Cutting edge: IL-6-dependent autoimmune disease: dendritic cells as a sufficient, but transient, source

The novel role of lymphatic vessels in the pathogenesis of ocular diseases

Historically, the eye has been considered as an organ free of lymphatic vessels. In recent years, however, it became evident, that lymphatic vessels or lymphatic-like vessels contribute to several ocular pathologies at various peri- and intraocular locations. The aim of this review is to outline the pathogenetic role of ocular lymphatics, the respective molecular mechanisms and to discuss current and future therapeutic options based thereon. We will give an overview on the vascular anatomy of the healthy ocular surface and the molecular mechanisms contributing to corneal (lymph)angiogenic privilege. In addition, we present (i) current insights into the cellular and molecular mechanisms occurring during pathological neovascularization of the cornea triggered e.g. by inflammation or trauma, (ii) the role of lymphatic vessels in different ocular surface pathologies such as dry eye disease, corneal graft rejection, ocular graft versus host disease, allergy, and pterygium, (iii) the involvement of lymphatic vessels in ocular tumors and metastasis, and (iv) the novel role of the lymphatic-like structure of Schlemm's canal in glaucoma. Identification of the underlying molecular mechanisms and of novel modulators of lymphangiogenesis will contribute to the development of new therapeutic targets for the treatment of ocular diseases associated with pathological lymphangiogenesis in the future. The preclinical data presented here outline novel therapeutic concepts for promoting transplant survival, inhibiting metastasis of ocular tumors, reducing inflammation of the ocular surface, and treating glaucoma. Initial data from clinical trials suggest first success of novel treatment strategies to promote transplant survival based on pretransplant corneal lymphangioregression.

The interleukin-6 family in tissues is closely related to the clinical outcomes of oral lichen planus

OBJECTIVE

We attempted to investigate the role of interleukin-6 (IL-6) family expression in local tissues as it relates to presentations and outcomes in oral lichen planus (OLP), which is a common chronic inflammatory oral disease.

MATERIALS AND METHODS

A clinical follow-up cohort of OLP patients was established, and a biological sample library was constructed with categorization into erosive type (EOLP) and nonerosive type (NEOLP). Transcriptome sequencing of the lesions was then performed. A multiple regression model was used to explore the differences in IL-6 family expression among patients with different clinical types and clinical outcomes.

RESULTS

OLP tissue transcriptome sequencing showed that IL-6 family expression in EOLP increased significantly. It was also found that IL-6 family factors in the OLP recurrent erosion group were significantly increased compared to the persistent nonerosion group. Based on the multiple regression analysis of the OLP clinical cohort, it was found that the increased expression of the IL-6 family was closely related to the clinical types and clinical outcomes of OLP.

CONCLUSION

The high expression of the IL-6 family is closely related to the erosion of local mucosa and poor prognosis of OLP patients. IL-6-related factors may be used as therapeutic targets for OLP patients.

Body Mass Index, Interleukin-6 Signaling and Multiple Sclerosis: A Mendelian Randomization Study

Objectives

We explored whether genetically predicted increased body mass index (BMI) modulates multiple sclerosis (MS) risk through interleukin-6 (IL-6) signaling.

Methods

We performed a two-sample Mendelian randomization (MR) study using multiple genome-wide association studies (GWAS) datasets for BMI, IL-6 signaling, IL-6 levels and c-reactive protein (CRP) levels as exposures and estimated their effects on risk of MS from GWAS data from the International Multiple Sclerosis Genetics Consortium (IMSGC) in 14,802 MS cases and 26,703 controls.

Results

In univariable MR analyses, genetically predicted increased BMI and IL-6 signaling were associated with higher risk of MS (BMI: odds ratio (OR) = 1.30, 95% confidence interval (CI) = 1.15-1.47, p = 3.76 × 10-5; IL-6 signaling: OR = 1.51, 95% CI = 1.11-2.04, p = 0.01). Furthermore, higher BMI was associated with increased IL-6 signaling (β = 0.37, 95% CI = 0.32,0.41, p = 1.58 × 10-65). In multivariable MR analyses, the effect of IL-6 signaling on MS risk remained after adjusting for BMI (OR = 1.36, 95% CI = 1.11-1.68, p = 0.003) and higher BMI remained associated with an increased risk for MS after adjustment for IL-6 signaling (OR = 1.16, 95% CI =1.00-1.34, p = 0.046). The proportion of the effect of BMI on MS mediated by IL-6 signaling corresponded to 43% (95% CI = 25%-54%). In contrast to IL-6 signaling, there was little evidence for an effect of serum IL-6 levels or CRP levels on risk of MS.

Conclusion

In this study, we identified IL-6 signaling as a major mediator of the association between BMI and risk of MS. Further explorations of pathways underlying the association between BMI and MS are required and will, together with our findings, improve the understanding of MS biology and potentially lead to improved opportunities for targeted prevention strategies.

Role of IL-6 in dendritic cell functions

Dendritic cells (DCs) are efficient antigen-presenting cells that serve as a link between the innate and adaptive immune systems. These cells are broadly involved in cellular and humoral immune responses by presenting antigens to initiate T cell reactions, cytokine and chemokine secretion, T cell differentiation and expansion, B cell activation and regulation, and the mediation of immune tolerance. The functions of DCs depend on their activation status, which is defined by the stages of maturation, phenotype differentiation, and migration ability, among other factors. IL-6 is a soluble mediator mainly produced by a variety of immune cells, including DCs, that exerts pleiotropic effects on immune and inflammatory responses through interaction with specific receptors expressed on the surface of target cells. Here, we review the role of IL-6, when generated in an inflammatory context or as derived from DCs, in modulating the biologic function and activation status of DCs and emphasize the importance of searching for novel strategies to target the IL-6/IL-6 signaling pathway as a means to diminish the inflammatory activity of DCs in immune response or to prime the immunogenic activity of DCs in immunosuppressive conditions.

Interleukin-6-knockdown of chimeric antigen receptor-modified T cells significantly reduces IL-6 release from monocytes

Background

T cells expressing a chimeric antigen receptor (CAR) engineered to target CD19 can treat leukemia effectively but also increase the risk of complications such as cytokine release syndrome (CRS) and CAR T cell related encephalopathy (CRES) driven by interleukin-6 (IL-6). Here, we investigated whether IL-6 knockdown in CART-19 cells can reduce IL-6 secretion from monocytes, which may reduce the risk of adverse events.

