Induced Treg Differentiation Research Articles

Reciprocal Regulation of Glycolysis-Driven Th17 Pathogenicity and Regulatory T Cell Stability by Cdc42.

A balance between Th17 cells and regulatory T cells (Tregs) is important for host immunity and immune tolerance. The underlying molecular mechanisms remain poorly understood. Here we have identified Cdc42 as a central regulator of Th17/Treg balance. Deletion of Cdc42 in T cells enhanced Th17 differentiation but diminished induced Treg differentiation and suppressive function. Treg-specific deletion of Cdc42 decreased natural Tregs but increased effector T cells including Th17 cells. Notably, Cdc42-deficient Th17 cells became pathogenic associated with enhanced glycolysis and Cdc42-deficient Tregs became unstable associated with weakened glycolytic signaling. Inhibition of glycolysis in Cdc42-deficient Th17 cells diminished their pathogenicity and restoration of glycolysis in Cdc42-deficient Tregs rescued their instability. Intriguingly, Cdc42 deficiency in T cells led to exacerbated wasting disease in mouse models of colitis and Treg-specific deletion of Cdc42 caused early, fatal lymphoproliferative diseases. In summary, we show that Cdc42 is a bona fide regulator of peripheral tolerance through suppression of Th17 aberrant differentiation/pathogenicity and promotion of Treg differentiation/stability/function involving metabolic signaling and thus Cdc42 pathway might be harnessed in autoimmune disease therapy.

Rutinosylated Ferulic Acid Attenuates Food Allergic Response and Colitis by Upregulating Regulatory T Cells in Mouse Models.

The purpose of this study was to screen phytochemicals capable of inducing immune tolerance via enhanced transforming growth factor-β1 (TGF-β1) secretion and investigate their effects in a mouse model of food allergy and colitis. In a screening test using THP-1-derived dendritic cells, a significant increase in TGF-β1 levels was observed upon treatment with ferulic acid and its glycosides, among which ferulic acid rutinoside (FAR) induced the highest level of TGF-β1 secretion. Oral administration of FAR suppressed serum levels of immunoglobulin E and histamine in ovalbumin-sensitized mice and triggered the differentiation of regulatory T (Treg) cells. In comparison to the control, FAR treatment also induced stronger TGF-β1 secretion from splenic dendritic cells. FAR treatment attenuated dextran-sulfate-sodium-induced colitis in the model mice and induced Treg differentiation. These results suggest that FAR exerts potent immunomodulatory effects against allergic and intestinal inflammatory responses by inducing Treg differentiation.

Complex Immune Evasion Strategies in Classical Hodgkin Lymphoma.

The cellular microenvironment in classical Hodgkin lymphoma (cHL) is dominated by a mixed infiltrate of inflammatory cells with typically only about 1% Hodgkin and Reed/Sternberg (HRS) tumor cells. T cells are usually the largest population of cells in the cHL microenvironment, encompassing T helper (Th) cells, regulatory T cells (Tregs), and cytotoxic T cells. Th cells and Tregs presumably provide essential survival signals for HRS cells. Tregs are also involved in rescuing HRS cells from antitumor immune responses. An understanding of the immune evasion strategies of HRS cells is not only relevant for a characterization of the pathophysiology of cHL but is also clinically relevant, given the current treatment approaches targeting checkpoint inhibitors. Here, we characterized the cHL-specific CD4+ T-cell infiltrate regarding its role in immune evasion. Global gene expression analysis of CD4+ Th cells and Tregs isolated from cHL lymph nodes and reactive tonsils revealed that Treg signatures were enriched in CD4+ Th cells of cHL. Hence, HRS cells may induce Treg differentiation in Th cells, a conclusion supported by in vitro studies with Th cells and cHL cell lines. We also found evidence for immune-suppressive purinergic signaling and a role of the inhibitory receptor-ligand pairs B- and T-cell lymphocyte attenuator-herpesvirus entry mediator and CD200R-CD200 in promoting immune evasion. Taken together, this study highlights the relevance of Treg induction and reveals new immune checkpoint-driven immune evasion strategies in cHL. Cancer Immunol Res; 5(12); 1122-32. ©2017 AACR.

Effects of ginsenosides on regulatory T cell differentiation.

