IL-10 permits transient activation of dendritic cells to tolerize T cells and protect from central nervous system autoimmune disease

A comprehensive overview of tolerogenic vaccine adjuvants and their modes of action

Tolerogenic vaccines represent a therapeutic approach to induce antigen-specific immune tolerance to disease-relevant antigens. As general immunosuppression comes with significant side effects, including heightened risk of infections and reduced anti-tumor immunity, antigen-specific tolerance by vaccination would be game changing in the treatment of immunological conditions such as autoimmunity, anti-drug antibody responses, transplantation rejection, and hypersensitivity. Tolerogenic vaccines induce antigen-specific tolerance by promoting tolerogenic antigen presenting cells, regulatory T cells, and regulatory B cells, or by suppressing or depleting antigen-specific pathogenic T and B cells. The design of tolerogenic vaccines vary greatly, but they all deliver a disease-relevant antigen with or without a tolerogenic adjuvant. Tolerogenic adjuvants are molecules which mediate anti-inflammatory or immunoregulatory effects and enhance vaccine efficacy by modulating the immune environment to favor a tolerogenic immune response to the vaccine antigen. Tolerogenic adjuvants act through several mechanisms, including immunosuppression, modulation of cytokine signaling, vitamin signaling, and modulation of immunological synapse signaling. This review seeks to provide a comprehensive examination of tolerogenic adjuvants currently utilized in tolerogenic vaccines, describing their mechanism of action and examples of their use in human clinical trials and animal models of disease.

Alleviation of experimental autoimmune encephalomyelitis by transferring low RelB expression tolerogenic dendritic cells

AIMS

Experimental autoimmune encephalomyelitis (EAE) is a widely used mouse model of multiple sclerosis. Rather than inducing immune response, tolerogenic dendritic cells (tDCs) have the ability to induce immune tolerance. In previous studies, we induced tDCs by 1,25-(OH)2D3 and 1,25-(OH)2D3 DCs significantly alleviated EAE symptoms. As downstream targets of 1,25-(OH)2D3, inhibition of RelB and MyD88 expression in DCs might induce tDCs and has therapeutic effect of MS.

METHODS

Knockdown the expression of RelB and MyD88 with shRNA lentivirus to induce tDCs, adoptive transfer these tDCs to EAE mice, and investigate their therapeutic effects.

RESULTS

Reduction of RelB expression induced tDCs. After transferring into EAE mice, tDCs with low RelB expression significantly alleviate their symptoms as well as reduce the immune cell infiltration and demyelination in spinal cord.

CONCLUSION

RelB plays a key role in the antigen presenting function of DCs, and tDCs with low RelB expression is a potential treatment for EAE and MS.

Inhibition of MC38 colon cancer growth by multicomponent chemoimmunotherapy with anti-IL-10R antibodies, HES-MTX nanoconjugate, depends on application of IL-12, IL-15 or IL-18 secreting dendritic cell vaccines

Background

The tumor microenvironment (TME) provides a conducive environment for the growth and survival of tumors. Negative factors present in TME, such as IL-10, may limit the effectiveness of cellular vaccines based on dendritic cells, therefore, it is important to control its effect. The influence of IL-10 on immune cells can be abolished e.g., by using antibodies against the receptor for this cytokine - anti-IL-10R. Furthermore, the anticancer activity of cellular vaccines can be enhanced by modifying them to produce proinflammatory cytokines, such as IL-12, IL-15 or IL-18. Additionally, an immunomodulatory dose of methotrexate and hydroxyethyl starch (HES-MTX) nanoconjugate may stimulate effector immune cells and eliminate regulatory T cells, which should enhance the antitumor action of immunotherapy based on DC vaccines. The main aim of our study was to determine whether the HES-MTX administered before immunotherapy with anti-IL-10R antibodies would change the effect of vaccines based on dendritic cells overproducing IL-12, IL-15, or IL-18.

Methods

The activity of modified DCs was checked in two therapeutic protocols - immunotherapy with the addition of anti-IL10R antibodies and chemoimmunotherapy with HES-MTX and anti-IL10R antibodies. The inhibition of tumor growth and the effectiveness of the therapy in inducing a specific antitumor response were determined by analyzing lymphoid and myeloid cell populations in tumor nodules, and the activity of restimulated splenocytes.

