Dendritic cells transduced with SOCS-3 exhibit a tolerogenic/DC2 phenotype that directs type 2 Th cell differentiation in vitro and in vivo

New insight into the role of SOCS family in immune regulation and autoimmune pathogenesis

BACKGROUND

Suppressor of cytokine signaling (SOCS) proteins regulate signal transduction by interacting with cytokine receptors and signaling proteins and targeting associated proteins for degradation. Recent studies have demonstrated that the SOCS proteins serve as crucial inhibitors in cytokine signaling networks and play a pivotal role in both innate and adaptive immune responses.

AIM OF REVIEW

In this review, we aim to discuss recent advancements in understanding the complex functions of SOCS proteins in various immune cells, as well as the effects of SOCS proteins in human health and diseases. Increasing evidence indicates that SOCS proteins are frequently dysregulated in developing autoimmune diseases, suggesting that therapeutic targeting of SOCS proteins could provide clinical benefit.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This review provides a comprehensive understanding of SOCS proteins in immune regulation and autoimmune pathogenesis, it also highlights the role of SOCS-related mimetic peptides in immunotherapy.

Immunomodulatory and growth-promoting effects of Rauwolfia serpentina root powder in broiler chicks challenged with Salmonella Gallinarum

Background

Amid growing concern about antimicrobial resistance due to the irrational use of antibiotics in treating common poultry diseases, particularly Salmonella which is a foodborne pathogen in humans. This study investigates the effects of ethnoveterinary supplementation of Rauwolfia serpentina (L. Benth. ex Kurz) powder (RSP) on three key immune-related genes; Suppressor of cytokine signaling 3 (SOCS3), the quiescence-related gene P20K (P20K), and the major histocompatibility complex Class IIβ (MHC class IIβ), gut morphology and growth performance of broiler chicks infected with Salmonella Gallinarum.

Methods

Two hundred and forty day-old Hubbard classic chickens were randomly assigned to four groups: non-challenged control (NC), and Salmonella Gallinarum challenge group (SGC), and two treatment groups fed a basic diet supplemented with 1.5% Rauwolfia serpentina powder (RSP) with SGC (RSP-1) and 3% RSP with SGC (RSP-2), respectively, from day 3 till 28 days of age. Each treatment was replicated 4 times with 15 bird/replicate pen. On day 7, all the birds in the RSP-1, RSP-2 and SGC groups received 1 ml of BHI broth containing 2 × 108 CFU of Salmonella Gallinarum via oral gavage. While control birds received an equivalent volume of sterile BHI broth. Gene expression analysis was conducted using real-time PCR to measure the expression of key immune-related genes: SOCS3, P20K, and MHC Class IIβ in spleen, liver, and caeca. Additionally, histopathological assessments of gut and growth performance parameters including feed intake, body weight gain, and feed conversion ratio (FCR) were monitored throughout the experimental period.

Result

The gene expression analysis at 3 and 21 days post-challenge revealed that SGC birds had significantly higher SOCS3, P20K, and lower MHC class IIβ expression (p < 0.001) in the caecum, liver, and spleen of broiler chickens. In contrast, the RSP-1 and RSP-2 groups showed significantly lower SOCS3 and P20K expression (p < 0.001), alongside improved gut morphology, weight gain, and FCR compared to the SGC group, with these benefits increasing over time.

Conclusion

In conclusion, these findings suggest that Rauwolfia serpentina supplementation modulates key immune-related gene expression (SOCS3, P20K, and MHC class IIβ), enhances intestinal health, and improves growth performance in broilers challenged with Salmonella Gallinarum.

GPR41 deficiency aggravates type 1 diabetes in streptozotocin-treated mice by promoting dendritic cell maturation

Disturbances in intestinal immune homeostasis predispose susceptible individuals to type 1 diabetes (T1D). G-protein-coupled receptor 41 (GPR41) is a receptor for short-chain fatty acids (SCFAs) mainly produced by gut microbiota, which plays key roles in maintaining intestinal homeostasis. In this study, we investigated the role of GPR41 in the progression of T1D. In non-obese diabetic (NOD) mice, we found that aberrant reduction of GPR41 expression in the pancreas and colons was associated with the development of T1D. GPR41-deficient (Gpr41-/-) mice displayed significantly exacerbated streptozotocin (STZ)-induced T1D compared to wild-type mice. Furthermore, Gpr41-/- mice showed enhanced gut immune dysregulation and increased migration of gut-primed IFN-γ+ T cells to the pancreas. In bone marrow-derived dendritic cells from Gpr41-/- mice, the expression of suppressor of cytokine signaling 3 (SOCS) was significantly inhibited, while the phosphorylation of STAT3 was significantly increased, thus promoting dendritic cell (DC) maturation. Furthermore, adoptive transfer of bone marrow-derived dendritic cells (BMDC) from Gpr41-/- mice accelerated T1D in irradiated NOD mice. We conclude that GPR41 is essential for maintaining intestinal and pancreatic immune homeostasis and acts as a negative regulator of DC maturation in T1D. GPR41 may be a potential therapeutic target for T1D.

TIM-3 increases the abundance of type-2 dendritic cells during Leishmania donovani infection by enhancing IL-10 production via STAT3

The outcome of the disease visceral leishmaniasis (VL), caused by Leishmania donovani (LD), largely relies on the relative dominance of host-protective type-1 T helper (Th1) cell response versus disease-promoting type-2 T helper (Th2) cell response. The Th1 and Th2 responses, in turn, are believed to be elicited by type-1 conventional dendritic cells (cDC1) and type-2 conventional DCs (cDC2), respectively. However, it is still unknown which DC subtype (cDC1 or cDC2) predominates during chronic LD infection and the molecular mechanism governing such occurrence. Here we report that in chronically infected mice, the splenic cDC1-cDC2 balance shifted toward the cDC2 subtype and that the receptor T cell immunoglobulin and mucin protein-3 (TIM-3) expressed by DCs played a key role in mediating this effect. Transfer of TIM-3-silenced DCs in fact prevented the predominance of the cDC2 subtype in mice with chronic LD infection. We also found that LD actually upregulated TIM-3 expression on DCs by triggering a TIM-3-mediated signaling pathway STAT3 (signal transducer and activator of transcription 3)→interleukin (IL)-10→c-Src→transcription factors Ets1, Ets2, USF1, and USF2. Notably, TIM-3 promoted STAT3 activation via a non-receptor tyrosine kinase Btk. Adoptive transfer experiments further demonstrated a critical role for STAT3-driven TIM-3 upregulation on DCs in increasing cDC2 abundance in chronically infected mice, which ultimately aided disease pathogenesis by augmenting Th2 responses. These findings document a new immunoregulatory mechanism contributing to disease pathology during LD infection and define TIM-3 as a key mediator of this process.

Cavin-1 promotes M2 macrophages/microglia polarization via SOCS3

PURPOSE

Our study aimed to investigate the function of Cavin-1 and SOCS3 in macrophages/microglia M2 polarization and further explored the relevant mechanism.

METHODS

Expression levels of Cavin-1 and SOCS3 in macrophages/microglia were measured by western blotting and RT-PCR, respectively. Then, Cavin-1 or SOCS3 was gene silenced by a siRNA approach, and gene silencing efficiency was determined by western blotting. Next, co-immunoprecipitation (Co-IP) was employed to further analyze the interaction between Cavin-1 and SOCS3. Finally, the activation of STAT6/PPAR-γ signaling was evaluated using western blotting, and the M2 macrophages/microglia polarization was validated by measuring the mRNA expression of M2 markers by RT-PCR.

RESULTS

In the polarization process of macrophages/microglia to M2 phenotype, both Cavin-1 and SOCS3 increased synchronously at protein and mRNA level, reached the peak at the 6 h, and then decreased. After Cavin-1 or SOCS3 silencing, the expression of Cavin-1 and SOCS3 declined. These results suggested that Cavin-1 and SOCS3 were positively correlated in macrophages/microglia, and this conjecture was verified by Co-IP. Besides, Cavin-1 silencing not only suppressed the activation of STAT6/PPAR-γ pathway, but also suppressed the release of anti-inflammatory factors. Finally, we found that SOCS3 overexpression reversed the inhibitory effect of Cavin-1 silencing on the release of anti-inflammatory factors in M2 macrophages/microglia.

