Neuropilin-1+ regulatory T cells promote skin allograft survival and modulate effector CD4+ T cells phenotypic signature

Activation of the aryl hydrocarbon receptor inhibits neuropilin-1 upregulation on IL-2-responding CD4+ T cells

Neuropilin-1 (Nrp1), a transmembrane protein expressed on CD4+ T cells, is mostly studied in the context of regulatory T cell (Treg) function. More recently, there is increasing evidence that Nrp1 is also highly expressed on activated effector T cells and that increases in these Nrp1-expressing CD4+ T cells correspond with immunopathology across several T cell-dependent disease models. Thus, Nrp1 may be implicated in the identification and function of immunopathologic T cells. Nrp1 downregulation in CD4+ T cells is one of the strongest transcriptional changes in response to immunoregulatory compounds that act though the aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor. To better understand the link between AhR and Nrp1 expression on CD4+ T cells, Nrp1 expression was assessed in vivo and in vitro following AhR ligand treatment. In the current study, we identified that the percentage of Nrp1 expressing CD4+ T cells increases over the course of activation and proliferation in vivo. The actively dividing Nrp1+Foxp3- cells express the classic effector phenotype of CD44hiCD45RBlo, and the increase in Nrp1+Foxp3- cells is prevented by AhR activation. In contrast, Nrp1 expression is not modulated by AhR activation in non-proliferating CD4+ T cells. The downregulation of Nrp1 on CD4+ T cells was recapitulated in vitro in cells isolated from C57BL/6 and NOD (non-obese diabetic) mice. CD4+Foxp3- cells expressing CD25, stimulated with IL-2, or differentiated into Th1 cells, were particularly sensitive to AhR-mediated inhibition of Nrp1 upregulation. IL-2 was necessary for AhR-dependent downregulation of Nrp1 expression both in vitro and in vivo. Collectively, the data demonstrate that Nrp1 is a CD4+ T cell activation marker and that regulation of Nrp1 could be a previously undescribed mechanism by which AhR ligands modulate effector CD4+ T cell responses.

Activation of the aryl hydrocarbon receptor inhibits neuropilin-1 upregulation on IL-2 responding CD4 + T cells

Neuropilin-1 (Nrp1), a transmembrane protein expressed on CD4 + T cells, is mostly studied in the context of regulatory T cell (Treg) function. More recently, there is increasing evidence that Nrp1 is also highly expressed on activated effector T cells and that increases in these Nrp1-expressing CD4 + T cells correspond with immunopathology across several T cell-dependent disease models. Thus, Nrp1 may be implicated in the identification and function of immunopathologic T cells. Nrp1 downregulation in CD4 + T cells is one of the strongest transcriptional changes in response to immunoregulatory compounds that act though the aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor. To better understand the link between AhR and Nrp1 expression on CD4 + T cells, Nrp1 expression was assessed in vivo and in vitro following AhR ligand treatment. In the current study, we identified that the percentage of Nrp1 expressing CD4 + T cells increases over the course of activation and proliferation in vivo . The actively dividing Nrp1 + Foxp3 - cells express the classic effector phenotype of CD44 hi CD45RB lo , and the increase in Nrp1 + Foxp3 - cells is prevented by AhR activation. In contrast, Nrp1 expression is not modulated by AhR activation in non-proliferating CD4 + T cells. The downregulation of Nrp1 on CD4 + T cells was recapitulated in vitro in cells isolated from C57BL/6 and NOD (non-obese diabetic) mice. CD4 + Foxp3 - cells expressing CD25, stimulated with IL-2, or differentiated into Th1 cells, were particularly sensitive to AhR-mediated inhibition of Nrp1 upregulation. IL-2 was necessary for AhR-dependent downregulation of Nrp1 expression both in vitro and in vivo . Collectively, the data demonstrate that Nrp1 is a CD4 + T cell activation marker and that regulation of Nrp1 could be a previously undescribed mechanism by which AhR ligands modulate effector CD4 + T cell responses.

