Emerging role of innate immunity in organ transplantation part III: the quest for transplant tolerance via prevention of oxidative allograft injury and its consequences

In parts I and II of this tripartite review, the innate immune system was briefly described, focusing on its emerging role in organ transplantation and by emphasizing the oxidative injury-induced allograft inflammation that promotes the generation of immunostimulatory donor- and recipient-derived dendritic cells (DCs) translating innate immune events into adaptive alloimmunity. This part III of the review discusses the possibility to induce adaptive antigen-specific T regulatory cells (Tregs) in the clinical situation by harnessing donor- and recipient-derived tolerogenic DCs (tolDCs) as inducers for alloantigen-specific adaptive Tregs, an effort that follows current trends to harnessing DCs for immunotherapy. This challenge is based on accumulating evidence from basic immunological work in support of the notion that presentation of antigens, including weak transplantation antigens under subimmunogenic conditions within a noninflammatory microenvironment, promotes generation of tolDCs. With respect to these basic immunological studies, which are expressively reviewed, prevention of oxidative allograft injury can be regarded as an efficient tool in the clinical situation to present alloantigens under subimmunogenic conditions within an intragraft noninflammatory milieu, thereby potentially generating tolDCs able to induce Tregs-mediated innate allotolerance. Various therapeutic strategies to prevent oxidative allograft injury occurring in both the brain-dead donor before/during organ removal and the recipient during/after donor organ reperfusion as well as therapeutic options to inhibit injury-induced molecular and cellular consequences are finally discussed.     

FasL基因转染树突状细胞在抑制实验性自身免疫性葡萄膜炎中的作用

目的:探讨FasL基因转染的抗原特异性树突状细胞(DC)对实验性自身免疫性葡萄膜炎(EAU)的抑制作用.方法:用携带FasL基因的腺病毒转染DC和负载自体抗原——光感受器间维生素A类结合蛋白(IRBP)R16肽段的DC,制备FasL转染的DC(FasL-DC)和抗原负载FasL-DC(“杀伤性”DC).检测FasL基因...     

New therapeutic approaches for type 1 diabetes: Disease-modifying therapies

It has been 100 years since the first successful clinical use of insulin, yet it remains the only treatment option for type 1 diabetes mellitus (T1DM) patients. Advances in diabetes care, such as insulin analogue therapies and new devices, including continuous glucose monitoring with continuous subcutaneous insulin infusion have improved the quality of life of patients but have no impact on the pathogenesis of the disease. They do not eliminate long-term complications and require several lifestyle sacrifices. A more ideal future therapy for T1DM, instead of supplementing the insufficient hormone production (a consequence of β-cell destruction), would also aim to stop or slow down the destructive autoimmune process. The discovery of the autoimmune nature of type 1 diabetes mellitus has presented several targets by which disease progression may be altered. The goal of disease-modifying therapies is to target autoimmune mechanisms and prevent β-cell destruction. T1DM patients with better β-cell function have better glycemic control, reduced incidence of long-term complications and hypoglycemic episodes. Unfortunately, at the time symptomatic T1DM is diagnosed, most of the insulin secreting β cells are usually lost. Therefore, to maximize the salvageable β-cell mass by disease-modifying therapies, detecting autoimmune markers in an early, optimally presymptomatic phase of T1DM is of great importance. Disease-modifying therapies, such as immuno- and regenerative therapies are expected to take a relevant place in diabetology. The aim of this article was to provide a brief insight into the pathogenesis and course of T1DM and present the current state of disease-modifying therapeutic interventions that may impact future diabetes treatment.     

Type 1 diabetes and polyglandular autoimmune syndrome: A review

Type 1 diabetes(T1D) is an autoimmune disorder caused by inflammatory destruction of the pancreatic tissue. The etiopathogenesis and characteristics of the pathologic process of pancreatic destruction are well described. In addition, the putative susceptibility genes for T1 D as a monoglandular disease and the relation to polyglandular autoimmune syndrome(PAS) have also been wellexplored. The incidence of T1 D has steadily increased in most parts of the world, especially in industrialized nations. T1 D is frequently associated with autoimmune endocrine and non-endocrine diseases and patients with T1 D are at a higher risk for developing several glandular autoimmune diseases. Familial clustering is observed, which suggests that there is a genetic predisposition. Various hypotheses pertaining to viral- and bacterialinduced pancreatic autoimmunity have been proposed, however a definitive delineation of the autoimmune pathomechanism is still lacking. In patients with PAS, pancreatic and endocrine autoantigens either colocalize on one antigen-presenting cell or are expressed on two/various target cells sharing a common amino acid, which facilitates binding to and activation of T cells. The most prevalent PAS phenotype is the adult type 3 variant or PAS type Ⅲ, which encompasses T1 D and autoimmune thyroid disease. This review discusses the findings of recent studies showing noticeable differences in the genetic background and clinical phenotype of T1 D either as an isolated autoimmune endocrinopathy or within the scope of polyglandular autoimmune syndrome.     