CONCLUSIONS

Cavin-1 and SOCS3 are actively involved in the process of M2 macrophages/microglia polarization. As a SOCS3 interacting protein, Cavin-1 can promote M2 macrophages/microglia polarization via SOCS3.

Differential immunological response detected in mRNA expression profiles among diverse chicken lines in response to Salmonella challenge

Salmonella enterica serovar Enteritidis is a bacterial pathogen that contributes to poultry production losses and human foodborne illness. The bacterium elicits a broad immune response involving both the innate and adaptive components of the immune system. Coordination of the immune response is largely directed by cytokines. The objective of the current study was to characterize the expression of a select set of cytokines and regulatory immune genes in three genetically diverse chicken lines after infection with S. Enteritidis. Leghorn, Fayoumi and broiler day-old chicks were orally infected with pathogenic S. Enteritidis or culture medium. At 2 and 18 h postinfection, spleens and ceca were collected and mRNA expression levels for 7 genes (GM-CSF, IL2, IL15, TGF-β1, SOCS3, P20K, and MHC class IIβ) were evaluated by real-time quantitative PCR. Genetic line had a significant effect on mRNA expression levels of IL15, TGF-β1, SOCS3 and P20K in the spleen and on P20K and MHC class IIβ in the cecum. Comparing challenged vs. unchallenged birds, the expression of SOCS3 and P20K mRNA were significantly higher in the spleen and cecum, while MHC class IIβ mRNA was significantly lower in spleen. Combining the current RNA expression results with those of previously reported studies on the same samples reveals distinct RNA expression profiles among the three genetic chicken lines and the 2 tissues. This study illustrates that these diverse genetic lines have distinctively different immune response to S. Enteritidis challenge within the spleen and the cecum.

Targeting cancer-associated fibroblast-secreted WNT2 restores dendritic cell-mediated antitumour immunity

OBJECTIVE

Solid tumours respond poorly to immune checkpoint inhibitor (ICI) therapies. One major therapeutic obstacle is the immunosuppressive tumour microenvironment (TME). Cancer-associated fibroblasts (CAFs) are a key component of the TME and negatively regulate antitumour T-cell response. Here, we aimed to uncover the mechanism underlying CAFs-mediated tumour immune evasion and to develop novel therapeutic strategies targeting CAFs for enhancing ICI efficacy in oesophageal squamous cell carcinoma (OSCC) and colorectal cancer (CRC).

DESIGN

Anti-WNT2 monoclonal antibody (mAb) was used to treat immunocompetent C57BL/6 mice bearing subcutaneously grafted mEC25 or CMT93 alone or combined with anti-programmed cell death protein 1 (PD-1), and the antitumour efficiency and immune response were assessed. CAFs-induced suppression of dendritic cell (DC)-differentiation and DC-mediated antitumour immunity were analysed by interfering with CAFs-derived WNT2, either by anti-WNT2 mAb or with short hairpin RNA-mediated knockdown. The molecular mechanism underlying CAFs-induced DC suppression was further explored by RNA-sequencing and western blot analyses.

RESULTS

A negative correlation between WNT2⁺ CAFs and active CD8⁺ T cells was detected in primary OSCC tumours. Anti-WNT2 mAb significantly restored antitumour T-cell responses within tumours and enhanced the efficacy of anti-PD-1 by increasing active DC in both mouse OSCC and CRC syngeneic tumour models. Directly interfering with CAFs-derived WNT2 restored DC differentiation and DC-mediated antitumour T-cell responses. Mechanistic analyses further demonstrated that CAFs-secreted WNT2 suppresses the DC-mediated antitumour T-cell response via the SOCS3/p-JAK2/p-STAT3 signalling cascades.

CONCLUSIONS

CAFs could suppress antitumour immunity through WNT2 secretion. Targeting WNT2 might enhance the ICI efficacy and represent a new anticancer immunotherapy.

Possible involvement of female sex steroid hormones in intracellular signal transduction mediated by cytokines following traumatic brain injury

INTRODUCTION

The aim of this study was to determine the anti-inflammatory effect of female sex hormones on the level of intracellular molecules of cytokine signaling pathway after diffuse traumatic brain injury (TBI) in ovariectomized rats.

METHODS

Female rats were divided into 10 groups: control, sham, TBI, Vehicle (oil), Vehicle E1 (33.3 µg/kg), E2 (1 mg / kg), P1 (1.7 mg/kg), P2 (8 mg / kg), E2 + P1. All drugs were injected 0.5 h after TBI. Brain edema and the brain levels of P-STAT-3, NFκB-P52, NFκB-P65, P-IκB, and SOCS-3 by immunohistochemistry measured at 24 h after TBI.

RESULTS

Increased brain edema after TBI was inhibited by different doses of estrogen, progesterone (P < 0.001), and E2 + P1 (P < 0.05). The brain levels of P-STAT-3, NFκB-P52, NFκB-P65, and p-IκBα that increased after TBI was decreased only by E2 (P < 0.05). E2 and E2 + P1 have increased the SOCS-3 level after TBI (P < 0.05). Also, there was a difference between the E2 with E1 and two progesterone doses (P < 0.05). So that in all cases, the effects of E2 were more significant than the other groups. The target cells for these effects of E2 were microglia and astrocytes.

CONCLUSION

The results indicate that one of the probable mechanism(s) of estrogen anti-inflammatory effect after TBI is either reduction of p-STAT-3, NFκB-P52, p-NFκB-P65, and p-IκBα or increase in SOCS-3 molecules involved in the signaling pathway of inflammatory cytokines.

IFN-γ inhibits ovarian cancer progression via SOCS1/JAK/STAT signaling pathway

PURPOSE

Ovarian cancer (OC) is a common malignancy, and IFN-γ, a multifunctional cytokine, is unveiled to impede the multiplication and enhance apoptosis in diverse tumor cells in previous research. Nonetheless, its function and mechanism in OC are blurred.

METHODS

OC cell lines SKOV3 and OVCAR3 were dealt with different concentrations (0-40 ng/ml) of IFN-γ. CCK-8 experiment was utilized to examine cell multiplication; Flow cytometry was executed to detect apoptosis and cell cycle; Wound healing assay was utilized to detect cell migration; and Transwell experiment was implemented to examine cell invasion. qRT-PCR analysis was applied to detect STAT5, STAT3, JAK2 and JAK3 mRNA expression in OC cell lines. Western blot experiment was applied to detect the protein and phosphorylation levels of SOCS1, STAT5 and STAT3.

RESULTS

IFN-γ suppressed OC cell multiplication in a concentration-dependent manner. Relative to the control group, IFN-γ restrained OC cell migration, invasion, enhanced apoptosis and prevented cell transformation from G0/G1 to S phase. Further analysis revealed that IFN-γ up-modulated SOCS1 expression and impeded STAT5 and STAT3 protein phosphorylation levels, and knockdown of SOCS1 partially counteracted the inhibitory effect of IFN-γ on STAT5 and STAT3 protein phosphorylation levels.

CONCLUSION

IFN-γ represses OC progression by facilitating SOCS1 to suppress STAT3 and STAT5 protein phosphorylation.

