Analysis of the role of palmitoleic acid in acute anterior uveitis

PurposeTo study the role of palmitoleic acid (PA) in the pathogenesis of acute anterior uveitis (AAU).MethodsPA levels in feces from AAU patients were measured by gas chromatography coupled with a mass spectrometer (GC-MS) and compared with samples obtained from healthy individuals. Enzyme linked immunosorbent assay (ELISA) and flow cytometry (FCM) were used to assess the effect of PA on dendritic cells (DCs) and CD4⁺T cells obtained from mice, AAU patients and healthy individuals. C57BL/6 mice were fed with PA or vehicle and experimental autoimmune uveitis (EAU) was induced with a human retinal IRBP651-670 peptide. Disease severity of EAU was evaluated by clinical manifestation and histology. Differentiation of splenic Type 1 helper T cells (Th1) and Th17 cells was evaluated by FCM. Tandem mass tag (TMT)-based proteomics analysis was used to identify differentially expressed proteins following incubation of DCs with PA.ResultsThe fecal concentration of PA was increased in AAU patients as compared with healthy individuals. In vitro, PA promoted apoptosis of DCs and inhibited the secretion of TNF-α from mouse bone-marrow-derived dendritic cells (BMDCs) as well as in DCs from AAU patients and healthy individuals. It only decreased DCs surface marker expression and IL-12p70 secretion in BMDCs and healthy individuals DCs but not in AAU patient DCs. PA-treated BMDCs inhibited Th cell differentiation from mouse naïve CD4⁺T cells and IL-17 and IFN-γ secretion in co-culture supernatants. PA also inhibited the differentiation of Th cells and secretion of IFN-γ and IL-17 in CD4⁺T cells from mice, AAU patients and healthy individuals. In vivo, PA-treated EAU mice showed milder clinical and histopathological intraocular manifestations as compared with the control group. PA feeding inhibited differentiation of splenic Th17 cells, whereas Th1 cells were not affected. Up to 30 upregulated and 77 downregulated proteins were identified when comparing PA-treated DCs with controls.ConclusionAn increased expression of fecal PA was observed in AAU patients. PA was shown to have immunoregulatory effects on DCs and CD4⁺T cells and attenuated disease severity in EAU mice.     

Therapeutic benefits of regulating inflammation in autoimmunity

Autoimmunity results from the dysregulation of the immune system leading to tissue damage. Th1 and Th17 cells are known to be cellular mediators of inflammation in autoimmune diseases. The specific cytokine milieu within the site of inflammation or within secondary lymphatic tissues is important during the priming and effector phases of T cell response. In this review, we will address the nature of the inflammatory response in the context of autoimmune disease, specifically we will discuss the role of dendritic cells following stimulation of their innate pathogen recognition receptors in directing the development of T cell responses. We will focus on how dendritic cell subsets change the balance between major players in autoimmunity, namely Th1, Th17 and regulatory T cells. Th17 cells, once thought to only act as pathogenic effectors through production of IL-17, have been shown to have regulatory properties as well with co-production of the anti-inflammatory cytokine IL-10 by a subset now referred to as regulatory Th17 cells. IL-17 is important in the induction of autoimmune diseases such as experimental autoimmune encephalomyelitis (EAE) and inflammatory bowel disease (IBD). Study of the inflammatory process following encounter with agents that stimulate the innate immune responses such as adjuvants opens a new horizon for the discovery of therapeutic agents including those derived from microorganisms. Microbial products such as adjuvants that function as TLR ligands may stimulate the immune system by interacting with Toll-like receptors (TLR) on antigen-presenting cells. Microbial agents such as Bacille Calmette-Guérin (BCG) or Freund's adjuvant (CFA) that induce a Th17 response are protective in models of autoimmune diseases particularly EAE and type 1 diabetes (T1D). The induction of innate immunity by these microbial products alters the balance in the cytokine microenvironment and may be responsible for modulation of the inflammation and protection from autoimmunity.     