Methods

Supernatants from cocultures of regular CART-19 cells and B lymphoma cells were added to monocytes in vitro, and the IL-6 levels in monocyte supernatants were measured 24 h later. IL-6 expression was knocked down in regular CART-19 cells by adding a short hairpin RNA (shRNA) (termed ssCART-19) expression cassette specific for IL-6 to the conventional CAR vector. Transduction efficiency and cell proliferation were measured by flow cytometry, and cytotoxicity was measured by evaluating the release of lactate dehydrogenase into the medium. Gene expression was assessed by qRT-PCR and RNA sequencing. A xenograft leukemia mouse model was established by injecting NOD/SCID/γc-/- mice with luciferase-expressing B lymphoma cells, and then the animals were treated with regular CART-19 cells or ssCART-19. Tumor growth was assessed by bioluminescence imaging.

Results

Both recombinant IL-6 and CART-19 derived IL-6 significantly triggered IL-6 release by monocytes. IL-6 knockdown in ssCART-19 cells dramatically reduced IL-6 release from monocytes in vitro stduy. In vivo study further demonstrated that the mice bearing Raji cells treated with ssCART-19 cells showed significant lower IL-6 levels in serum than those treated with regular CART-19 cells, but comparable anti-tumor efficacy between the animal groups.

Conclusion

CAR T-derived IL-6 is one of the most important initiators to amplify release of IL-6 from monocytes that further drive sCRS development. IL-6 knockdown in ssCART-19 cells by shRNA technology provide a promising strategy to improve the safety of CAR T cell therapy.

Early astragaloside IV administration attenuates experimental autoimmune encephalomyelitis in mice by suppressing the maturation and function of dendritic cells

AIMS

Dendritic cells (DCs) actively participate in the pathogenesis of multiple sclerosis (MS), an autoimmune disease. Astragaloside IV (ASI), an active monomer isolated from the Chinese medicine Astragalus membranaceus, has a wide range of pharmacological effects. We aimed to elucidate the effects of ASI on the development of DCs in the early stage of MS/EAE.

MAIN METHODS

The mice were administered with ASI (20 mg/kg) daily 3 days in advance of EAE induction and continuously until day 7 post-immunization. The effect of ASI on CD11c⁺ DC cells from bone marrow (BMDCs) or the spleen of EAE mice at day 7 post-immunization were investigated respectively by flow cytometry, ELISA, western blot, real-time PCR and immunofluorescence.

KEY FINDINGS

ASI administration in the early stage of EAE was demonstrated to delay the onset and alleviate the severity of the disease. ASI inhibited the maturation and the antigen presentation of DCs in spleen of EAE mice and LPS-stimulated BMDCs, as evidenced by decreased expressions of CD11c, CD86, CD40 and MHC II. Accordingly, DCs treated by ASI secreted less IL-6 and IL-12, and prevented the differentiation of CD4⁺ T cells into Th1 and Th17 cells, which was probably through inhibiting the activation of NFκB and MAPKs signaling pathways.

SIGNIFICANCE

Our results implicated the alleviative effect of early ASI administration on EAE might be mediated by suppressing the maturation and function of DCs. The novel findings may add to our knowledge of ASI in the potentially clinical treatment of MS.

Analysis of Polymorphism and Expression Profile of ASIC1 and IL-6 Genes in Patients with Gastric Cancer

Gastric cancer is one of the most common upper gastrointestinal malignancies. Some Iranian provinces, such as in the northern and northwestern areas, are at a high risk, whereas the central and western provinces are at a medium and the southern regions at low risk. This study was carried out to estimate the impact of the expression patterns of ASIC1 and IL-6 genes and the IL-6rs-174 and ASIC1rs 75624685 polymorphisms in the pathogenesis of gastric cancer. Materials and methods: Tetra-ARMS PCR was employed to analyze the polymorphism status of the ASIC1 and IL-6 genes with 85 paraffin-embedded tissue blocks from cases and 117 normal blood samples as controls. We also investigated mRNA expression levels of these genes in 12 cases and controls using real-time PCR. Results: Our results showed a significant association between expression of ASIC1 and elevated risk of gastric cancer (p<0.001).

Calcitonin gene-related peptide decreases IL-1beta, IL-6 as well as Ym1, Arg1, CD163 expression in a brain tissue context-dependent manner while ameliorating experimental autoimmune encephalomyelitis

Activation states of immune cells (among them, the so-called pro- or anti-inflammatory states) influence the pathogenesis of multiple sclerosis (MS). The neuropeptide calcitonin gene-related peptide (CGRP) can exert a pro- or anti-inflammatory role in a context-dependent manner. In mice CGRP was found to attenuate the development of experimental autoimmune encephalomyelitis (EAE, a common MS animal model). We analyzed CGRP effects on the expression of cytokines and markers of activation states, as well as its intracellular cascade, following intrathecal administration during EAE immunization. Real Time quantitative-PCR (RT-PCR) showed that IL-1beta and IL-6 (associated to a pro-inflammatory state in EAE), but also Ym1 (also known as Chil3), Arg1 and CD163 (associated to an anti-inflammatory state in EAE) were decreased in the encephalon (devoid of cerebellum). In the cerebellum itself, IL-1beta and Ym1 were decreased. TNF-alpha (associated to a pro-inflammatory state in EAE), but also IL-10 (associated to another type of anti-inflammatory state) and BDNF were unchanged in these two regions. No changes were detected in the spinal cord. Additional tendencies toward a change (as revealed by RT-PCR) were again decreases: IL-10 in the encephalon and Arg1 in the spinal cord. CGRP decreased percentage of Ym1⁺/CD68⁺ immunoreactive cells and cell density of infiltrates in the cervical spinal cord pia mater. Instead, Ym1 in the underlying parenchyma and at thoracic and lumbar levels, as well as Arg1, were unchanged. In cultured microglia the neuropeptide decreased Ym1, but not Arg1, immunoreactivity. Inducible NOS (iNOS) was unchanged in spinal cord microglia and astrocytes. The neuropeptide increased the activation of ERK1/2 in the astrocytes of the spinal cord and in culture, but did not influence the activation of ERK1/2 or p38 in the spinal cord microglia. Finally, in areas adjacent to infiltration sites CGRP-treated microglia showed a larger ramification radius. In conclusion, CGRP-induced EAE amelioration was associated to a concomitant, context-dependent decrease in the expression of markers belonging to both pro- or anti-inflammatory activation states of immune cells. It can be hypothesized that CGRP-induced EAE attenuation is obtained through a novel mechanism that promotes down-regulation of immune cell activation that facilitates the establishment of a beneficial environment in EAE provided possibly also by other factors.