Regulatory T cells (Treg cells) are a subpopulation of T cells defined as CD4+Foxp3+CD25+. They mainly function as immunosuppressive T cells by downregulating the induction and proliferation of effector T cells, but also modulate the immune system by maintaining self-tolerance and preventing autoimmune disease. In this study, the regulatory roles of ginsenosides, one of the active components in ginseng, Panax ginseng C. A. Meyer, in Treg cell differentiation were examined. The results demonstrated that ginsenoside Rd induced Treg differentiation by upregulating Foxp3 expression and increased the generation of TGF-β1, IL-10 and IL-35. The data suggest that ginsenoside Rd may be a potential immunomodulating agent or supplement that can be applied for transplantation and autoimmune disorders.

Decitabine inhibits T cell proliferation via a novel TET2-dependent mechanism and exerts potent protective effect in mouse auto- and allo-immunity models.

Multiple sclerosis (MS) is an autoimmune disease characterized by the dysregulated immune response including innate and adaptive immune responses. Increasing evidence has proven the importance of epigenetic modification in the progression of MS. Recent studies revealed that low-dose decitabine (Dec, 5-Aza-2′-deoxycytidine), which incorporates into replicating DNA and inhibits DNA methylation, could prevent experimental autoimmune encephalomyelitis (EAE) development by increasing the number of regulatory T cells (Tregs). Here, we showed that higher-dose decitabine relative to previous studies could also distinctly protect mice from EAE and allogeneic cardiac transplantation. Mechanistic studies revealed decitabine suppressed innate responses in EAE mice through inhibiting the activation of microglia and monocyte-derived macrophages that contributed to reduce the severity of EAE. Furthermore, differentiation of naïve CD4+ T cells into Th1 and Th17 cells was significantly suppressed by decitabine in vivo and in vitro. Though in vitro studies showed decitabine could induce Treg differentiation, there was no obvious change in the percentage of Tregs in Dec-treated EAE mice. Most importantly, we found that T cell proliferation was potently inhibited in vivo and in vitro by higher-dose decitabine through increased gene expression of the DNA dioxygenase TET2 which facilitated the expression of several cell cycle inhibitors. Collectively, our study provides novel mechanistic insights of using the epigenetic modifying agents in the management of both allo- and auto-immune responses.

Exosomal miR-24-3p impedes T-cell function by targeting FGF11 and serves as a potential prognostic biomarker for nasopharyngeal carcinoma.

Recent studies have shown that extracellular microRNAs are not only potential biomarkers but are also involved in cell interactions to regulate the intercommunication between cancer cells and their microenvironments in various types of malignancies. In this study, we isolated exosomes from nasopharyngeal carcinoma (NPC) cell lines and patient sera (T-EXOs), or control NP69 cells and healthy donor sera (HD-EXOs). We found that miR-24-3p was markedly enriched in T-EXOs as compared with HD-EXOs; the serum exosomal miR-24-3p level was correlated with worse disease-free survival of patients (p < 0.05). Knockdown of exosomal miR-24-3p (miR-24-3p-sponge-T-EXOs) by a sponge RNA targeting miR-24-3p restored the T-EXO-mediated (control-sponge-T-EXO) inhibition of T-cell proliferation and Th1 and Th17 differentiation, and the induction of regulatory T cells (Tregs). Mechanistic analyses revealed that administration of exosomal miR-24-3p increased P-ERK, P-STAT1 and P-STAT3 expression while decreasing P-STAT5 expression during T-cell proliferation and differentiation. Moreover, by in vivo and in vitro assessments, we found FGF11 to be a direct target of miR-24-3p. However, both miR-24-3p-sponge-T-EXOs and T-EXOs (control-sponge-T-EXOs) impeded proliferation and Th1 and Th17 differentiation, but induced Treg differentiation, of lenti-shFGF11-transfected T cells. The levels of phosphorylated ERK and STAT proteins were different in lenti-ScshRNA-transfected T cells and lenti-shFGF11-transfected T cells following administration of miR-24-3p-sponge-T-EXO. Interestingly, tumour FGF11 expression was positively correlated with the number of CD4+ and CD8+ T cells in vivo, and predicted favourable patient DFS (p < 0.05). Additionally, hypoxia increased cellular and exosomal miR-24-3p levels and enhanced the inhibitory effect of T-EXO on T-cell proliferation and differentiation. Collectively, our findings suggest that exosomal miR-24-3p is involved in tumour pathogenesis by mediating T-cell suppression via repression of FGF11, and may serve as a potential prognostic biomarker in NPC. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Dichloroacetate induces regulatory T-cell differentiation and suppresses Th17-cell differentiation by pyruvate dehydrogenase kinase-independent mechanism.

