Distinct in vivo roles of CD80 and CD86 in the effector T-cell responses inducing antigen-induced arthritis

Results of flow cytometric detection of gamma-deltaT cells in peripheral blood of patients with ankylosing spondylitis: a pilot study

Previous studies have suggested that gamma-delta T cells play an important role in the pathogenesis of ankylosing spondylitis (AS). In this pilot study, the peripheral blood mononuclear cells (PBMCs) of patients with ankylosing spondylitis (AS) and healthy volunteers were stained and analyzed by flow cytometry to distinguish gamma-delta T cells and its subtypes, and then to report the distribution of gamma-delta T cells and iyts subtypes and their correlation with ankylosing spondylitis. A total of 17 patients with active AS and 10 age- and gender- matched healthy volunteers were enrolled in this study, and their peripheral blood were drawn to collect mononuclear cells (PBMCs). Flow cytometry was used to analyze gamma-delta T cell subpopulations by measuring the surface and intracellular expressions of phenotypic markers. Serum levels of inflammatory and bone turnover markers were measured, and their correlations with subpopulations of gamma-delta T cells were evaluated. In patients with AS, the Vdelta2 fractions within gamma-delta T cells and CD3+ T cells decreased significantly, in particular, the proportions of CD27+ Vdelta2 T cells, CD86+CD80+ Vdelta1 T cells, and IL17A-secreting and TNFalpha-secreting Vdelta1 T cells within the parental cells decreased significantly. gamma-delta T cells/PBMCs, Vdelta2 cells/gamma-delta T cells, and Vdelta2 cells/CD3+ T cells were negatively correlated with CRP, whereas Vdelta1 cells/CD3+ T cells were negatively correlated with ESR. Vdelta1 cells/gamma-delta T cells were positively correlated with CRP, gamma-deltaT cells/PBMCs were positively correlated with beta-CTx, CD69+CD25+ and IL-17A-secreting Vdelta1 cells were positively correlated with TP1NP, and CD69+CD25+ Vdelta1 and Vdelta2 cells were positively correlated with osteocalcin. Decreases in peripheral Vdelta2, CD27+ Vdelta2, CD86+CD80+ Vdelta1, and IL17A or TNFalpha-secreting Vdelta1 T cells are associated with AS. The correlations between gamma-delta T cell subpopulations and CRP and the CD69+CD25+ subpopulation with TP1NP or osteocalcin suggest that an imbalance in peripheral gamma-delta T cell subpopulations contributes to the pathogenesis of AS.

Quantitative analysis of soluble costimulatory molecules as potential diagnostic biomarkers for rheumatoid arthritis using LC-MS/MS in MRM mode

BACKGROUND AND AIMS

Rheumatoid arthritis (RA) is a chronic autoimmune disease. RA-induced immunological responses are coordinated by T-cell stimulation. The costimulatory signal CD28-B7 is essential for T-cell activation by interacting CD28 with CD80 and CD86 costimulatory proteins. CTLA4 is another costimulatory protein that binds to CD80 and CD86 to inhibit T-cell activity. The soluble costimulatory proteins: sCD80, sCD86, sCD28, and sCTLA-4 were detected and quantified in human plasma and correlated with RA development. As potential diagnostic biomarkers for RA, developing a sensitive, specific, and reproducible method for quantifying these costimulatory molecules in human plasma and establishing quantitative ranges for each protein in healthy and RA patients' plasma is essential for advancing the clinical diagnostic and health outcomes.

MATERIALS AND METHODS

A novel quantitative liquid chromatography-tandem spectrometry (LC-MS/MS) technique using multiple reaction monitoring (MRM) modes was developed and validated to measure soluble costimulatory molecules sCTLA4, sCD28, sCD80, and sCD86 in human plasma samples. Furthermore, the method was applied to determine sCTLA4, sCD28, sCD80, and sCD86 levels in plasma samples from RA patients (n = 23) and healthy controls (n = 21).

RESULTS

The method was successfully developed and validated according to international inter- and intra-assay precision and accuracy guidelines. The linearity of the method was achieved between 0.5 nM and 100 nM for each protein with a correlation coefficient of > 0.998. The plasma level of sCTLA4, sCD80, and sCD86 in RA patients was significantly elevated compared to controls. RA patients had 63.32 ± 17.63 nM sCTLA4 and controls 36.05 ± 18.83 nM; p < 0.0001. The performance of the four proteins was determined using ROC curves, where sCTLA4 showed the highest diagnostic and clinical performance compared to the others.

CONCLUSIONS

This study reports the first use of LC-MS/MS in MRM mode to accurately quantify soluble costimulatory molecules in plasma samples as potential RA diagnostic biomarkers. Determination of the reference range for each protein with high selectivity and sensitivity increases the potential for utilizing this method as a clinical diagnostic.

Cell-penetrating TLR inhibitor peptide alleviates ulcerative colitis by the functional modulation of macrophages

Toll-like receptors (TLRs) have a crucial role not only in triggering innate responses against microbes but in orchestrating an appropriate adaptive immunity. However, deregulated activation of TLR signaling leads to chronic inflammatory conditions such as inflammatory bowel disease (IBD). In this study, we evaluated the immunomodulatory potential of a TLR inhibitor in the form of a cell-penetrating peptide using an ulcerative colitis animal model. A peptide derived from the TIR domain of the TLR adaptor molecule TIRAP that was conjugated with a cell-penetrating sequence (cpTLR-i) suppressed the induction of pro-inflammatory cytokines such as TNF-α and IL-1β in macrophages. In DSS-induced colitis mice, cpTLR-i treatment ameliorated colitis symptoms, colonic tissue damage, and mucosal inflammation. Intriguingly, cpTLR-i attenuated the induction of TNF-α-expressing proinflammatory macrophages while promoting that of regulatory macrophages expressing arginase-1 and reduced type 17 helper T cell (Th17) responses in the inflamed colonic lamina propria. An in vitro study validated that cpTLR-i enhanced the differentiation of monocyte-driven macrophages into mature macrophages with a regulatory phenotype in a microbial TLR ligand-independent manner. Furthermore, the cocultivation of CD4 T cells with macrophages revealed that cpTLR-i suppressed the activation of Th17 cells through the functional modulation of macrophages. Taken together, our data show the immunomodulatory potential of the TLR inhibitor peptide and suggest cpTLR-i as a novel therapeutic candidate for the treatment of IBD.

Majoon chobchini reinstates PDL-1 expression and blocks dendritic cell -T helper 17 pathogenic axis in rheumatoid arthritis animal model

Dendritic cells (DCs) are the critical players in the puzzle of rheumatoid arthritis (RA) disease pathogenesis. Blockade of DC activation has been shown to curtail Th17 cell differentiation and its aberrant function in RA. Recent studies have pointed to the role of the PI3K/AKT signaling axis in the maturation and activation of DCs. However, it is yet to be established how PI3K/AKT inhibition would lead to the abolishment of DC activation and Th17 cell plasticity in RA. Herein, our study decoded whether and how majoon chobchini, an unani compound, abated dendritic cell maturation and regulated the Th17/Treg paradigm in RA. Given our results, majoon chobchini conspicuously restrained MHC II, CD86 expression and, subsequently elevated PDL-1 levels in DCs in-vivo. Of note, inhibition of DC maturation by majoon chobchini, in turn, favoured suppression of the Th17 cell population while driving Treg cell development in adjuvant induced arthritic (AA) rats. Concurrently, majoon chobchini decreased the catabolic effects of IL-17 (Th17 associated cytokine) via a reciprocal increase in IL-10 (Treg associated cytokine) levels in AA rats. Mechanistically, majoon chobchini sustained FoxO1 nuclear localization signaled through dampened PI3K/AKT phosphorylation in-vitro. In concert, PDL-1 expression was heightened in majoon chobchini treated activated DCs that provides a framework for ablation of the DC-Th17 cell pathogenic axis in RA. Notwithstanding, the PI3K inhibitor LY294002 exhibited similar inhibitory effects. In essence, majoon chobchini enhanced PDL-1 expression that abolished DC maturation via regulation of the PI3K/AKT/FoxO1 axis, thereby hindering Th17 differentiation in an animal model of RA. This further warrants a clinical investigation that could validate majoon chobchini as a prospective therapeutic drug in the treatment of RA.

Pertussis toxin-induced inhibition of Wnt/β-catenin signaling in dendritic cells promotes an autoimmune response in experimental autoimmune uveitis

BACKGROUND

Previous reports have indicated that disrupting the Wnt/β-catenin pathway in dendritic cells (DCs) may affect the progression of autoimmune inflammation; however, the factors and timing that regulate Wnt/β-catenin signaling have not been clearly understood.