Pre-differentiated Th1 and Th17 effector T cells in autoimmune gastritis: Ag-specific regulatory T cells are more potent suppressors than polyclonal regulatory T cells

Naïve antigen-specific CD4⁺ T cells (TxA23) induce autoimmune gastritis when transferred into BALB/c nu/nu mice. Transfer of in vitro pre-differentiated Th1 or Th17 TxA23 effector T cells into BALB/c nu/nu recipients induces distinct histological patterns of disease. We have previously shown that co-transfer of polyclonal naturally occurring Treg (nTreg) suppressed development of Th1-, but not Th17-mediated disease. Therefore, we analysed the suppressive capacity of different types of Treg to suppress Th1- and Th17-mediated autoimmune gastritis. We compared nTreg with polyclonal TGFβ-induced WT Treg (iTreg) or TGFβ-induced antigen-specific TxA23 iTreg in co-transfer experiments with Th1 or Th17 TxA23 effector T cells. 6 weeks after transfer in vitro pre-differentiated TxA23 Th1 and Th17 effector cells induced destructive gastritis. Th1-mediated disease was prevented by co-transfer of nTreg and also antigen-specific iTreg, whereas WT iTreg did not show an effect. However, Th17-mediated disease was only suppressed by antigen-specific iTreg. Pre-activation of nTreg in vitro prior to transfer did not increase their suppressive activity in Th17-mediated gastritis. Thus, antigen-specific iTreg are potent suppressors of autoimmune gastritis induced by both, fully differentiated Th1 and Th17 effector cells.     

The shiitake mushroom-derived immuno-stimulant lentinan protects against murine malaria blood-stage infection by evoking adaptive immune-responses

Lentinan, a (1-3)-beta glucan from Lentinus edodes, is an effective immunostimulatory drug. We tested the effects of lentinan during blood-stage infection by Plasmodium yoelii 17XL (P.y17XL). Pre-treatment of mice with lentinan significantly decreased the parasitemia and increased their survival after infection. Enhanced IL-12, IFN-γ and NO production induced by lentinan in spleen cells of infected mice revealed that the Th1 immune response was stimulated against malaria infection. In vitro and in vivo, lentinan can result in enhanced expression of MHC II, CD80/CD86, and Toll-like receptors (TLR2/TLR4), and increased production of IL-12 in spleen dendritic cells (DCs) co-cultured with parasitized red blood cells (pRBCs). Moreover, both the number of CD4⁺CD25⁺ regulatory T cells (Tregs) and the levels of IL-10 secreted by Tregs were reduced by pre-treatment with lentinan in the spleen of malaria-infected mice. Meanwhile, apoptosis of CD4⁺ T cell in spleens of mice pretreated with lentinan was significantly reduced. In summary, lentinan can induce protective Th1 immune responses to control the proliferation of malaria parasites during the blood-stage of P.y17XL infection by stimulating maturation of DCs to inhibit negative regulation of the Th1 immune response by Tregs. Taken together, our findings suggest that lentinan has prophylactic potential for the treatment of malaria.     

Current Views on the Roles of Th1 and Th17 Cells in Experimental Autoimmune Encephalomyelitis

Multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE), are autoimmune demyelinating diseases of the central nervous system (CNS). Interferon-γ-producing Th1 and interleukin-17-producing Th17 CD4⁺ T helper (Th) cells mediate disease pathogenesis in EAE and likely in MS as well. However, the relative contribution of each Th subset to autoimmune processes in the CNS remains unclear. Emerging data suggest that both Th1 and Th17 cells contribute to CNS autoimmunity, albeit through different mechanisms. A better understanding of the roles that Th1 and Th17 cells play in autoimmune inflammation will be helpful in developing new therapeutic approaches. In this review, we discuss recent findings on the roles of Th1 and Th17 cells in the pathogenesis of EAE.     