Distinctive waves of innate immune response in the retina in experimental autoimmune encephalomyelitis

Neurodegeneration mediates neurological disability in inflammatory demyelinating diseases of the CNS. The role of innate immune cells in mediating this damage has remained controversial with evidence for destructive and protective effects. This has complicated efforts to develop treatment. The time sequence and dynamic evolution of the opposing functions are especially unclear. Given limits of in vivo monitoring in human diseases such as multiple sclerosis (MS), animal models are warranted to investigate the association and timing of innate immune activation with neurodegeneration. Using noninvasive in vivo retinal imaging of experimental autoimmune encephalitis (EAE) in CX3CR1^GFP/+–knock-in mice followed by transcriptional profiling, we are able to show 2 distinct waves separated by a marked reduction in the number of innate immune cells and change in cell morphology. The first wave is characterized by an inflammatory phagocytic phenotype preceding the onset of EAE, whereas the second wave is characterized by a regulatory, antiinflammatory phenotype during the chronic stage. Additionally, the magnitude of the first wave is associated with neuronal loss. Two transcripts identified — growth arrest–specific protein 6 (GAS6) and suppressor of cytokine signaling 3 (SOCS3) — might be promising targets for enhancing protective effects of microglia in the chronic phase after initial injury.

Increased expression of IFN-γ in preeclampsia impairs human trophoblast invasion via a SOCS1/JAK/STAT1 feedback loop

The weakening of extravillous trophoblast (EVT) invasion results in shallow placenta implantation. In HTR8/SVneo cells, IFN-γ can activate STAT1 and reduce cell invasion, and suppressor of cytokine signaling (SOCS) is an important negative regulatory protein in the Janus kinase (JAK)/STAT activator pathway and has a negative feedback function on JAK/STAT1. The aim of the present study was to elucidate how SOCS1 feedback regulates JAK/STAT1 and affects EVT cell invasion, which in turn affects the development of preeclampsia (PE). MTT and Annexin V/phosphatidylserine (PS) assays were performed to evaluate the viability and apoptosis of HTR8/SVneo cells treated with IFN-γ, respectively. Wound healing and invasion assays were also conducted to measure the migratory and invasive abilities of IFN-γ-treated HTR8/SVneo cells. The mRNA and protein expression levels of genes were detected using reverse transcription-quantitative PCR and western blot analysis. Small interfering RNA knockdown of SOCS1 was used to verify the role of feedback regulation in the IFN-γ-activated JAK/STAT1 signaling pathway. IFN-γ can inhibit HTR8/SVneo migration and invasion, and promote apoptosis by increasing the expression of phosphorylated (p)-JAK, p-STAT1 and caspase3, and reducing the expression of platelet-derived growth factor receptor A and Ezrin. Furthermore, SOCS1 may negatively regulate JAK/STAT1 and affect HTR-8/SVneo invasiveness. Evaluation of clinical samples demonstrated that the expression levels of SOCS1 and IFN-γ were higher in patients with PE compared with the healthy group. Collectively, the present results indicated that IFN-γ reduced the invasion of HTR-8/SVneo cells by activating JAK/STAT1, concurrently leading to an increase in SOCS1, which negatively regulates JAK/STAT1 and eliminates the pro-inflammatory effects of IFN-γ, thus forming a feedback loop.

H. pylori modulates DC functions via T4SS/TNFα/p38-dependent SOCS3 expression

Background

Helicobacter pylori (H. pylori) is a gram-negative bacterium that chronically infects approximately 50% of the world’s human population. While in most cases the infection remains asymptomatic, 10% of infected individuals develop gastric pathologies and 1–3% progress to gastric cancer. Although H. pylori induces severe inflammatory responses, the host’s immune system fails to clear the pathogen and H. pylori can persist in the human stomach for decades. As suppressor of cytokine signaling (SOCS) proteins are important feedback regulators limiting inflammatory responses, we hypothesized that H. pylori could modulate the host’s immune responses by inducing SOCS expression.

Methods

The phenotype of human monocyte-derived DCs (moDCs) infected with H. pylori was analyzed by flow cytometry and multiplex technology. SOCS expression levels were monitored by qPCR and signaling studies were conducted by means of Western blot. For functional studies, RNA interference-based silencing of SOCS1–3 and co-cultures with CD4⁺ T cells were performed.

Results

We show that H. pylori positive gastritis patients express significantly higher SOCS3, but not SOCS1 and SOCS2, levels compared to H. pylori negative patients. Moreover, infection of human moDCs with H. pylori rapidly induces SOCS3 expression, which requires the type IV secretion system (T4SS), release of TNFα, and signaling via the MAP kinase p38, but appears to be independent of TLR2, TLR4, MEK1/2 and STAT proteins. Silencing of SOCS3 expression in moDCs prior to H. pylori infection resulted in increased release of both pro- and anti-inflammatory cytokines, upregulation of PD-L1, and decreased T-cell proliferation.

Conclusions

This study shows that H. pylori induces SOCS3 via an autocrine loop involving the T4SS and TNFα and p38 signaling. Moreover, we demonstrate that high levels of SOCS3 in DCs dampen PD-L1 expression on DCs, which in turn drives T-cell proliferation.

A Uromodulin Mutation Drives Autoimmunity and Kidney Mononuclear Phagocyte Endoplasmic Reticulum Stress

We identified a family with a UMOD gene mutation (C106F) resulting in glomerular inflammation and complement deposition. To determine if the observed phenotype is due to immune system activation by mutant uromodulin, a mouse strain with a homologous cysteine to phenylalanine mutation (C105F) in the UMOD gene was generated using CRISPR-Cas9 gene editing and the effect of this mutation on mononuclear phagocytic cells was examined. Mutant mice developed high levels of intracellular and secreted aggregated uromodulin, resulting in anti-uromodulin antibodies and circulating uromodulin containing immune complexes with glomerular deposition and kidney fibrosis with aging. F4/80⁺ and CD11c⁺ kidney cells phagocytize uromodulin. Differential gene expression analysis by RNA sequencing of F4/80⁺ phagocytic cells revealed activation of the activating transcription factor 5 (ATF5)-mediated stress response pathway in mutant mice. Phagocytosis of mutant uromodulin by cultured dendritic cells resulted in activation of the endoplasmic reticulum stress response pathway and markers of cell inactivation, an effect not seen with wild-type protein. Mutant mice demonstrate a twofold increase in T-regulatory cells, consistent with induction of immune tolerance, resulting in decreased inflammatory response and improved tissue repair following ischemia-reperfusion injury. The C105F mutation results in autoantibodies against aggregated misfolded protein with immune complex formation and kidney fibrosis. Aggregated uromodulin may induce dendritic cell tolerance following phagocytosis through an unfolded protein/endoplasmic reticulum stress response pathway, resulting in decreased inflammation following tissue injury.

Curcumin Regulates Anti-Inflammatory Responses by JAK/STAT/SOCS Signaling Pathway in BV-2 Microglial Cells

Microglia play important physiological roles in central nervous system (CNS) homeostasis and in the pathogenesis of inflammatory brain diseases. Inflammation stimulates microglia to secrete cytokines and chemokines that guide immune cells to sites of injury/inflammation. Neuroinflammation is also strongly implicated in the pathogenesis of a number of neurodegenerative diseases, including Alzheimer’s disease and Parkinson’s disease, for which nutritional intervention could represent a benefit due to a lack of clinically efficacious drugs. To this end, the anti-inflammatory mechanisms of several phytochemicals, including curcumin, have been extensively studied. The present experiments show that the administration of curcumin is able to increase the production of the anti-inflammatory cytokines, IL-4 and IL-10, in murine BV-2 microglial cells treated with lipopolysaccharide (LPS). Consistent with these data, curcumin stimulation upregulates the expression of Suppressors of cytokine signaling (SOCS)-1, whereas phosphorylation of the JAK2 and STAT3 was reduced. Taken together, these results provide evidence that curcumin is able to regulate neuroinflammatory reactions by eliciting anti-inflammatory responses in microglia through JAK/STAT/SOCS signaling pathway modulation.

Role of SOCS3 in enhanced acute-phase protein genes by neonatal macrophages in response to IL-6

BACKGROUND

Interleukin 6 (IL-6) induce the inflammatory response directly related with the morbidity and mortality of neonatal. Here we aimed to explore the mechanism of IL-6 in neonatal inflammatory response by studying the IL-6/STAT3 signaling pathway.