Recently, there has been a growing interest in the mechanism of action of dichloroacetate (DCA) for T-cell differentiation; however, this mechanism has not been elucidated in detail. Therefore, this study aimed to investigate the mechanism of action of DCA for Treg and Th17 differentiation with pyruvate dehydrogenase kinase (PDHK) inhibitor (AZD7545) and PDHK knockdown. Inhibitory activity of DCA and AZD7545 against recombinant PDHK and intracellular PDH phosphorylation was measured. The effects of DCA and AZD7545 on T-cell differentiation were assessed by analysing Foxp3+ T-cell populations for Treg differentiation and IL-17A production for Th17 differentiation. For reactive oxygen species (ROS) production, DCFDA was used as an indicator. Dichloroacetate and AZD7545 inhibited PDHK activity of recombinant PDHK and intracellular PDH phosphorylation. DCA was capable of inducing Treg differentiation and suppressing Th17 differentiation. The effects of DCA were independent of PDHK because neither AZD7545 nor knockdown of PDHK1 or PDHK3 affected T-cell differentiation. DCA was determined to be capable of inducing ROS production, and the effects of DCA on T-cell differentiation were shown to be dependent on ROS production. Dichloroacetate possesses Treg induction and Th17 suppression, which is independent of PDHK and dependent on ROS production.

Baicalein induces CD4(+)Foxp3(+) T cells and enhances intestinal barrier function in a mouse model of food allergy.

The incidence of food allergy, which is triggered by allergen permeation of the gastrointestinal tract followed by a T-helper (Th) 2-mediated immune response, has been increasing annually worldwide. We examined the effects of baicalein (5,6,7-trihydroxyflavone), a flavonoid from Scutellaria baicalensis used in oriental herbal medicine, on regulatory T (Treg) cell induction and intestinal barrier function through the regulation of tight junctions in a mouse model of food allergy. An allergic response was induced by oral challenge with ovalbumin, and the incidence of allergic symptoms and T cell-related activity in the mesenteric lymph nodes were analyzed with and without the presence of baicalein. Our results demonstrated that the administration of baicalein ameliorated the symptoms of food allergy and attenuated serum IgE and effector T cells. However, Treg-related factors were up-regulated by baicalein. Furthermore, baicalein was shown to enhance intestinal barrier function through the regulation of tight junctions. We also found that baicalein treatment induced the differentiation of Treg cells via aryl hydrocarbon receptors (AhRs). Thus, the action of baicalein as an agonist of AhR can induce Treg differentiation and enhance barrier function, suggesting that baicalein might serve as an effective immune regulator derived from foods for the treatment of food allergy.

Differential effects of the two amino acid sensing systems, the GCN2 kinase and the mTOR complex 1, on primary human alloreactive CD4⁺ T-cells.

Amino acid deprivation activates general control nonderepressible 2 (GCN2) kinase and inhibits mammalian target of rapamycin (mTOR), affecting the immune response. In this study, the effects of GCN2 kinase activation or mTOR inhibition on human alloreactive CD4+ T-cells were evaluated. The mixed lymphocyte reaction, as a model of alloreactivity, the GCN2 kinase activator, tryptophanol (TRP), and the mTOR complex 1 inhibitor, rapamycin (RAP), were used. Both TRP and RAP suppressed cell proliferation and induced cell apoptosis. These events were p53-independent in the case of RAP, but were accompanied by an increase in p53 levels in the case of TRP. TRP decreased the levels of the Th2 signature transcription factor, GATA-3, as RAP did, yet the latter also decreased the levels of the Th1 and Th17 signature transcription factors, T-bet and RORγt, whereas it increased the levels of the Treg signature transcription factor, FoxP3. Accordingly, TRP decreased the production of interleukin (IL)-4, as RAP did, but RAP also decreased the levels of interferon-γ (IFN-γ) and IL-17. Both TRP and RAP increased the levels of IL-10. As regards hypoxia-inducible factor-1α (HIF-1α), which upregulates the Th17/Treg ratio, its levels were decreased by RAP. TRP increased the HIF-1α levels, which however, remained inactive. In conclusion, our findings indicate that, in primary human alloreactive CD4+ T-cells, the two systems that sense amino acid deprivation affect cell proliferation, apoptosis and differentiation in different ways or through different mechanisms. Both mTOR inhibition and GCN2 kinase activation exert immunosuppressive effects, since they inhibit cell proliferation and induce apoptosis. As regards CD4+ T-cell differentiation, mTOR inhibition exerted a more profound effect, since it suppressed differentiation into the Th1, Th2 and Th17 lineages, while it induced Treg differentiation. On the contrary, the activation of GCN2 kinase suppressed only Th2 differentiation.