METHODS

Experimental autoimmune uveitis (EAU) mice and Vogt-Koyanagi-Harada disease (VKH) patient samples were used to detect the expression of Wnt/β-catenin pathway genes. Western blot, real-time PCR, flow cytometry, and ELISA were performed to examine the expression of components of the Wnt/β-catenin pathway and inflammatory factors. DC-specific β-catenin knockout mice and 6-bromoindirubin-3'-oxime (BIO) administered mice were used to observe the effect of disrupting the Wnt pathway on EAU pathogenesis.

RESULTS

Wnt/β-catenin signaling was inhibited in DCs during the induction phase of EAU. The inhibition was mediated by pertussis toxin (PTX), which promoted DC maturation, in turn promoting pathogenic T cell proliferation and differentiation. In vivo experiments confirmed that deleting β-catenin in DCs enhanced EAU severity, and pre-injection of PTX advanced EAU onset. Administration of a Wnt activator (BIO) limited the effects of PTX, in turn ameliorating EAU.

CONCLUSIONS

Our results demonstrate that PTX plays a key role as a virulence factor in initiating autoimmune inflammation via DCs by inhibiting Wnt/β-catenin signaling in EAU, and highlight the potential mechanism by which infection can trigger apparent autoimmunity.

Whole Transcriptome Mapping Identifies an Immune- and Metabolism-Related Non-coding RNA Landscape Remodeled by Mechanical Stress in IL-1β-Induced Rat OA-like Chondrocytes

Background: Osteoarthritis (OA) is a common degenerative joint disease. The aims of this study are to explore the effects of mechanical stress on whole transcriptome landscape and to identify a non-coding transcriptome signature of mechanical stress.

Methods: Next-generation RNA sequencing (RNA-seq) was performed on IL-1β-induced OA-like chondrocytes stimulated by mechanical stress. Integrated bioinformatics analysis was performed and further verified by experimental validations.

Results: A total of 5,022 differentially expressed mRNAs (DEMs), 88 differentially expressed miRNAs (DEMIs), 1,259 differentially expressed lncRNAs (DELs), and 393 differentially expressed circRNAs (DECs) were identified as the transcriptome response to mechanical stress. The functional annotation of the DEMs revealed the effects of mechanical stress on chondrocyte biology, ranging from cell fate, metabolism, and motility to endocrine, immune response, and signaling transduction. Among the DELs, ∼92.6% were identified as the novel lncRNAs. According to the co-expressing DEMs potentially regulated by the responsive DELs, we found that these DELs were involved in the modification of immune and metabolism. Moreover, immune- and metabolism-relevant DELs exhibited a notable involvement in the competing endogenous RNA (ceRNA) regulation networks. Silencing lncRNA TCONS_00029778 attenuated cellular senescence induced by mechanical stress. Moreover, the expression of Cd80 was elevated by mechanical stress, which was rescued by silencing TCONS_00029778.

Conclusion: The transcriptome landscape of IL-1β-induced OA-like chondrocytes was remarkably remodeled by mechanical stress. This study identified an immune- and metabolism-related ncRNA transcriptome signature responsive to mechanical stress and provides an insight of ncRNAs into chondrocyte biology and OA.

Proinflammatory and bone protective role of calcitonin gene-related peptide alpha in collagen antibody-induced arthritis

OBJECTIVES

Calcitonin gene-related peptide alpha (αCGRP) represents an immunomodulatory neuropeptide implicated in pain perception. αCGRP also functions as a critical regulator of bone formation and is overexpressed in patients with rheumatoid arthritis (RA). In the present study, we investigated the role of αCGRP in experimental RA regarding joint inflammation and bone remodelling.

METHODS

Collagen II-antibody-induced arthritis (CAIA) was induced in wild type (WT) and αCGRP-deficient (αCGRP-/-) mice. Animals were monitored over 10 and 48 days with daily assessments of the semiquantitative arthritis score and grip strength test. Joint inflammation, cartilage degradation and bone erosions were assessed by histology, gene expression analysis and µCT.

RESULTS

CAIA was accompanied by an overexpression of αCGRP in WT joints. αCGRP-/- mice displayed reduced arthritic inflammation and cartilage degradation. Congruently, the expression of TNF-α, IL-1β, CD80 and MMP13 was induced in WT, but not αCGRP-/- animals. WT mice displayed an increased bone turnover during the acute inflammatory phase, which was not the case in αCGRP-/- mice. Interestingly, WT mice displayed a full recovery from the inflammatory bone disease, whereas αCGRP-/- mice exhibited substantial bone loss over time.

CONCLUSION

This study demonstrates a proinflammatory and bone protective role of αCGRP in CAIA. Our data indicate that αCGRP not only enhances joint inflammation, but also controls bone remodelling as part of arthritis resolution. As novel αCGRP inhibitors are currently introduced clinically for the treatment of migraine, their potential impact on RA progression warrants further clinical investigation.

Anti-inflammatory and immune-modulatory impacts of berberine on activation of autoreactive T cells in autoimmune inflammation

Autoreactive inflammatory CD4+ T cells, such as T helper (Th)1 and Th17 subtypes, have been found to associate with the pathogenesis of autoimmune disorders. On the other hand, CD4+ Foxp3+ T regulatory (Treg) cells are crucial for the immune tolerance and have a critical role in the suppression of the excessive immune and inflammatory response promoted by these Th cells. In contrast, dendritic cells (DCs) and macrophages are immune cells that through their inflammatory functions promote autoreactive T-cell responses in autoimmune conditions. In recent years, there has been increasing attention to exploring effective immunomodulatory or anti-inflammatory agents from the herbal collection of traditional medicine. Berberine, an isoquinoline alkaloid, is one of the main active ingredients extracted from medicinal herbs and has been shown to exert various biological and pharmacological effects that are suggested to be mainly attributed to its anti-inflammatory and immunomodulatory properties. Several lines of experimental study have recently investigated the therapeutic potential of berberine for treating autoimmune conditions in animal models of human autoimmune diseases. Here, we aimed to seek mechanisms underlying immunomodulatory and anti-inflammatory effects of berberine on autoreactive inflammatory responses in autoimmune conditions. Reported data reveal that berberine can directly suppress functions and differentiation of pro-inflammatory Th1 and Th17 cells, and indirectly decrease Th cell-mediated inflammation through modulating or suppressing other cells assisting autoreactive inflammation, such as Tregs, DCs and macrophages.

Macrophage Activation in the Synovium of Healthy and Osteoarthritic Equine Joints

Synovitis is a major component of osteoarthritis and is driven primarily by macrophages. Synovial macrophages are crucial for joint homeostasis (M2-like phenotype), but induce inflammation (M1-like) when regulatory functions become overwhelmed. Macrophage phenotypes in synovium from osteoarthritic and healthy joints are poorly characterized; however, comparative knowledge of their phenotypes during health and disease is paramount for developing targeted treatments. This study compared patterns of macrophage activation in healthy and osteoarthritic equine synovium and correlated histology with cytokine/chemokine profiles in synovial fluid. Synovial histology and immunohistochemistry for M1-like (CD86), M2-like (CD206, IL-10), and pan macrophage (CD14) markers were performed on biopsies from 29 healthy and 26 osteoarthritic equine joints. Synovial fluid cytokines (MCP-1, IL-10, PGE2, IL-1β, IL-6, TNF-α, IL-1ra) and growth factors (GM-CSF, SDF-1α+β, IGF-1, and FGF-2) were quantified. Macrophage phenotypes were not as clearly defined in vivo as they are in vitro. All macrophage markers were expressed with minimal differences between OA and normal joints. Expression for all markers increased proportionate to synovial inflammation, especially CD86. Synovial fluid MCP-1 was higher in osteoarthritic joints while SDF-1 and IL-10 were lower, and PGE2 concentrations did not differ between groups. Increased CD14/CD86/CD206/IL-10 expression was associated with synovial hyperplasia, consistent with macrophage recruitment and activation in response to injury. Lower synovial fluid IL-10 could suggest that homeostatic mechanisms from synovial macrophages became overwhelmed preventing inflammation resolution, resulting in chronic inflammation and OA. Further investigations into mechanisms of arthritis resolution are warranted. Developing pro-resolving therapies may provide superior results in the treatment of OA.