The impact of infection on the incidence of autoimmune disease

Falling infection rates in the developed world are being matched by a rapidly rising incidence of allergic and autoimmune diseases. This review explores the hypothesis that there is a causal link between these phenomena and that infections can prevent the onset of autoimmune disease. The hypothesis is discussed with particular reference to Type I diabetes in the NOD mouse and the ability of the helminth infection Schistosoma mansoni to prevent its onset. The article addresses the possible mechanisms that underly this protection. The effects of protective pathogen-derived agents on key cells of the innate immune system such as dendritic cells are distinct and include the production of anti-inflammatory cytokines such as IL-10. The most likely mechanisms by which these innate changes prevent the subsequent adaptive autoimmune destruction are: (1) the production of systemically high levels of cytokines that oppose the production of cytokines that drive the autoimmune process - possibly via the action of natural killer T (NKT) cells (2) the induction of regulatory T cells that inhibit the action of autoreactive cells and (3) the production of pathogen-specific T cells that are not autoreactive and compete with autoreactive cells for survival signals such as cytokines and T cell receptor ligation.     

Outer membrane protein A of Acinetobacter baumannii induces differentiation of CD4+ T cells toward a Th1 polarizing phenotype through the activation of dendritic cells

Acinetobacter baumannii is an increasing hospital-acquired pathogen that causes a various type of infections, but little is known about the protective immune response to this microorganism. Outer membrane protein A of A. baumannii (AbOmpA) is a major porin protein and plays an important role in pathogenesis. We analyzed interaction between AbOmpA and dendritic cells (DCs) to characterize the role of this protein in promoting innate and adaptive immune responses. AbOmpA functionally activates bone marrow-derived DCs by augmenting expression of the surface markers, CD40, CD54, B7 family (CD80 and CD86) and major histocompatibility complex class I and II. AbOmpA induces production of Th1-promoting interleukin-12 from DCs and augments the syngeneic and allogeneic immunostimulatory capacity of DCs. AbOmpA stimulates production of interferon-γ from T cells in mixed lymphocyte reactions, which suggesting Th1-polarizing capacity. CD4⁺ T cells stimulated by AbOmpA-stimulated DCs show a Th1-polarizing cytokine profile. The expression of surface markers on DCs is mediated by both mitogen-activated protein kinases and NF-κB pathways. Our findings suggest that AbOmpA induces maturation of DCs and drives Th1 polarization, which are important properties for determining the nature of immune response against A. baumannii.     

Triptolide regulates T cell-mediated immunity via induction of CD11c dendritic cell differentiation

Triptolide(TPT) isolated from one of the Chinese herbs, Tripterygium wilfordii Hook. F. (TWHF), are known to have a variety of immunomodulatory activities. This study was performed to investigate the effect of TPT on the differentiation of splenic DCs and its influence on T cell-mediated immunity regarding to DC subsets CD11c^lowI-a/e^lowCD45RB⁺(CD11c^low DCs) and CD11c^highI-a/e^highCD45RB^- (CD11c^high DCs) in male C57BL/6 mice spleens in vitro. The percentage of CD11c^low DCs was significantly increased after treatment with TPT compared to their counterparts (CD11c^high DCs). It was found that unlike the gradually decreasing interleukin (IL)-12 secretion of CD11c^high DCs induced by TPT, CD11c^low DCs showed a obvious dose-dependent response between the increasing of IL-10 production and TPT stimulation. After treatment with anti-IL-12R or anti-IL-10 monoclonal antibody in CD4⁺ T cells + CD11c^high DCs or CD11c^low DCs mixed lymphocyte reaction, the induction of these DCs on T cells was inhibited dramatically. These data demonstrated that TPT might induce the differentiation of splenic DCs to CD11c^low DCs followed by shifting of Th1 to Th2 with enhancement of T lymphocyte immune function in vitro.     

Immunomodulatory effects of vitamin D receptor ligands in autoimmune diseases

The active form of vitamin D, 1,25-Dihydroxyvitamin D3 [l,25(OH)2D3], is a secosteroid hormone that binds to the vitamin D receptor (VDR), a member of the superfamily of nuclear receptors for steroid hormones, thyroid hormone, and retinoic acid. VDR ligands regulate calcium and bone metabolism, control cell proliferation and differentiation, and exert immunoregulatory activities. The immunoregulatory properties of VDR ligands are currently exploited clinically for the topical treatment of psoriasis, a Th1 cell-mediated autoimmune disease of the skin, but recent advances in understanding their functions and novel insights into the immunomodulatory mechanisms they control suggest a wider applicability in the treatment of autoimmune diseases. In addition to direct effects on T cell activation, VDR ligands modulate with different mechanisms the phenotype and function of antigen-presenting cells (APCs), and, in particular, of dendritic cells (DCs). In vitro and in vivo experiments have shown that VDR ligands induce DCs to acquire tolerogenic properties that favor the induction of regulatory rather than effector T cells. These intriguing actions of VDR ligands have been demonstrated in several experimental models and could be exploited, in principle, to treat a variety of human autoimmune diseases.     