A Psychrophilic GelMA: Breaking Technical and Immunological Barriers for Multimaterial High-Resolution 3D Bioprinting

The increasing demand for tissue replacement has encouraged scientists worldwide to focus on developing new biofabrication technologies. Multimaterials/cells printed with stringent resolutions are necessary to address the high complexity of tissues. Advanced inkjet 3D printing can use multimaterials and attain high resolution and complexity of printed structures. However, a decisive yet limiting aspect of translational 3D bioprinting is selecting the befitting material to be used as bioink; there is a complete lack of cytoactive bioinks with adequate rheological, mechanical, and reactive properties. This work strives to achieve the right balance between resolution and cell support through methacrylamide functionalization of a psychrophilic gelatin and new fluorosurfactants used to engineer a photo-cross-linkable and immunoevasive bioink. The syntonized parameters following optimal formulation conditions allow proficient printability in a PolyJet 3D printer comparable in resolution to a commercial synthetic ink (∼150 μm). The bioink formulation achieved the desired viability (∼80%) and proliferation of co-printed cells while demonstrating in vivo immune tolerance of printed structures. The practical usage of existing high-resolution 3D printing systems using a novel bioink is shown here, allowing 3D bioprinted structures with potentially unprecedented complexity.

Neuropilin-1 is present on Foxp3+ T regulatory cell-derived small extracellular vesicles and mediates immunity against skin transplantation

Among the mechanisms of suppression that T regulatory (Treg) cells exert to control the immune responses, the secretion of small extracellular vesicles (sEV) has been recently proposed as a novel contact‐independent immunomodulatory mechanism. Previous studies have demonstrated that Treg cells produce sEV, including exosomes, able to modulate the effector function of CD4+ T cells, and antigen presenting cells (APCs) such as dendritic cells (DCs) through the transfer of microRNA, cytokines, the production of adenosine, among others. Previously, we have demonstrated that Neuropilin‐1 (Nrp1) is required for Tregs‐mediated immunosuppression mainly by impacting on the phenotype and function of effector CD4+ T cells. Here, we show that Foxp3+ Treg cells secrete sEV, which bear Nrp1 in their membrane. These sEV modulate effector CD4+ T cell phenotype and proliferation in vitro in a Nrp1‐dependent manner. Proteomic analysis indicated that sEV obtained from wild type (wt) and Nrp1KO Treg cells differed in proteins related to immune tolerance, finding less representation of CD73 and Granzyme B in sEV obtained from Nrp1KO Treg cells. Likewise, we show that Nrp1 is required in Treg cell‐derived sEV for inducing skin transplantation tolerance, since a reduction in graft survival and an increase on M1/M2 ratio were found in animals treated with Nrp1KO Treg cell‐derived sEV. Altogether, this study describes for the first time that Treg cells secrete sEV containing Nrp1 and that this protein, among others, is necessary to promote transplantation tolerance in vivo via sEV local administration.

Neuropilin-1 Is Expressed on Highly Activated CD4+ Effector T Cells and Dysfunctional CD4+ Conventional T Cells from Naive Mice

Neuropilin-1 (Nrp-1) is a well described marker molecule for CD4+Foxp3+ thymus-derived regulatory T cells (Tregs). In addition, a small population of CD4+Foxp3- conventional (conv) T cells expresses Nrp-1 in naive mice, and Nrp-1 expression has been described to be upregulated on activated CD4+ T cells. However, the function of Nrp-1 expression on CD4+ non-Tregs still remains elusive. In this study, we demonstrate that Nrp-1 expression was induced upon stimulation of CD4+Foxp3- T cells in vitro and during an ongoing immune response in vivo. This activation-induced Nrp-1+CD4+ T cell subset (iNrp-1+) showed a highly activated phenotype in terms of elevated CD25 and CD44 expression, enhanced production of proinflammatory cytokines, and increased proliferation compared with the Nrp-1-CD4+ counterpart. In contrast, Nrp-1+CD4+Foxp3- conv T cells from naive mice (nNrp-1+) were dysfunctional. nNrp-1+CD4+ conv T cells upregulated activation-associated molecules to a lesser extent, exhibited impaired proliferation and produced fewer proinflammatory cytokines than Nrp-1-CD4+ conv T cells upon stimulation in vitro. Moreover, the expression of PD-1 and CTLA-4 was significantly higher on nNrp-1+CD4+Foxp3- T cells compared with iNrp-1+CD4+Foxp3- T cells and Nrp-1-CD4+Foxp3- T cells after stimulation and under homeostatic conditions. Strikingly, transfer of Ag-specific iNrp-1+CD4+ conv T cells aggravated diabetes development, whereas Ag-specific nNrp-1+CD4+ conv T cells failed to induce disease in a T cell transfer model of diabetes. Overall, our results indicate that Nrp-1 expression has opposite functions in recently activated CD4+ non-Tregs compared with CD4+ non-Tregs from naive mice.