Results and conclusions

Using the HES-MTX nanoconjugate before immunotherapy based on multiple administrations of anti-IL-10R antibodies and cellular vaccines capable of overproducing proinflammatory cytokines IL-12, IL-15 or IL-18 created optimal conditions for the effective action of these vaccines in murine colon carcinoma MC38 model. The applied chemoimmunotherapy caused the highest inhibition of tumor growth in the group receiving DC/IL-15/IL-15Rα/TAg + DC/IL-18/TAg at the level of 72.4%. The use of cellular vaccines resulted in cytotoxic activity increase in both immuno- or chemoimmunotherapy. However, the greatest potential was observed both in tumor tissue and splenocytes obtained from mice receiving two- or three-component vaccines in the course of combined application. Thus, the designed treatment schedule may be promising in anticancer therapy.

Dendritic Cells as a Nexus for the Development of Multiple Sclerosis and Models of Disease

Multiple sclerosis (MS) results from an autoimmune attack on the central nervous system (CNS). Dysregulated immune cells invade the CNS, causing demyelination, neuronal and axonal damage, and subsequent neurological disorders. Although antigen-specific T cells mediate the immunopathology of MS, innate myeloid cells have essential contributions to CNS tissue damage. Dendritic cells (DCs) are professional antigen-presenting cells (APCs) that promote inflammation and modulate adaptive immune responses. This review focuses on DCs as critical components of CNS inflammation. Here, evidence from studies is summarized with animal models of MS and MS patients that support the critical role of DCs in orchestrating CNS inflammation.

Nanovaccines silencing IL-10 production at priming phase for boosting immune responses to melanoma

Despite the significant efforts in developing cancer vaccines, there are still numerous challenges that need to be addressed to ensure their clinical efficacy. Herein, a lymphatic dendritic cell (DC)-targeted artificial nanovaccine mimicking tumor cell membrane (ATM-NV) is developed to boost effector immune response and control immunosuppression simultaneously. The NVs are formulated with lipids, tumor cell membrane proteins, imiquimod (IMQ), and IL-10 siRNA. IL-10 siRNA is incorporated to inhibit the secretion of IL-10, an immunosuppressive cytokine, of maturated DCs upon IMQ. To enhance the DC targeting ability, the nanovaccine surface was non-covalently conjugated with the anti-CD205 antibody. The IMQ and IL-10 siRNA co-loaded, CD205 receptor-targeted artificial tumor membrane NVs (IMQ/siR@ATM-NVs) efficiently migrate to the tumor-draining lymph node and target DCs. Furthermore, immunization with IMQ/siR@ATM-NVs reduces the production of IL-10 and increases T_h1-driven antitumor immunity resulted in a great tumor inhibition efficacy. Our results suggest a potential strategy to promote the vaccination's antitumor efficacy by blocking the intrinsic negative regulators in DCs.

Advancement of antigen-specific immunotherapy: knowledge transfer between allergy and autoimmunity

Targeted restoration of immunological tolerance to self-antigens or innocuous environmental allergens represents the ultimate aim of treatment options in autoimmune and allergic disease. Antigen-specific immunotherapy (ASI) is the only intervention that has proven disease-modifying efficacy as evidenced by induction of long-term remission in a number of allergic conditions. Mounting evidence is now indicating that specific targeting of pathogenic T cells in autoinflammatory and autoimmune settings enables effective restoration of immune homeostasis between effector and regulatory cells and alters the immunological course of disease. Here, we discuss the key lessons learned during the development of antigen-specific immunotherapies and how these can be applied to inform future interventions. Armed with this knowledge and current high-throughput technology to track immune cell phenotype and function, it may no longer be a matter of ‘if’ but ‘when’ this ultimate aim of targeted tolerance restoration is realised.