Bone-derived MSCs encapsulated in alginate hydrogel prevent collagen-induced arthritis in mice through the activation of adenosine A2A/2B receptors in tolerogenic dendritic cells

Tolerogenic dendritic cells (tolDCs) facilitate the suppression of autoimmune responses by differentiating regulatory T cells (Treg). The dysfunction of immunotolerance results in the development of autoimmune diseases, such as rheumatoid arthritis (RA). As multipotent progenitor cells, mesenchymal stem cells (MSCs), can regulate dendritic cells (DCs) to restore their immunosuppressive function and prevent disease development. However, the underlying mechanisms of MSCs in regulating DCs still need to be better defined. Simultaneously, the delivery system for MSCs also influences their function. Herein, MSCs are encapsulated in alginate hydrogel to improve cell survival and retention in situ, maximizing efficacy in vivo. The three-dimensional co-culture of encapsulated MSCs with DCs demonstrates that MSCs can inhibit the maturation of DCs and the secretion of pro-inflammatory cytokines. In the collagen-induced arthritis (CIA) mice model, alginate hydrogel encapsulated MSCs induce a significantly higher expression of CD39⁺CD73⁺ on MSCs. These enzymes hydrolyze ATP to adenosine and activate A_2A/2B receptors on immature DCs, further promoting the phenotypic transformation of DCs to tolDCs and regulating naïve T cells to Tregs. Therefore, encapsulated MSCs obviously alleviate the inflammatory response and prevent CIA progression. This finding clarifies the mechanism of MSCs-DCs crosstalk in eliciting the immunosuppression effect and provides insights into hydrogel-promoted stem cell therapy for autoimmune diseases.     

Molecular control of pathogenic Th17 cells in autoimmune diseases

IL-17A-producing CD4⁺ T helper cells (Th17) are crucial for the development of inflammatory and autoimmune diseases and thus are exploited for clinical immunotherapies. Emerging evidence suggests Th17 cells are heterogeneous and able to adopt both pathogenic and non-pathogenic phenotypes which are shaped by environmental and genetic factors. On one hand, IL-6 in concert with TGFβ1 can induce non-pathogenic Th17 cells (non-pTh17), which are not effective in inducing tissue inflammation. On the other hand, IL-6, IL-1β with IL-23 induce pathogenic Th17 cells (pTh17) to induce immune pathologies in various tissues. Th17 cells could be both pathogenic and non-pathogenic in a content-dependent manner in vivo. Understanding how the generation and pathogenicity of pTh17 cells are regulated will aid us to devise more effective immunotherapy. In this review, we summarize recent advances in the differentiation and regulation of Th17 cells especially pTh17 cells in vitro and in vivo. The emerging results revealing the specific molecular control of pTh17 cells are highlighted.     

Cortistatin as a potential multistep therapeutic agent for inflammatory disorders

The induction of immune tolerance is critical for the prevention of autoimmunity and the maintenance of immune homeostasis. The identification of factors involved in the maintenance or restoration of such tolerance has become the focus of new therapies for inflammatory and autoimmune diseases. Cortistatin, a recently discovered cyclic neuropeptide related to somatostatin, has emerged as a potential endogenous antiinflammatory factor based on its production by, as well as its binding to, immune cells. Thus, cortistatin has been found to downregulate the inflammatory response mediated by activated macrophages. The present work reviews various recent studies involving different experimental models of sepsis, rheumatoid arthritis and inflammatory bowel disease, demonstrating that cortistatin treatment offers great benefits at both the clinical and pathological levels. These include the downregulation of both inflammatory and Th1-mediated autoimmune disease components and the emergence of regulatory T cells (Treg) that suppress autoreactive T cells, both of which contribute to the restoration of immune tolerance. While many questions need to be resolved, cortistatin appears to be an exciting and promising candidate for the treatment of several chronic inflammatory diseases and autoimmune disorders.     