Dysfunction of Decidual Macrophages Is a Potential Risk Factor in the Occurrence of Preeclampsia

Preeclampsia is a multi-factorial and multi-genetic disorder that affects more than eight million mother and baby pairs each year. Currently, most of the attention to the pathogenesis of preeclampsia has been focused on placenta, but recent progresses suggest that excellent decidualization lays foundation for placentation and growth. Moreover, preeclampsia is associated with an imbalance in immunoregulatory mechanisms, however, how the immune regulatory system in the decidua affects preeclampsia is still unclear. In our study, after intersecting the genes of differentially expressed between preeclampsia and the control gotten by conventional expression profile analysis and the genes contained in the ligand receptor network, we found eight differentially expressed genes in a ligand-receptor relationship, and the eight genes have a characteristic: most of them participate in the interaction between decidual macrophages and other decidual immune cells. The results of single-cell sequencing of decidual cells further demonstrated that decidual macrophages affect the functions of other immune cells through export. As a result, abnormal gene expression affects the export function of decidual macrophages, which in turn affects the interaction of decidual macrophages with other immune cells, thereby destroying the original immune regulation mechanism, and ultimately leading to the occurrence of preeclampsia.

Selective deletion of Eos (Ikzf4) in T-regulatory cells leads to loss of suppressive function and development of systemic autoimmunity

Eos (lkzf4) is a member of the Ikaros family of transcription factors and is preferentially expressed in T-regulatory (Treg) cells. However, the role of Eos in Treg function is controversial. One study using siRNA knock down of Eos demonstrated that it was critical for Treg suppressor function. In contrast, Treg from mice with a global deficiency of Eos had normal Treg function in vitro and in vivo. To further dissect the function of Eos in Tregs, we generated mice with a conditional knock out of Eos in Treg cells (lkzf4fl/fl X Foxp3YFP-cre, Eos cKO). Deletion of Eos in Treg resulted in activation of CD4+Foxp3- and CD8+ T cells at the age of 3 months, cellular infiltration in non-lymphoid tissues, hyperglobulinemia, and anti-nuclear antibodies. While Tregs from Eos cKO mice displayed normal suppressive function in vitro, Eos cKO mice developed severe Experimental Autoimmune Encephalomyletis (EAE) following immunization with myelin oligodendrocyte glycoprotein (MOG) and Eos cKO Treg were unable to suppress Inflammatory Bowel Disease (IBD). Eos cKO mice had decreased growth of the transplantable murine adenocarcinoma MC38 tumor accompanied by enhanced IFN-γ/TNF-α production by CD8+ T cells in tumor draining lymph nodes. Mice with a global deficiency of Eos or a deficiency of Eos only in T cells developed autoimmunity at a much older age (12 months or 7-8 months, respectively). Taken together, Eos appears to play an essential role in multiple aspects of Treg suppressor function, but also plays an as yet unknown role in the function of CD4+Foxp3- and CD8+ T cells and potentially in non-T cells.

Neuropilin-1 Expression on CD4 T Cells Is Atherogenic and Facilitates T Cell Migration to the Aorta in Atherosclerosis

Neuropilin 1 (Nrp1) is a type I transmembrane protein that plays important roles in axonal guidance, neuronal development, and angiogenesis. Nrp1 also helps migrate thymus-derived regulatory T cells to vascular endothelial growth factor (VEGF)-producing tumors. However, little is known about the role of Nrp1 on CD4 T cells in atherosclerosis. In ApoE^-/- mice fed a Western diet for 15 wk, we found a 2-fold increase in Nrp1⁺Foxp3^- CD4 T cells in their spleens, periaortic lymph nodes, and aortas, compared with chow-fed mice. Nrp1⁺Foxp3^- CD4 T cells had higher proliferation potential, expressed higher levels of the memory marker CD44, and produced more IFN-γ when compared with Nrp1^- CD4 T cells. Treatment of CD4 T cells with oxLDL increased Nrp1 expression. Furthermore, atherosclerosis-susceptible mice selectively deficient for Nrp1 expression on T cells developed less atherosclerosis than their Nrp1-sufficient counterparts. Mechanistically, we found that CD4 T cells that express Nrp1 have an increased capacity to migrate to the aorta and periaortic lymph nodes compared to Nrp1^- T cells, suggesting that the expression of Nrp1 facilitates the recruitment of CD4 T cells into the aorta where they can be pathogenic. Thus, we have identified a novel role of Nrp1 on CD4 T cells in atherosclerosis. These results suggest that manipulation of Nrp1 expression on T cells can affect the outcome of atherosclerosis and lower disease incidence.