Coenzyme Q10 Exerts Anti-Inflammatory Activity and Induces Treg in Graft Versus Host Disease.

The objective of this study was to determine whether coenzyme Q10 (CoQ10) can reduce the severity of graft versus host disease (GVHD) by inducing regulatory T cells (Tregs). CoQ10 or vehicle was orally administrated once a day for 22 days to mice with GVHD. We measured the alloresponse of the T cells and the GVHD clinical scores. Real-time polymerase chain reaction was used to examine messenger RNA (mRNA) level. Flow cytometry and enzyme-linked immunosorbent assay were used to evaluate protein expression. CoQ10 reduced the T-cell alloresponse and the expression of interferon (IFN)-γ and interleukin (IL)-17. The severity of GVHD and gene expressions of IL-6 and tumor necrosis factor (TNF)-α decreased with CoQ10 treatment. Furthermore, CoQ10 promoted weight gain and survival in GVHD mice. Flow cytometry revealed that CoQ10 dose dependently induced Treg differentiation, but FK506, an immunosuppressive drug, decreased Treg differentiation dose dependently. In conclusion, CoQ10 downregulates the alloreactivity of T cells and reduces GVHD severity, enhancing the differentiation of Tregs.

Combination therapy with metformin and coenzyme Q10 in murine experimental autoimmune arthritis

Metformin (Met) and coenzyme Q10 (CoQ10) are reported to have therapeutic functions in several inflammatory diseases. These drugs have shown anti-inflammatory effects and have been utilized in mouse models of rheumatoid arthritis (RA). However, there is no evidence of the additive effect of Met and CoQ10 in RA. Although Met and CoQ10 may be involved in the improvement of mitochondrial dysfunction, limited information is available regarding whether this effect can improve mitochondrial dysfunction in RA in particular. In this study, we sought to determine whether Met and CoQ10 attenuate the severity of collagen-induced arthritis (CIA) and show an additive effect in a mouse model. The combination of Met and CoQ10 improved CIA, reducing joint inflammation, Th17 differentiation and IgG production. In contrast, the combination of Met and CoQ10 induced Treg differentiation. Osteoclastogenesis was reduced by the combination of Met and CoQ10. The protein expression of interleukin-1β, interleukin-6 and tumor necrosis factor-alpha in mice splenocytes exposed to lipopolysaccharide decreased after drug combination therapy. We also found that the expression of JC-1 and COX IV were enhanced by treatment with the combination of Met and CoQ10. Moreover, the combination of Met and CoQ10 promoted mitochondrial O2 consumption. These findings suggest that the combination of Met and CoQ10 reduced CIA severity, improving mitochondrial dysfunction compared to Met or CoQ10 alone. These results present a novel, significant preventive targets in RA and may enhance our understanding of its pathogenesis.

Targeting JAK2 By Gene Knockout or Pacritinib Treatment Reduces Gvhd and Xenograft Rejection By Promoting Induced Treg Differentiation