METHODS

Cord blood samples from health term neonatal and peripheral venous blood from health volunteers were collected. The monocytes of adults and cord blood were isolated and induced into macrophages. Then the macrophages were pretreated with or without MG132 before IL-6 stimulation. Proteins were analyzed by Western blot, mRNA by real time PCR and membrane molecule by flow cytometry.

RESULTS

The acute phase protein gene expression in neonatal macrophages after stimulated with IL-6 were higher than that in adult. Significantly enhanced phosphorylation of STAT3 was seen in neonatal macrophages. Both mRNA and protein expression of SOCS3 in neonatal macrophages were lower than that in adult. After pretreated with MG132, the expression of SOCS3 protein was increased which lead to attenuate the STAT3 phosphorylation and APP gene expression.

CONCLUSION

Neonatal exhibit an enhanced expression of downstream target genes and IL-6/STAT3 signal pathway which is related with the diminished SOCS3. This provides a new sight into inflammatory responses in neonatal.

The Mycobacterium tuberculosis glycoprotein Rv1016c protein inhibits dendritic cell maturation, and impairs Th1 /Th17 responses during mycobacteria infection

The myobacterial factors and the associated mechanism by which Mycobacterium tuberculosis (Mtb) evades the host immune surveillance system remain widely unexplored. Here, we found that overexpressing Rv1016c, a mannosylated protein of M. tuberculosis in BCG (rBCG-Rv1016c) led to increased virulence of the recombined BCG in the severe-combined immunodeficient (SCID) mice model and to a loss of protective efficacy in a zebrafish-M. marinum model, compared to wild type BCG. Further investigations on the effects of rBCG-Rv1016c on the host innate immunity revealed that rBCG-Rv1016c decreased the production of cytokines IL-2, IL-12p70, TGF-β, IL-6 as well as of the co-stimulatory molecules CD80, CD86, MHC-I and MHC-II by the infected DCs. These effects were mimicked by rBCG-Rv1016cHis, which carried an extra 6-His tag at the C-terminus of Rv1016c. Relatively to BCG infected DCs, the rBCG-Rv1016c-infected DCs failed to polarize naïve T cells to Th1- and Th17-type cells to secret IFN-γ and IL-17. Additionally, T lymphocytes from BCG- infected mice showed significantly less proliferation and production of IFN-γ and IL-17. Similarly, rBCG-Rv1016c mice released a higher level of IL-10 in response to rBCG-Rv1016c stimulation than wild type BCG infected mice. Furthermore, DCs from TLR-2 knockout mice showed no reduction in IL-6, IL-12 p70 and TGF-β secretion in response to rBCG-Rv1016c infection, compared to DCs infected with BCG. We propose that Rv1016c interferes in differentiation of the DCs by targeting suppressor of cytokine signaling (SOCS) 1 and SOCS3 expression, which subsequently leads to the reduction in STAT-1 and STAT-6 phosphorylation. These findings open new perspectives regarding the immunosuppressive strategies adopted by Mtb to survive in the host.

Tolerising cellular therapies: what is their promise for autoimmune disease?

The current management of autoimmunity involves the administration of immunosuppressive drugs coupled to symptomatic and functional interventions such as anti-inflammatory therapies and hormone replacement. Given the chronic nature of autoimmunity, however, the ideal therapeutic strategy would be to reinduce self-tolerance before significant tissue damage has accrued. Defects in, or defective regulation of, key immune cells such as regulatory T cells have been documented in several types of human autoimmunity. Consequently, it has been suggested that the administration of ex vivo generated, tolerogenic immune cell populations could provide a tractable therapeutic strategy. Several potentially tolerogenic cellular therapies have been developed in recent years; concurrent advances in cell manufacturing technologies promise scalable, affordable interventions if safety and efficacy can be demonstrated. These therapies include mesenchymal stromal cells, tolerogenic dendritic cells and regulatory T cells. Each has advantages and disadvantages, particularly in terms of the requirement for a bespoke versus an 'off-the-shelf' treatment but also their suitability in particular clinical scenarios. In this review, we examine the current evidence for these three types of cellular therapy, in the context of a broader discussion around potential development pathway(s) and their likely future role. A brief overview of preclinical data is followed by a comprehensive discussion of human data.

Novel immune signatures associated with dysplastic naevi and primary cutaneous melanoma in human skin

Dysplastic naevi (DN) are benign lesions with atypical features intermediate between that of common melanocytic naevi (CMN) and malignant melanoma (MM). Debate remains over whether DN represent progressive lesions from CMN. Through gene expression profiling and analysis of molecular gene signatures, our study revealed progressive increases in immune activation and regulation, along with pathways implicated in melanomagenesis, from CMN to DN to MM. Using criteria of 1.5-fold change and false discovery rate ≤0.05, we found differential expression of 7186 probes (6370 unique genes) with the largest difference detected between DN and MM from the standpoint of genomic melanoma progression. Despite progressive increases in the T-helper type 1 (Th1)-inducing gene (IL-12), RT-PCR indicated impaired Th1 or cytotoxic T-cell response (decreased IFN-γ) in MM. Concordantly, our results indicated progressive increases in molecular markers associated with regulatory T cells, exhausted T cells and tolerogenic dendritic cells, including detection of increased expression of suppressor of cytokine signalling 3 (SOCS3) in dendritic cells associated with MM. All together, our findings suggest that the increased immunosuppressive microenvironment of melanoma may contribute to unhampered proliferation of neoplastic cells. In addition, the detection of increased markers associated with tolerogenic dendritic cells in MM suggests that targeting these suppressive immune cell types may represent an alternative avenue for future immunotherapy.

Searching for the Transcriptomic Signature of Immune Tolerance Induction-Biomarkers of Safety and Functionality for Tolerogenic Dendritic Cells and Regulatory Macrophages

The last years have witnessed a breakthrough in the development of cell-based tolerance-inducing cell therapies for the treatment of autoimmune diseases and solid-organ transplantation. Indeed, the use of tolerogenic dendritic cells (tolDC) and regulatory macrophages (Mreg) is currently being tested in Phase I and Phase II clinical trials worldwide, with the aim of finding an effective therapy able to abrogate the inflammatory processes causing these pathologies without compromising the protective immunity of the patients. However, there exists a wide variety of different protocols to generate human tolDC and Mreg and, consequently, the characteristics of each product are heterogeneous. For this reason, the identification of biomarkers able to define their functionality (tolerogenicity) is of great relevance, on the one hand, to guarantee the safety of tolDC and Mreg before administration and, on the other hand, to compare the results between different cell products and laboratories. In this article, we perform an exhaustive review of protocols generating human tolDC and Mreg in the literature, aiming to elucidate if there are any common transcriptomic signature or potential biomarkers of tolerogenicity among the different approaches. However, and although several effectors seem to be induced in common in some of the most reported protocols to generate both tolDC or Mreg, the transcriptomic profile of these cellular products strongly varies depending on the approach used to generate them.

MBD2-mediated Th17 differentiation in severe asthma is associated with impaired SOCS3 expression

T helper 17 (Th17) cells has proven to be crucial in the pathogenesis of severe asthma. Although it is known that Suppressor of cytokine signaling 3 (SOCS3) is involved in differentiation of Th17 cells but, how it affects severe asthma is uncertain. Since previous studies indicated that Methtyl-CpG binding domain protein 2 (MBD2) null mice was deficient in Th17 cell differentiation, the aim of the present study was to understand how MBD2 interacts with SOCS3 to regulate Th17 cell differentiation in severe asthma. Here, we show that SOCS3 expression was significantly decreased in Th17-mediated severe asthmatic mice, accompanied by elevated STAT3 phosphorylation and RORγt expression. Knock-down of SOCS3 promoted the differentiation of naïve T cells into Th17 cells through STAT3/RORγt pathway. Meanwhile, MBD2 was overexpressed in Th17-mediated severe asthmatic mice. Intervention of MBD2 expression lead to a negative change of SOCS3 expression, whereas the differentiation of Th17 cells showed positive change. In addition, MBD2 knockout (MBD2-KO) mice displayed increased SOCS3 expression and decreased Th17 differentiation after severe asthma modeling. Taken together, our results suggest that MBD2 might facilitate Th17 cell differentiation via down-regulating SOCS3 expression in severe asthma. These findings uncover new roles for SOCS3 and MBD2, and provide a potential target for treatment of severe asthma.

