδ2 T cells is dependent on their virulence rather than their HMBPP levels. Unlike zoledronic acid, immunization with ΔactA prfAG155S Lm induces large expansions of Vγ2Vδ2 T cells that retain central memory phenotypes and responsiveness.

Co-Stimulation–Induced AP-1 Activity is Required for Chromatin Opening During T Cell Activation

Abstract Activation of T cells is dependent on organized and timely opening and closing of chromatin. Herein, we identify AP-1 as the transcription factor that directs most of this remodeling. Chromatin accessibility profiling showed quick opening of closed chromatin in naïve T cells within 5 hours of activation. These newly open regions were strongly enriched for the AP-1 motif, and indeed, ChIP-seq demonstrated AP-1 binding at more than 70% of them. Broad inhibition of AP-1 activity prevented chromatin opening at AP-1 sites and reduced expression of nearby genes. Similarly, induction of anergy in the absence of co-stimulation during activation, was associated with reduced induction of AP-1 and a failure of proper chromatin remodeling. The translational relevance of these findings was highlighted by the substantial overlap of AP-1–dependent elements with risk loci for multiple immune diseases, most notably multiple sclerosis. Our findings define AP-1 as the key link between T cell activation and chromatin remodeling.

Development of a Novel Antigen-Specific Therapy for Autoimmune Diabetes Using an Insulin-ChgA Hybrid Peptide Neoantigen

Abstract In Type 1 Diabetes (T1D) patients and non-obese diabetic (NOD) mice, autoreactive CD4 T cells contribute to destruction of insulin-producing β-cells in the pancreatic islets. Our lab has discovered that in NOD mice the endogenous ligand for the diabetogenic CD4 T cell clone BDC-2.5 is a hybrid insulin peptide (2.5HIP), consisting of a fragment from proinsulin fused to a peptide from chromogranin A (ChgA). The purpose of this study was to determine if tolerogenic poly(lactide-co-glycolide) (PLG) nanoparticles (NPs) coupled with 2.5HIP (2.5HIP-PLG) could be used to induce antigen-specific T cell tolerance. We have found that treatment with 2.5HIP-PLG NPs synergizes with a short course of low-dose recombinant IL-2, leading to robust induction of 2.5HIP-specific Foxp3+ regulatory T cells (Tregs) and prevention of spontaneous diabetes in 50% of NOD mice. In a disease reversal model, spontaneously diabetic NOD mice were transplanted with 500 syngeneic islets and recipients were infused with HEL-PLG (control) or 2.5HIP-PLG NPs pre- and post-transplant. In contrast to HEL-PLG treated mice that showed aggressive disease recurrence in around 2 weeks, graft destruction in 2.5HIP-PLG treated mice was significantly delayed up to an average of 8 weeks, indicating that targeting graft-infiltrating 2.5HIP-specific T cells dampens ongoing autoimmunity. Our current goal is to determine whether the therapeutic effects observed in the transplantation model are due to expansion of antigen-specific Tregs, induction of anergy in effector T cells, or both. This novel antigen-specific therapy using a disease-relevant neoantigen may have implications for development of an immune-modifying treatment for T1D patients.

Foxp3 cooperates with Ikaros to control the suppressive function of regulatory T cells

Abstract Ikaros (encoded by Ikzf1) is a lymphocyte-specific transcription factor that controls a wide spectrum of T cell functions, including T helper differentiation, cytokine production, and tolerance in response to antigenic stimuli. Using heterozygous and dominant-negative mouse models, we have shown previously that Ikaros controls IL-2 production by conventional T cells, T helper differentiation, CD8+ effector differentiation, and anergy induction. While the role of Ikaros in many T cell subsets has been established, its role in Treg-mediated peripheral tolerance has not been examined. To examine the Treg-specific role of Ikaros, we generated Ikzf1-fl/fl-Foxp3-YFP-Cre+ mouse with conditional deletion of Ikaros in Tregs. Ikzf1-fl/fl-Foxp3-YFP-Cre+ mouse exhibited enlarged secondary lymphoid tissues, with increased frequencies of effector memory Tconv and Treg. We show that Ikaros expression by Tregs is required for immune tolerance in an allogenic cardiac transplant model. While CD28- and CD40L-blockade induced long-term cardiac allograft tolerance in control recipients, Ikzf1-fl/fl-Foxp3-YFP-Cre+ recipients rejected the allografts in a short duration (p<0.01). We show that Ikaros forms a complex with Foxp3, which is required for Foxp3 to bind to and repress inflammatory cytokine genes. Ikaros is also required for normal iTreg development in vitro, as TGF-B/IL-2-induced iTreg development is impaired in conventional CD4+ T cells with reduced Ikaros activity. These studies suggest that Ikaros interacts with Foxp3 and directs Foxp3 to exert its suppressive function in Tregs.