Generation of dendritic cells with regulatory properties

Dendritic cells (DCs) are professional antigen presenting cells with the ability to induce and regulate an immune response. DCs that capture and present antigen under noninflammatory conditions maintain an immature phenotype and acquire tolerogenic properties. These DCs generate regulatory T lymphocytes that potentiate tolerogenic responses. Here we developed a method for the generation of immature murine DCs able to process and present a specific antigen in a tolerogenic context. Immature DCs were prepared from bone marrow precursors after differentiation with granulocyte-macrophage colony-stimulating factor (GM-CSF) in the presence of vitamin D₃ and characterized by their low expression of major histocompatibility complex class (MHC) II and CD86 molecules. Purified phagosomes containing either MHC II molecules or ovalbumin were used to deliver antigens to immature DCs. More than 80% of the DCs captured the phagosomes, while maintaining a low expression of maturation markers and showing basal levels of secretion of activating cytokines such as interleukin (IL)-2 and IL-12. Treatment of the immature DCs with lipopolysaccharides (LPS) increased IL-10 secretion, in agreement with their anti-inflammatory and immune regulatory properties. Cocultures of transgenic OT-II T lymphocytes with the immature DCs carrying OVA-phagosomes succeeded in generating a subpopulation of regulatory T lymphocytes characterized by the expression of CD4, CD25, CD62L, and Foxp3. Taken together, our results suggest that vitamin D₃ generates immune tolerance through the modulation of DC phenotype and could be useful to induce tolerance to allotransplants.     

Status of autoimmune diabetes 20-year after generation of BDC2.5-TCR transgenic non-obese diabetic mouse

Type 1 diabetes(T1D) is an autoimmune disease that results from the destruction of insulin-producing cells by autoreactive T cells,leading to lifelong dependency on insulin therapy and increased risk of long-term cardiovascular complications.Here we take the opportunity of the 20thanniversary of the generation of the BDC2.5 TCR transgenic non-obese diabetic(NOD) mouse model,to provide a brief overview of the significant progress that has been made in understanding the role of T cells in the disease pathogenesis period.This included development of hundreds of reagents that block or even reverse new-onset disease by directly or indirectly controlling T cells.We also reflect on the sobering fact that none of these strategies has shown significant efficacy in clinical trials and discuss potential reasons hindering translation of the preclinical findings into successful therapeutic strategies and potential ways forward.     

Minocycline induces tolerance to dendritic cell production probably by targeting the SOCS1/ TLR4/NF-κB signaling pathway

ObjectiveDendritic cells (DCs) are professional antigen-presenting cells that play a key role in maintaining peripheral immune tolerance. The use of tolerogenic DCs (tolDCs), i.e., semi-mature DCs that express co-stimulatory molecules but not pro-inflammatory cytokines, has been proposed. However, the mechanism of tolDCs induced by minocycline is still unclear. Our previous bioinformatics analyses based on multiple databases suggested that the suppressor of cytokine signaling 1/Toll-like receptor 4/NF-κB (SOCS1/TLR4/NF-κB) signal pathway was associated with DCs maturation. Thus, we studied whether minocycline could induce DC tolerance through this pathway.MethodsA search for potential targets was carried out through public databases, and pathway analysis was performed on these potential targets to obtain pathways relevant to the experiment. Flow cytometry was used to detect the expression of DC surface markers CD11c, CD86, and CD80, and major histocompatibility complex II. The secretion of interleukin (IL)-12p70, tumor necrosis factor alpha (TNF- α), and IL-10 in the DC supernatant was detected by enzyme-linked immunoassay. The ability of three groups (Ctrl-DCs, Mino-DCs, and LPS-DCs) of DCs to stimulate allogeneic CD4+ T cells was analyzed using a mixed lymphocyte reaction assay. Western blotting was used to detect the expression of TLR4, NF-κB-p65, NF-κB-p-p65, IκB-α, and SOCS1 proteins.ResultsThe hub gene plays a vital role in biological processes; in related pathways, the regulation of other genes is often affected by it. The SOCS1/TLR4/NF-κB signaling pathway was further validated by searching for potential targets through public databases to obtain relevant pathways. The minocycline-induced tolDCs showed characteristics of semi-mature DCs. Moreover, the IL-12p70 and TNF-α levels in the minocycline-stimulated DC group (Mino-DC group) were lower than those in the lipopolysaccharide (LPS)-DC group, and the IL-10 levels were higher in the Mino-DC group than in the LPS-DC and control DC groups. In addition, the Mino-DC group had decreased protein expression levels of TLR4 and NF-κB-p65 and upregulated protein levels of NF-κB-p-p65, IκB-α, and SOCS1 compared with the other groups.ConclusionThe results of this study indicate that minocycline could improve the tolerance of DCs probably by blocking the SOCS1/TLR4/NF-κB signaling pathway.     