Inflamed synovial fluid induces a homeostatic response in bone marrow mononuclear cells in vitro: Implications for joint therapy

Synovial inflammation is a central feature of osteoarthritis (OA), elicited when local regulatory macrophages (M2-like) become overwhelmed, activating an inflammatory response (M1-like). Bone marrow mononuclear cells (BMNC) are a source of naïve macrophages capable of reducing joint inflammation and producing molecules essential for cartilage metabolism. This study investigated the response of BMNC to normal (SF) and inflamed synovial fluid (ISF). Equine BMNC cultured in autologous SF or ISF (n = 8 horses) developed into macrophage-rich cultures with phenotypes similar to cells native to normal SF and became more confluent in ISF (~100%) than SF (~25%). BMNC cultured in SF or ISF were neither M1- nor M2-like, but exhibited aspects of both phenotypes and a regulatory immune response, characterized by increasing counts of IL-10⁺ macrophages, decreasing IL-1β concentrations and progressively increasing IL-10 and IGF-1 concentrations. Changes were more marked in ISF and suggest that homeostatic mechanisms were preserved over time and were potentially favored by progressive cell proliferation. Collectively, our data suggest that intra-articular BMNC could increase synovial macrophage counts, potentiating the macrophage- and IL-10-associated mechanisms of joint homeostasis lost during the progression of OA, preserving the production of cytokines involved in tissue repair (PGE₂ , IL-10) generally impaired by frequently used corticosteroids.

Samsum ant venom modulates the immune response and redox status at the acute toxic dose in vivo

Background:

Ant venoms express surface molecules that participate in antigen presentation involving pro- and anti-inflammatory cytokines. This work aims to investigate the expression of MHC-II, CD80 and CD86 on the polymorphonuclear cells (PMNs) in rats injected with samsum ant venom (SAV).

Methods:

Rats were divided into three groups - control, SAV-treated (intraperitoneal route, 600 μg/kg), and SAV-treated (subcutaneous route, 600 μg/kg). After five doses, animals were euthanized and samples collected for analysis.

Results:

The subcutaneous SAV-trated rats presented decreased levels of glutathione with increased cholesterol and triglyceride levels. Intraperitoneal SAV-treated animals displayed significantly reduced concentrations of both IFN-γ and IL-17 in comparison with the control group. However, intraperitoneal and subcutaneous SAV-treated rats were able to upregulate the expressions of MHC-II, CD80 and CD86 on PMNs in comparison with the control respectively. The histological examination showed severe lymphocyte depletion in the splenic white pulp of the intraperitoneal SAV-injected rats.

Conclusion:

Stimulation of PMNs by SAV leads to upregulation of MHC-II, CD 80, and CD 86, which plays critical roles in antigen presentation and consequently proliferation of T-cells. Subcutaneous route was more efficient than intraperitoneal by elevating MHC-II, CD80 and CD86 expression, disturbing oxidative stability and increasing lipogram concentration.

Autologous bone marrow mononuclear cells modulate joint homeostasis in an equine in vivo model of synovitis

Osteoarthritis (OA) is characterized by macrophage-driven synovitis. Macrophages promote synovial health but become inflammatory when their regulatory functions are overwhelmed. Bone marrow mononuclear cells (BMNCs) are a rich source of macrophage progenitors used for treating chronic inflammation and produce essential molecules for cartilage metabolism. This study investigated the response to autologous BMNC injection in normal and inflamed joints. Synovitis was induced in both radiocarpal joints of 6 horses. After 8 h, 1 inflamed radiocarpal and 1 normal tarsocrural joint received BMNC injection. Contralateral joints were injected with saline. Synovial fluid was collected at 24, 96, and 144 h for cytology, cytokine quantification, and flow cytometry. At 144 h, horses were euthanatized, joints were evaluated, and synovium was harvested for histology and immunohistochemistry. Four days after BMNC treatment, inflamed joints had 24% higher macrophage counts with 10% more IL-10⁺ cells than saline-treated controls. BMNC-treated joints showed gross and analytical improvements in synovial fluid and synovial membrane, with increasing regulatory macrophages and synovial fluid IL-10 concentrations compared with saline-treated controls. BMNC-treated joints were comparable to healthy joints histologically, which remained abnormal in saline-treated controls. Autologous BMNCs are readily available, regulate synovitis through macrophage-associated effects, and can benefit thousands of patients with OA.-Menarim, B. C., Gillis, K. H., Oliver, A., Mason, C., Ngo, Y., Werre, S. R., Barrett, S. H., Luo, X., Byron, C. R., Dahlgren, L. A. Autologous bone marrow mononuclear cells modulate joint homeostasis in an equine in vivo model of synovitis.

NP30 stimulates Th17 differentiation through DC in Schistosomiasis Japonicum

The murine monoclonal anti‐idiotypic antibody, NP30, is a potential vaccine candidate against Schistosoma japonicum. Previous studies have revealed that NP30 has an immunoregulatory effect, but the underlying mechanism for this effect remains unknown. This study shows that NP30 induces dendritic cell (DC) maturation and increases the production of pro‐inflammatory cytokines. The expression of CD86 and MHC II was upregulated in DCs following stimulation with NP30 in vitro. Moreover, NP30 induced Th17 polarization by increasing the production of IL‐6 and TGF‐β. In vivo, Th17 differentiation was induced by the production of key pro‐inflammatory cytokines, including IL‐6and TGF‐β, from DCs of NP30‐immunized mice. These results indicate that NP30 promotes Th17 polarization through DC activation, preventing serious schistosomiasis.

Generation of Macrophages from Cynomolgus-Monkey Bone Marrow as a Model to Evaluate Effects of Drugs on Innate Immunity

Macrophages are innate immune cells that play important roles in various physiological and pathological processes. Evaluation of pro-inflammatory effects of drugs on macrophages has become commonplace in preclinical drug development prior to human clinical trials. Despite their body-wide distribution, tissue macrophages are often difficult to collect from large animals and humans in a noninvasive manner. Therefore, in vitro-differentiated macrophages are important tools to facilitate cross-species analysis of macrophage function. Although cynomolgus monkeys are an essential non-rodent species for preclinical research, in vitro differentiation of cynomolgus-monkey macrophages has been poorly characterized. In the present unit, we describe a protocol to differentiate cynomolgus-monkey macrophages from isolated bone marrow mononuclear cells (BMMCs). In contrast to monocytes, cynomolgus-monkey BMMCs show robust expansion in the presence of macrophage colony-stimulating factor in vitro, which allows expansion of many cells from a single animal donor. Macrophages differentiated from BMMCs retain many of the macrophage phenotypes and functions, including phagocytosis and cytokine release, and therefore can be used as a surrogate to assess effects of drugs on cynomolgus-monkey macrophages. © 2019 by John Wiley & Sons, Inc.

Fas receptor induces apoptosis of synovial bone and cartilage progenitor populations and promotes bone loss in antigen-induced arthritis

Rheumatoid arthritis (RA) is an inflammatory joint disease that eventually leads to permanent bone and cartilage destruction. Fas has already been established as the regulator of inflammation in RA, but its role in bone formation under arthritic conditions is not completely defined. The aim of this study was to assess the effect of Fas inactivation on the bone damage during murine antigen-induced arthritis. Subchondral bone of wild-type (WT) and Fas-knockout (Fas^-/-) mice was evaluated by histomorphometry and microcomputerized tomography. Proportions of synovial bone and cartilage progenitors were assessed by flow cytometry. Synovial bone and cartilage progenitors were purified by fluorescence-activated cell sorting and expression of Fas and Fas-induced apoptosis were analyzed in vitro. Results showed that Fas^-/- mice developed attenuated arthritis characterized by preserved epiphyseal bone and cartilage. A proportion of the earliest CD200⁺ bone and cartilage progenitors was reduced in WT mice with arthritis and was unaltered in Fas^-/- mice. During osteoblastic differentiation in vitro, CD200⁺ cells express the highest levels of Fas and are removed by Fas ligation. These results suggest that Fas-induced apoptosis of early CD200⁺ osteoprogenitor population represents potential mechanism underlying the impaired bone formation in arthritis, so their preservation may represent the bone-protective mechanism during arthritis.-Lazić Mosler, E., Lukač, N., Flegar, D., Fadljević, M., Radanović, I., Cvija, H., Kelava, T., Ivčević, S., Šućur, A., Markotić, A., Katavić, V., Marušić, A., Grčević, D., Kovačić, N. Fas receptor induces apoptosis of synovial bone and cartilage progenitor populations and promotes bone loss in antigen-induced arthritis.