Rapid fabrication of reinforced and cell-laden vascular grafts structurally inspired by human coronary arteries

Design strategies for small diameter vascular grafts are converging toward native-inspired tissue engineered grafts. A new automated technology is presented that combines a dip-spinning methodology for depositioning concentric cell-laden hydrogel layers, with an adapted solution blow spinning (SBS) device for intercalated placement of aligned reinforcement nanofibres. This additive manufacture approach allows the assembly of bio-inspired structural configurations of concentric cell patterns with fibres at specific angles and wavy arrangements. The middle and outer layers were tuned to structurally mimic the media and adventitia layers of native arteries, enabling the fabrication of small bore grafts that exhibit the J-shape mechanical response and compliance of human coronary arteries. This scalable automated system can fabricate cellularized multilayer grafts within 30 min. Grafts were evaluated by hemocompatibility studies and a preliminary in vivo carotid rabbit model. The dip-spinning-SBS technology generates constructs with native mechanical properties and cell-derived biological activities, critical for clinical bypass applications.

CD4+Foxp3+T Regulatory Cells Promote Transplantation Tolerance by Modulating Effector CD4+ T Cells in a Neuropilin-1-Dependent Manner

Several mechanisms of immune suppression have been attributed to Foxp3+ T regulatory cells (Treg) including modulation of target cells via inhibition of cell proliferation, alteration of cytokine secretion, and modification of cell phenotype, among others. Neuropilin-1 (Nrp1), a co-receptor protein highly expressed on Treg cells has been involved in tolerance-mediated responses, driving tumor growth and transplant acceptance. Here, we extend our previous findings showing that, despite expressing Foxp3, Nrp1KO Treg cells have deficient suppressive function in vitro in a contact-independent manner. In vivo, the presence of Nrp1 on Treg cells is required for driving long-term transplant tolerance. Interestingly, Nrp1 expression on Treg cells was also necessary for conventional CD4+ T cells (convT) to become Nrp1+Eos+ T cells in vivo. Furthermore, adoptive transfer experiments showed that the disruption of Nrp1 expression on Treg cells not only reduced IL-10 production on Treg cells, but also increased the frequency of IFNγ+ Treg cells. Similarly, the presence of Nrp1KO Treg cells facilitated the occurrence of IFNγ+CD4+ T cells. Interestingly, we proved that Nrp1KO Treg cells are also defective in IL-10 production, which correlates with deficient Nrp1 upregulation by convT cells. Altogether, these findings demonstrate the direct role of Nrp1 on Treg cells during the induction of transplantation tolerance, impacting indirectly the phenotype and function of conventional CD4+ T cells.

Unique properties of thymic antigen-presenting cells promote epigenetic imprinting of alloantigen-specific regulatory T cells

Regulatory T cells (Tregs) are potential immunotherapeutic candidates to induce transplantation tolerance. However, stability of Tregs still remains contentious and may potentially restrict their clinical use. Recent work suggested that epigenetic imprinting of Foxp3 and other Treg-specific signature genes is crucial for stabilization of immunosuppressive properties of Foxp3⁺ Tregs, and that these events are initiated already during early stages of thymic Treg development. However, the mechanisms governing this process remain largely unknown. Here we demonstrate that thymic antigen-presenting cells (APCs), including thymic dendritic cells (t-DCs) and medullary thymic epithelial cells (mTECs), can induce a more pronounced demethylation of Foxp3 and other Treg-specific epigenetic signature genes in developing Tregs when compared to splenic DCs (sp-DCs). Transcriptomic profiling of APCs revealed differential expression of secreted factors and costimulatory molecules, however neither addition of conditioned media nor interference with costimulatory signals affected Foxp3 induction by thymic APCs in vitro. Importantly, when tested in vivo both mTEC- and t-DC-generated alloantigen-specific Tregs displayed significantly higher efficacy in prolonging skin allograft acceptance when compared to Tregs generated by sp-DCs. Our results draw attention to unique properties of thymic APCs in initiating commitment towards stable and functional Tregs, a finding that could be highly beneficial in clinical immunotherapy.