Development and Functional Characterization of Murine Tolerogenic Dendritic Cells

The immune system operates by maintaining a tight balance between coordinating responses against foreign antigens and maintaining an unresponsive state against self-antigens as well as antigens derived from commensal organisms. The disruption of this immune homeostasis can lead to chronic inflammation and to the development of autoimmunity. Dendritic cells (DCs) are the professional antigen-presenting cells of the innate immune system involved in activating naïve T cells to initiate immune responses against foreign antigens. However, DCs can also be differentiated into TolDCs that act to maintain and promote T cell tolerance and to suppress effector cells contributing to the development of either autoimmune or chronic inflammation conditions. The recent advancement in our understanding of TolDCs suggests that DC tolerance can be achieved by modulating their differentiation conditions. This phenomenon has led to tremendous growth in developing TolDC therapies for numerous immune disorders caused due to break in immune tolerance. Successful studies in preclinical autoimmunity murine models have further validated the immunotherapeutic utility of TolDCs in the treatment of autoimmune disorders. Today, TolDCs have become a promising immunotherapeutic tool in the clinic for reinstating immune tolerance in various immune disorders by targeting pathogenic autoimmune responses while leaving protective immunity intact. Although an array of strategies has been proposed by multiple labs to induce TolDCs, there is no consistency in characterizing the cellular and functional phenotype of these cells. This protocol provides a step-by-step guide for the development of bone marrow-derived DCs in large numbers, a unique method used to differentiate them into TolDCs with a synthetic triterpenoid 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid-difluoro-propyl-amide (CDDO-DFPA), and the techniques used to confirm their phenotype, including analyses of essential molecular signatures of TolDCs. Finally, we show a method to assess TolDC function by testing their immunosuppressive response in vitro and in vivo in a preclinical model of multiple sclerosis.

A Context-Dependent Role for αv Integrins in Regulatory T Cell Accumulation at Sites of Inflammation

Several inflammatory diseases including multiple sclerosis and inflammatory bowel disease have been associated with dysfunctional and/or reduced numbers of Foxp3+ regulatory T cells (Treg). While numerous mechanisms of action have been discovered by which Treg can exert their function, disease-specific Treg requirements remain largely unknown. We found that the integrin αv, which can pair with several β subunits including β8, is highly upregulated in Treg at sites of inflammation. Using mice that lacked αv expression or β8 expression specifically in Treg, we demonstrate that there was no deficit in Treg accumulation in the central nervous system during experimental autoimmune encephalomyelitis and no difference in the resolution of disease compared to control mice. In contrast, during a curative T cell transfer model of colitis, Treg lacking all αv integrins were found at reduced proportions and numbers in the inflamed gut. This led to a quantitative impairment in the ability of αv-deficient Treg to reverse disease when Treg numbers in the inflamed colon were below a threshold. Increase of the number of curative Treg injected was able to rescue this phenotype, indicating that αv integrins were not required for the immunosuppressive function of Treg per se. In accordance with this, αv deficiency did not impact on the capacity of Treg to suppress proliferation of naive conventional T cells in vitro as well as in vivo. These observations demonstrate that despite the general upregulation of αv integrins in Treg at sites of inflammation, they are relevant for adequate Treg accumulation only in specific disease settings. The understanding of disease-specific mechanisms of action by Treg has clear implications for Treg-targeted therapies.

[Cytokine neutralization at specific cellular source : A new therapeutic paradigm? German Version]

BACKGROUND

Currently, treatment of autoimmune diseases is based on manipulation of general control mechanisms, including those mediated by immunoregulatory cytokines. This approach is non-curative and may cause unwanted side effects due to numerous beneficial and non-redundant functions of a particular cytokine.

METHODS

Techniques of reverse genetics, such as conditional gene targeting, were employed to uncover the contributions of two proinflammatory and immunomodulatory cytokines, tumour necrosis factor (TNF) and interleukin 6 (IL-6), in various disease states.

RESULTS

Several non-redundant functions of TNF from distinct cellular sources were identified. TNF from myeloid cells is pathogenic in several autoimmune diseases, whereas TNF produced by T cells showed non-redundant protective functions in experimental arthritis and in a Mycobacterium tuberculosis infection model. To test the idea of selective pharmacological inhibition of "bad" TNF produced by myeloid cells while sparing "good" TNF produced by T lymphocytes, a myeloid-specific TNF inhibitor (MYSTI) was designed - a recombinant mini-antibody with dual specificity that can bind to the surface molecule F4/80 on myeloid cells and to TNF. In vitro experiments confirmed retention of TNF on the surface of TNF-producing cells and in vivo experiments indicated that MYSTI can protect mice from lethal TNF-mediated hepatotoxicity. MYSTI is also effective in experimental arthritis.

CONCLUSION

The proposed therapeutic strategy may be more effective than systemic anti-cytokine therapy in several human autoimmune diseases, as it would preserve the potentially beneficial effects of the same cytokine produced by other cell types. Such bispecific biological agents may become interesting tools for experimental studies and, eventually, drug development.

NKT cells are important mediators of hepatic ischemia-reperfusion injury

Introduction

IRI results from the interruption then reinstatement of an organ's blood supply, and this poses a significant problem in liver transplantation and resectional surgery.

In this paper, we explore the role T cells play in the pathogenesis of this injury.

Materials & methods

We used an in vivo murine model of warm partial hepatic IRI, genetically-modified mice, in vivo antibody depletion, adoptive cell transfer and flow cytometry to determine which lymphocyte subsets contribute to pathology. Injury was assessed by measuring serum alanine aminotransfersase (ALT) and by histological examination of liver tissue sections.

Results

The absence of T cells (CD3εKO) is associated with significant protection from injury (p = 0.010). Through a strategy of antibody depletion it appears that NKT cells (p = 0.0025), rather than conventional T (CD4 + or CD8 +) (p = 0.11) cells that are the key mediators of injury.