Macrophages: Their Untold Story in T Cell Activation and Function

The complexity of T cell activation to maintain homeostasis and provide host defense is highlighted by the intricate step-wise process which is coordinated by multiple cell types. Crucial to T cell activation is the requirement of antigen-presenting cells (APCs) such as macrophages at each step of the activation and effector stages. Macrophages are central regulators in T cell activation and are involved in each step including initiating the series of events leading to T cell activation. Macrophages identify and present foreign antigens in classes I and II major histocompatibility complexes (MHC) to T cells, which recognize the MHC-antigen complex through their T cell receptor. This initial step is all in vain if additional costimulatory and cytokine signaling does not occur concurrently. Macrophages can mediate and provide the required costimulatory signaling and cytokine secretion required for effective T cell activation. While other cell types, especially other APCs, may be capable of playing a role during different stages of T cell activation, this review will focus on how macrophages can modulate T cell activation and effector function. This is in no way an attempt to minimize the role of other APCs but instead to bring to light to the role macrophages can play during this process. Here, the role macrophages play in cancer to either activate or inhibit T cells based on macrophage phenotype, costimulatory molecules, and cytokine secretion is highlighted as an example of how macrophages can significantly alter T cell activation and effector function in human disease.

Formyl peptide receptor activation inhibits the expansion of effector T cells and synovial fibroblasts and attenuates joint injury in models of rheumatoid arthritis

The effects of formyl peptide receptors (FPRs) on effector T cells and inflammation-causing tissue-resident cells are not well known. Here, we explored the effect of FPR activation on efferent T cell responses in models of rheumatoid arthritis (RA) and on the expansion of fibroblast-like synoviocytes (FLS). Compound 43 (Cpd43; FPR1/2 agonist) was administered to mice with collagen-induced arthritis (CIA) or antigen-induced arthritis (AIA) after disease onset. Joint inflammation/damage and immunity were assessed. FLS were cultured with Cpd43 to test its effects on cell apoptosis and proliferation. To explore the effects of endogenous FPR2 ligands on FLS proliferation, FLS FPR2 was blocked or Annexin A1 (AnxA1) expression silenced. Cpd43 reduced arthritis severity in both models. In CIA, Cpd43 decreased CD4 T cell proliferation and survival and increased the production of the protective cytokine, IFNγ, in lymph nodes. In AIA, Cpd43 increased CD4 apoptosis and production of the anti-inflammatory IL-4, while augmenting the proportion of splenic regulatory T cells and their expression of IL-2Rα. In both models, Cpd43 increased CD4 IL-17A production, without affecting humoral immunity. FPR2 inhibitors reversed Cpd43-mediated effects on AIA and T cell immunity. Cpd43 decreased TNF-induced FLS proliferation and augmented FLS apoptosis in association with intracellular FPR2 accumulation, while endogenous AnxA1 and FPR2 reduced FLS proliferation via the ERK and NFκB pathways. Overall, FPR activation inhibits the expansion of arthritogenic effector CD4 T cells and FLS, and reduces joint injury in experimental arthritis. This suggests the therapeutic potential of FPR ligation for the treatment of RA.

Estrogen receptor β activation stimulates the development of experimental autoimmune thyroiditis through up-regulation of Th17-type responses

Estrogens play important roles in autoimmune thyroiditis, but it remains unknown which estrogen receptor (ER) subtype mediates the stimulatory effects. Herein we treated ovariectomized mice with ERα or ERβ selective agonist followed by thyroglobulin-immunization to induce experimental autoimmune thyroiditis (EAT), and observed the aggravation of EAT after diarylpropionitrile (DPN, ERβ selective agonist) administration. The mRNA levels of interleukin(IL)-17A, IL-21 and RORγt and percentages of T helper (Th) 17 cells were up-regulated in the splenocytes of DPN-treated mice. Activated ERβ was found directly binding to IL-17A and IL-21 gene promoters, and also indirectly promoting IL-21 and RORγt gene transcription through interaction with NF-κB. The expressions of co-stimulatory molecules were increased on antigen-presenting cells (APCs) after DPN administration. It suggests that ERβ is the predominant ER subtype responsible for EAT development, and its activation may enhance Th17-type responses through genomic pathways and alteration of APCs' activities.

Novel identified aluminum hydroxide-induced pathways prove monocyte activation and pro-inflammatory preparedness

Aluminum-based adjuvants are the most widely used adjuvants in human vaccines. A comprehensive understanding of the mechanism of action of aluminum adjuvants at the molecular level, however, is still elusive. Here, we unravel the effects of aluminum hydroxide Al(OH)₃ by a systems-wide analysis of the Al(OH)₃-induced monocyte response. Cell response analysis by cytokine release was combined with (targeted) transcriptome and full proteome analysis. Results from this comprehensive study revealed two novel pathways to become activated upon monocyte stimulation with Al(OH)₃: the first pathway was IFNβ signaling possibly induced by DAMP sensing pathways like TLR or NOD1 activation, and second the HLA class I antigen processing and presentation pathway. Furthermore, known mechanisms of the adjuvant activity of Al(OH)₃ were elucidated in more detail such as inflammasome and complement activation, homeostasis and HLA-class II upregulation, possibly related to increased IFNγ gene expression. Altogether, our study revealed which immunological pathways are activated upon stimulation of monocytes with Al(OH)₃, refining our knowledge on the adjuvant effect of Al(OH)₃ in primary monocytes.

SIGNIFICANCE

Aluminum salts are the most used adjuvants in human vaccines but a comprehensive understanding of the working mechanism of alum adjuvants at the molecular level is still elusive. Our Systems Vaccinology approach, combining complementary molecular biological, immunological and mass spectrometry-based techniques gave a detailed insight in the molecular mechanisms and pathways induced by Al(OH)₃ in primary monocytes. Several novel immunological relevant cellular pathways were identified: type I interferon secretion potentially induced by TLR and/or NOD like signaling, the activation of the inflammasome and the HLA Class-I and Class-II antigen presenting pathways induced by IFNγ. This study highlights the mechanisms of the most commonly used adjuvant in human vaccines by combing proteomics, transcriptomics and cytokine analysis revealing new potential mechanisms of action for Al(OH)₃.

Spirulina lipopolysaccharides inhibit tumor growth in a Toll-like receptor 4-dependent manner by altering the cytokine milieu from interleukin-17/interleukin-23 to interferon-γ

Th17 cells and the cytokine they produce, interleukin (IL)-17, play an important role in tumor progression in humans and in mice. IL-6 and IL-23 are critical cytokines for the differentiation and propagation of Th17 cells, respectively. Bacterial lipopolysaccharides (LPS) are known to stimulate immune cells to produce such inflammatory cytokines. Contrary to Escherichia coli (E. coli) LPS, LPS from Spirulina has low toxicity and barely induces in vivo production of IL-6 and IL-23 in mice. We examined the antitumor effects of Spirulina LPS compared to E. coli LPS in an MH134 hepatoma model. Administration of Spirulina LPS suppressed tumor growth in C3H/HeN mice, but not in Toll-like receptor 4 (TLR4)-mutant C3H/HeJ mice, by reducing serum levels of IL-17 and IL-23, while increasing interferon (IFN)-γ levels. The antitumor activity and IFN-γ production were mediated by T cells. Moreover, in vitro experiments showed that Spirulina LPS impaired the antigen-presenting function that supports the generation of IL-17-producing cells in a toll-like receptor (TLR)4-dependent manner. Of note, injection of anti-IL-17 antibody in tumor-bearing C3H/HeN mice in the absence of Spirulina LPS markedly suppressed tumor growth and augmented IFN-γ responses. Thus, our results support the notion that IFN-γ and IL-17/IL-23 mutually regulate Th17 and Th1 responses in tumor-bearing hosts, and Spirulina LPS modulates the balance of the IFN-γ-IL-17/IL-23 axis towards IFN-γ production, which leads to tumor inhibition. Furthermore, Spirulina LPS effectively inhibited the spontaneous development of mammary tumors. This study has important implications for the exploitation of TLR-based immunomodulators for cancer immunotherapy.