Lymphocytic choriomeningitis virus infection of dendritic cells interferes with TLR-induced IL-12/IL-23 cytokine production in an IL-10 independent manner

Dendritic cells produce IL-12 and IL-23 in response to viral and bacterial infection and these cytokines are responsible for successful pathogen clearance. How sequential viral and bacterial infections affect the production of IL-12 and IL-23 is currently not known. Our study demonstrates that in dendritic cells infected with Lymphocytic choriomeningitis virus (LCMV), TLR activation with bacterial PAMPs resulted in reduced IL-12 and IL-23 expression compared to non-infected cells. Furthermore, expression of other proinflammatory cytokines, TNF-α and IL-6, were not inhibited under these conditions. We discovered that TLR-induced phosphorylation of p38 was significantly inhibited in LCMV-infected cells. We detected enhanced expression of suppressor of cytokine signalling (SOCS)-3 and IL-10. Yet, neutralizing IL-10 did not restore IL-12/IL-23 expression. Taken together, these results show that virus infection interferes with the magnitude of TLR-mediated inflammatory responses by repressing specific cytokine expression.

Tolerogenic Transcriptional Signatures of Steady-State and Pathogen-Induced Dendritic Cells

Dendritic cells (DCs) are key directors of tolerogenic and immunogenic immune responses. During the steady state, DCs maintain T cell tolerance to self-antigens by multiple mechanisms including inducing anergy, deletion, and Treg activity. All of these mechanisms help to prevent autoimmune diseases or other hyperreactivities. Different DC subsets contribute to pathogen recognition by expression of different subsets of pattern recognition receptors, including Toll-like receptors or C-type lectins. In addition to the triggering of immune responses in infected hosts, most pathogens have evolved mechanisms for evasion of targeted responses. One such strategy is characterized by adopting the host’s T cell tolerance mechanisms. Understanding these tolerogenic mechanisms is of utmost importance for therapeutic approaches to treat immune pathologies, tumors and infections. Transcriptional profiling has developed into a potent tool for DC subset identification. Here, we review and compile pathogen-induced tolerogenic transcriptional signatures from mRNA profiling data of currently available bacterial- or helminth-induced transcriptional signatures. We compare them with signatures of tolerogenic steady-state DC subtypes to identify common and divergent strategies of pathogen induced immune evasion. Candidate molecules are discussed in detail. Our analysis provides further insights into tolerogenic DC signatures and their exploitation by different pathogens.

Opportunities for Translation from the Bench: Therapeutic Intervention of the JAK/STAT Pathway in Neuroinflammatory Diseases

Pathogenic CD4+ T cells and myeloid cells play critical roles in the pathogenesis of multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE), an animal model of MS. These immune cells secrete aberrantly high levels of pro-inflammatory cytokines that pathogenically bridge the innate and adaptive immune systems and damage neurons and oligodendrocytes. These cytokines include interleukin-2 (IL-2), IL-6, IL-12, IL-21, IL-23, granulocyte macrophage-colony stimulating factor (GM-CSF), and interferon-γ (IFN-γ). It is, therefore, not surprising that both the dysregulated expression of these cytokines and the subsequent activation of their downstream signaling cascades is a common feature in MS/EAE. The Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway is utilized by numerous cytokines for signal transduction and is essential for the development and regulation of immune responses. Unbridled activation of the JAK/STAT pathway by pro-inflammatory cytokines has been demonstrated to be critically involved in the pathogenesis of MS/EAE. In this review, we discuss recent advancements in our understanding of the involvement of the JAK/STAT signaling pathway in the pathogenesis of MS/EAE, with a particular focus on therapeutic approaches to target the JAK/STAT pathway.

Increased expression of negative regulators of cytokine signaling during chronic HIV disease cause functionally exhausted state of dendritic cells

Mechanisms of functional impairment of dendritic cells (DCs) during chronic HIV-1 infection are not well understood. In order to understand this phenomenon, we aimed to study the expression of negative regulators of cytokine signaling and correlate with DC exhaustion during chronic HIV-1 disease. Monocyte-derived DCs (mo-DCs) from 27 HIV-1 infected patients (CD4+ T-cell counts: 429±44 cells/μL, plasma viral load: Log₁₀3.9±1.0copies/ml) and 19 healthy controls (HCs) were stimulated ex vivo with TLR4 agonist, lipopolysaccharide (LPS) for 2days to evaluate their functional fitness. The expression of a set of genes associated with cytokine signaling was evaluated in a custom designed PCR array by Real-Time PCR. The mo-DCs from HIV-1 infected patients depicted functional exhaustion as evident by decreased allo-stimulation index (mean±SD: 10±6 vs. 24±16) (p<0.05), decreased cytokine production (pg/ml) (IL-12: 4.6±16 vs. 25±85; TNF-α: 128±279 vs. 286±544; IL-10: 6±12 vs. 13±20; IL-8: 10,688±11,748 vs. 17,470±125,049) and retained endocytosis (1.1±0.3 vs. 1.0±0.29) (p<0.05) even after LPS-stimulation, as compared to HCs. Significantly upregulated expression of SOCS-1 (mean±SD fold change: 2.2±2vs.0.8±0.6), SOCS-3 (6.3±7.4vs.1.4±0.4), PIAS-1 (1.6±0.1vs.1.0±0.3) and SHP-1 (0.8±0.4vs.0.4±0.2) correlated positively with PD-L1 expression in these DCs (Spearman's coefficient, SOCS-1: 0.63, SOCS-3: 1.0 and PIAS-1: 0.7) (p<0.05). The expression of these molecules trended positively with plasma viral load and negatively with CD4+ T-cell counts. These findings suggest that the upregulation of negative regulatory factors during chronic HIV disease have profound down-modulatory effects on DC functions and establishment of an overall exhausted state. Understanding mechanisms causing upregulation of these factors may lead to the design of new generation therapeutics based on silencing of their gene expression.

Curcumin Suppressed Activation of Dendritic Cells via JAK/STAT/SOCS Signal in Mice with Experimental Colitis

Dendritic cells (DCs) play a pivotal role as initiators in the pathogenesis of inflammatory bowel disease and are regulated by the JAK/STAT/SOCS signaling pathway. As a potent anti-inflammatory compound, curcumin represents a viable treatment alternative or adjunctive therapy in the management of chronic inflammatory bowel disease (IBD). The mechanism of curcumin treated IBD on DCs is not completely understood. In the present study, we explored the mechanism of curcumin treated experimental colitis by observing activation of DCs via JAK/STAT/SOCS signaling pathway in colitis mice. Experimental colitis was induced by 2, 4, 6-trinitrobenzene sulfonic acid. After 7 days treatment with curcumin, its therapeutic effect was verified by decreased colonic weight, histological scores, and remitting pathological injury. Meanwhile, the levels of major histocompatibility complex class II and DC costimulatory molecules (CD83, CD28, B7-DC, CD40, CD40 L, and TLR2) were inhibited and followed the up-regulated levels of IL-4, IL-10, and IFN-γ, and down-regulated GM-CSF, IL-12p70, IL-15, IL-23, and TGF-β1. A key finding was that the phosphorylation of the three members (JAK2, STAT3, and STAT6) of the JAK/STAT/SOCS signaling pathway was inhibited, and the three downstream proteins (SOCS1, SOCS3, and PIAS3) from this pathway were highly expressed. In conclusion, curcumin suppressed the activation of DCs by modulating the JAK/STAT/SOCS signaling pathway to restore immunologic balance to effectively treat experimental colitis.