Discussion

Our results indicate that tissue-resident NKT cells, but not other lymphocyte populations are responsible for the injury in hepatic IRI. Targeting the activation of NKT cells and/or their effector apparatus would be a novel approach in protecting the liver during transplantation and resection surgery; this may allow us to expand our current criteria for surgery.

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Hepatic IRI worsens outcome in liver transplantation.

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T cells are important in hepatic IRI.

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These are tissue-resident rather than recruited T cells.

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NKT, but not conventional T or NK cells, are key mediators of hepatic IRI.

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Targeting NKT activation or their effector apparatus may offer therapeutic potential.

Monocyte lineage-derived IL-6 does not affect chimeric antigen receptor T-cell function

BACKGROUND AIMS

Chimeric antigen receptor (CAR) T-cell therapy targeting CD19 has demonstrated remarkable success in targeting B-cell malignancies but is often complicated by serious systemic toxicity in the form of cytokine release syndrome (CRS). CRS symptoms are primarily mediated by interleukin 6 (IL-6), and clinical management has focused on inhibition of IL-6 signaling. The cellular source and function of IL-6 in CRS remain unknown.

METHODS

Using co-culture assays and data from patients on our clinical CAR T-cell trials, we investigated the cellular source of IL-6, as well as other CRS-associated cytokines, during CAR T-cell activation. We also explored the effect that IL-6 has on T-cell function.

RESULTS

We demonstrated that IL-6 is secreted by monocyte-lineage cells in response to CAR T-cell activation in a contact-independent mechanism upon T-cell engagement of target leukemia. We observed that the presence of antigen-presenting cell-derived IL-6 has no impact on CAR T-cell transcriptional profiles or cytotoxicity. Finally, we confirm that CAR T cells do not secrete IL-6 in vivo during clinical CRS.

DISCUSSION

These findings suggest that IL-6 blockade will not affect CD19 CAR T-cell-driven anti-leukemic cytotoxicity, permitting enhanced control of CRS while maintaining CAR T-cell efficacy.

Paeoniflorin Ameliorates Experimental Autoimmune Encephalomyelitis via Inhibition of Dendritic Cell Function and Th17 Cell Differentiation

Paeoniflorin (PF) is a monoterpene glycoside and exhibits multiple effects, including anti-inflammation and immunoregulation. To date, the effect of PF on multiple sclerosis (MS) has not been investigated. In this study, we investigated the effect of PF in experimental autoimmune encephalomyelitis (EAE), an animal model for MS. After administered with PF, the onset and clinical symptoms of EAE mice were significantly ameliorated, and the number of Th17 cells infiltrated in central nervous system (CNS) and spleen was also dramatically decreased. Instead of inhibiting the differentiation of Th17 cells directly, PF influenced Th17 cells via suppressing the expression of costimulatory molecules and the production of interlukin-6 (IL-6) of dendritic cells (DCs) in vivo and in vitro, which may be attributable to the inhibition of IKK/NF-κB and JNK signaling pathway. When naïve CD4⁺ T cells were co-cultured with PF-treated dendritic cells under Th17-polarizing condition, the percentage of Th17 cells and the phosphorylation of STAT3 were decreased, as well as the mRNA levels of IL-17, RORα, and RORγt. Our study provided insights into the role of PF as a unique therapeutic agent for the treatment of multiple sclerosis and illustrated the underlying mechanism of PF from a new perspective.

Cytokine neutralization at specific cellular source : A new therapeutic paradigm?

BACKGROUND

Currently, treatment of autoimmune diseases is based on manipulation of general control mechanisms, including those mediated by immunoregulatory cytokines. This approach is non-curative and may cause unwanted side effects due to numerous beneficial and non-redundant functions of a particular cytokine.

METHODS

Techniques of reverse genetics, such as conditional gene targeting, were employed to uncover the contributions of two proinflammatory and immunomodulatory cytokines, tumour necrosis factor (TNF) and interleukin 6 (IL-6), in various disease states.

RESULTS

Several non-redundant functions of TNF from distinct cellular sources were identified. TNF from myeloid cells is pathogenic in several autoimmune diseases, whereas TNF produced by T cells showed non-redundant protective functions in experimental arthritis and in a Mycobacterium tuberculosis infection model. To test the idea of selective pharmacological inhibition of "bad" TNF produced by myeloid cells while sparing "good" TNF produced by T lymphocytes, a myeloid-specific TNF inhibitor (MYSTI) was designed-a recombinant mini-antibody with dual specificity that can bind to the surface molecule F4/80 on myeloid cells and to TNF. In vitro experiments confirmed retention of TNF on the surface of TNF-producing cells and in vivo experiments indicated that MYSTI can protect mice from lethal TNF-mediated hepatotoxicity. MYSTI is also effective in experimental arthritis.

CONCLUSION

The proposed therapeutic strategy may be more effective than systemic anti-cytokine therapy in several human autoimmune diseases, as it would preserve the potentially beneficial effects of the same cytokine produced by other cell types. Such bispecific biological agents may become interesting tools for experimental studies and, eventually, drug development.

Cytokine-producing B cells: a translational view on their roles in human and mouse autoimmune diseases

B-cell depletion therapy has beneficial effects in autoimmune diseases. This is only partly explained by an elimination of autoantibodies. How does B-cell depletion improve disease? Here, we review preclinical studies showing that B cells can propagate autoimmune disorders through cytokine production. We also highlight clinical observations indicating the relevance of these B-cell functions in human autoimmunity. Abnormalities in B-cell cytokine production have been observed in rheumatoid arthritis, multiple sclerosis, inflammatory bowel disease, and systemic lupus erythematosus. In the first two diseases, B-cell depletion erases these abnormalities, and improves disease progression, suggesting a causative role for defective B-cell cytokine expression in disease pathogenesis. However, in the last two disorders, the pathogenic role of B cells and the effect of B-cell depletion on cytokine-producing B cells remain to be clarified. A better characterization of cytokine-expressing human B-cell subsets, and their modulation by B cell-targeted therapies might help understanding both the successes and failures of current B cell-targeted approaches. This may even lead to the development of novel strategies to deplete or amplify selectively pathogenic or protective subsets, respectively, which might be more effective than global depletion of the B-cell compartment.