The tyrosine kinase inhibitor tyrphostin AG126 reduces activation of inflammatory cells and increases Foxp3+ regulatory T cells during pathogenesis of rheumatoid arthritis

Protein tyrosine kinases are key mediators of the signal transduction cascades that control expression of many genes involved in the induction of inflammation caused by arthritis. Here we investigate the effect of the tyrosine kinase inhibitor tyrphostin AG126 on a mouse model of adjuvant-induced arthritis (AIA). We report that when given at 5mg/kg i.p. every 48h from days 0-21, AG126 exerts potent anti-arthritic effects. Further, we investigated the role of AG126 on the key mediators of arthritic inflammation, namely, edema, arthritic score, presence of immunophenotypes including Foxp3⁺, CD4⁺Foxp3⁺, and CD25⁺Foxp3⁺ T regulatory (Treg) cells, as well as pro- and anti-inflammatory mediators. AG126 treatment significantly attenuated the severity of AIA and caused a substantial reduction in the percentage of CD2⁺, CD3⁺, CD4⁺, CD8⁺, CD23⁺, CD80⁺, CD86⁺ CD122⁺, CD195⁺, TCRβ⁺, and GITR⁺ cells in whole blood. Moreover, administration of AG126 under arthritis-inducing conditions resulted in suppression of IL-17A⁺, IFN-γ⁺, CD4⁺ and CD25⁺ populations while causing an increase in the Foxp3⁺, CD4⁺Foxp3⁺, and CD25⁺Foxp3⁺ Treg populations in the spleen. In addition, RT-PCR analysis revealed increased expression of CD4, CD8, IL-17A, IFN-γ, TNF-α, and NF-κB p65 mRNAs and decreased IL-4 mRNA in the arthritic control (AC) mice, while treatment of animals with AG126 reversed these effects. Western blot analysis confirmed the decreased expression of IL-17, GITR, NF-κB p65 proteins and increased Foxp3 and IL-4 proteins following AG126 treatment of knee tissue. Thus, our findings provide new evidence that inhibition of protein tyrosine kinase activity decreases the progression of arthritis.

Delivery of siRNAs to Dendritic Cells Using DEC205-Targeted Lipid Nanoparticles to Inhibit Immune Responses

Due to their ability to knock down the expression of any gene, siRNAs have been heralded as ideal candidates for treating a wide variety of diseases, including those involving "undruggable" targets. However, the therapeutic potential of siRNAs remains severely limited by a lack of effective delivery vehicles. Recently, lipid nanoparticles (LNPs) containing ionizable cationic lipids have been developed for hepatic siRNA delivery. However, their suitability for delivery to other cell types has not been determined. We have modified LNPs for preferential targeting to dendritic cells (DCs), central regulators of immune responses. To achieve directed delivery, we coated LNPs with a single-chain antibody (scFv; DEC-LNPs), specific to murine DEC205, which is highly expressed on distinct DC subsets. Here we show that injection of siRNAs encapsulated in DEC-LNPs are preferentially delivered to DEC205(+) DCs. Gene knockdown following uptake of DEC-LNPs containing siRNAs specific for the costimulatory molecules CD40, CD80, and CD86 dramatically decreases gene expression levels. We demonstrate the functionality of this knockdown with a mixed lymphocyte response (MLR). Overall, we report that injection of LNPs modified to restrict their uptake to a distinct cell population can confer profound gene knockdown, sufficient to inhibit powerful immune responses like the MLR.

Impact of Notch1 Deletion in Macrophages on Proinflammatory Cytokine Production and the Outcome of Experimental Autoimmune Encephalomyelitis

Notch signaling is involved in regulating TLR-mediated responses in activated macrophages. In this study, we investigated the impact of Notch signaling in macrophages in an experimental autoimmune encephalomyelitis (EAE) model. To examine the impact of deficiency in Notch signaling in activated macrophages in EAE, an adoptive transfer of activated macrophages derived from Notch1(fl/fl) × Mx1cre(+/-) (Notch1 knockout [N1KO]) or CSL/Rbp-jκ(fl/fl) × Mx1cre(+/-) (CSL/RBP-Jκ KO) mice was performed prior to induction of EAE. Mice receiving activated N1KO macrophages showed decreased severity of EAE compared with mice receiving wild-type or CSL/RBP-Jκ KO macrophages. In vitro restimulation of splenocytes by myelin oligodendrocyte glycoprotein 35-55 peptide from these mice revealed that cells from mice receiving N1KO macrophages produced significantly less IL-17 compared with the control mice, whereas IFN-γ production was similar in both groups. We found that activated N1KO, but not CSL/RBP-Jκ KO, macrophages produced less IL-6 and had lower CD80 expression compared with wild-type and did not exhibit any defect in IL-12p40/70 production, whereas activated macrophages from CSL/RBP-Jκ KO mice phenocopied γ-secretase inhibitor treatment for reduced IL-12p40/70 production. Furthermore, the nuclear translocation of the NF-κB subunit c-Rel was compromised in γ-secretase inhibitor-treated and CSL/RBP-Jκ KO but not N1KO macrophages. These results suggest that Notch1 and CSL/RBP-Jκ in macrophages may affect the severity of EAE differently, possibly through modulating IL-6 and CD80 expression, which is involved in the Th17 but not Th1 response.

Histamine 4 receptor promotes expression of costimulatory B7.1/B7.2 molecules, CD28 signaling and cytokine production in stress-induced immune responses

Recently, the expression of histamine 4 receptor (H4R) on neurons was reported, however its function in cells within the central nervous system (CNS) remains poorly understood. To this end, we used the H4R agonist, 4-methylhistamine (4-MeH), and the H4R antagonist, JNJ77777120 (JNJ), to investigate the function of H4R signaling in immune cells in a murine model of chronic stress. Treatment of stressed mice with 4-MeH resulted in an increase in the proportion of lymphocyte subsets (CD3(+), CD8(+), CD28(+), and CD4(+)CD28(+)) and cells expressing the co-stimulatory molecules CD80(+) (B7.1) and CD86(+) (B7.2) in heparinized blood as compared to normal control (NC) and stressed control (SC) groups. We also observed that as compared to NC and SC mice, 4-MeH-treated mice showed greater production of IL-2(+), IL-6(+), IL-9(+), IL-21(+), and IL-27(+) cytokines in the spleen and by splenic CD4(+) T cells. Furthermore, 4-MeH treatment of stressed mice led to an increase in the levels of serum Th1/Th17 cytokines and corticosterone, and a decrease in Th2 cytokines. Treatment of chronically-stressed mice with 4-MeH also augmented expression of IL-6, IL-21, NF-κB p65, and STAT3 mRNA. Moreover, Western blot analyses confirmed increased protein expression of NF-κB, iNOS, and STAT3 expression following 4-MeH treatment of chronically-stressed mice as compared to controls. These proteins provide a novel relevant targets for the manipulation of chronic stress induced immune regulation. In striking contrast, treatment of stressed mice with the H4R antagonist, JNJ, resulted in a substantial reduction in all of the aforementioned effects upon immune cell percentages and cytokine production.

Endogenous myeloperoxidase is a mediator of joint inflammation and damage in experimental arthritis

OBJECTIVE

Myeloperoxidase (MPO) is implicated as a local mediator of tissue damage when released extracellularly in many chronic inflammatory diseases. The purpose of this study was to explore the role of endogenous MPO in experimental rheumatoid arthritis (RA).

METHODS

K/BxN serum-transfer arthritis was induced in C57BL/6 wild-type (WT) and MPO knockout (MPO(-/-) ) mice, and disease development was assessed. MPO activity was measured in joint tissues from mice with or without K/BxN arthritis. Collagen-induced arthritis (CIA) was induced in WT and MPO(-/-) mice, and disease development and immune responses were examined. MPO expression was assessed in synovial biopsy samples from patients with active RA, and the effect of MPO on synovial fibroblasts was tested in vitro.

RESULTS

MPO was up-regulated in the joints of mice with K/BxN arthritis, and MPO deficiency attenuated the severity of the disease without affecting circulating cytokine levels. In CIA, MPO(-/-) mice had enhanced CD4+ T cell responses and reduced frequency of regulatory T cells in the lymph nodes and spleen, as well as augmented interleukin-17A and diminished interferon-γ secretion by collagen-stimulated splenocytes, without an effect on circulating anticollagen antibody levels. Despite enhanced adaptive immunity in secondary lymphoid organs, CIA development was attenuated in MPO(-/-) mice. Intracellular and extracellular MPO was detected in the synovium of patients with active RA, and human MPO enhanced the proliferation and decreased the apoptosis of synovial fibroblasts in vitro.

CONCLUSION

MPO contributes to the development of arthritis despite suppressing adaptive immunity in secondary lymphoid organs. This suggests distinct effects of local MPO on arthritogenic effector responses.

OCILRP2 signaling synergizes with LPS to induce the maturation and differentiation of murine dendritic cells

Osteoclast Inhibitory Lectin-related Protein 2 (OCILRP2) is a typical type II transmembrane protein and belongs to C-type lectin-related protein family. It is preferentially expressed in dendritic cells (DC), B lymphocytes, and activated T lymphocytes. Upon binding to its ligand, OCILRP2 can promote CD28-mediated co-stimulation and enhance T cell activation. However, the role of OCILRP2 in DC development and activation is unclear. In this report, we present evidence that recombinant protein OCILRP2-Fc inhibits the generation and LPS-induced maturation of murine bone marrow-derived dendritic cells (BMDCs) by downregulating the expression of CD11c, MHC-II, and co-stimulators CD80 and CD86. OCILRP2-Fc also reduces the capacity of BMDCs to take up antigens, activates T cells, and secret inflammatory cytokines such as IL-6, IL-12, and TNF-α. Additionally, we show that OCILRP2-Fc may cause the aforementioned effects through inhibiting NF-κB activation. Therefore, OCILRP2 is a new regulator of DC maturation and differentiation following TLR4 activation.