A novel role for RGMa in modulation of bone marrow-derived dendritic cells maturation induced by lipopolysaccharide

Repulsive guidance molecule a (RGMa) is known to mediate immune responses and has been indicated to modulates T cell activation and autoimmune diseases by dendritic cells (DCs), which hints its significant function in the latter cells. The aim of our study, therefore, was to evaluate the function of RGMa in DC maturation. We found that small interfering RNA (siRNA) successfully silenced the expression of RGMa in DCs. Even after LPS stimulation, RGMa-silenced DCs displayed an immature morphology, characterized by small, round cells with a few cell processes and organelles, and many pinocytotic vesicles. In the presence of LPS, RGMa siRNA transfection markedly reduced levels of CD80, CD86, CD40, and MHC II expression, as well as the secretion of IL-12p70 and TNF-α. With LPS treatment, RGMa siRNA-transfected DCs also showed increased levels of IL-10 and endocytosis. Moreover, in the presence of LPS, RGMa siRNA-transfected DCs displayed a low ability to induce T cell proliferation and differentiation, compared with negative control (NTi)-transfected or control DCs (p<0.05 for both). We conclude that after LPS stimulation, RGMa siRNA-transfected DCs show immunoregulatory and tolerogenic characteristics, which provides new insights into the immune system.

Therapeutic effect of baicalin on experimental autoimmune encephalomyelitis is mediated by SOCS3 regulatory pathway

Natural compounds derived from medicinal plants have long been considered a rich source of novel therapeutic agents. Baicalin (Ba) is a bioactive flavonoid compound derived from the root of Scutellaria baicalensis, an herb widely used in traditional medicine for the treatment of various inflammatory diseases. In this study, we investigate the effects and mechanism of action of Ba in experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS). Ba treatment effectively ameliorated clinical disease severity in myelin oligodendrocyte glycoprotein (MOG)35–55 peptide-induced EAE, and reduced inflammation and demyelination of the central nervous system (CNS). Ba reduced infiltration of immune cells into the CNS, inhibited expression of proinflammatory molecules and chemokines, and prevented Th1 and Th17 cell differentiation via STAT/NFκB signaling pathways. Further, we showed that SOCS3 induction is essential to the effects of Ba, given that the inhibitory effect of Ba on pathogenic Th17 responses was largely abolished when SOCS3 signaling was knocked down. Taken together, our findings demonstrate that Ba has significant potential as a novel anti-inflammatory agent for therapy of autoimmune diseases such as MS.

Translational utility of experimental autoimmune encephalomyelitis: recent developments

Multiple sclerosis (MS) is a complex autoimmune condition with firmly established genetic and environmental components. Genome-wide association studies (GWAS) have revealed a large number of genetic polymorphisms in the vicinity of, and within, genes that associate to disease. However, the significance of these single-nucleotide polymorphisms in disease and possible mechanisms of action remain, with a few exceptions, to be established. While the animal model for MS, experimental autoimmune encephalomyelitis (EAE), has been instrumental in understanding immunity in general and mechanisms of MS disease in particular, much of the translational information gathered from the model in terms of treatment development (glatiramer acetate and natalizumab) has been extensively summarized. In this review, we would thus like to cover the work done in EAE from a GWAS perspective, highlighting the research that has addressed the role of different GWAS genes and their pathways in EAE pathogenesis. Understanding the contribution of these pathways to disease might allow for the stratification of disease subphenotypes in patients and in turn open the possibility for new and individualized treatment approaches in the future.

Vibrio cholerae porin OmpU induces LPS tolerance by attenuating TLR-mediated signaling

Porins can act as pathogen-associated molecular patterns, can be recognized by the host immune system and modulate immune responses. Vibrio choleraeporin OmpU aids in bacterial survival in the human gut by increasing resistance against bile acids and anti-microbial peptides. V. choleraeOmpU is pro-inflammatory in nature. However, interestingly, it can also down-regulate LPS-mediated pro-inflammatory responses. In this study, we have explored how OmpU-pretreatment affects LPS-mediated responses. Our study indicates that OmpU-pretreatment followed by LPS-activation does not induce M2-polarization of macrophages/monocytes. Further, OmpU attenuates LPS-mediated TLR2/TLR6 signaling by decreasing the association of TLRs along with recruitment of MyD88 and IRAKs to the receptor complex. This results in decreased translocation of NFκB in the nucleus. Additionally, OmpU-pretreatment up-regulates expression of IRAK-M, a negative regulator of TLR signaling, in RAW 264.7 mouse macrophage cells upon LPS-stimulation. Suppressor cytokine IL-10 is partially involved in OmpU-induced down-regulation of LPS-mediated TNFα production in human PBMCs. Furthermore, OmpU-pretreatment also affects macrophage function, by enhancing phagocytosis in LPS-treated RAW 264.7 cells, and down-regulates LPS-induced cell surface expression of co-stimulatory molecules. Altogether, OmpU causes suppression of LPS-mediated responses by attenuating the LPS-mediated TLR signaling pathway.

Dendritic cells: The warriors upfront-turned defunct in chronic hepatitis C infection

Hepatitis C virus (HCV) infection causes tremendous morbidity and mortality with over 170 million people infected worldwide. HCV gives rise to a sustained, chronic disease in the majority of infected individuals owing to a failure of the host immune system to clear the virus. In general, an adequate immune response is elicited by an efficient antigen presentation by dendritic cells (DCs), the cells that connect innate and adaptive immune system to generate a specific immune response against a pathogen. However, HCV seems to dysregulate the activity of DCs, making them less proficient antigen presenting cells for the optimal stimulation of virus-specific T cells, hence interfering with an optimal anti-viral immune response. There are discordant reports on the functional status of DCs in chronic HCV infection (CHC), from no phenotypic or functional defects to abnormal functions of DCs. Furthermore, the molecular mechanisms behind the impairment of DC function are even so not completely elucidated during CHC. Understanding the mechanisms of immune dysfunction would help in devising strategies for better management of the disease at the immunological level and help to predict the prognosis of the disease in the patients receiving antiviral therapy. In this review, we have discussed the outcomes of the interaction of DCs with HCV and the mechanisms of DC impairment during HCV infection with its adverse effects on the immune response in the infected host.

Guard of delinquency? A role of microglia in inflammatory neurodegenerative diseases of the CNS

Activation of microglia and inflammation-mediated neurotoxicity are believed to play an important role in the pathogenesis of several neurodegenerative disorders, including multiple sclerosis. Studies demonstrate complex functions of activated microglia that can lead to either beneficial or detrimental outcomes, depending on the form and the timing of activation. Combined with genetic and environmental factors, overactivation and dysregulation of microglia cause progressive neurotoxic consequences which involve a vicious cycle of neuron injury and unregulated neuroinflammation. Thus, modulation of microglial activation appears to be a promising new therapeutic target. While current therapies do attempt to block activation of microglia, they indiscriminately inhibit inflammation thus also curbing beneficial effects of inflammation and delaying recovery. Multiple signaling cascades, often cross-talking, are involved in every step of microglial activation. One of the key challenges is to understand the molecular mechanisms controlling cytokine expression and phagocytic activity, as well as cell-specific consequences of dysregulated cytokine expression. Further, a better understanding of how the integration of multiple cytokine signals influences the function or activity of individual microglia remains an important research objective to identify potential therapeutic targets for clinical intervention to promote repair.