Synthetic glycolipid ligands for human iNKT cells as potential therapeutic agents for immunotherapy

Invariant natural killer T (iNKT) cells are an attractive therapeutic target in autoimmune diseases, since they play a major role in immune regulation. iNKT cells recognize glycolipid antigens presented by CD1d molecules that resemble the non-polymorphic MHC class I protein. alpha-galactosylceramide (alpha-GalCer) isolated from marine sponge has long been used as a prototype iNKT cell ligand in the laboratory. As alpha-GalCer is the most efficacious ligand for iNKT cells, its potential to treat autoimmune disease has been evaluated in animal models. Previous studies showed that alpha-GalCer effectively suppressed disease in some autoimmunity models, but not in others. This inconsistency may be attributed to the ability of alpha-GalCer to induce the production of both proinflammatory Th1 and anti-inflammatory Th2 cytokines by iNKT cells. To overcome this issue, we and other groups have synthesized new, unnatural glycolipids by modifying the structure of alpha-GalCer. These efforts have led to an identification of glycolipid compounds that provoke the production of Th2 (but not Th1) cytokines by iNKT cells. Among these novel ligands, an alpha-GalCer analogue named OCH, which contains a truncated sphingosine chain, induces a Th2 biased response by murine iNKT cells. Here we describe that OCH also polarizes human iNKT cells towards Th2, which opens up a new avenue for the clinical application of glycolipid compounds in treating of autoimmune diseases such as multiple sclerosis. The pursuit of synthetic glycolipid antigens has the great potential to lead to a better understanding of the regulatory effects of human iNKT cells and development of a new therapeutic agent for autoimmune diseases.     

Toll-like receptor-positive cells and recognition of pathogens: how human myeloid dendritic cells respond to in vitro infection with Leishmania infantum

Dendritic cells (DCs), instructed by the priming signals from microbial factors, can produce interleukin (IL)-12p70 and promote T helper (Th)1 proliferation and interferon (IFN)-gamma production. This event seems to be critical for the containment of infections caused by intracellular pathogens, even including Leishmania infection. In the present in vitro study we have investigated: 1) phagocytic capacities and IL-12 production by human monocyte-derived DCs and macrophages (M?s), infected with Leishmania infantum promastigotes; 2) IFN-gamma production by human CD4+ T cells co-incubated with DCs or macrophages pulsed with live promastigotes. Monocyte-derived myeloid DCs and M?s from healthy donors were infected with live metacyclic Leishmania infantum (MON-1) promastigotes, previously opsonized with 5% autologous serum, at 1:4 cell/parasite ratio. Percentage and index of phagocytosis were calculated after 2, 24 and 48 h of incubation. IL-12 production was evaluated by an ELISA in supernatants from 48 h Leishmania-infected or lipopolysaccharides (LPS)-stimulated DCs and M?s, also in the presence of phytohemagglutinin-activated or inactivated CD4+ T cells. For IFN-gamma production, CD4+ T cells were repeatedly stimulated with DCs or M?s, pulsed with live Leishmania promastigotes or activated with LPS. The number of IFN-gamma-secreting cells was evaluated by an ELISpot assay. Results showed that M?s have a higher phagocytic capacity towards L. infantum promastigotes than DCs. Moreover, unlike M?s, Leishmania-infected DCs were able to release IL-12p70; this production significantly increased in the presence of activated CD4+ T cells. Finally, DCs pulsed with live parasites and added to autologous CD4+ T cells induced a higher number of IFN-gamma-secreting cells than M?s, thus indicating their ability to polarize Th cells toward the Th1 subset. These data indicate that DCs are able to promote protective Th1 immune responses in our experimental model of Leishmania infantum infection, thus representing the grounds for initiating immunoterapeutic and vaccinal strategies.     