Delivery of alloantigens via apoptotic cells generates dendritic cells with an immature tolerogenic phenotype

Background

Dendritic cells (DCs) are professional antigen-presenting cells able to induce immunity or tolerance. The interactions of immature DCs with naive T lymphocytes induce peripheral tolerance through mechanisms that include anergy or deletion of lymphocytes or the generation of regulatory T cells. Because of the central role of DCs in the immune response, they are potential targets for the induction of experimental tolerance. Thus, the generation of immature (tolerogenic) DCs able to capture and present alloantigens to T cells represents an important aim in our efforts to achieve better transplant acceptance.

Methods

In this work, we generated immature DCs by using vitamin D₃ (VD3) during the process of DC differentiation.

Results

The VD3-DCs showed an immature phenotype characterized by a low expression of major histocompatibility complex antigens of class II, CD86, and CD80 molecules and the secretion of a tolerogenic cytokine pattern. Furthermore, we showed that VD3-DCs phagocytose apoptotic allogeneic cells efficiently without inducing DC maturation or activation. Most important, our experiments demonstrated that mice treated with VD3 produce immature DCs in vivo, and that DCs from VD3-treated mice immunized with allogeneic apoptotic cells maintained their tolerogenic phenotype.

Conclusion

Our results show that allogeneic apoptotic cells in combination with VD3 generate DCs with tolerogenic characteristics that could be used to induce tolerance towards alloantigens.     

Type 1 diabetes mellitus and its oral tolerance therapy

As a T cell-mediated autoimmune disease,type 1 diabetes mellitus(T1 DM) is marked by insulin defect resulting from the destruction of pancreatic β-cells.The understanding of various aspects of T1 DM,such as its epidemiology,pathobiology,pathogenesis,clinical manifestations,and complications,has been greatly promoted by valuable research performed during the past decades.However,these findings have not been translated into an effective treatment.The ideal treatment should safely repair the destroyed immune balance in a longlasting manner,preventing or stopping the destruction of β-cells.As a type of immune hypo-responsiveness to the orally administrated antigen,oral tolerance may be induced by enhancement of regulatory T cells(Tregs) or by anergy/deletion of T cells,depending on the dosage of orally administrated antigen.Acting as an antigen-specific immunotherapy,oral tolerance therapy for T1 DM has been mainly performed using animal models and some clinical trials have been completed or are still ongoing.Based on the review of the proposed mechanism of the development of T1 DM and oral tolerance,we give a current overview of oral tolerance therapy for T1 DM conducted in both animal models and clinical trials.     

Aspirin-Treated Human DCs Up-Regulate ILT-3 and Induce Hyporesponsiveness and Regulatory Activity in Responder T Cells

Mature dendritic cells (mDCs) are potent antigen presenting cells, but immature DCs (iDCs) have been shown to have reduced antigen stimulatory capacity. Different strategies have been investigated to augment the tolerogenic capacity of dendritic cells (DCs). We demonstrate that in aspirin‐treated human DCs, there is reduced expression of CD1a, HLA‐DR and CD86, up‐regulation of ILT‐3 expression and marginal increases in PDL‐1. Aspirin‐treated DCs are partially resistant to phenotypic changes following maturational stimuli, such as lipopolysaccharide (LPS) or TNFα, IL‐1α and PGE₂. Aspirin‐treated DCs demonstrate normal endocytic function, but have a reduced ability to stimulate allogeneic T cells, which is comparable to iDCs. Furthermore, they induce hyporesponsiveness and regulatory activity in responder naïve and memory T cells; for naïve T cells this is achieved more quickly and efficiently than with iDCs. We investigated the mechanism of this regulatory activity and found that both cell‐cell contact and inhibitory cytokine activity are involved, although no one cytokine predominates in importance. Blocking ILT‐3 or IL‐12 does not diminish the capacity of these DCs to induce regulation or Foxp3 expression on the regulatory T cells. Results demonstrate that aspirin‐treated DCs display tolerogenic potential, which is of interest in their therapeutic potential in reducing chronic allograft rejection.     