Janus kinase 2 (JAK2) signal transduction is a critical mediator of immune response. JAK2 activation promotes T-cell allosensitization, as well as Th1 and Th17 differentiation. JAK2-mediated STAT3 phosphorylation limits the generation of induced regulatory T cells (iTregs) by disrupting interactions between STAT5 and Foxp3. JAK2 is implicated in the onset of graft-versus-host disease (GVHD), which is a significant cause of transplant-related mortality after allogeneic hematopoietic cell transplantation (allo-HCT). Using murine models of allo-HCT we show here that transfer of donor JAK2-/- T cells is associated with significantly less GVHD, compared with wild-type or JAK2 replete donors (Figure 1, P =.003 and 0.01, respectively). Th1 differentiation among JAK2-/- T-cells is dramatically decreased, compared with controls. Conversely, iTreg polarization and stability are significantly increased among the JAK2 deficient T cells. To investigate the effect of pharmacologic JAK2 inhibition on T-cell alloresponses, pacritinib (supplied by CTI BioPharma), was chosen as it does not induce myelosuppression or increase risk for opportunistic infections in myelofibrosis patients - unlike JAK1/JAK2 inhibitors. Pacritinib potently inhibits JAK2, but also has suppressive activity toward JAK3, CSF1R, and IRAK1. Pacritinib was administered at 100mg/kg twice a day by oral gavage for 4 weeks beginning on the day of MHC-disparate allo-HCT, significantly reducing GVHD in recipient mice compared with methylcellulose vehicle control. In allogeneic mixed leukocyte reactions using human cells, pacritinib (2.5μM) significantly reduces T-cell proliferation after 5 days of culture (P <.0001). In vitro studies verified pacritinib eliminates STAT3 activity by IL-6 in human CD4+ T-cells, while permitting IL-2 induced STAT5 phosphorylation despite its effects on JAK3. This offers a platform to reduce Th17 development, while promoting iTreg populations. As such, pacritinib dramatically suppresses Th17 differentiation reflected by RORgammaT expression among naïve CD4+ T cells stimulated by allogeneic dendritic cells (DC), compared with DMSO (P <.0001). iTregs were generated with allogeneic DCs in the presence of pacritinib or DMSO for 5 days, and then cultured with self T-cell responders and fresh DCs without additional drug exposure. The suppressive potency of either pacritinib- or DMSO-treated iTregs was similar, suggesting JAK2 is not required for iTreg function. We then evaluated whether JAK2 inhibition could prevent human skin graft rejection in an NSG mouse xenograft model. A 1x1 cm split-thickness human skin graft was transplanted onto the animal dorsally. The mice rested for 30 days after surgery to permit engraftment, then received 5x106 allogeneic peripheral blood mononuclear cells (PBMC) by intraperitoneal injection. Pacritinib was administered at the same dose and schedule for 2 weeks beginning at time of PBMC injection as tolerated by the NSG mice. The treatment significantly delayed allograft rejection by the human donor PBMCs, compared with vehicle control (Figure 2: Median graft survival 32.5 v 51 days, Day +60 survival 0% v 33.3%, pooled data from 2 experiments, n=5-6 mice per arm, P =.0011). Collectively, these data clearly identify JAK2 as a therapeutic target to control donor alloreactivity and promote iTreg responses after HCT or solid organ transplantation.*BCB and DB contributed equally to this work. [Display omitted] [Display omitted] DisclosuresSinger:CTI BioPharma, Corp: Employment, Equity Ownership.

Eosinophils from Murine Lamina Propria Induce Differentiation of Naïve T Cells into Regulatory T Cells via TGF-β1 and Retinoic Acid.

Treg cells play a crucial role in immune tolerance, but mechanisms that induce Treg cells are poorly understood. We here have described eosinophils in lamina propria (LP) that displayed high aldehyde dehydrogenase (ALDH) activity, a rate-limiting step during all-trans retinoic acid (ATRA) synthesis, and expressed TGF-β1 mRNA and high levels of ATRA. Co-incubation assay confirmed that LP eosinophils induced the differentiation of naïve T cells into Treg cells. Differentiation promoted by LP eosinophils were inhibited by blocked either TGF-β1 or ATRA. Peripheral blood (PB) eosinophils did not produce ATRA and could not induce Treg differentiation. These data identifies LP eosinophils as effective inducers of Treg cell differentiation through a mechanism dependent on TGF-β1 and ATRA.

CD4+Foxp3+ regulatory T cell differentiation mediated by endometrial stromal cell-derived TECK promotes the growth and invasion of endometriotic lesions.