Emerging Therapeutics for Immune Tolerance: Tolerogenic Vaccines, T cell Therapy, and IL-2 Therapy

Autoimmune diseases affect roughly 5-10% of the total population, with women affected more than men. The standard treatment for autoimmune or autoinflammatory diseases had long been immunosuppressive agents until the advent of immunomodulatory biologic drugs, which aimed at blocking inflammatory mediators, including proinflammatory cytokines. At the frontier of these biologic drugs are TNF-α blockers. These therapies inhibit the proinflammatory action of TNF-α in common autoimmune diseases such as rheumatoid arthritis, psoriasis, ulcerative colitis, and Crohn's disease. TNF-α blockade quickly became the "standard of care" for these autoimmune diseases due to their effectiveness in controlling disease and decreasing patient's adverse risk profiles compared to broad-spectrum immunosuppressive agents. However, anti-TNF-α therapies have limitations, including known adverse safety risk, loss of therapeutic efficacy due to drug resistance, and lack of efficacy in numerous autoimmune diseases, including multiple sclerosis. The next wave of truly transformative therapeutics should aspire to provide a cure by selectively suppressing pathogenic autoantigen-specific immune responses while leaving the rest of the immune system intact to control infectious diseases and malignancies. In this review, we will focus on three main areas of active research in immune tolerance. First, tolerogenic vaccines aiming at robust, lasting autoantigen-specific immune tolerance. Second, T cell therapies using Tregs (either polyclonal, antigen-specific, or genetically engineered to express chimeric antigen receptors) to establish active dominant immune tolerance or T cells (engineered to express chimeric antigen receptors) to delete pathogenic immune cells. Third, IL-2 therapies aiming at expanding immunosuppressive regulatory T cells in vivo.

10-hydroxy-2-decenoic acid a bio-immunomodulator in tissue engineering; generates tolerogenic dendritic cells by blocking the toll-like receptor4

Dendritic cells (DCs), in response to the biomaterials, utilize toll-like receptors (TLRs) to become mature or tolerogenic through TLRs-dependent signaling pathways, especially TLR4. Regarding the physicochemical properties of biomaterials, some of such signaling pathways are activated. Unsaturated fatty acids have been explored as an antagonist for TLRs and lead to the tolerogenic phenotype of DCs. Here we showed that, although cultured DCs on both chitosan and Alginate-polyethyleneimine (Alg-PEI) films became fully mature, 10-hydroxy-2-decanoic acid (10-HDA), an unsaturated fatty acid found in royal jelly, led to the tolerogenic immunophenotype of DCs on both films. The cultured cells on the films possessed iDCs-like morphology in the presence of 10-HDA. Moreover, 10-HDA expressed lower levels of CD80, CD83, CD86, and HLA-DR, a higher level of IL-10, and lower level of IL-12 in the cultured DCs on both films. Furthermore, HEK293T cells expressing only TLR4 (HEK-TLR4 cells) were co-cultured with LPS, a specific agonist for TLR4, and 10-HDA. The 10-HDA significantly reduced the expression of tumor necrosis factor-a (TNF-α) in the HEK-TLR4 cells compared to treated only with LPS. These findings indicate that the 10-HDA acts as an antagonist of TLR4; therefore, potentially can be used in autoimmune diseases and preventing the rejection of biomaterials implantation and allograft transplantation.

Prolongation of rat-to-mouse islets xenograft survival by co-transplantation of autologous IL-10 differentiated murine tolerogenic dendritic cells

BACKGROUND

Tolerogenic dendritic cells (DCs) represent a promising approach to promote transplantation tolerance. In this study, the potential of autologous bone marrow (BM)-derived murine DC to protect rat-to-mouse islets xenografts was analyzed.

METHODS

Tolerogenic DCs were generated by differentiating BM cells in the presence of granulocyte-macrophage colony-stimulating factor and interleukin 10 (IL-10, IL-10 DC). The phenotype of IL-10 DC was characterized in vitro by expression of costimulatory/inhibitory molecules (flow cytometry) and cytokines (Luminex and ELISA), their function by phagocytosis and T-cell stimulation assays. To study transplant tolerance in vivo, rat islets were transplanted alone or in combination with autologous murine IL-10 DC under the kidney capsule of streptozotocin-induced diabetic C57BL/6 mice. Xenograft survival was evaluated by monitoring glycemia, cellular infiltration of xenografts by microscopy and flow cytometry 10 days post-transplantation.