Dendritic cells (I): Biological functions

Dendritic cells (DCs) are potent antigen presenting cells (APCs) that possess the ability to stimulate na?ve T cells. They comprise a system of leukocytes widely distributed in all tissues, especially in those that provide an environmental interface. DCs posses a heterogeneous haemopoietic lineage, in that subsets from different tissues have been shown to posses a differential morphology, phenotype and function. The ability to stimulate na?ve T cell proliferation appears to be shared between these various DC subsets. It has been suggested that the so-called myeloid and lymphoid-derived subsets of DCs perform specific stimulatory or tolerogenic function, respectively. DCs are derived from bone marrow progenitors and circulate in the blood as immature precursors prior to migration into peripheral tissues. Within different tissues, DCs differentiate and become active in the taking up and processing of antigens (Ags), and their subsequent presentation on the cell surface linked to major histocompatibility (MHC) molecules. Upon appropriate stimulation, DCs undergo further maturation and migrate to secondary lymphoid tissues where they present Ag to T cells and induce an immune response. DCs are receiving increasing scientific and clinical interest due to their key role in anti-cancer host responses and potential use as biological adjuvants in tumour vaccines, as well as their involvement in the immunobiology of tolerance and autoimmunity.     

Direct and indirect cross-tolerance of alloreactive T cells by dendritic cells retained in the immature stage

BACKGROUND: Rejection of allografts entails the direct and indirect cross-recognition of donor major histocompatibility complex molecules by recipient alloreactive T cells. The ability to manipulate the state of dendritic cell (DC) maturation in vitro has enabled us to induce tolerance specifically targeting the alloreactive T-cell compartment. In this study, the immunoregulatory effect of alloantigen presentation by ex vivo-generated donor and recipient DCs retained in immature stage was investigated. METHODS: Dendritic cell were generated by culturing monocytes with granulocyte-macrophage colony-stimulating factor and interleukin-4. Ex vivo-generated tolerogenic DCs were characterized by flow cytometry and confocal microscopy. Recipient T-cell responses to donor or recipient DCs loaded with donor-derived apoptotic cells were assessed in a two-step culture system. RESULTS: Dendritic cells maintained their phagocytic and endocytic activities, and had significantly reduced capacity to prime recipient T cells. Moreover, primary coculture of recipient T cells with donor tolerogenic DCs rendered alloantigen-specific T cells hyporesponsive to a subsequent challenge with donor immunogenic DCs as evidenced by decreased proliferation and cytokine secretion. Importantly, recipient tolerogenic DCs loaded with donor-derived apoptotic cells were able to cross-tolerize recipient T cells. This was revealed by alloantigen-specific T-cell hyporesponsiveness on restimulation with the recipient immunogenic DCs loaded with different tissue-derived apoptotic cells obtained from the same donor.CONCLUSIONS: Dendritic cells retained in immature stage induce direct and most importantly indirect cross-tolerance of alloantigen-specific T cells. It may be likely that administration of donor and/or recipient DCs could be one means with which to promote tolerance induction in acute and chronic phases of organ transplant.     

Redirection of human autoreactive T-cells Upon interaction with dendritic cells modulated by TX527, an analog of 1,25 dihydroxyvitamin D(3)

The active form of vitamin D(3), 1alpha,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)), is a potent immunomodulator known to affect T-cells through targeting antigen-presenting cells such as dendritic cells (DCs). We studied the effects of a novel nonhypercalcemic 1,25(OH)(2)D(3) analog, TX527, on DC differentiation, maturation, and function with respect to stimulation of a committed human GAD65-specific autoreactive T-cell clone. Continuous addition of TX527 impaired interleukin (IL)-4 and granulocyte/macrophage colony-stimulating factor (GM-CSF)-driven DC differentiation as well as lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma)-induced maturation into Th1-promoting DC (DC1), as characterized by marked changes in DC morphology and abrogation of IL-12p70 release upon CD40 ligation. Addition of TX527 during maturation did not affect DC morphology but significantly changed DC cytokine profiles. The potential of treated DCs to alter the response pattern of committed autoreactive T-cells was found to depend on the timing of TX527 exposure. Continuously TX527-treated DCs significantly inhibited T-cell proliferation and blocked IFN-gamma, IL-10, but not IL-13 production, whereas DCs treated during maturation failed to inhibit T-cell proliferation but affected IL-10 and IFN-gamma production. Collectively, we provide evidence that nonhypercalcemic TX527 is a potent in vitro DC modulator, yielding DCs with the potential to change cytokine responses of committed autoreactive T-cells.     