Endometriosis is associated with an abnormal immune response to endometrial cells, which can facilitate the implantation and proliferation of ectopic endometrial tissue. The proportion of CD4+Foxp3+ regulatory T cells (Tregs) is significantly increased in the peritoneal fluid of women with endometriosis. The thymus-expressed chemokine TECK/CCL25 directly promotes the invasiveness of endometrial stromal cells (ESCs). The aim of this study was to investigate the effects of ESC-derived TECK on the crosstalk between Tregs and ESCs in the progress of endometriosis. We determined that the percentage of Tregs and the concentration of TECK increased in the peritoneal fluid with the progression of endometriosis. The supernatant from co-cultured human ESCs and macrophages not only induced Treg differentiation and increased Treg expression of interleukin-10 (IL-10), transforming growth factor-β (TGF-β) and CD73 by activating the AKT/STAT3 signaling pathway but also repressed Treg apoptosis by downregulating Fas and FasL expression and enhanced the Treg-mediated suppression of CD4+CD25− T cells. In addition, in vitro and in vivo trials confirmed that these effects could be inhibited by anti-TECK neutralizing Abs. The secretion of IL-10 and TGF-β by Tregs increased MMP2 expression and decreased TIMP1 expression and further stimulated the proliferation and invasion of ESCs and the growth of ectopic lesions. These results indicate that TECK derived from ESCs and macrophages upregulates the number and function of Tregs in the ectopic milieu, which contributes to endometriotic immunotolerance and high levels of ESC proliferation and invasion, thereby facilitating the progression of endometriosis.

Release of active TGF-β1 from the latent TGF-β1/GARP complex on T regulatory cells is mediated by integrin β8.

Activated T regulatory cells (Tregs) express latent TGF-β1 on their cell surface bound to GARP. Although integrins have been implicated in mediating the release of active TGF-β1 from the complex of latent TGF-β1 and latent TGF-β1 binding protein, their role in processing latent TGF-β1 from the latent TGF-β1/GARP complex is unclear. Mouse CD4(+)Foxp3(+) Treg, but not CD4(+)Foxp3(-) T cells, expressed integrin β8 (Itgb8) as detected by quantitative RT-PCR. Itgb8 expression was a marker of thymically derived (t)Treg, because it could not be detected on Foxp3(+)Helios(-) Tregs or on Foxp3(+) T cells induced in vitro. Tregs from Itgb8 conditional knockouts exhibited normal suppressor function in vitro and in vivo in a model of colitis but failed to provide TGF-β1 to drive Th17 or induced Treg differentiation in vitro. In addition, Itgb8 knockout Tregs expressed higher levels of latent TGF-β1 on their cell surface consistent with defective processing. Thus, integrin αvβ8 is a marker of tTregs and functions in a cell intrinsic manner in mediating the processing of latent TGF-β1 from the latent TGF-β1/GARP complex on the surface of tTregs.

Mesenchymal Stem Cells Alleviate Renal Ischemia/Reperfusion Injury in Mice By Inducing Regulatory Dendritic Cells.

Renal ischemia/reperfusion (I/R) injury is an inevitable consequence of kidney transplantation and can lead to fibrosis and graft failure. Mesenchymal stem cells (MSCs) have been proposed as a promising therapeutic approach for I/R injury. In this study, using a murine model of renal I/R injury, we demonstrated that administration of both syngeneic and allogeneic MSCs significantly ameliorated I/R injury. Treatment efficacy of MSCs could be attributed to inhibited I/R-induced infiltration of neutrophils macrophages, Th1 cells, elevation of serum creatinine levels, reduced renal tubular cell death, and induction of regulatory T cells (Tregs) in kidneys. Intriguingly, a distinct kidney population of CD11chiMHCIIhiCD80loCD86lo regulatory dendritic cells (DCs) was induced by MSCs. Moreover, these DCs induced Treg differentiation through transforming growth factor-b production. Further mechanistic studies demonstrated that MSC-derived inducible nitric oxide synthase played an essential role in the differentiation of DC precursors into regulatory DCs in a SOCS3-dependent manner. Taken together, our findings demonstrated, for the first time, critical regulatory properties of MSCs for induction of regulatory DCs from DC precursors in I/R injury. This study elucidates an immunoregulatory mechanism of MSCs and further lays a solid foundation for application of MSCs in acute kidney injury therapy.

M2a and M2c Macrophages Induce Treg Differentiation through the SOCS3 Pathway.

M2a and M2c Macrophages Induce Treg Differentiation through the SOCS3 Pathway.