Anti-inflammatory effects of activated protein C on human dendritic cells

Activated protein C (APC) has an anticoagulant action and plays an important role in blood coagulation homeostasis. In addition to its anticoagulant action, APC is known to have cytoprotective effects, such as anti-apoptotic action and endothelial barrier protection, on vascular endothelial cells and monocytes. However, the effects of APC on DCs have not been clarified. To investigate the effects of APC on human DCs, monocytes were isolated from peripheral blood and DC differentiation induced with LPS. APC significantly inhibited the production of inflammatory cytokines TNF-α and IL-6 during differentiation of immature DCs to mature DCs, but did not inhibit the production of IL-12 and anti-inflammatory cytokine IL-10. Interestingly, treatment with 5 μg/mL, but not 25 μg/mL, of APC significantly enhanced production of IL-10. In addition, protein C, which is the zymogen of APC, did not affect production of these cytokines. On the other hand, flow cytometric analysis of DC's surface molecules indicated that APC does not significantly affect expression of CD83, a marker of mDC differentiation, and the co-stimulatory molecules CD40, CD80 and CD86. These results suggest that APC has anti-inflammatory effects on human DCs and may be effective against some inflammatory diseases in which the pathogenesis involves TNF-α and/or IL-6 production.

Seeking balance: Potentiation and inhibition of multiple sclerosis autoimmune responses by IL-6 and IL-10

The cytokines IL-6 and IL-10 are produced by cells of the adaptive and innate arms of the immune system and they appear to play key roles in genetically diverse autoimmune diseases such as relapsing remitting multiple sclerosis (MS), rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). Whereas previous intense investigations focused on the generation of autoantibodies and their contribution to immune-mediated pathogenesis in these diseases; more recent attention has focused on the roles of cytokines such as IL-6 and IL-10. In response to pathogens, antigen presenting cells (APC), including B cells, produce IL-6 and IL-10 in order to up-or down-regulate immune cell activation and effector responses. Evidence of elevated levels of the proinflammatory cytokine IL-6 has been routinely observed during inflammatory responses and in a number of autoimmune diseases. Our recent studies suggest that MS peripheral blood B cells secrete higher quantities of IL-6 and less IL-10 than B cells from healthy controls. Persistent production of IL-6, in turn, contributes to T cell expansion and the functional hyperactivity of APC such as MS B cells. Altered B cell activity can have a profound impact on resultant T cell effector functions. Enhanced signaling through the IL-6 receptor can effectively inhibit cytolytic activity, induce T cell resistance to IL-10-mediated immunosuppression and increase skewing of autoreactive T cells to a pathogenic Th17 phenotype. Our recent findings and studies by others support a role for the indirect attenuation of B cell responses by Glatiramer acetate (GA) therapy. Our studies suggest that GA therapy temporarily permits homeostatic regulatory mechanisms to be reinstated. Future studies of mechanisms underlying dysregulated B cell cytokine production could lead to the identification of novel targets for improved immunoregulatory therapies for autoimmune diseases.

FTY720 (fingolimod) treatment tips the balance towards less immunogenic antigen-presenting cells in patients with multiple sclerosis

OBJECTIVE

We aimed to clarify whether fingolimod has direct effects on antigen-presenting cells in multiple sclerosis patients.

METHODS

Frequency and phenotype of directly ex vivo dendritic cells and monocytes were analyzed in 43 individuals, including fingolimod-treated and untreated multiple sclerosis patients as well as healthy subjects. These cells were further stimulated with lipopolysaccharide to determine functional effects of fingolimod treatment.

RESULTS

Absolute numbers of CD1c+ dendritic cells and monocytes were not significantly reduced in fingolimod-treated patients indicating that fingolimod did not block the migration of antigen-presenting cells to peripheral blood. CD86 was upregulated on CD1c+ dendritic cells and thus their activation was not impaired under fingolimod treatment. Quantitative analyses of gene transcription in cells and protein content in supernatants from ex vivo CD1c+ dendritic cells and monocytes, however, showed lower secretion of TNFα, IL1-β and IL-6 upon lipopolysaccharide-stimulation. These results could be matched with CD4+MOG-specific transgenic T cells exhibiting reduced levels of TNFα and IFN-γ but not IL-4 upon stimulation with murine dendritic cells loaded with MOG, when treated with fingolimod.

CONCLUSIONS

Our data indicate that fingolimod - apart from trapping lymphocytes in lymph nodes - exerts its disease-modulating activity by rebalancing the immune tolerance networks by modulation of antigen-presenting cells.

Role of the immunogenic and tolerogenic subsets of dendritic cells in multiple sclerosis

Multiple sclerosis (MS) is an immune-mediated disorder in the central nervous system (CNS) characterized by inflammation and demyelination as well as axonal and neuronal degeneration. So far effective therapies to reverse the disease are still lacking; most therapeutic drugs can only ameliorate the symptoms or reduce the frequency of relapse. Dendritic cells (DCs) are professional antigen presenting cells (APCs) that are key players in both mediating immune responses and inducing immune tolerance. Increasing evidence indicates that DCs contribute to the pathogenesis of MS and might provide an avenue for therapeutic intervention. Here, we summarize the immunogenic and tolerogenic roles of DCs in MS and review medicinal drugs that may affect functions of DCs and have been applied in clinic for MS treatment. We also describe potential therapeutic molecules that can target DCs by inducing anti-inflammatory cytokines and inhibiting proinflammatory cytokines in MS.

Epigenetic modification of the PD-1 (Pdcd1) promoter in effector CD4(+) T cells tolerized by peptide immunotherapy

Clinically effective antigen-based immunotherapy must silence antigen-experienced effector T cells (Teff) driving ongoing immune pathology. Using CD4⁺ autoimmune Teff cells, we demonstrate that peptide immunotherapy (PIT) is strictly dependent upon sustained T cell expression of the co-inhibitory molecule PD-1. We found high levels of 5-hydroxymethylcytosine (5hmC) at the PD-1 (Pdcd1) promoter of non-tolerant T cells. 5hmC was lost in response to PIT, with DNA hypomethylation of the promoter. We identified dynamic changes in expression of the genes encoding the Ten-Eleven-Translocation (TET) proteins that are associated with the oxidative conversion 5-methylcytosine and 5hmC, during cytosine demethylation. We describe a model whereby promoter demethylation requires the co-incident expression of permissive histone modifications at the Pdcd1 promoter together with TET availability. This combination was only seen in tolerant Teff cells following PIT, but not in Teff that transiently express PD-1. Epigenetic changes at the Pdcd1 locus therefore determine the tolerizing potential of TCR-ligation.

