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Methicillin resistant Staphylococcus aureus (MRSA) constitute a serious health care problem worldwide. This study addresses the effect of β-lactam treatment on the ability of clinically relevant MRSA strains to induce IL-12 and IL-23. MRSA strains induced a dose-dependent IL-12 response in murine bone-marrow-derived dendritic cells that was dependent on endocytosis and acidic degradation. Facilitated induction of IL-12 (but not of IL-23) called for activation of the MAP kinase JNK, and was suppressed by p38. Compromised peptidoglycan structure in cefoxitin-treated bacteria - as denoted by increased sensitivity to mutanolysin -caused a shift from IL-12 towards IL-23. Moreover, cefoxitin treatment of MRSA led to a p38 MAPK-dependent early up-regulation of Dual Specificity Phosphatase (DUSP)-1. Compared to common MRSA, characteristics associated with a persister phenotype increased intracellular survival and upon cefoxitin treatment, the peptidoglycan was not equally compromised and the cytokine induction still required phagosomal acidification. Together, these data demonstrate that β-lactam treatment changes the MRSA-induced IL-12/IL-23 pattern determined by the activation of JNK and p38. We suggest that accelerated endosomal degradation of the peptidoglycan in cefoxitin-treated MRSA leads to an early expression of DUSP-1 and accordingly, a reduction in the IL-12/IL-23 ratio in dendritic cells. This may influence the clearance of S. aureus., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Leukotriene B 4 (LTB 4 ) receptor 1 (BLT1) is a chemotactic G protein-coupled receptor expressed by leukocytes, such as granulocytes, macrophages, and activated T cells. Although there is growing evidence that BLT1 plays crucial roles in immune responses, its role in dendritic cells remains largely unknown. Here, we identified novel DC subsets defined by the expression of BLT1, namely, BLT1 hi and BLT1 lo DCs. We also found that BLT1 hi and BLT1 lo DCs differentially migrated toward LTB 4 and CCL21, a lymph node-homing chemoattractant, respectively. By generating LTB 4 -producing enzyme LTA 4 H knockout mice and CD11c promoter-driven Cre recombinase-expressing BLT1 conditional knockout (BLT1 cKO) mice, we showed that the migration of BLT1 hi DCs exacerbated allergic contact dermatitis. Comprehensive transcriptome analysis revealed that BLT1 hi DCs preferentially induced Th1 differentiation by upregulating IL-12p35 expression, whereas BLT1 lo DCs accelerated T cell proliferation by producing IL-2. Collectively, the data reveal an unexpected role for BLT1 as a novel DC subset marker and provide novel insights into the role of the LTB 4 -BLT1 axis in the spatiotemporal regulation of distinct DC subsets.

Dendritic cells (DCs) are play critical roles in the priming and regulation of immune responses. DCs rapidly process and convey these antigens to prime antigen-specific T cells. Therefore, regulation of DCs functions is important for immunity and immunotherapies. Immune adjuvants for DCs activation are needed to improve the efficacy of vaccines against tumors and many infectious diseases. Therefore, we demonstrate that H. fusiformis extract can regulate DCs maturation and activation. H. fusiformis extract induced costimulatory molecules (CD 80 and CD86), antigen-presenting molecules (major histocompatibility complex (MHC) I and II), CCR7 expression, and interleukin (IL)-12 production in DCs. These effects are associated with upregulation of mitogen-activated protein kinase (MAPK) signaling pathway. In addition, H. fusiformis extract induces costimulatory molecules on splenic DCs and activated CD8 + T cells in vivo . Taken together, these findings suggest that H. fusiformis extract may be a potential efficient immune therapeutic compound in DCs-mediated immunotherapies., Abbreviations: CTL: cytotoxic T lymphocytes; DCs: dendritic cells; ERK: extracellular signal-regulated kinases; IL: interleukini; JNK: c-Jun N-terminal kinase; MAPK: mitogen-activated protein kinase; MHC: major histocompatibility complex.