Differential IL-10 production by DCs determines the distinct adjuvant effects of LPS and PTX in EAE induction

Pertussis toxin (PTX) is used as an adjuvant to induce EAE in mice as a model of MS. Although LPS and PTX are similar in their ability to mature dendritic cells (DCs) and in their adjuvant properties, here we demonstrate that LPS does not induce EAE development. We also demonstrate that DCs treated with PTX (PTX-DCs) are able to induce EAE, whereas DCs treated with LPS (LPS-DCs) fail to induce EAE. We determine that a key difference between LPS-DCs and PTX-DCs is that LPS-DCs produce larger amounts of IL-10. IL-10(-/-) -DCs treated with LPS promote stronger IFN-γ and IL-17 production and T-cell proliferation than WT DCs treated with LPS in a coculture system. Finally, we demonstrate that EAE can be successfully induced when IL-10(-/-) -DCs treated with LPS are used as an adjuvant, whereas the use of PTX-DCs overexpressing IL-10 as an adjuvant markedly controls EAE development. These results indicate that the inability of LPS to induce EAE is based on the induction of high levels of IL-10 in the targeted DCs, providing insight into the mechanisms responsible for the induction of EAE.

Mycoplasma superantigen initiates a TLR4-dependent Th17 cascade that enhances arthritis after blocking B7-1 in Mycoplasma arthritidis-infected mice

Mycoplasma arthritidis is a natural pathogen of rodents causing arthritis, toxic shock and necrotizing fasciitis. It secretes a potent superantigen (SAg), MAM, that differentially affects the immune system depending upon presence or absence of TLR4, thus potentially influencing disease outcomes. Here, we establish that antibody to co-stimulatory molecule B7-1(CD80) enhances arthritis in wild-type C3H/HeSnJ (TLR2+4+) mice but suppresses arthritis in TLR4-defect C3H/HeJ (TLR2+4-) mice. Also, blockade of the B7-1/CD28 co-stimulatory pathway in C3H/HeSnJ mice resulted in a marked increase in an alternative co-stimulatory pathway ICOS/ICOSL that was associated with elevation of the IL-17/Th17cascade with enhanced IL-23, IL-6, and the RORγt and STAT3 transcriptional factors on CD4+ T cells. Anti- B7-1 also increased inflammatory chemokines and the stress protein HMGB1 that promotes cellular infiltration to joints. Using a MAM-deficient strain of M. arthritidis, a monoclonal antibody to TLR4 and a TLR4-defective mouse strain, we established that both MAM and TLR4 are required for the systemic and local joint triggering of the Th17/IL-17 cascade in mice treated with anti-B7-1 antibody. Importantly, blocking of IL-17 with anti-IL-17 antibody suppressed the elevated arthritis in M. arthritidis-infected mice treated with anti-B7-1 antibody. Thus, this unique model of arthritis illustrates how microbial agonists can bridgeinnate and adaptive immune responses to redirect signalling pathways, thus promoting chronic inflammatory and autoimmune disease.

Equivalent functions for B7.1 and B7.2 costimulation in mediating host resistance to Mycobacterium tuberculosis

B7.1 and B7.2 are homologous costimulatory molecules expressed predominantly on antigen-presenting cells (APC). Interaction of these B7 molecules with CD28 and CTLA-4 expressed on T cells is a critical step in T cell activation. Previously, we reported that Mycobacterium tuberculosis infection in the combined absence of B7.1 and B7.2 resulted in impaired host resistance to the pathogen. Despite their structural similarities, the individual contribution of B7.1 and B7.2 to the development of pathogenic T cells in autoimmune diseases and protective T cells in infectious diseases is markedly distinct. In the current study, we therefore examined whether B7.1 and B7.2 have discrete, equivalent, or overlapping functions in mediating host resistance to M. tuberculosis. We found that the individual absence of either B7.1 or B7.2 had no effect on the ability of the host to contain bacterial load in the lungs, recruit immune cells to the lung, generate a Th1 response, or induce a pulmonary granulomatous response. These results indicate that B7.1 and B7.2 molecules have equal ability to mediate host resistance to M. tuberculosis, underscoring the therapeutic utility of individual B7.1 and B7.2 antagonists in treating inflammatory disorders.

Novel immunomodulators from hard ticks selectively reprogramme human dendritic cell responses

Hard ticks subvert the immune responses of their vertebrate hosts in order to feed for much longer periods than other blood-feeding ectoparasites; this may be one reason why they transmit perhaps the greatest diversity of pathogens of any arthropod vector. Tick-induced immunomodulation is mediated by salivary components, some of which neutralise elements of innate immunity or inhibit the development of adaptive immunity. As dendritic cells (DC) trigger and help to regulate adaptive immunity, they are an ideal target for immunomodulation. However, previously described immunoactive components of tick saliva are either highly promiscuous in their cellular and molecular targets or have limited effects on DC. Here we address the question of whether the largest and globally most important group of ticks (the ixodid metastriates) produce salivary molecules that specifically modulate DC activity. We used chromatography to isolate a salivary gland protein (Japanin) from Rhipicephalus appendiculatus ticks. Japanin was cloned, and recombinant protein was produced in a baculoviral expression system. We found that Japanin specifically reprogrammes DC responses to a wide variety of stimuli in vitro, radically altering their expression of co-stimulatory and co-inhibitory transmembrane molecules (measured by flow cytometry) and their secretion of pro-inflammatory, anti-inflammatory and T cell polarising cytokines (assessed by Luminex multiplex assays); it also inhibits the differentiation of DC from monocytes. Sequence alignments and enzymatic deglycosylation revealed Japanin to be a 17.7 kDa, N-glycosylated lipocalin. Using molecular cloning and database searches, we have identified a group of homologous proteins in R. appendiculatus and related species, three of which we have expressed and shown to possess DC-modulatory activity. All data were obtained using DC generated from at least four human blood donors, with rigorous statistical analysis. Our results suggest a previously unknown mechanism for parasite-induced subversion of adaptive immunity, one which may also facilitate pathogen transmission.

Dendritic cells (DC) are specialised cells of the vertebrate immune system. DC can sense different types of infectious agents and parasites, and both trigger and help regulate the specific types of immunity needed to eliminate them. We have discovered that the largest and globally most important group of hard ticks produce a unique family of proteins in their saliva that selectively targets DC, radically altering functions that would otherwise induce robust immune responses; these proteins also prevent DC developing from precursor cells. The production of these salivary molecules may help to explain two highly unusual features of these hard ticks compared with other blood-feeding parasites: their ability to feed continuously on their vertebrate hosts for considerable lengths of time (7 days or more) without eliciting potentially damaging immune responses, and their capacity to transmit possibly the greatest variety of pathogens of any type of invertebrate.

Low dose decitabine treatment induces CD80 expression in cancer cells and stimulates tumor specific cytotoxic T lymphocyte responses

Lack of immunogenicity of cancer cells has been considered a major reason for their failure in induction of a tumor specific T cell response. In this paper, we present evidence that decitabine (DAC), a DNA methylation inhibitor that is currently used for the treatment of myelodysplastic syndrome (MDS), acute myeloid leukemia (AML) and other malignant neoplasms, is capable of eliciting an anti-tumor cytotoxic T lymphocyte (CTL) response in mouse EL4 tumor model. C57BL/6 mice with established EL4 tumors were treated with DAC (1.0 mg/kg body weight) once daily for 5 days. We found that DAC treatment resulted in infiltration of IFN-γ producing T lymphocytes into tumors and caused tumor rejection. Depletion of CD8⁺, but not CD4⁺ T cells resumed tumor growth. DAC-induced CTL response appeared to be elicited by the induction of CD80 expression on tumor cells. Epigenetic evidence suggests that DAC induces CD80 expression in EL4 cells via demethylation of CpG dinucleotide sites in the promoter of CD80 gene. In addition, we also showed that a transient, low-dose DAC treatment can induce CD80 gene expression in a variety of human cancer cells. This study provides the first evidence that epigenetic modulation can induce the expression of a major T cell co-stimulatory molecule on cancer cells, which can overcome immune tolerance, and induce an efficient anti-tumor CTL response. The results have important implications in designing DAC-based cancer immunotherapy.