RESULTS

Compared with control DC, IL-10 DC exhibited lower levels of major histocompatibility complex class II, costimulatory molecules (CD40, CD86, CD205), lower production of pro-inflammatory cytokines (IL-12p70, TNF, IL-6), and higher production of IL-10. Phagocytosis of xenogeneic rat splenocytes was not impaired in IL-10 DC, whereas stimulation of T-cell proliferation was reduced in the presence of IL-10 DC. Xenograft survival of rat islets in diabetic mice co-transplanted with autologous murine IL-10 DC was significantly prolonged from 12 to 21 days, without additional immunosuppressive treatment. Overall, infiltration of xenografts by T cells and myeloid cells was not different in IL-10 DC recipient mice, but enriched for CD8⁺ T cells and myeloid cells with suppressor-associated phenotype.

CONCLUSIONS

Autologous IL-10-differentiated DC with tolerogenic properties prolong rat-to-mouse islets xenograft survival, potentially by locally inducing immune regulatory cells, indicating their potential for regulatory immune cell therapy in xenotransplantation.

Inhibition of experimental autoimmune encephalomyelitis by tolerance-promoting DNA vaccination focused to dendritic cells

In this study we analysed the effects of prophylactic biolistic DNA vaccination with plasmids encoding the encephalitogenic protein myelin oligodendrocyte glycoprotein (MOG) on the severity of a subsequently MOGp35-55-induced EAE and on the underlying immune response. We compared the outcome of vaccination with MOG-encoding plasmids alone or in combination with vectors encoding the regulatory cytokines IL-10 and TGF-ß1, respectively. MOG expression was restricted to skin dendritic cells (DCs) by the use of the DC-specific promoter of the fascin1 gene (pFscn-MOG). For comparison, the strong and ubiquitously active CMV promoter was employed (pCMV-MOG), which allows MOG expression in all transfected cells. Expression of IL-10 and TGF-ß1 was controlled by the CMV promoter to yield maximal synthesis (pCMV-IL10, pCMV-TGFß). Co-application of pFscn-MOG and pCMV-IL10 significantly ameliorated EAE pathology, while vaccination with pCMV-MOG plus pCMV-IL10 did not affect EAE outcome. In contrast, vaccination with either of the two MOG-encoding plasmids in combination with pCMV-TGFß significantly attenuated the clinical EAE symptoms. Mechanistically, we observed diminished infiltration of Th17 and Th1 cells as well as macrophages/DCs into the CNS, which correlated with decreased MOGp35-55-specific production of IL-17 and IFN-ϫ by spleen cells and reduced peptide-specific T cell proliferation. Our findings suggest deletion of or anergy induction in MOG-specific CD4⁺ T cells by the suppressive vaccination platform employed. MOG expression driven by the DC-specific fascin1 promoter yielded similar inhibitory effects on EAE progression as the ubiquitously active viral CMV promoter, when coapplying pCMV-TGFß. Our finding that pCMV-IL10 promoted tolerogenic effects only, when coapplied with pFscn-MOG, but not pCMV-MOG suggests that IL-10 affected only directly transfected DCs (pFscn-MOG), but not neighbouring DCs that engulfed MOG-containing vesicles derived from transfected keratinocytes (pCMV-MOG). Thus, due to its DC-restricted expression, the fascin1 promoter might be an interesting alternative to ubiquitously expressed promoters for vaccination strategies.

Dendritic cells as gatekeepers of tolerance

Dendritic cells (DC) are unique hematopoietic cells, linking innate and adaptive immune responses. In particular, they are considered as the most potent antigen presenting cells, governing both T cell immunity and tolerance. In view of their exceptional ability to present antigen and to interact with T cells, DC play distinct roles in shaping T cell development, differentiation and function. The outcome of the DC-T cell interaction is determined by the state of DC maturation, the type of DC subset, the cytokine microenvironment and the tissue location. Both regulatory T cells (Tregs) and DC are indispensable for maintaining central and peripheral tolerance. Over the past decade, accumulating data indicate that DC critically contribute to Treg differentiation and homeostasis.