Tuftsin prevents the negative immunoregulation of neuropilin-1highCD4+CD25+Regulatory T cells and improves survival rate in septic mice

Our previous research showed that neuropilin (Nrp) -1highCD4+CD25+Regulatory T cells (Tregs) exhibited primary negative immunoregulation in sepsis induced immune dysfunction. Tuftsin is the typical ligand of Nrp-1. Herein, we investigated the potential therapeutic value and mechanisms of tuftsin in sepsis. Sepsis per se markedly decreased the serum concentration of tuftsin, administration of tuftsin improved the survival rate of septic mice with cecal ligation and puncture (CLP). In vitro study, tuftsin prevented the negative immunoregulation of Nrp-1highCD4+CD25+Tregs, including weakening the expression of forkhead/winged helix transcription factor (Foxp)- 3/cytotoxic T lymphocyte associated antigen (CTLA)-4, inhibiting the secretion of transforming growth factor (TGF)-β, and weakening the immunosuppressive function of Nrp-1highCD4+CD25+Tregs to conventional CD4+CD25-T cells. Tuftsin markedly inhibited the demethylation of Foxp3-Tregs specific demethylated region (TSDR) of Nrp-1highCD4+CD25+Tregs. Tuftsin could represent a new potential therapeutic agentia to improve the outcome of septic mice, and associate with preventing the negative immunoregulation of Tregs via Nrp-1.

Vitamin C Fosters the In Vivo Differentiation of Peripheral CD4+ Foxp3- T Cells into CD4+ Foxp3+ Regulatory T Cells but Impairs Their Ability to Prolong Skin Allograft Survival

Regulatory T cells (Tregs) are critical players of immunological tolerance due to their ability to suppress effector T cell function thereby preventing transplant rejection and autoimmune diseases. During allograft transplantation, increases of both Treg expansion and generation, as well as their stable function, are needed to ensure allograft acceptance; thus, efforts have been made to discover new molecules that enhance Treg-mediated tolerance and to uncover their mechanisms. Recently, vitamin C (VitC), known to regulate T cell maturation and dendritic cell-mediated T cell polarization, has gained attention as a relevant epigenetic remodeler able to enhance and stabilize the expression of the Treg master regulator gene Foxp3, positively affecting the generation of induced Tregs (iTregs). In this study, we measured VitC transporter (SVCT2) expression in different immune cell populations, finding Tregs as one of the cell subset with the highest levels of SVCT2 expression. Unexpectedly, we found that VitC treatment reduces the ability of natural Tregs to suppress effector T cell proliferation in vitro, while having an enhancer effect on TGFβ-induced Foxp3⁺ Tregs. On the other hand, VitC increases iTregs generation in vitro and in vivo, however, no allograft tolerance was achieved in animals orally treated with VitC. Lastly, Tregs isolated from the draining lymph nodes of VitC-treated and transplanted mice also showed impaired suppression capacity ex vivo. Our results indicate that VitC promotes the generation and expansion of Tregs, without exhibiting CD4⁺ T cell-mediated allograft tolerance. These observations highlight the relevance of the nutritional status of patients when immune regulation is needed.

Contributions of immune cell populations in the maintenance, progression, and therapeutic modalities of glioma

Immunotherapies are becoming a promising strategy for malignant disease. Selectively directing host immune responses to target cancerous tissue is a milestone of human health care. The roles of the innate and adaptive immune systems in both cancer progression and elimination are now being realized. Defining the immune cell environment and identifying the contributions of each sub-population of these cells has lead to an understanding of the immunotherapeutic processes, and demonstrated the potential of the immune system to drive cancer shrinkage and sustained immunity against disease. Poorly treated diseases, such as high-grade glioma, suffer from lack of therapeutic efficacy and rapid progression. Immunotherapeutic success in other solid malignancies, such as melanoma, now provides the principals for which this treatment paradigm can be adapted for primary brain cancers. The central nervous system is complex, and relative contributions of immune sub-populations to high grade glioma progression are not fully characterized. Here, we summarize recent research in both animal and humans which add to the knowledge base of how innate and adaptive immune cells contribute to glioma progression, and outline work which has demonstrated their potential to elicit anti-tumorigenic responses. Additionally, we highlight Neuropilin 1, a cell surface receptor protein, describe its signaling functions in the context of immunity, and point to its potential to slow glioma progression.