Cutting Edge: Committed Th1 CD4+ T Cell Differentiation Blocks Pregnancy-Induced Foxp3 Expression with Antigen-Specific Fetal Loss

Pregnancy stimulates induced Foxp3 expression among maternal CD4(+) T cells with fetal specificity. Although sustained maternal regulatory CD4(+) T cell (Treg) expansion is essential for maintaining fetal tolerance during pregnancy, the necessity for Foxp3(+) cells with fetal specificity remains undefined. In this study, we demonstrate that mitigating Treg differentiation among maternal CD4(+) T cells with a single surrogate fetal specificity elicits Ag-specific fetal loss. Using recombinant Listeria monocytogenes to prime stably differentiated Th1 CD4(+) T cells with fetal I-A(b):2W1S55-68 specificity refractory to pregnancy-induced Foxp3 expression, we show that Ag delivery by cytoplasmic L. monocytogenes causes selective loss of 2W1S(+) offspring through CD4 cell- and IFN-γ-dependent pathways. In contrast, CD4(+) T cells primed by L. monocytogenes restricted from the cell cytoplasm are markedly more plastic for induced Foxp3 expression, with normal pregnancy outcomes. Thus, committed Th1 polarization blocks pregnancy induced Treg differentiation among maternal CD4(+) T cells with fetal specificity and triggers Ag-specific fetal loss.

Mesenchymal stem cells alleviate bacteria‐induced liver injury in mice by inducing regulatory dendritic cells

Fulminant hepatic failure (FHF) is a clinical syndrome characterized by sudden and severe impairment of liver function. Mesenchymal stem cells (MSCs) have been proposed as a promising therapeutic approach for FHF. In this study we used Propionibacterium acnes (P. acnes)-primed, lipopolysaccharide (LPS)-induced liver injury in mice as an animal model of human FHF. We demonstrated that administration of MSCs significantly ameliorated liver injury and improved the survival rates of mice subjected to P. acnes plus LPS-induced FHF. Allogeneic MSCs showed similar treatment efficacy as autologous MSCs did in FHF. Treatment efficacy of MSCs could be attributed to decreased infiltration and activation of CD4+ T cells in the liver, inhibition of T helper 1 cells, and induction of regulatory T cells (Tregs). Moreover, decreased DNA copies of P. acnes were detected in the liver of MSC-treated mice. Intriguingly, a distinct liver population of CD11c+MHCIIhiCD80loCD86lo regulatory dendritic cells (DCs) was induced by MSCs. Moreover, these DCs induced Treg differentiation through transforming growth factor-β production. Further mechanistic studies demonstrated that MSC-derived prostaglandin E2 and one of its receptors, EP4, played essential roles in the differentiation of CD11c+B220− DC precursors into regulatory DCs in a phosphoinositide 3-kinase-dependent manner. Conclusion: MSCs induce regulatory DCs from CD11c+B220− DC precursors. This study elucidates an immunoregulatory mechanism of MSCs and lays a foundation for application of MSCs in FHF therapy. (Hepatology 2014;59:671–682)

Differential Influences of the Aryl Hydrocarbon Receptor on Th17 Mediated Responses in vitro and in vivo

The aryl hydrocarbon receptor (AhR) has been attributed with anti-inflammatory effects in the development of pathological immune responses leading to experimental autoimmune encephalomyelitis (EAE) via the induction of regulatory T cells. In agreement with previously published findings, we find that TCDD administration confers protection from EAE, however, this immuno-modulatory effect was not the consequence of de novo Treg generation, but the inhibition of Th17 cell differentiation. Systemic application of FICZ at the time of immunization also reduced EAE pathology albeit to a lesser degree than TCDD. In vitro Th17 differentiation in the presence of AhR agonists, including TCDD, promoted IL-17 and IL-22 expression, but did not induce Treg differentiation. AhR affinity influenced the amounts of IL-17 and IL-22 protein that was secreted by Th17 cells, but did not seem to affect susceptibility to EAE in vivo. Making use of conditional AhR-deficient mice, we show that the anti-inflammatory effect of TCDD depends on AhR activation in both T cells and dendritic cells, further emphasising the ability of TCDD to interfere with T effector cell differentiation in vivo. The dichotomy between the in vivo and in vitro effects of AhR reveals the complexity of the AhR pathway, which has the capacity of affecting different AhR-expressing cell types involved in mounting immune responses, thus participating in defining their outcome.