Estradiol enhances capacity of TLR-matured splenic dendritic cells to polarize CD4+ lymphocytes into IL-17/GM-CSF-producing cells in vitro

There are little data on modulatory effects of estrogens on rat dendritic cell (DC) responses to inflammatory stimuli, and consequently their ability to activate and polarize CD4+ T lymphocyte-mediated immune responses. Splenic conventional DCs from young female Albino Oxford rats were activated in vitro with LPS (TLR4 agonist) or R848 (TLR7/8 agonist) in the presence and absence of 17β-estradiol (E2), and their allostimulatory and CD4+ lymphocyte polarizing ability in mixed leukocyte culture (MLC) were studied. Irrespective of the E2 presence, LPS and R848 up-regulated the expression of MHC II on DCs, so they exhibited enhanced allostimulatory capacity in co-culture with CD4+ lymphocytes. On the other hand, E2 promoted stimulatory action of both TLRs on OX62+ DC IL-23 production, augmented their stimulatory effects on IL-6 and IL-1β production, but diminished their enhancing effects on the expression IL-10 and IL-27 by DCs. Consequently, in MLC, OX62+ DCs activated/matured in the co-presence of E2 and either LPS or R848 increased the levels of IL-17, the signature Th17 cell cytokine, when compared with those activated/matured in the absence of E2. GM-CSF levels were also increased in these MLC. Given that the expression of IL-7 mRNA was diminished in DCs activated/matured in the co-presence of E2 and TLR, this increase most likely did not reflect enhanced differentiation of Th cells producing GM-CSF only (Th-GM).

CONCLUSIONS

E2 augments capacity of LPS- and R848-activated/matured DCs from young rat spleen to induce differentiation of IL-17- and GM-CSF-producing 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.

Therapeutic potential of tolerogenic dendritic cells in IBD: from animal models to clinical application

The gut mucosa undergoes continuous antigenic exposure from food antigens, commensal flora derived ligands, and pathogens. This constant stimulation results in controlled inflammatory responses that are effectively suppressed by multiple factors. This tight regulation, necessary to maintain intestinal homeostasis, is affected during inflammatory bowel diseases (IBD) resulting in altered immune responses to harmless microorganisms. Dendritic cells (DCs) are sentinels of immunity, located in peripheral and lymphoid tissues, which are essential for homeostasis of T cell-dependent immune responses. The expression of a particular set of pathogen recognition receptors allows DCs to initiate immune responses. However, in the absence of danger signals, different DC subsets can induce active tolerance by inducing regulatory T cells (Treg), inhibiting inflammatory T helper cell responses, or both. Interestingly, several protocols to generate clinical grade tolerogenic DC (tol-DCs) in vitro have been described, opening the possibility to restore the intestinal homeostasis to bacterial flora by cellular therapy. In this review, we discuss different DC subsets and their role in IBD. Additionally, we will review preclinical studies performed in animal models while describing recent characterization of tol-DCs from Crohn's disease patients for clinical application.

Dendritic cell-based vaccines: barriers and opportunities

Dendritic cells (DCs) have several characteristics that make them an ideal vehicle for tumor vaccines, and with the first US FDA-approved DC-based vaccine in use for the treatment of prostate cancer, this technology has become a promising new therapeutic option. However, DC-based vaccines face several barriers that have limited their effectiveness in clinical trials. A major barrier includes the activation state of the DC. Both DC lineage and maturation signals must be selected to optimize the antitumor response and overcome immunosuppressive effects of the tumor microenvironment. Another barrier to successful vaccination is the selection of target antigens that will activate both CD8(+) and CD4(+) T cells in a potent, immune-specific manner. Finally, tumor progression and immune dysfunction limit vaccine efficacy in advanced stages, which may make DC-based vaccines more efficacious in treating early-stage disease. This review underscores the scientific basis and advances in the development of DC-based vaccines, focuses on current barriers to success and highlights new research opportunities to address these obstacles.