Little is known about how tuberculosis (TB) impairs dendritic cell (DC) function and anti-TB immune responses. We previously showed that the B and T lymphocyte attenuator (BTLA), an immune inhibitory receptor, is involved in TB pathogenesis. Here, we examined whether BTLA expression in TB affects phenotypic and functional aspects of DCs. Active TB patients exhibited higher expression of BTLA in myeloid dendritic cells (mDCs) and plasmacytoid DCs (pDCs) subsets compared with healthy controls (HCs). BTLA expression was similarly high in untreated TB, TB relapse, and sputum-bacillus positive TB, but anti-TB therapy reduced TB-driven increases in frequencies of BTLA + DCs. BTLA + DCs in active TB showed decreased expression of the DC maturation marker CD83, with an increased expression of CCR7 in mDCs. BTLA + DCs in active TB displayed a decreased ability to express HLA-DR and to uptake foreign antigen, with a reduced expression of the co-stimulatory molecule CD80, but not CD86. Functionally, BTLA + DCs in active TB showed a decreased production of IL-12 and IFN-α as well as a reduced ability to stimulate allogeneic T-cell proliferative responses. BTLA + mDCs produced larger amounts of IL-4 and TGF-β than BTLA - mDCs in both HCs and APT patients. BTLA + DCs from active TB patients showed a reduced ability to stimulate Mtb antigen-driven Th17 and Th22 polarizations as compared to those from HCs. Conversely, these BTLA + DCs more readily promoted the differentiation of T regulatory cells (Treg) and Th2 than those from HCs. These findings suggest that TB-driven BTLA expression in DCs impairs the expression of functional DC surrogate markers and suppress the ability of DCs to induce anti-TB Th17 and Th22 response while promoting Th2 and Foxp3 + Tregs., (Copyright © 2020 Zhang, Lu, Wang, Liu, Chen, Shen, Luo, Xu, Peng, Luo, Huang, Wu, Zheng, Yi, Chen and Xu.)

Dendritic cells (DC) from diabetes-prone NOD mice and patients with type 1 diabetes (T1D) produce excess IL-12 that drives development of β-cell-destroying IFN-γ-producing T cells. The molecular mechanisms that control IL-12 production in T1D are unclear. In this study, we report that β-catenin, a multifunctional protein involved in inflammation, is dramatically increased in DC from NOD mice. We further investigated the mechanisms leading to accumulation of β-catenin in NOD DC and its role in the inflammatory pathogenic responses associated with T1D. Hyperphosphorylation of β-catenin at a stabilizing residue, serine 552, mediated by activation of Akt, appears to lead to β-catenin accumulation in NOD DC. Elevated β-catenin in DC correlated with IL-12 production and induction of IFN-γ-producing CD4 cells. On the one hand, knockdown/inhibition of β-catenin significantly reduced NOD DC production of IL-12 and their ability to induce IFN-γ-producing CD4 cells. On the other hand, overexpression of β-catenin in control DC resulted in increased IL-12 production and induction of IFN-γ-production in T cells. Additionally, we found that β-catenin inhibitors decreased NF-κB activation in NOD DC and IFN-γ production by NOD T cells in vivo. These data strongly suggest that accumulation of β-catenin in DC from NOD mice drives IL-12 production, and consequently, development of pathogenic IFN-γ-producing T cells. Targeting the defect responsible for β-catenin accumulation and subsequent overproduction of pro-inflammatory cytokines by NOD DC could be an effective therapeutic strategy for the prevention and/or treatment of T1D., (©2019 Society for Leukocyte Biology.)