The novel therapeutic effect of phosphoinositide 3-kinase-γ inhibitor AS605240 in autoimmune diabetes

Type 1 diabetes (T1D) remains a major health problem worldwide, with a steadily rising incidence yet no cure. Phosphoinositide 3-kinase-γ (PI3Kγ), a member of a family of lipid kinases expressed primarily in leukocytes, has been the subject of substantial research for its role in inflammatory diseases. However, the role of PI3Kγ inhibition in suppressing autoimmune T1D remains to be explored. We tested the role of the PI3Kγ inhibitor AS605240 in preventing and reversing diabetes in NOD mice and assessed the mechanisms by which this inhibition abrogates T1D. Our data indicate that the PI3Kγ pathway is highly activated in T1D. In NOD mice, we found upregulated expression of phosphorylated Akt (PAkt) in splenocytes. Notably, T regulatory cells (Tregs) showed significantly lower expression of PAkt compared with effector T cells. Inhibition of the PI3Kγ pathway by AS605240 efficiently suppressed effector T cells and induced Treg expansion through the cAMP response element-binding pathway. AS605240 effectively prevented and reversed autoimmune diabetes in NOD mice and suppressed T-cell activation and the production of inflammatory cytokines by autoreactive T cells in vitro and in vivo. These studies demonstrate the key role of the PI3Kγ pathway in determining the balance of Tregs and autoreactive cells regulating autoimmune diabetes.     

The characteristics of tolerogenic plasmacytoid dendritic cells stimulated with interleukin-3

This study focused on whether bone marrow would differentiate tolerogenic dendritic cells (DCs) by comparing interleukin-3 (IL-3) DCs (induced by IL-3+IL-4) with GM-CSF DCs (induced by GM-CSF+IL-4, generating myeloid DCs). Mouse bone marrow progenitors were induced in vitro to differentiate into DCs by exposure to IL-3. The morphology and yields of IL-3 DCs and GM-CSF DCs were compared by scanning electron microscopy and laser scanning confocal microscopy. Immunohistochemistry and flow cytometer (FCM) were used to identify immune phenotypes. The results showed that IL-3 DCs and GM-CSF DCs both expressed the specific marker DEC-205 with about 80% and 70% purity, respectively. IL-3 DCs had similar morphology as plasma cells, but a different immune phenotype, namely, CD80(-), CD86(-), CD14(-), and MHC class II(+). IL-3 DCs remained in the costimulatory molecule-deficient state when TNF-alpha was supplemented into the culture. We therefore propose that IL-3 induces a high purity and yield of DCs from bone marrow. Since IL-3 DCs possess a tolerogenic phenotype (MHC class II(+), B7(-)), they may induce alloantigen-specific hyporesponsiveness in vitro.     

Treatment with granulocyte colony-stimulating factor prevents diabetes in NOD mice by recruiting plasmacytoid dendritic cells and functional CD4(+)CD25(+) regulatory T-cells

Accumulating evidence that granulocyte colony-stimulating factor (G-CSF), the key hematopoietic growth factor of the myeloid lineage, not only represents a major component of the endogenous response to infections, but also affects adaptive immune responses, prompted us to investigate the therapeutic potential of G-CSF in autoimmune type 1 diabetes. Treatment with G-CSF protected NOD mice from developing spontaneous diabetes. G-CSF triggered marked recruitment of dendritic cells (DCs), particularly immature CD11c(lo)B220(+) plasmacytoid DCs, with reduced costimulatory signal expression and higher interferon-alpha but lower interleukin-12p70 release capacity than DCs in excipient-treated mice. G-CSF recipients further displayed accumulation of functional CD4(+)CD25(+) regulatory T-cells that produce transforming growth factor-beta1 (TGF-beta1) and actively suppressed diabetes transfer by diabetogenic effector cells in secondary NOD-SCID recipients. G-CSF's ability to promote key tolerogenic interactions between DCs and regulatory T-cells was demonstrated by enhanced recruitment of TGF-beta1-expressing CD4(+)CD25(+) cells after adoptive transfer of DCs isolated from G-CSF- relative to vehicle-treated mice into naive NOD recipients. The present results suggest that G-CSF, a promoter of tolerogenic DCs, may be evaluated for the treatment of human type 1 diabetes, possibly in association with direct inhibitors of T-cell activation. They also provide a rationale for a protective role of the endogenous G-CSF produced during infections in early diabetes.     