Human adipose-derived mesenchymal stem cells engineered to secrete IL-10 inhibit APC function and limit CNS autoimmunity

Interleukin (IL)-10 is an important immunoregulatory cytokine shown to impact inflammatory processes as manifested in patients with multiple sclerosis (MS) and in its animal model, experimental autoimmune encephalomyelitis (EAE). Several lines of evidence indicate that the effectiveness of IL-10-based therapies may be dependent on the timing and mode of delivery. In the present study we engineered the expression of IL-10 in human adipose-derived mesenchymal stem cells (Adi-IL-10-MSCs) and transplanted these cells early in the disease course to mice with EAE. Adi-IL-10-MSCs transplanted via the intraperitoneal route prevented or delayed the development of EAE. This protective effect was associated with several anti-inflammatory response mechanisms, including a reduction in peripheral T-cell proliferative responses, a decrease in pro-inflammatory cytokine secretion as well as a preferential inhibition of Th17-mediated neuroinflammation. In vitro analyses revealed that Adi-IL-10-MSCs inhibited the phenotypic maturation, cytokine production and antigen presenting capacity of bone marrow-derived myeloid dendritic cells, suggesting that the mechanism of action may involve an indirect effect on pathogenic T-cells via the modulation of antigen presenting cell function. Collectively, these results suggest that early intervention with gene modified Adi-MSCs may be beneficial for the treatment of autoimmune diseases such as MS.

Concurrent bacterial stimulation alters the function of helminth-activated dendritic cells, resulting in IL-17 induction

Infection with schistosome helminths is associated with granulomatous inflammation that forms around parasite eggs trapped in host tissues. In severe cases, the resulting fibrosis can lead to organ failure, portal hypertension, and fatal bleeding. Murine studies identified IL-17 as a critical mediator of this immunopathology, and mouse strains that produce high levels of IL-17 in response to schistosome infection show increased mortality. In this article, we demonstrate that schistosome-specific IL-17 induction by dendritic cells from low-pathology C57BL/6 mice is normally regulated by their concomitant induction of IL-10. Simultaneous stimulation of schistosome-exposed C57BL/6 dendritic cells with a heat-killed bacterium enabled these cells to overcome IL-10 regulation and induce IL-17, even in wild-type C57BL/6 recipients. This schistosome-specific IL-17 was dependent on IL-6 production by the copulsed dendritic cells. Coimmunization of C57BL/6 animals with bacterial and schistosome Ags also resulted in schistosome-specific IL-17, and this response was enhanced in the absence of IL-10-mediated immune regulation. Together, our data suggest that the balance of pro- and anti-inflammatory cytokines that determines the severity of pathology during schistosome infection can be influenced not only by host and parasite, but also by concurrent bacterial stimulation.

Tolerance induced by apoptotic antigen-coupled leukocytes is induced by PD-L1+ and IL-10-producing splenic macrophages and maintained by T regulatory cells

Ag-specific tolerance is a highly desired therapy for immune-mediated diseases. Intravenous infusion of protein/peptide Ags linked to syngeneic splenic leukocytes with ethylene carbodiimide (Ag-coupled splenocytes [Ag-SP]) has been demonstrated to be a highly efficient method for inducing peripheral, Ag-specific T cell tolerance for treatment of autoimmune disease. However, little is understood about the mechanisms underlying this therapy. In this study, we show that apoptotic Ag-SP accumulate in the splenic marginal zone, where their uptake by F4/80(+) macrophages induces production of IL-10, which upregulates the expression of the immunomodulatory costimulatory molecule PD-L1 that is essential for Ag-SP tolerance induction. Ag-SP infusion also induces T regulatory cells that are dispensable for tolerance induction but required for long-term tolerance maintenance. Collectively, these results indicate that Ag-SP tolerance recapitulates how tolerance is normally maintained in the hematopoietic compartment and highlight the interplay between the innate and adaptive immune systems in the induction of Ag-SP tolerance. To our knowledge, we show for the first time that tolerance results from the synergistic effects of two distinct mechanisms, PD-L1-dependent T cell-intrinsic unresponsiveness and the activation of T regulatory cells. These findings are particularly relevant as this tolerance protocol is currently being tested in a Phase I/IIa clinical trial in new-onset relapsing-remitting multiple sclerosis.