DOI:http://dx.doi.org/10.7554/eLife.03416.001

The immune system protects the body from dangerous microbes and removes damaged cells. However, in some cases, the immune system can malfunction and attack healthy tissues, which can lead to type-1 diabetes, multiple sclerosis, and other autoimmune diseases. Many of the current treatments for these disorders suppress the immune system, which can make the individuals more susceptible to infections.

It may be possible to treat autoimmune diseases using small pieces of protein—called peptides—that are based on proteins found on the cells that the immune system attacks by mistake. This strategy would target the specific immune cells that are malfunctioning, but allow the rest of the immune system to continue to work as normal. Peptide-based therapies for autoimmune diseases are currently being tested in clinical trials, and although the results look promising, it is not known precisely how they work.

McPherson et al. used mice that develop a disease similar to multiple sclerosis because some of their immune cells, known as effector T cells, attack a protein found in the mouse brain called MBP. The mice were treated with a peptide based on part of MBP, which prevented them from developing the autoimmune disease. The success of the peptide therapy depended on the T cells producing large amounts of a protein called PD-1. This protein stops the T-cells from activating immune responses when they detect the MBP protein.

The gene that makes PD-1 can have a methyl-tag—a chemical modification to DNA—which alters how much PD-1 is made in the T cells. When the gene has this methyl-tag, it can only be switched on for a short time to make a small amount of PD-1, which helps to control the immune responses activated by the T cell. However, when the methyl-tag was removed as a result of the peptide therapy the gene could be switched on for much longer, so that much more PD-1 was produced.

This work helps us to understand how peptide therapy works and should improve the chances of using this therapy to successfully treat patients with autoimmune diseases.

DOI:http://dx.doi.org/10.7554/eLife.03416.002

Immune responses to non-tumor antigens in the central nervous system

The central nervous system (CNS), once viewed as an immune-privileged site protected by the blood-brain barrier (BBB), is now known to be a dynamic immunological environment through which immune cells migrate to prevent and respond to events such as localized infection. During these responses, endogenous glial cells, including astrocytes and microglia, become highly reactive and may secrete inflammatory mediators that regulate BBB permeability and recruit additional circulating immune cells. Here, we discuss the various roles played by astrocytes, microglia, and infiltrating immune cells during host immunity to non-tumor antigens in the CNS, focusing first on bacterial and viral infections, and then turning to responses directed against self-antigens in the setting of CNS autoimmunity.

Exposure to inflammatory cytokines selectively limits GM-CSF production by induced T regulatory cells

Interest in manipulating the immunosuppressive powers of Foxp3-expressing T regulatory cells as an immunotherapy has been tempered by their reported ability to produce proinflammatory cytokines when manipulated in vitro, or in vivo. Understanding processes that can limit this potentially deleterious effect of Treg cells in a therapeutic setting is therefore important. Here, we have studied this using induced (i) Treg cells in which de novo Foxp3 expression is driven by TCR-stimulation in vitro in the presence of TGF-β. We show that iTreg cells can produce significant amounts of three proinflammatory cytokines (IFN-γ, GM-CSF and TNF-α) upon secondary TCR stimulation. GM-CSF is a critical T-cell derived cytokine for the induction of EAE in mice. Despite their apparent capacity to produce GM-CSF, myelin autoantigen-responsive iTreg cells were unable to provoke EAE. Instead, they maintained strong suppressive function in vivo, preventing EAE induction by their CD4⁺Foxp3⁻ counterparts. We identified that although iTreg cells maintained the ability to produce IFN-γ and TNF-α in vivo, their ability to produce GM-CSF was selectively degraded upon antigen stimulation under inflammatory conditions. Furthermore, we show that IL-6 and IL-27 individually, or IL-2 and TGF-β in combination, can mediate the selective loss of GM-CSF production by iTreg cells.

Neuroantigen-specific autoregulatory CD8+ T cells inhibit autoimmune demyelination through modulation of dendritic cell function

Experimental autoimmune encephalomyelitis (EAE) is a well-established murine model of multiple sclerosis, an immune-mediated demyelinating disorder of the central nervous system (CNS). We have previously shown that CNS-specific CD8+ T cells (CNS-CD8+) ameliorate EAE, at least in part through modulation of CNS-specific CD4+ T cell responses. In this study, we show that CNS-CD8+ also modulate the function of CD11c+ dendritic cells (DC), but not other APCs such as CD11b+ monocytes or B220+ B cells. DC from mice receiving either myelin oligodendrocyte glycoprotein-specific CD8+ (MOG-CD8+) or proteolipid protein-specific CD8+ (PLP-CD8+) T cells were rendered inefficient in priming T cell responses from naïve CD4+ T cells (OT-II) or supporting recall responses from CNS-specific CD4+ T cells. CNS-CD8+ did not alter DC subset distribution or MHC class II and CD86 expression, suggesting that DC maturation was not affected. However, the cytokine profile of DC from CNS-CD8+ recipients showed lower IL-12 and higher IL-10 production. These functions were not modulated in the absence of immunization with CD8-cognate antigen, suggesting an antigen-specific mechanism likely requiring CNS-CD8-DC interaction. Interestingly, blockade of IL-10 in vitro rescued CD4+ proliferation and in vivo expression of IL-10 was necessary for the suppression of EAE by MOG-CD8+. These studies demonstrate a complex interplay between CNS-specific CD8+ T cells, DC and pathogenic CD4+ T cells, with important implications for therapeutic interventions in this disease.

MS14, a Marine Herbal Medicine, an Immunosuppressive Drug in Experimental Autoimmune Encephalomyelitis

Background:

Cytokines are secreted signaling proteins which play essential roles in immune responses during experimental autoimmune encephalomyelitis (EAE), a demyelinating model that mimics many features of multiple sclerosis (MS). Interleukin 6 (IL-6) is a multifunctional cytokine produced by different cells, mediating inflammatory reactions and immune-mediated processes. Several studies have described immunosuppressive potentials of several herbal medicines. MS14 as an Iranian marine herbal medicine has anti-inflammatory and immunomodulatory activities.