Involvement of the janus kinase/signal transducer and activator of transcription signaling pathway in multiple sclerosis and the animal model of experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) and its animal model of experimental autoimmune encephalomyelitis (EAE) are characterized by focal inflammatory infiltrates into the central nervous system, demyelinating lesions, axonal damage, and abundant production of cytokines that activate immune cells and damage neurons and oligodendrocytes, including interleukin-12 (IL-12), IL-6, IL-17, IL-21, IL-23, granulocyte macrophage-colony stimulating factor, and interferon-gamma. The Janus Kinase/Signal Transducer and Activator of Transcription (JAK/STAT) signaling pathway mediates the biological activities of these cytokines and is essential for the development and regulation of immune responses. Dysregulation of the JAK/STAT pathway contributes to numerous autoimmune diseases, including MS/EAE. The JAK/STAT pathway is aberrantly activated in MS/EAE because of excessive production of cytokines, loss of expression of negative regulators such as suppressors of cytokine signaling proteins, and significant enrichment of genes encoding components of the JAK/STAT pathway, including STAT3. Specific JAK/STAT inhibitors have been used in numerous preclinical models of MS and demonstrate beneficial effects on the clinical course of disease and attenuation of innate and adaptive immune responses. In addition, other drugs such as statins, glatiramer acetate, laquinimod, and fumarates have beneficial effects that involve inhibition of the JAK/STAT pathway. We conclude by discussing the feasibility of the JAK/STAT pathway as a target for neuroinflammatory diseases.

Interleukin-4 affects the mature phenotype and function of rat bone marrow-derived dendritic cells

Granulocyte macrophage‑colony stimulating factor (GM‑CSF), and GM‑CSF plus interleukin‑4 (GM‑CSF + IL‑4) are two commonly‑used cytokine therapies for the generation of bone marrow‑derived dendritic cells (DCs). However, the mechanisms underlying IL‑4 involvement in DC generation and maturation remain unclear. In order to investigate the effect of IL‑4 on DC generation, DCs from rat bone marrow progenitors were generated using GM‑CSF, with and without IL‑4. GM‑CSF + IL‑4 DCs exhibited more mature phenotypes, and the levels of naïve allogeneic T cell stimulation were greater compared with GM‑CSF DCs. Phosphorylated signal transducer and activator of transcription 6 (p‑STAT6), the active form of STAT6, was expressed in GM‑CSF + IL‑4 DCs but not in GM‑CSF DCs. The present study demonstrated that IL‑4 influences DC morphology and immune function, and that this process may be associated with the activation of STAT6.

Skewing dendritic cell differentiation towards a tolerogenic state for recovery of tolerance in rheumatoid arthritis

To date, the available options to treat autoimmune diseases such as rheumatoid arthritis (RA) include traditional corticoids and biological drugs, which are not exempt of adverse effects. The development of cellular therapies based on dendritic cells with tolerogenic functions (TolDCs) has opened a new possibility to efficiently eradicate symptoms and control the immune response in the field of autoimmunity. TolDCs are an attractive tool for antigen-specific immunotherapy to restore self-tolerance in RA and other autoimmune disorders. A promising strategy is to inject autologous self-antigen-loaded TolDCs, which are able to delete or reprogram autoreactive T cells. Different protocols for the generation of stable human TolDCs have been established and the therapeutic effect of TolDCs has been investigated in multiple rodent models of arthritis. Pilot studies in humans confirmed that TolDC application is safe, encouraging clinical trials using self-antigen-loaded TolDCs in RA patients. Although an abundance of molecular regulators of DC functions has been discovered in the last decade, no master regulator of tolerogenicity has been identified yet. Further research is required to define biomarkers or key regulators of tolerogenicity that might facilitate the induction and monitoring of TolDCs.

Adiponectin receptor signaling on dendritic cells blunts antitumor immunity

Immune escape is a fundamental trait of cancer. Dendritic cells (DC) that interact with T cells represent a crucial site for the development of tolerance to tumor antigens, but there remains incomplete knowledge about how DC-tolerizing signals evolve during tumorigenesis. In this study, we show that DCs isolated from patients with metastatic or locally advanced breast cancer express high levels of the adiponectin receptors AdipoR1 and AdipoR2, which are sufficient to blunt antitumor immunity. Mechanistic investigations of ligand-receptor interactions on DCs revealed novel signaling pathways for each receptor. AdipoR1 stimulated IL10 production by activating the AMPK and MAPKp38 pathways, whereas AdipoR2 modified inflammatory processes by activating the COX-2 and PPARγ pathways. Stimulation of these pathways was sufficient to block activation of NF-κB in DC, thereby attenuating their ability to stimulate antigen-specific T-cell responses. Together, our findings reveal novel insights into how DC-tolerizing signals evolve in cancer to promote immune escape. Furthermore, by defining a critical role for adiponectin signaling in this process, our work suggests new and broadly applicable strategies for immunometabolic therapy in patients with cancer.

Quantitative analysis of the suppressors of cytokine signaling 1 and 3 in peripheral blood leukocytes of patients with multiple sclerosis

Multiple sclerosis (MS) is an autoimmune disease characterized by a triad of inflammation, demyelination and gliosis. Because the suppressors of cytokine signaling (Socs) regulate the immune response, we quantified SOCS1 and SOCS3 transcription in peripheral blood leukocytes of patients with MS. SOCS1 transcription decreased significantly in MS patients compared with neurologically healthy persons (0.08±0.02 vs. 1.02±0.23; p=0.0001); while SOCS3 transcription increased in MS patients compared with controls (2.76±0.66 vs. 1.03±0.27; p=0.0008). Our results showed an imbalance of SOCS1 and SOCS3 transcription in MS patients, and a moderated negative correlation between them (Spearman's r=-0.57; p=0.0003).

SOCS signaling in autoimmune diseases: molecular mechanisms and therapeutic implications

Suppressor of cytokine signaling (SOCS) proteins are mainly induced by various cytokines and have been described as classical inhibitors of cytokine signaling. SOCS signaling is involved in the regulation of immune cells, and recent findings suggest that SOCS proteins, especially SOCS1 and SOCS3, are often dysregulated in a wide variety of autoimmune diseases, including systemic lupus erythematosus, rheumatoid arthritis, type 1 diabetes, psoriasis, and multiple sclerosis. Recent studies suggest that SOCS signaling could be therapeutically targeted in various autoimmune diseases. In this review, we discuss recent studies on the role of SOCS proteins in the development and pathogenesis of autoimmune diseases, as well as their clinical implications.

SOCS3, a Major Regulator of Infection and Inflammation

In this review, we describe the role of suppressor of cytokine signaling-3 (SOCS3) in modulating the outcome of infections and autoimmune diseases as well as the underlying mechanisms. SOCS3 regulates cytokine or hormone signaling usually preventing, but in some cases aggravating, a variety of diseases. A main role of SOCS3 results from its binding to both the JAK kinase and the cytokine receptor, which results in the inhibition of STAT3 activation. Available data also indicate that SOCS3 can regulate signaling via other STATs than STAT3 and also controls cellular pathways unrelated to STAT activation. SOCS3 might either act directly by hampering JAK activation or by mediating the ubiquitination and subsequent proteasome degradation of the cytokine/growth factor/hormone receptor. Inflammation and infection stimulate SOCS3 expression in different myeloid and lymphoid cell populations as well as in diverse non-hematopoietic cells. The accumulated data suggest a relevant program coordinated by SOCS3 in different cell populations, devoted to the control of immune homeostasis in physiological and pathological conditions such as infection and autoimmunity.

Endothelin receptor antagonist exacerbates autoimmune myocarditis in mice

AIMS

Myocarditis and subsequent dilated cardiomyopathy are major causes of heart failure in young adults. Experimental autoimmune myocarditis (EAM) is a mouse model of post-infectious myocarditis and inflammatory cardiomyopathy. The pathological role of endothelin (ET) in myocarditis has not been elucidated.

MAIN METHODS

EAM was induced by immunization of cardiac myosin peptide with complete Freund's adjuvant on days 0 and 7 in BALB/c mice. An ETA/ETB dual receptor antagonist, SB209670, was administered by a continuous infusion from a subcutaneous pump for 2 weeks.

KEY FINDINGS

An increase in the heart-to-body weight ratio was observed in SB209670-treated mice compared with vehicle-treated mice. Heart pathology in SB209670-treated mice was remarkable for gross inflammatory infiltration, in contrast to the lesser inflammation in the hearts of vehicle-treated mice. We found that an ET blockade decreased the number of Foxp3(+) regulatory T cells in the heart. The ET blockade also inhibited the expression of the suppressor of cytokine signaling 3 that plays a key role in the negative regulation of both Toll-like receptor- and cytokine receptor-mediated signaling. EAM is a CD4(+) T cell-mediated disease. CD4(+) T cells isolated from SB209670-treated EAM mice produced less IL-10 and more inflammatory cytokines, IL-6 and IL-17, than those isolated from vehicle-treated mice.