Montelukast inhibits leukotriene stimulation of human dendritic cells in vitro

BACKGROUND

Leukotrienes are potent inflammatory mediators which modulate immune responses and induce bronchoconstriction in susceptible individuals. Montelukast (MK) is a leukotriene receptor (CysLT1) antagonist that has been shown to prevent exacerbation of asthma. Considering the plethora of potential cellular targets for MK, specific mechanisms for its therapeutic action are still not fully understood. In vitro, we determined whether human dendritic cell function could be affected by leukotriene C(4) (LTC(4)) treatment and whether MK had potential in modulating this response. We also studied the effect of LTC(4) in the context of response to an airway virus (respiratory syncytial virus, RSV).

METHODS

Human monocyte-derived dendritic cells (moDCs) exposed to LTC(4), MK, or both, were cocultured with autologous T cells, with or without RSV. The effects of LTC(4) and MK on cell function were determined by ELISA and proliferation assays.

RESULTS

Both moDCs and their precursors--monocytes--express LTC(4) receptor CysLT1, making them potential targets for MK. moDCs cultured with LTC(4) release the eosinophil chemoattractant RANTES (CCL5) and induce greater T cell proliferation. Both were blocked by the presence of MK. MK treatment, albeit anti-inflammatory, did not interfere with the moDC-dependent T cell-proliferative responses induced by RSV.

CONCLUSIONS

LTC(4), chronically present in the airways of asthma patients, could induce an exaggerated inflammatory response to airway infection via dendritic cell activation, which would be prevented by MK. Our study provides additional insight into the mechanisms of action of this leukotriene receptor antagonist.

Regulation of TH17 cell differentiation by innate immune signals

Upon antigen stimulation, naive T helper cells differentiate into distinct lineages to attain specialized properties and effector functions. T(H)17 cells, a recently identified lineage of CD4(+) effector T cells, play a key role in the immune defense against fungi and extracellular bacteria, but also contribute to the pathogenesis of many autoimmune conditions. The differentiation of T(H)17 cells is orchestrated by an intricate network of signaling pathways and transcriptional regulators in T cells. While the involvement of T cell-intrinsic pathways has been described extensively, we are just beginning to appreciate how T(H)17 cell development is shaped by extrinsic pathways, especially the innate immune signals. Dendritic cells (DCs), the most important cell type to bridge innate and adaptive immunity, drive T(H)17 cell differentiation by providing antigenic, costimulatory and cytokine signals. This is mediated by the recognition of innate and inflammatory signals by DCs via pattern recognition receptors, cytokine receptors and other immunomodulatory receptors that in turn activate the intracellular signaling network. In particular, p38α MAP kinase has emerged as a critical pathway to program DC-dependent T(H)17 cell differentiation by integrating multiple instructive signals in DCs. Here, we summarize the current knowledge on the mechanisms by which DC-derived innate immune signals drive T(H)17 cell differentiation.

Signaling via the kinase p38α programs dendritic cells to drive TH17 differentiation and autoimmune inflammation

Dendritic cells (DCs) bridge innate and adaptive immunity, but how DC-derived signals regulate T cell lineage choices remains unclear. We report that p38α MAP kinase programs DCs to drive T_H17 differentiation. Deletion of p38α in DCs, but not macrophages or T cells, protects mice from T_H17-mediated autoimmune neuroinflammation. p38α orchestrates expression of cytokines and co-stimulatory molecules in DCs, and further imprints T cell IL-23R signaling to promote T_H17 differentiation. Moreover, p38α is required for tissue-infiltrating DCs to sustain T_H17 responses. This activity of p38α is conserved between mouse and human DCs, and is dynamically regulated by pattern recognition and fungal infection. Our results identify p38α as a central pathway to integrate instructive signals in DCs for T_H17 differentiation and inflammation.

Streptococcus thermophilus ST28 ameliorates colitis in mice partially by suppression of inflammatory Th17 cells

The effects of Streptococcus thermophilus ST28 on cytokine production by murine splenocytes stimulated with transforming growth factor-β plus interleukin- (IL-) 6 were evaluated. The addition of ST28 significantly repressed IL-17 production compared to ATCC 19258 (type strain). ST28 also decreased the number of Th17 cells in the stimulated splenocytes. The anti-inflammatory effects of ST28 administration were evaluated in mice with colitis induced by dextran sodium sulphate (DSS). Oral treatment of mice with ST28 ameliorated the intestinal lesions by DSS. Upon DSS treatment, IL-17 production in lamina propria lymphocytes (LPLs) was induced, but ST28 significantly decreased its production. ST28 also decreased the percentage of Th17 cells in LPL from DSS-induced colitis. The present results imply that ST28 suppresses the Th17 response in inflamed intestines and would be useful in the treatment of Th17-mediated diseases, such as inflammatory bowel disease.

Interleukin-17A promotes early but attenuates established disease in crescentic glomerulonephritis in mice

T helper (Th)17 cells might contribute to immune-mediated renal injury. Thus, we sought to define the time course of IL-17A-induced kidney damage and examined the relation between Th17 and Th1 cells in a model of crescentic anti-glomerular basement membrane glomerulonephritis. Renal injury and immune responses were assessed in wild-type and in IL-17A-deficient mice on days 6, 14, and 21 of disease development. On day 6, when mild glomerulonephritis developed, IL-17A-deficient mice were protected from renal injury. On day 14, when more severe disease developed, protection from renal injury due to IL-17A deficiency was less evident. On day 21, when crescentic glomerulonephritis was fully established, disease was enhanced in IL-17A(-/-) mice, with increased glomerular T-cell accumulation and fibrin deposition, and augmented Th1 responses. Mice lacking the Th17-promoting cytokine, IL-23 (p19), also developed more severe disease than wild-type animals on day 21. In contrast, mice deficient in the key Th1-promoting cytokine, IL-12 (p35), had decreased Th1 and increased Th17 responses and developed less severe crescentic glomerulonephritis than wild-type animals. These studies show that IL-17A contributes to early glomerular injury, but it attenuates established crescentic glomerulonephritis by suppressing Th1 responses. They provide further evidence that Th1 cells mediate crescentic injury in this model and that Th1 and Th17 cells counterregulate each other during disease development.

Human dendritic cells promote an antiviral immune response when stimulated by CVT-E002

Objectives

There is interest in developing new compounds to enhance the immune response to airway virus infections. CVT-E002 is a patented ginseng extract shown to decrease symptoms of virus infection in clinical trials. We hypothesized that the mechanism for this antiviral effect could be through modulation of dendritic cells leading to enhanced T-cell activation.

Methods

Human monocyte-derived dendritic cells (moDC) exposed to CVT-E002 (or not) were co-cultured with autologous T cells, with or without virus (respiratory syncytial virus or parainfluenza virus). Effects of CVT-E002 on cell function were determined through flow cytometry, 5-bromo-2′-deoxyuridine (BrdU) incorporation and ELISA.

Key findings

moDC cultured with CVT-E002 or virus induced greater activation of T cells, as measured by CD25 expression and BrdU incorporation, compared with untreated moDC. Responding T cells were CD4+CD45RO+. Co-cultures of CVT-E002 treated moDC with T cells responded with increased release of Th1-type cytokines (interferon-gamma, tumour necrosis factor and interleukin-12). CVT-E002-treated moDC showed increased expression of CD83, CD80 and CD86. Lipopolysaccharide levels were not detected in CVT-E002 and antagonists for Toll-like receptor-4 did not inhibit CVT-E002-induced moDC maturation.

Conclusions

CVT-E002 induced moDC maturation, which caused increased memory T-cell activation and Th1-type cytokine response.

Regulation of Th1 and Th17 cell differentiation and amelioration of experimental autoimmune encephalomyelitis by natural product compound berberine

Berberine (BBR), an isoquinoline alkaloid derived from plants, is widely used as an anti-inflammatory remedy in traditional Chinese medicine. In this study, we showed that BBR was efficacious in the amelioration of experimental autoimmune encephalomyelitis (EAE) through novel regulatory mechanisms involving pathogenic Th1 and Th17 cells. BBR inhibited differentiation of Th17 cells and, to a lesser degree, Th1 cells through direct actions on the JAK/STAT pathway, whereas it had no effect on the relative number of CD4(+)Foxp3(+) regulatory T cells. In addition, BBR indirectly influenced Th17 and Th1 cell functions through its effect on the expression and function of costimulatory molecules and the production of IL-6, which was attributable to the inhibition of NF-kappaB activity in CD11b(+) APCs. BBR treatment completely abolished the encephalitogenicity of MOG(35-55)-reactive Th17 cells in an adoptive transfer EAE model, and the same treatment significantly inhibited the ability of MOG(35-55)-reactive Th1 cells to induce EAE. This study provides new evidence that natural compounds, such as BBR, are of great value in the search for novel anti-inflammatory agents and therapeutic targets for autoimmune diseases.