Objectives:

The present study investigated the immunosuppressive potential of MS14 as an herbal drug as well as the IL-6 level in EAE model. We hope it will be a new approach for neurologic diseases and autoimmune originated diseases therapy.

Patients and Methods:

The present experimental study was a collaboration between Department of Anatomical Sciences of Tabriz University of Medical Sciences and Shefa Neuroscience Research Center of Tehran. We used 30 C57BL/6 mice. The animals were immunized with myelin oligodendrocyte glycoprotein (MOG) to induce EAE and treated with MS14-containing (30%) diets. Subjects were selected by simple random sampling and then they were randomly allocated to two groups. EAE symptoms were assessed using the standard 10–point EAE scoring system from the seventh to the 35th day after immunization. Afterwards, the spleen was removed and its cells were cultured with or without MOG 35-55; then, the IL-6 level was analyzed by ELISA. In addition, histopathological studies were carried out for demyelination lesion evaluation in the spinal cord.

Results:

MS14 significantly improved clinical symptoms of EAE compared with the control (P < 0.05). It also suppressed proliferative responses of T cells and decreased IL-6 expression (16.93 ± 2.7 vs. 21.4 ± 3.33) (P < 0.05).

Conclusions:

Our results strongly suggested that IL-6 as a potential molecule could have a role in neuroimmunology and neuroinflammation, which is in congruent with previous studies. Therefore, it can be a clear target in strategic therapies and support effective properties of phytotherapy in EAE and MS treatment.

Human ESC-derived MSCs outperform bone marrow MSCs in the treatment of an EAE model of multiple sclerosis

Current therapies for multiple sclerosis (MS) are largely palliative, not curative. Mesenchymal stem cells (MSCs) harbor regenerative and immunosuppressive functions, indicating a potential therapy for MS, yet the variability and low potency of MSCs from adult sources hinder their therapeutic potential. MSCs derived from human embryonic stem cells (hES-MSCs) may be better suited for clinical treatment of MS because of their unlimited and stable supply. Here, we show that hES-MSCs significantly reduce clinical symptoms and prevent neuronal demyelination in a mouse experimental autoimmune encephalitis (EAE) model of MS, and that the EAE disease-modifying effect of hES-MSCs is significantly greater than that of human bone-marrow-derived MSCs (BM-MSCs). Our evidence also suggests that increased IL-6 expression by BM-MSCs contributes to the reduced anti-EAE therapeutic activity of these cells. A distinct ability to extravasate and migrate into inflamed CNS tissues may also be associated with the robust therapeutic effects of hES-MSCs on EAE.

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hES-MSCs show increased anti-EAE effects relative to adult human BM-MSCs

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hES-MSCs express fewer proinflammatory cytokines than BM-MSCs

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hES-MSCs enter the CNS more efficiently than BM-MSCs in EAE

Cytokines are both villains and potential therapeutic targets in thyroid-associated ophthalmopathy: From bench to bedside

The pathophysiology underlying Graves' disease and its ocular manifestation, thyroid associated ophthalmopathy (TAO) is incompletely understood. Characterization of the mononuclear cells driving the disease and the cytokines they produce has led to significant advances in our understanding of TAO. This in turn has resulted in the identification of potentially attractive drug targets. For instance, development of inhibitors of specific cytokine pathways for use in other autoimmune diseases now presents an opportunity for their application in TAO. In this paper, we review the rationale for considering anti-cytokine therapy in TAO, evidence linking specific cytokines such as interleukin-6, tumor necrosis factor-α, and interleukin-17 pathways to TAO, and explore the potential for targeting of these pathways as therapy.

Mitogen-activated protein kinase phosphatase 1 as an inflammatory factor and drug target

Mitogen-activated protein kinases (MAPKs) are signaling proteins that are activated through phosphorylation, and they regulate many physiological and pathophysiological processes in cells. Mitogen-activated protein kinase phosphatase 1 (MKP-1) is an inducible nuclear phosphatase that dephosphorylates MAPKs, and thus, it is a negative feedback regulator of MAPK activity. MKP-1 has been found as a key endogenous suppressor of innate immune responses, as well as a regulator of the onset and course of adaptive immune responses. Altered MKP-1 signaling is implicated in chronic inflammatory diseases in man. Interestingly, MKP-1 expression and protein function have been found to be regulated by certain anti-inflammatory drugs, namely by glucocorticoids, antirheumatic gold compounds and PDE4 inhibitors, and MKP-1 has been shown to mediate many of their anti-inflammatory effects. In this Mini Review, we summarize the effect of MKP-1 in the regulation of innate and adaptive immune responses and its role as a potential anti-inflammatory drug target and review recent findings concerning the role of MKP-1 in certain anti-inflammatory drug effects.

Kinetics of IL-6 production defines T effector cell responsiveness to regulatory T cells in multiple sclerosis

In multiple sclerosis (MS) autoaggressive T effector cells (Teff) are not efficiently controlled by regulatory T cells (Treg) but the underlying mechanisms are incompletely understood. Proinflammatory cytokines are key factors facilitating Teff activity in chronic inflammation. Here we investigated the influence of IL-6 on Treg sensitivity of Teff from therapy-naïve MS patients with or without active disease. Compared to healthy volunteers and independent of disease course CD4⁺ and especially CD8⁺ MS-Teff were insensitive against functional active Treg from healthy controls. This unresponsiveness was caused by accelerated production of IL-6, elevated IL-6 receptor expression and phosphorylation of protein kinase B (PKB)/c-Akt in MS-Teff. In a positive feedback loop, IL-6 itself induced its accelerated synthesis and enhanced phosphorylation of PKB/c-Akt that finally mediated Treg resistance. Furthermore, accelerated IL-6 release especially by CD8⁺ Teff prevented control of surrounding Teff, described here as “bystander resistance”. Blockade of IL-6 receptor signaling or direct inhibition of PKB/c-Akt phosphorylation restored Treg responsiveness of Teff and prevented bystander resistance. In Teff of healthy controls (HC) exogenous IL-6 also changed the kinetics of IL-6 production and induced Treg unresponsiveness. This modulation was only transient in Teff from healthy volunteers, whereas accelerated IL-6 production in MS-Teff maintained also in absence of IL-6. Hence, we showed that the kinetics of IL-6 production instead of elevated IL-6 levels defines the Teff responsiveness in early Treg-T cell communication in MS independent of their disease course and propose IL-6 and associated PKB/c-Akt activation as effective therapeutic targets for modulation of Teff activity in MS.