Multifaceted Role of Neuropilins in the Immune System: Potential Targets for Immunotherapy

Neuropilins (NRPs) are non-tyrosine kinase cell surface glycoproteins expressed in all vertebrates and widely conserved across species. The two isoforms, such as neuropilin-1 (NRP1) and neuropilin-2 (NRP2), mainly act as coreceptors for class III Semaphorins and for members of the vascular endothelial growth factor family of molecules and are widely known for their role in a wide array of physiological processes, such as cardiovascular, neuronal development and patterning, angiogenesis, lymphangiogenesis, as well as various clinical disorders. Intriguingly, additional roles for NRPs occur with myeloid and lymphoid cells, in normal physiological as well as different pathological conditions, including cancer, immunological disorders, and bone diseases. However, little is known concerning the molecular pathways that govern these functions. In addition, NRP1 expression has been characterized in different immune cellular phenotypes including macrophages, dendritic cells, and T cell subsets, especially regulatory T cell populations. By contrast, the functions of NRP2 in immune cells are less well known. In this review, we briefly summarize the genomic organization, structure, and binding partners of the NRPs and extensively discuss the recent advances in their role and function in different immune cell subsets and their clinical implications.

The Ikaros family of zinc-finger proteins

Ikaros represents a zinc-finger protein family important for lymphocyte development and certain other physiological processes. The number of family members is large, with alternative splicing producing various additional isoforms from each of the five homologous genes in the family. The functional forms of Ikaros proteins could be even more diverse due to protein–protein interactions readily established between family members. Emerging evidence suggests that targeting Ikaros proteins is feasible and effective in therapeutic applications, although the exact roles of Ikaros proteins remain elusive within the intricate regulatory networks in which they are involved. In this review we collect existing knowledge as to the functions, regulatory pathways, and molecular mechanisms of this family of proteins in an attempt to gain a better understanding through the comparison of activities and interactions among family members.

Neuropilin-1highCD4⁺CD25⁺ Regulatory T Cells Exhibit Primary Negative Immunoregulation in Sepsis

Regulatory T cells (Tregs) appear to be involved in sepsis-induced immune dysfunction; neuropilin-1 (Nrp-1) was identified as a surface marker for CD4⁺CD25⁺Tregs. In the current study, we investigated the negative immunoregulation of Nrp-1^highCD4⁺CD25⁺Tregs and the potential therapeutic value of Nrp-1 in sepsis. Splenic CD4⁺CD25⁺Tregs from cecal ligation and puncture (CLP) mouse models were further segregated into Nrp-1^highTregs and Nrp-1^lowTregs; they were cocultured with CD4⁺CD25⁻  T cells. The expression of forkhead/winged helix transcription factor-3 (Foxp-3), cytotoxic T-lymphocyte associated antigen-4 (CTLA-4), membrane associated transforming growth factor-β (TGF-β^m+), apoptotic rate, and secretive ability [including TGF-β and interleukin-10 (IL-10)] for various types of Tregs, as well as the immunosuppressive ability of Tregs on CD4⁺CD25⁻  T cells, were determined. Meanwhile, the impact of recombinant Nrp-1 polyclonal antibody on the demethylation of Foxp-3-TSDR (Treg-specific demethylated region) was measured in in vitro study. Sepsis per se markedly promoted the expression of Nrp-1 of CD4⁺CD25⁺Tregs. Foxp-3/CTLA-4/TGF-β^m+ of Nrp-1^highTregs were upregulated by septic challenge. Nrp-1^highTregs showed strong resilience to apoptosis and secretive ability and the strongest immunosuppressive ability on CD4⁺CD25⁻  T cells. In the presence of lipopolysaccharide (LPS), the recombinant Nrp-1 polyclonal antibody reduced the demethylation of Foxp-3-TSDR. Nrp-1^highTregs might reveal primary negative immunoregulation in sepsis; Nrp-1 could represent a new potential therapeutic target for the study of immune regulation in sepsis.