SIGNIFICANCE

The ET receptor antagonist exacerbated autoimmune myocarditis in mice. Our novel findings suggest that ET may play an important role in the regulation of inflammation in myocarditis.

Novel mechanisms underlying the immediate and transient global tolerization of splenic dendritic cells after vaccination with a self-antigen

Dendritic cells (DCs) are important orchestrators of the immune response, ensuring that immunity against pathogens is generated, whereas immunity against healthy tissues is prevented. Using the tumor Ag MUC1, we previously showed that i.v. immunization of MUC1 transgenic mice, but not wild-type, with a MUC1 peptide resulted in transient tolerization of all splenic DCs. These DCs did not upregulate costimulatory molecules and induced regulatory T cells rather than effector T cells. They were characterized by suppressed expression of a cohort of pancreatic enzymes not previously reported in DCs, which were upregulated in DCs presenting the same MUC1 peptide as a foreign Ag. In this article, we examined the self-antigen-tolerized DC phenotype, function, and mechanisms responsible for inducing or maintaining their tolerized state. Tolerized DCs share some characteristics with immature DCs, such as a less inflammatory cytokine/chemokine profile, deficient activation of NF-κB, and sustained expression of zDC and CCR2. However, tolerized DCs demonstrated a novel inducible expression of aldehyde dehydrogenase 1/2 and phospho-STAT3. Suppressed expression of one of the pancreatic enzymes, trypsin, in these DC impeded their ability to degrade extracellular matrix, thus affecting their motility. Suppressed metallopeptidases, reflected in low expression of carboxypeptidase B1, prevented optimal Ag-specific CD4(+) T cell proliferation suggesting their role in Ag processing. Tolerized DCs were not refractory to maturation after stimulation with a TLR3 agonist, demonstrating that this tolerized state is not terminally differentiated and that tolerized DCs can recover their ability to induce immunity to foreign Ags.

Latency-associated protein Acr1 impairs dendritic cell maturation and functionality: a possible mechanism of immune evasion by Mycobacterium tuberculosis

Mycobacterium tuberculosis (M. tuberculosis) in latently infected individuals survives and thwarts the attempts of eradication by the immune system. During latency, Acr1 is predominantly expressed by the bacterium. However, whether M. tuberculosis exploits its Acr1 in impairing the host immunity remains widely unexplored. Hence, currently we have investigated the role of Acr1 in influencing the differentiation and function of dendritic cells (DCs), which play a cardinal role in innate and adaptive immunity. Therefore, for the first time, we have revealed a novel mechanism of mycobacterial Acr1 in inhibiting the maturation and differentiation of DCs by inducing tolerogenic phenotype by modulating the expression of PD-L1; Tim-3; indoleamine 2, 3-dioxygenase (IDO); and interleukin 10. Furthermore, Acr1 interferes in the differentiation of DCs by targeting STAT-6 and STAT-3 pathways. Continuous activation of STAT-3 inhibited the translocation of NF-κB in Acr1-treated DCs. Furthermore, Acr1 also augmented the induction of regulatory T cells. These DCs displayed decline in their antigen uptake capacity and reduced ability to help T cells. Interestingly, M. tuberculosis exhibited better survival in Acr1-treated DCs. Thus, this study provides a crucial insight into a strategy adopted by M. tuberculosis to survive in the host by impairing the function of DCs.

SOCS3: An essential physiological inhibitor of signaling by interleukin-6 and G-CSF family cytokines

SOCS3 is an inducible negative feedback inhibitor of cytokine signaling. Conditional deletion of SOCS3 in mice using the Cre-lox system has now been applied to a range of cell types in the steady-state and under inflammatory, pathogenic, or tumorigenic stress, with the resulting phenotypes demonstrating the effects of SOCS3 in physiological and disease contexts. Together with recent structural and biochemical studies on the mechanisms of SOCS3 binding to cytokine receptors and associated kinases, we now have a better understanding of the non-redundant roles of SOCS3 in the inhibition of cytokine signaling via the receptors gp130, G-CSFR, leptinR, and IL-12Rβ. This review discusses the known functional activities of SOCS3 in fertility and development, inflammation, innate and adaptive immunity, and malignancy as determined by genetic studies in mice.

Multiple roles of SOCS proteins: differential expression of SOCS1 and SOCS3 in atherosclerosis

Pro-inflammatory cytokines play a key pathogenic role in atherosclerosis, which are induced by the Janus kinase/signal transducer and activator of transduction (JAK/STAT) pathway. Furthermore, the JAK/STAT pathway is negatively regulated by the suppressor of cytokine signaling (SOCS) proteins. However, the change in SOCS expression levels and the correlation between SOCS expression and cholesterol levels in atherosclerosis is not yet well understood. To this end, a mouse model of atherosclerosis was established using apolipoprotein-deficient (ApoE(-/-)) mice. The mice were fed either a chow or high-fat diet. The mRNA and protein expression of SOCS1 and SOCS3 in plaque and vessels were determined at different time points. Furthermore, SOCS1 and SOCS3 mRNA expression was detected in the peripheral blood mononuclear cells (PBMCs) obtained from 18 male subjects with no coronary heart disease (non-CHD) population. The expression of SOCS1 in the ApoE(-/-) mice first increased and then decreased and the high-fat diet accelerated the appearance of the peak; the expression of SOCS3 increased with the increased feeding duration, and this trend was more pronounced in the mice fed the high-fat diet. SOCS1/CD68 and SOCS3/CD68 showed opposite trends in expression with the increased duration of the high-fat diet. Interleukin-6 (IL-6) expression in the main aorta of the ApoE(-/-) mice fed the high-fat diet also increased with the increased feeding duration. In the non-CHD population, the total serum cholesterol levels positively correlated with SOCS3 mRNA expression in the PBMCs (r=0.433, P=0.012). These results demonstrate the differential expression of SOCS1 and SOCS3 in atherosclerosis and suggest that SOCS3, together with IL-6 may promote the formation and development of atherosclerosis.

Antigen choice determines vaccine-induced generation of immunogenic versus tolerogenic dendritic cells that are marked by differential expression of pancreatic enzymes

Dendritic cells (DC) elicit immunity to pathogens and tumors while simultaneously preserving tolerance to self. Efficacious cancer vaccines have been a challenge because they are based on tumor Ags, some of which are self-Ags and thus subject to self-tolerance. One such Ag is the tumor-associated mucin MUC1. Preclinical testing of MUC1 vaccines revealed existence of peripheral tolerance to MUC1 that compromises their efficacy. To identify mechanisms that act early postvaccination and might predict vaccine outcome, we immunized human MUC1 transgenic mice (MUC1.Tg) i.v. with a MUC1 peptide vaccine against which they generate weak immunity and wild-type (WT) mice that respond strongly to the same peptide. We analyzed differences in splenic DC phenotype and function between the two mouse strains at 24 and 72 h postvaccination and also performed unbiased total gene expression analysis of the spleen. Compared to WT, MUC1.Tg spleens had significantly fewer DC, and they exhibited significantly lower expression of costimulatory molecules, decreased motility, and preferential priming of Ag-specific Foxp3(+) regulatory T cells. This tolerogenic DC phenotype and function was marked by a new putative biomarker revealed by the microarray: a cohort of pancreatic enzymes (trypsin, carboxypeptidase, elastase, and others) not previously reported in DC. These enzymes were strongly upregulated in the splenic DC from vaccinated WT mice and suppressed in the splenic DC of vaccinated MUC1.Tg mice. Suppression of the enzymes was dependent on regulatory T cells and on signaling through the IL-10R and correlated with global downregulation of DC immunostimulatory phenotype and function.