Interleukin (IL)-31 induces pro-inflammatory cytokines in human monocytes and macrophages following stimulation with staphylococcal exotoxins

BACKGROUND

IL-31 is a cytokine expressed by T cells following activation with cytokines or staphylococcal exotoxins. A major function of IL-31 in atopic dermatitis (AD) is the induction of pruritus in the skin via the IL-31 receptor on sensory nerve cells. However, the regulation of the IL-31 receptor and pro-inflammatory functions of IL-31 in human monocytes and monocyte-derived cells are yet to be studied in detail.

OBJECTIVE

To investigate the regulation and function of IL-31 receptors in resting and activated human monocytes, macrophages and dendritic cells.

METHODS

Human monocytes, macrophages and dendritic cells were stimulated with staphylococcal exotoxins (SEB, alpha-toxin) or cytokines (IFN-gamma, IL-13). IL-31RA expression and regulation were then investigated at both the mRNA and the protein level. Subsequently, functional effects of IL-31 stimulation on cytokine secretion were measured at the protein level.

RESULTS

Staphylococcal exotoxins significantly up-regulated IL-31RA expression on monocytes and macrophages but not on dendritic cells at both the mRNA and the protein level. IL-31 enhanced the secretion of IL-1beta, IL-6 and IL-18 and up-regulated CD86 expression. In patients with AD, functional IL-31RA was also detected following stimulation of PBMC with IFN-gamma. However, this was not observed in healthy individuals.

CONCLUSION

IL-31 induces pro-inflammatory effects in activated human monocytes and macrophages. This may have implications for cutaneous inflammation in eczema where an over-expression of IL-31 has been described previously. Moreover, our findings provide a new link between staphylococcal colonization and the worsening of inflammation via IL-31. Further therapeutic considerations may include IL-31 as a target in AD.

Chlamydial respiratory infection during allergen sensitization drives neutrophilic allergic airways disease

Neutrophilic asthma is a prevalent, yet recently described phenotype of asthma. It is characterized by neutrophilic rather than eosinophilic airway inflammation and airways hyperresponsiveness (AHR) and may have an infectious origin. Chlamydial respiratory infections are associated with asthma, but how these Th1-inducing bacteria influence Th2-mediated asthma remains unknown. The effects of chlamydial infection on the development of asthma were investigated using a BALB/c mouse model of OVA-induced allergic airways disease (AAD). The effects of current and resolved Chlamydia muridarum infection during OVA sensitization on AAD were assessed and compared with uninfected and nonsensitized controls. Current, but not resolved, infection attenuated hallmark features of AAD: pulmonary eosinophil influx, T cell production of IL-5, mucus-secreting cell hyperplasia, and AHR. Current infection also induced robust OVA-driven neutrophilic inflammation and IFN-gamma release from T cells. The phenotype of suppressed but persistent Th2 responses in association with enhanced neutrophilia is reminiscent of neutrophilic asthma. This phenotype was also characterized by increased pulmonary IL-12 and IL-17 expression and activation of APCs, as well as by reduced thymus- and activation-regulated chemokine. Inhibition of pulmonary neutrophil influx during infection blocked OVA-induced neutrophilic inflammation and T cell IFN-gamma production and reversed the suppressive effects on mucus-secreting cell hyperplasia and AHR during AAD. These changes correlated with decreased IL-12 and IL-17 expression, increased thymus- and activation-regulated chemokine and altered APC activation. Blocking IFN-gamma and IL-17 during OVA challenge had no effect. Thus, active chlamydial respiratory infection during sensitization enhances subsequent neutrophilic inflammation and Th1/Th17 responses during allergen exposure and may have a role in the pathogenesis of neutrophilic asthma.

Lack of B7-1 and B7-2 costimulatory molecules modulates the severity of group B Streptococcus-induced arthritis

Group B streptococci have long been known as a leading cause of life-threatening infection in neonates, young infants and pregnant women, and recently have been recognized as an ever-growing cause of serious invasive infections in nonpregnant adults. B7-1 and B7-2 are two molecules with immunoregulatory functions implicated in the differentiation of T cells. The present study examined the role of B7-1 and B7-2 during group B streptococci-induced sepsis and arthritis. B7-1- or B7-2-deficient mice were infected with 1x10(7) streptococci, and mortality, appearance of arthritis, growth of microorganisms in the organs and cytokine profile were assessed. Lack of B7-1 was associated with amelioration of arthritis, while worsening of articular lesions was found in B7-2 deficient mice, in comparison to controls. Amelioration of arthritis in B7-1 deficient mice was accompanied by a lower local production of IL-1 beta and IL-18, and increase in IL-4 and IL-10 secretion. On the contrary, B7-2 deficient mice showed an higher proinflammatory cytokine production and lower IL-10 secretion than controls. Taken together, our results provide evidence that signaling delivered by B7-1 and B7-2 plays a role in determining the outcome of group B streptococcal induced arthritis, likely due to the different local secretory pattern.

Mesenchymal stromal cells ameliorate experimental autoimmune encephalomyelitis by inhibiting CD4 Th17 T cells in a CC chemokine ligand 2-dependent manner

The administration of ex vivo culture-expanded mesenchymal stromal cells (MSCs) has been shown to reverse symptomatic neuroinflammation observed in experimental autoimmune encephalomyelitis (EAE). The mechanism by which this therapeutic effect occurs remains unknown. In an effort to decipher MSC mode of action, we found that MSC conditioned medium inhibits EAE-derived CD4 T cell activation by suppressing STAT3 phosphorylation via MSC-derived CCL2. Further analysis demonstrates that the effect is dependent on MSC-driven matrix metalloproteinase proteolytic processing of CCL2 to an antagonistic derivative. We also show that antagonistic CCL2 suppresses phosphorylation of AKT and leads to a reciprocal increased phosphorylation of ERK associated with an up-regulation of B7.H1 in CD4 T cells derived from EAE mice. CD4 T cell infiltration of the spinal cord of MSC-treated group was robustly decreased along with reduced plasma levels of IL-17 and TNF-alpha levels and in vitro from restimulated splenocytes. The key role of MSC-derived CCL2 was confirmed by the observed loss of function of CCL2(-/-) MSCs in EAE mice. In summary, this is the first report of MSCs modulating EAE biology via the paracrine conversion of CCL2 from agonist to antagonist of CD4 Th17 cell function.

GATA-3 protects against severe joint inflammation and bone erosion and reduces differentiation of Th17 cells during experimental arthritis

OBJECTIVE

Rheumatoid arthritis is associated with the infiltration of T helper cells into the joints. It is unclear whether interferon-gamma (IFNgamma)-producing Th1 cells or the novel T helper subset, interleukin-17 (IL-17)-producing Th17 cells, are the pathogenic mediators of joint inflammation in chronic nonautoimmune arthritis. Therefore, this study was aimed at examining whether the Th2-specific transcription factor GATA-3 can regulate arthritis, in an experimental murine model, by modulating Th1 and/or Th17 cell polarization.

METHODS

Arthritis was induced with methylated bovine serum albumin (mBSA) in both wild-type and CD2 T cell-specific GATA-3 (CD2-GATA-3)-transgenic mice. At days 1 and 7 after the induction of arthritis, knee joints were scored macroscopically for arthritis severity and for histologic changes. Single-cell suspensions were generated from the spleens, lymph nodes, and inflamed knee joints. Cytokine expression by CD4+ T cells was determined using flow cytometry, and IL-17 expression in the inflamed knee joints was determined by enzyme-linked immunosorbent assay. Analyses of gene expression were performed for Th17-associated factors.

RESULTS

Wild-type mice developed severe joint inflammation, including massive inflammatory cell infiltration and bone erosion that increased significantly over time, reaching maximal arthritis scores at day 7. In contrast, only mild joint inflammation was observed in CD2-GATA-3-transgenic mice. This mild effect was further accompanied by systemic and local reductions in the numbers of IL-17+IFNgamma- and IL-17+IFNgamma+, but not IL-17-IFNgamma+, CD4+ T cells, and by induction of Th2 cytokine expression. Moreover, GATA-3 overexpression resulted in reduced gene expression of the Th17-associated transcription factor retinoic acid-related orphan receptor gammat.

CONCLUSION

These results indicate that enforced GATA-3 expression protects against severe joint inflammation and bone erosion in mice, accompanied by reduced differentiation of Th17 cells, but not Th1 cells, during mBSA-induced arthritis.