Peptide immunotherapies in Type 1 diabetes: lessons from animal models

Insulin dependent diabetes mellitus (Type 1 diabetes, T1D) is a chronic autoimmune disorder characterized by the destruction of insulin-producing pancreatic beta cells by proinflammatory autoreactive T cells. In the past, several therapeutic approaches have been exploited by immunologists aiming to regulate the autoimmune response; this can occur by deleting lymphocyte subsets and/or re-establishing immune tolerance via activation of regulatory T cells. The use of broad immunosuppressive drugs was the first approach to be explored. Subsequently, antibody-based immunotherapies failed to discriminate between autoreactive versus non-autoimmune effectors. Antigen-based immunotherapy is a third approach developed to manipulate beta cell autoimmunity. This approach allows the selective targeting of disease-relevant T cells, while leaving the remainder of the immune system intact. Animal models have been successfully employed to prevent or treat T1D by injection of either the self proteins or peptides derived from them. Peptide immunotherapies have been mainly experimented in the NOD mouse spontaneous model of disease. In this review we therefore report the main approaches that rely on the use of peptides obtained from relevant autoantigens such as glutamic acid decarboxylase, isoform 65 (GAD65), insulin, proinsulin and islet-specific glucose 6 phosphatase catalytic subunit-related protein (IGRP). Protective peptides have proven to be effective in treating or delaying the diabetic process. We also highlight the main difficulties encountered in extrapolating data to guide clinical translational investigations in humans.     

Pathophysiology of interleukin-23 in experimental autoimmune encephalomyelitis

Interleukin-23 (IL-23) is a heterodimeric cytokine that is composed of a p40 subunit, shared with the closely related cytokine IL-12, and a smaller IL-23p19 subunit. It belongs to a family of heterodimeric cytokines that also includes IL-12 and IL-27. Experimental autoimmune encephalomyelitis (EAE) is an autoimmune disease that serves as a model for multiple sclerosis, an inflammatory demyelinating disease of the central nervous system that is a frequent cause of disability in young adults. EAE is thought to be initiated by CD4+ T cells. The production of interferon-gamma and tumor necrosis factor-alpha (T helper 1 [Th1] phenotype) was considered a marker for the ability of such cells to induce disease. Consistent with this view, IL-12, a cytokine that induces the differentiation of Th1 cells, was considered essential for EAE susceptibility. However, it is now clear that IL-23 rather than IL-12 is required for EAE susceptibility. IL-23 induces a population of IL-17-producing cells that is more critically involved in EAE pathogenesis than Th1 cells. Here, we review the role of the IL-23 system in the pathophysiology of EAE.     

A novel antagonist of the prostaglandin E2 EP4 receptor inhibits Th1 differentiation and Th17 expansion and is orally active in arthritis models

Background and purpose:

Rheumatoid arthritis (RA) is an autoimmune disorder involving subsets of activated T cells, in particular T helper (Th) 1 and Th17 cells, which infiltrate and damage tissues and induce inflammation. Prostaglandin E₂ (PGE₂) enhances the Th17 response, exacerbates collagen-induced arthritis (CIA) and promotes inflammatory pain. The current study investigated whether selective antagonism of the PGE₂ EP₄ receptor would suppress Th1/Th17 cell development and inflammatory arthritis in animal models of RA.

Experimental approach:

Effects of PGE₂ and a novel EP₄ receptor antagonist ER-819762 on Th1 differentiation, interleukin-23 (IL-23) production by dendritic cells (DCs), and Th17 development were assessed in vitro. The effect of ER-819762 was evaluated in CIA and glucose-6-phosphate isomerase (GPI)-induced arthritis models. In addition, the effects of ER-819762 on pain were evaluated in a model of chronic inflammatory pain induced by complete Freund''s adjuvant (CFA) in the rat.

Key results:

Stimulation of the EP₄ receptor enhanced Th1 differentiation via phosphatidylinositol 3 kinase signalling, selectively promoted Th17 cell expansion, and induced IL-23 secretion by activated DCs, effects suppressed by ER-819762 or anti-PGE₂ antibody. Oral administration of ER-19762 suppressed Th1 and Th17 cytokine production, suppressed disease in collagen- and GPI-induced arthritis in mice, and suppressed CFA-induced inflammatory pain in rats.