Mannan-binding lectin directly interacts with Toll-like receptor 4 and suppresses lipopolysaccharide-induced inflammatory cytokine secretion from THP-1 cells

Mannan-binding lectin (MBL) plays a key role in the lectin pathway of complement activation and can influence cytokine expression. Toll-like receptor 4 (TLR4) is expressed extensively and has been demonstrated to be involved in lipopolysaccharide (LPS)-induced signaling. We first sought to determine whether MBL exposure could modulate LPS-induced inflammatory cytokine secretion and nuclear factor-κB (NF-κB) activity by using the monocytoid cell line THP-1. We then investigated the possible mechanisms underlying any observed regulatory effect. Using ELISA and reverse transcriptase polymerase chain reaction (RT-PCR) analysis, we found that at both the protein and mRNA levels, treatment with MBL suppresses LPS-induced tumor-necrosis factor (TNF)-α and IL-12 production in THP-1 cells. An electrophoretic mobility shift assay and western blot analysis revealed that MBL treatment can inhibit LPS-induced NF-κB DNA binding and translocation in THP-1 cells. While the binding of MBL to THP-1 cells was evident at physiological calcium concentrations, this binding occurred optimally in response to supraphysiological calcium concentrations. This binding can be partly inhibited by treatment with either a soluble form of recombinant TLR4 extracellular domain or anti-TLR4 monoclonal antibody (HTA125). Activation of THP-1 cells by LPS treatment resulted in increased MBL binding. We also observed that MBL could directly bind to the extracellular domain of TLR4 in a dose-dependent manner, and this interaction could attenuate the binding of LPS to cell surfaces. Taken together, these data suggest that MBL may affect cytokine expression through modulation of LPS-/TLR-signaling pathways. These findings suggest that MBL may play an important role in both immune regulation and the signaling pathways involved in cytokine networks.

Tolerogenic dendritic cells induce CD4+CD25hiFoxp3+ regulatory T cell differentiation from CD4+CD25-/loFoxp3- effector T cells

IL-10-differentiated dendritic cells (DC10) induce allergen tolerance in asthmatic mice, during which their lung Th2 effector T cells (Teffs) are displaced by activated CD4(+)CD25(hi)Foxp3(+) T cells. Intestinal DCs promote oral tolerance by inducing Ag-naive T cells to differentiate into CD4(+)CD25(+)Foxp3(+) regulatory T cells (Tregs), but whether DCs can induce Teffs to differentiate into Tregs remains uncertain. In this study, we addressed this question in OVA-asthmatic mice that were treated with DC10. OVA-presenting DC10 treatment maximally activated lung Tregs in these animals at 3 wk posttreatment, as determined by upregulation of activation markers (ICOS, programmed cell death-1, glucocorticoid-induced TNFR-related protein, LAG3, and CTLA-4) and in functional assays. This in vitro regulatory activity was ≥90% reduced by treatment with anti-IL-10 but not anti-TGF-β Abs. In parallel cultures, OVA- but not house dust mite (HDM)-presenting DC10 induced ≈43% of CFSE-labeled CD25(-/lo)Foxp3(-) Teffs from asthmatic OVA-TCR transgenic mice to differentiate into tolerogenic CD25(hi)Foxp3(+) Tregs. We recapitulated this in vivo using OVA-asthmatic mice that were coinjected with OVA- or HDM-presenting DC10 (i.p.) and CFSE-labeled CD4(+)CD25(-/lo)Foxp3(-) Teffs (i.v.) from the lungs of asthmatic DO11.10 mice. From ≈7 to 21% of the activated (i.e., dividing) DO11.10 Teffs that were recovered from the lungs, lung-draining lymph nodes, or spleens of the OVA-DC10 recipients had differentiated into CD4(+)CD25(hi)Foxp3(+) Tregs, whereas no CFSE-positive Tregs were recovered from the HDM-DC10-treated animals. These data indicate that DC10 treatments induce tolerance at least in part by inducing Teffs to differentiate into CD4(+)CD25(hi)Foxp3(+) Tregs.

Langerhans cells: critical regulators of skin immunity?