Role of glucocorticoid-induced leucine zipper (GILZ) expression by dendritic cells in tolerance induction

Dendritic cells (DCs) play a crucial role in T cell allorecognition in the context of organ transplantation and allogeneic hematopoietic stem cell transplantation (allo-HSCT). This DC function is believed to be directly involved in allo-HSCT morbidity and mortality. DC functions range from immunoaggressive responses to the promotion of tolerance, reflecting functional plasticity. This unique characteristic offers a rationale to propose generation of tolerogenic DCs as a therapeutic tool for graft-versus-host disease (GVHD). The accumulated preclinical findings support the concept that glucocorticoid-induced leucine zipper (GLIZ) expression redirects mature DC function toward a tolerogenic mode, driving differentiation of antigen-specific regulatory T cells. Taking into account the unique role of DCs within the allo-HSCT context, novel preventive and curative therapeutics for GVHD might be based on the selective induction of GILZ expression in vivo.     

Combination therapy with sirolimus and interleukin-2 prevents spontaneous and recurrent autoimmune diabetes in NOD mice

Sirolimus is an immunosuppressant that inhibits interleukin (IL)-2 signaling of T-cell proliferation but not IL-2-induced T-cell apoptosis. Therefore, we hypothesized that administration of IL-2, together with sirolimus, might shift T-cell proliferation to apoptosis and prevent autoimmune destruction of islet beta-cells. We found that sirolimus and IL-2 therapy of female NOD mice, beginning at age 10 weeks, was synergistic in preventing diabetes development, and disease prevention continued for 13 weeks after stopping sirolimus and IL-2 therapy. Similarly, sirolimus and IL-2 were synergistic in protecting syngeneic islet grafts from recurrent autoimmune destruction after transplantation in diabetic NOD mice, and diabetes did not recur after stopping sirolimus and IL-2 combination therapy. Immunocytochemical examination of islet grafts revealed significantly decreased numbers of leukocytes together with increased apoptosis of these cells in mice treated with sirolimus and IL-2, whereas beta-cells were more numerous, and significantly fewer were apoptotic. In addition, Th1-type cells (gamma-interferon-positive and IL-2(+)) were decreased the most, and Th2-type cells (IL-4(+) and IL-10(+)) and Th3-type cells (transforming growth factor-beta1(+)) were increased the most in islet grafts of sirolimus and IL-2-treated mice. We conclude that 1) combination therapy with sirolimus and IL-2 is synergistic in protecting islet beta-cells from autoimmune destruction; 2) diabetes prevention continues after withdrawal of therapy; and 3) the mechanism of protection involves a shift from Th1- to Th2- and Th3-type cytokine-producing cells, possibly due to deletion of autoreactive Th1 cells.     

Tolerogenic Dendritic Cells Shape a Transmissible Gut Microbiota That Protects From Metabolic Diseases

Excess chronic contact between microbial motifs and intestinal immune cells is known to trigger a low-grade inflammation involved in many pathologies such as obesity and diabetes. The important skewing of intestinal adaptive immunity in the context of diet-induced obesity (DIO) is well described, but how dendritic cells (DCs) participate in these changes is still poorly documented. To address this question, we challenged transgenic mice with enhanced DC life span and immunogenicity (DC^hBcl-2 mice) with a high-fat diet. Those mice display resistance to DIO and metabolic alterations. The DIO-resistant phenotype is associated with healthier parameters of intestinal barrier function and lower intestinal inflammation. DC^hBcl-2 DIO-resistant mice demonstrate a particular increase in tolerogenic DC numbers and function, which is associated with strong intestinal IgA, T helper 17, and regulatory T-cell immune responses. Microbiota composition and function analyses reveal that the DC^hBcl-2 mice microbiota is characterized by lower immunogenicity and an enhanced butyrate production. Cohousing experiments and fecal microbial transplantations are sufficient to transfer the DIO resistance status to wild-type mice, demonstrating that maintenance of DCs’ tolerogenic ability sustains a microbiota able to drive DIO resistance. The tolerogenic function of DCs is revealed as a new potent target in metabolic disease management.