Characterization of Diabetogenic CD8+ T Cells: IMMUNE THERAPY WITH METABOLIC BLOCKADE

Type 1 diabetes mellitus is caused by the killing of insulin-producing β cells by CD8+T cells. The disease progression, which is chronic, does not follow a course like responses to conventional antigens such as viruses, but accelerates as glucose tolerance deteriorates. To identify the unique features of the autoimmune effectors that may explain this behavior, we analyzed diabetogenic CD8+ T cells that recognize a peptide from the diabetes antigen IGRP (NRP-V7-reactive) in prediabetic NOD mice and compared them to others that shared their phenotype (CD44(+)CD62L(lo)PD-1(+)CXCR3(+)) but negative for diabetes antigen tetramers and to LCMV (lymphocytic choriomeningitis)-reactive CD8+ T cells. There was an increase in the frequency of the NRP-V7-reactive cells coinciding with the time of glucose intolerance. The T cells persisted in hyperglycemic NOD mice maintained with an insulin pellet despite destruction of β cells. We compared gene expression in the three groups of cells compared with the other two subsets of cells, and the NRP-V7-reactive cells exhibited gene expression of memory precursor effector cells. They had reduced cellular proliferation and were less dependent on oxidative phosphorylation. When prediabetic NOD mice were treated with 2-deoxyglucose to block aerobic glycolysis, there was a reduction in the diabetes antigen versus other cells of similar phenotype and loss of lymphoid cells infiltrating the islets. In addition, treatment of NOD mice with 2-deoxyglucose resulted in improved β cell granularity. These findings identify a link between metabolic disturbances and autoreactive T cells that promotes development of autoimmune diabetes.

Exogenous interleukin-33 targets myeloid-derived suppressor cells and generates periphery-induced Foxp3⁺ regulatory T cells in skin-transplanted mice

Interleukin-33 (IL-33) has been a focus of study because of its variety of functions shaping CD4(+) T-cell biology. In the present work, we evaluated the modulatory effect of IL-33 on suppressor cells in an in vivo transplantation model. C57BL/6 wild-type mice were grafted with syngeneic or allogeneic skin transplants and treated with exogenous IL-33 daily. After 10 days of treatment, we analysed draining lymph node cellularity and found in allogeneic animals an increment in myeloid-derived suppressor cells, which co-express MHC-II, and become enriched upon IL-33 treatment. In line with this observation, inducible nitric oxide synthase and arginase 1 expression were also increased in allogeneic animals upon IL-33 administration. In addition, IL-33 treatment up-regulated the number of Foxp3(+) regulatory T (Treg) cells in the allogeneic group, complementing the healthier integrity of the allografts and the increased allograft survival. Moreover, we demonstrate that IL-33 promotes CD4(+) T-cell expansion and conversion of CD4(+)  Foxp3(-) T cells into CD4(+)  Foxp3(+) Treg cells in the periphery. Lastly, the cytokine pattern of ex vivo-stimulated draining lymph nodes indicates that IL-33 dampens interferon-γ and IL-17 production, stimulating IL-10 secretion. Altogether, our work complements previous studies on the immune-modulatory activity of IL-33, showing that this cytokine affects myeloid-derived suppressor cells at the cell number and gene expression levels. More importantly, our research demonstrates for the first time that IL-33 allows for in vivo Foxp3(+) Treg cell conversion and favours an anti-inflammatory or tolerogenic state by skewing cytokine production. Therefore, our data suggest a potential use of IL-33 to prevent allograft rejection, bringing new therapeutics to the transplantation field.

Eos Is Redundant for Regulatory T Cell Function but Plays an Important Role in IL-2 and Th17 Production by CD4+ Conventional T Cells

Eos belongs to the Ikaros family of transcription factors. It was reported to be a regulatory T cell (Treg) signature gene, to play a critical role in Treg suppressor functions, and to maintain Treg stability. We used mice with a global deficiency in Eos to re-examine the role of Eos expression in both Tregs and conventional T cells (Tconvs). Tregs from Eos-deficient (Eos(-/-)) mice developed normally, displayed a normal Treg phenotype, and exhibited normal suppressor function in vitro. Eos(-/-) Tregs were as effective as Tregs from wild-type (WT) mice in suppressing inflammation in a model of inflammatory bowel disease. Bone marrow (BM) from Eos(-/-) mice was as effective as that from WT mice in controlling T cell activation when used to reconstitute immunodeficient mice in the presence of scurfy fetal liver cells. Surprisingly, Eos was expressed in activated Tconvs and was required for IL-2 production, CD25 expression, and proliferation in vitro by CD4(+) Tconvs. Eos(-/-) mice developed more severe experimental autoimmune encephalomyelitis than WT mice, displayed increased numbers of effector T cells in the periphery and CNS, and amplified IL-17 production. In conclusion, our studies are not consistent with a role for Eos in Treg development and function but demonstrate that Eos plays an important role in the activation and differentiation of Tconvs.