Conclusion and implications:

PGE₂ stimulates EP₄ receptors to promote Th1 differentiation and Th17 expansion and is critically involved in development of arthritis in two animal models. Selective suppression of EP₄ receptor signalling may have therapeutic value in RA both by modifying inflammatory arthritis and by relieving pain.     

Paeoniflorin suppresses IL-6/Stat3 pathway via upregulation of Socs3 in dendritic cells in response to 1-chloro-2,4-dinitrobenze

Mounting evidence has suggested that inflammation is associated with IL-6/Stat3 pathway in dendritic cells (DCs) and Th17 cells, which are critical for development of allergic contact dermatitis (ACD). Paeoniflorin (PF) has been clinically proved to be effective in the treatment of inflammatory skin diseases such as ACD. We have previously demonstrated the effect of PF on DCs stimulated with 1-chloro-2,4-dinitrobenze (DNCB) and naïve CD4⁺ CD45RA⁺ T cells for Th17 cell differentiation. However, whether PF down-regulates IL-6/Stat3 in DCs and Th17 cells remains to be explored. In this study, we show clearly that PF markedly decreases IL-6/Stat3 in DCs stimulated with DNCB at both gene and protein levels compared with control DCs in vitro. Meanwhile, PF up-regulates suppressor of cytokine signaling 3 (Socs3). Such decreased expression of IL-6/Stat3 is abolished in DCs that were transfected with Socs3 short interfering RNA (siRNA). When mice CD4⁺ CD45 RA⁺ T cells were co-cultured with PF-treated DCs stimulated with/without DNCB, the gene expression of the Th17 cell markers such as retinoic acid-related orphan nuclear hormone receptor γt (RORγt), IL-17A, and IL-23R decreased, in accordance with the less secretions of IL-17 and IL-23 in vitro and in vivo. Finally, the suppressed Th17 differentiation induced by PF can be abolished by additional recombinant mouse IL-6. Our results suggest that the anti-inflammatory mechanisms introduced by depletion of Socs3 expression or inactivation of the negative regulator such as Socs3 may represent a promising strategy for the prevention of ACD.     

Dendritic cells treated with a prostaglandin I2 analog,iloprost, promote antigen-specific regulatory T cell differentiation in mice

Iloprost, a stable prostaglandin I₂ (PGI₂) analog, can inhibit allergic inflammation in an ovalbumin (OVA)-induced asthma model via inhibition of airway dendritic cell (DC) function. However, the underlying mechanism of PGI₂ signaling-mediated immunosuppression remains unclear. This study explored whether iloprost-treated DCs can suppress inflammation by promoting antigen-specific regulatory T cell (Treg) differentiation through PGI₂-G-protein-coupled receptor (IP). We established an allergic lung inflammation model using a hydrogel biomaterial delivery system and observed that iloprost significantly suppressed OVA-induced Th2 lung inflammation and increased the frequency of OVA-specific Tregs in vivo. We further observed that iloprost-treated DCs displayed tolerogenic characteristics, including low inflammatory cytokine (IL-12, TNF-α, IL-6, IL-23) expression levels, high anti-inflammatory cytokine (IL-10) production, and a semimature phenotype. In addition, iloprost-treated DCs increased OVA-specific CD4⁺Foxp3⁺ T cell differentiation from naïve T cells in an IP-dependent pathway in vitro and in vivo. Blocking experiments showed that iloprost-treated DCs promoted Treg differentiation, at least in part, through programmed death ligand 1 (PD-L1), whereas iloprost-induced PD-L1 expression in DCs was through the IP receptor. Furthermore, iloprost treatment suppressed DC-mediated airway inflammation and increased the frequency of OVA-specific Tregs through PD-L1 in vivo. Taken together, these results show that PGI₂-IP signaling mediated by iloprost in DCs may lead to immune tolerance, suggesting that the PGI₂ analog has the potential to be applied therapeutically for tolerogenic DC immunotherapy in autoimmune diseases or allergic asthma.