Langerhans cells (LC) are members of the heterogenous family of professional antigen presenting dendritic cells (DC). They are identified by the C-type lectin receptor Langerin and form a contiguous network in the epidermis. Consequently, LC are an integral part of the skin barrier to the environment and were considered to be critical inducers of skin immunity, whereas dermal DC were largely overlooked. However, with the identification of a distinct subset of Langerin expressing dermal DC, the situation in the skin has become more complex and the relative contribution of the different cutaneous DC populations in balancing immunity and tolerance has become a matter of active debate. Here, we briefly review the classical paradigm and recent challenges of LC function, before focusing on advances concerning their role in contact hypersensitivity and ultraviolet radiation-induced immunosuppression obtained with in vivo LC ablation models. We then discuss novel LC/DC-specific gene targeting approaches currently used to dissect the role of the regulatory cytokines transforming growth factor-beta and interleukin-10 to govern LC and DC function in vivo. This second generation of LC-specific genetically engineered mice will considerably extend our understanding of the molecular control of LC function in regulating skin immunity and tolerance in the near future.

Systemic but not local infections elicit immunosuppressive IL-10 production by natural killer cells

Surviving infection represents a balance between the proinflammatory responses needed to eliminate the pathogen, and anti-inflammatory signals limiting damage to the host. IL-10 is a potent immunosuppressive cytokine whose impact is determined by the timing and localization of release. We show that NK cells rapidly express IL-10 during acute infection with diverse rapidly disseminating pathogens. The proinflammatory cytokine IL-12 was necessary and sufficient for NK cell induction of IL-10. NK cells from mice with systemic parasitic infection inhibited dendritic cell release of IL-12 in an IL-10-dependent manner, and NK cell depletion resulted in elevated serum IL-12. These data suggest an innate, negative feedback loop in which IL-12 limits its own production by eliciting IL-10 from NK cells. In contrast to disseminating pathogens, locally restricted infections did not elicit NK cell IL-10. Thus systemic infections uniquely engage NK cells in an IL-10-mediated immunoregulatory circuit that functions to alleviate inflammation.

Interleukin-10 and interleukin-12 modulation in patients with relapsing-remitting multiple sclerosis on therapy with interferon-beta 1a: differences in responders and non responders

We examined the effects of interferon (IFN)beta-1a on interleukin (IL)-12p70 and IL-10 secretion in 27 Relapsing Remitting Multiple Sclerosis (RRMS) patients, divided in responders and non-responders. In responders, IFNbeta-1a does not change the IL-12p70 concentrations, but it leads to a remarkable increase in the IL-10 production. Besides, a high IL-10/IL-12 ratio is demonstrated during the first six months of therapy. In non-responders, there were not significant alterations in the cytokine profile. We suggest that IFNbeta-1a effect in RRMS patients could be explained by its modifying effect on cytokine pattern. Moreover, we propose a possible role of IL-10/IL-12 ratio as a serum marker predictive of favorable clinical course.

Co-operative action of interleukin-10 and interferon-gamma to regulate dendritic cell functions

Interleukin-10 (IL-10) and interferon-gamma (IFN-gamma) double producer is found in a subpopulation of T regulatory type 1 (Tr1) and T helper type 1 (Th1) cells. Consequently, it is of interest how IL-10 and IFN-gamma influence the immune system. However, few studies have addressed the co-operative action of these 'immunosuppressive' and 'immunostimulatory' cytokines. Here, we examine the effect of IL-10 combined with IFN-gamma on dendritic cell (DC) functions. Murine bone marrow-derived conventional DCs were stimulated with IL-10 and/or IFN-gamma for 24 hr. Tumour necrosis factor-alpha and IL-12 p40 production by DCs treated with both IL-10 and IFN-gamma was significantly lower than that by DCs treated with IL-10 or IFN-gamma alone. Major histocompatibility complex class II expression on DCs treated with both cytokines was attenuated compared with that on DCs treated with either cytokine alone. In contrast, levels of inducible nitric oxide synthase and indoleamine 2,3-dioxygenase, which appear to suppress T-cell responses and promote tolerance, in DCs treated with both cytokines were higher than those in DCs treated with IL-10 or IFN-gamma alone. Simultaneous treatment with IL-10 and IFN-gamma significantly suppressed the ability of DCs to activate CD4+ T cells compared with treatment with either cytokine. Therefore, IL-10 and IFN-gamma co-operatively suppress the immunostimulatory functions of DCs.