Fms-like tyrosine kinase 3 ligand-dependent dendritic cells in autoimmune inflammation

Dendritic cells (DCs) are specialized in capture, processing and presentation of antigens to T cells. Depending on the type of DC and its activation state, the interaction of DCs with naive T cells can lead to different types of immune response, or to T-cell tolerance. The existence of many specialized subtypes of DCs with particular functions has raised the need to distinguish DCs formed in steady-state from those produced during an inflammatory response. In patients with autoimmune disease and in experimental animal models of autoimmunity, DCs show abnormalities in both numbers and activation state, expressing immunogenic levels of co-stimulatory molecules and pro-inflammatory cytokines. Initial in vitro studies of cytokines in DC development revealed distinct and important roles for the receptor tyrosine kinases, granulocyte-macrophage colony-stimulating factor (GM-CSF), macrophage colony-stimulating factor (M-CSF, also called CSF1) and fms-like tyrosine kinase 3 ligand (Flt3L) in the generation of DCs. Flt3L is critical for instructing DC generation throughout different organs and regulates DC development from Flt3(+) lymphoid and myeloid-committed progenitors to DCs in vivo. The aim of this review is to provide an overview of the role of Flt3L-dependent DCs in the immunopathogenesis of autoimmunity and chronic inflammation and its potential as therapeutic targets.

Syndecan-1, a cell surface proteoglycan, negatively regulates initial leukocyte recruitment to the brain across the choroid plexus in murine experimental autoimmune encephalomyelitis

The cell surface heparan sulfate proteoglycan, syndecan-1, has been reported to be a negative regulator of various inflammatory processes, but its precise mode of action is poorly defined. In this study, we use the murine model of the 35-55 peptide of myelin oligodendrocyte glycoprotein-induced experimental autoimmune encephalomyelitis (EAE), a T lymphocyte-mediated inflammation where the steps in disease development and recovery are well characterized, to decipher how syndecan-1 impacts on the inflammatory reaction. Syndecan-1 knockout (Sdc-1(-/-)) mice show enhanced disease severity and impaired recovery. The use of bone marrow chimeric mice reveals that both an immune cell and a CNS-resident source of syndecan-1 contribute to this phenotype. Epithelial cells of the choroid plexus, where initial CCL20-induced leukocyte recruitment to the brain occurs, are identified as the predominant site of syndecan-1 expression. Syndecan-1 is lost from this site during the course of EAE by shedding into the cerebrospinal fluid, which correlates with loss of epithelial cell surface-bound CCL20 and is associated with the upregulation of IL-6 expression. In Sdc-1(-/-) mice, early leukocyte recruitment via the choroid plexus is enhanced, and IL-6 is elevated, which collectively results in higher numbers of the disease inducing Th17 cells in the CNS, thereby contributing to enhanced disease severity. Furthermore, Sdc-1(-/-) mice have intrinsically elevated plasma cell numbers and higher myelin oligodendrocyte glycoprotein-specific Ab levels during EAE, which we propose contributes to impaired recovery. Our data identify the choroid plexus epithelium as a novel source of IL-6 in EAE and demonstrate that its expression negatively correlates with syndecan-1 expression at this site.

T-bet is essential for Th1-mediated, but not Th17-mediated, CNS autoimmune disease

T cells that produce both IL-17 and IFN-γ, and co-express ROR-γt and T-bet, are often found at sites of autoimmune inflammation. However, it is unknown whether this co-expression of T-bet with ROR-γt is a prerequisite for immunopathology. We show here that T-bet is not required for the development of Th17-driven experimental autoimmune encephalomyelitis (EAE). The disease was not impaired in T-bet(-/-) mice and was associated with low IFN-γ production and elevated IL-17 production among central nervous system (CNS) infiltrating CD4(+) T cells. T-bet(-/-) Th17 cells generated in the presence of IL-6/TGF-β/IL-1 and IL-23 produced GM-CSF and high levels of IL-17 and induced disease upon transfer to naïve mice. Unlike their WT counterparts, these T-bet(-/-) Th17 cells did not exhibit an IL-17→IFN-γ switch upon reencounter with antigen in the CNS, indicating that this functional change is not critical to disease development. In contrast, T-bet was absolutely required for the pathogenicity of myelin-responsive Th1 cells. T-bet-deficient Th1 cells failed to accumulate in the CNS upon transfer, despite being able to produce GM-CSF. Therefore, T-bet is essential for establishing Th1-mediated inflammation but is not required to drive IL-23-induced GM-CSF production, or Th17-mediated autoimmune inflammation.

Immune privilege as an intrinsic CNS property: astrocytes protect the CNS against T-cell-mediated neuroinflammation

Astrocytes have many functions in the central nervous system (CNS). They support differentiation and homeostasis of neurons and influence synaptic activity. They are responsible for formation of the blood-brain barrier (BBB) and make up the glia limitans. Here, we review their contribution to neuroimmune interactions and in particular to those induced by the invasion of activated T cells. We discuss the mechanisms by which astrocytes regulate pro- and anti-inflammatory aspects of T-cell responses within the CNS. Depending on the microenvironment, they may become potent antigen-presenting cells for T cells and they may contribute to inflammatory processes. They are also able to abrogate or reprogram T-cell responses by inducing apoptosis or secreting inhibitory mediators. We consider apparently contradictory functions of astrocytes in health and disease, particularly in their interaction with lymphocytes, which may either aggravate or suppress neuroinflammation.

Adaptive immune responses in CNS autoimmune disease: mechanisms and therapeutic opportunities

The processes underlying autoimmune CNS inflammation are complex, but key roles for autoimmune lymphocytes seem inevitable, based on clinical investigations in multiple sclerosis (MS) and related diseases such as neuromyelitis optica, together with the known pathogenic activity of T cells in experimental autoimmune encephalomyelitis (EAE) models. Despite intense investigation, the details of etiopathology in these diseases have been elusive. Here we describe recent advances in the rodent models that begin to allow a map of pathogenic and protective immunity to be drawn. This map might illuminate previous successful and unsuccessful therapeutic strategies targeting particular pathways, whilst also providing better opportunities for the future, leading to tailored intervention based on understanding the quality of each individual's autoimmune response.