The mannose receptor (MR) is a C-type lectin involved in endocytosis and with a poorly defined ability to modulate cellular activation. We investigated the effect of mannan treatment prior to stimulation of murine bone marrow-derived dendritic cells with the Gram-positive bacteria Lactobacillus acidophilus NCFM (L. acidophilus ) on the induction of Interleukin (IL)-12. Mannan enhanced the IL-12 production induced by L. acidophilus in a dose dependent manner (up to 230% enhancement). Additionally, mannan-enhanced IL-12 induction was also demonstrated with another Gram-positive bacteria, Staphylococcus aureus (S. aureus) , while an IL-12 reducing effect was seen on Escherichia coli stimulated cells. Furthermore, the expression of Interferon β ( Ifnb ) was increased in cells treated with mannan prior to stimulation with L. acidophilus . The addition of mannan but not of bacteria led to endocytosis of MR, while addition of mannan prior to L. acidophilus or S. aureus resulted in increased endocytosis of bacteria, a faster killing of endocytosed bacteria, and increased reactive oxygen species production. Expression of signaling lymphocytic activation molecule (SLAMF)1 shown previously to be involved in the facilitation of endosomal degradation was upregulated by mannan but not by L. acidophilus and S. aureus . The IL-12 enhancement by mannan but not the IL-12 induced by the bacteria was abrogated by addition of inhibitors of clathrin coated pits (chlorpromazine and monodansylcadaverine). Furthermore, the addition of acid sphingomyelinase, a facilitator of ceramide raft formation, prior to addition of L. acidophilus enhanced the IL-12 production and the endocytosis of bacteria. In summary, our results show that mannan increases the IL-12 production induced by some Gram-positive bacteria through MR-endocytosis, which increases bacterial endocytosis and endosomal killing. The differential effect of MR activation on the IL-12 production induced by Gram-positive and Gram-negative bacteria may influence the immune response toward allergens and other glycoproteins., (Copyright © 2019 Mathiesen, Eld, Sørensen, Fuglsang, Lund, Taverniti and Frøkiær.)

The main effectors in tumor control are the class I MHC molecule-restricted CD8 + cytotoxic T lymphocytes (CTLs). Tumor-specific CTL induction can be regulated by dendritic cells (DCs) expressing both tumor-derived epitopes and co-stimulatory molecules. Immunosuppressive tolerogenic DCs, having down-regulated co-stimulatory molecules, are seen within the tumor mass and can suppress tumor-specific CTL induction. The tolerogenic DCs expressing down-regulated XCR1 + CD141 + appear to be induced by tumor-derived soluble factors or dexamethasone, while the immunogenic DCs usually express XCR1 + CD141 + molecules with a cross-presentation function in humans. Thus, if tolerogenic DCs can be reactivated into immunogenic DCs with sufficient co-stimulatory molecules, tumor-specific CD8 + CTLs can be primed and activated in vivo. In the present study, we converted human tolerogenic CD141 + DCs with enhanced co-stimulatory molecule expression of CD40, CD80, and CD86 through stimulation with non-toxic mycobacterial lipids such as mycolic acid (MA) and lipoarabinomannan (LAM), which synergistically enhanced both co-stimulatory molecule expression and interleukin (IL)-12 secretion by XCR1 + CD141 + DCs. Moreover, MA and LAM-stimulated DCs captured tumor antigens and presented tumor epitope(s) in association with class I MHCs and sufficient upregulated co-stimulatory molecules to prime naïve CD3 + T cells to become CD8 + tumor-specific CTLs. Repeat CD141 + DC stimulation with MA and LAM augmented the secretion of IL-12. These findings provide us a new method for altering the tumor environment by converting tolerogenic DCs to immunogenic DCs with MA and LAM from Mycobacterium tuberculosis.

Contact hypersensitivity (CHS) is a CD8 T cell-mediated response to hapten skin sensitization and challenge. Sensitization of wild-type (WT) mice induces hapten-reactive effector CD8 T cells producing IFN-γ and IL-17- and IL-4-producing CD4 T cells that cannot mediate CHS. Although CXCR2-dependent Ly6G + (neutrophil) cell recruitment into hapten-challenged skin is required to direct effector CD8 T cell infiltration into the challenge site to elicit CHS, 2,4-dinitrofluorobenezene (DNFB) sensitization of CXCR2 -/- mice and neutrophil-depleted WT mice induced both hapten-reactive CD4 and CD8 T cells producing IFN-γ and IL-17. CD4 T cell-mediated CHS responses were not generated during DNFB sensitization of neutrophil-depleted WT mice treated with anti-IL-12 mAb or neutrophil-depleted IL-12 -/- mice. Neutrophil depletion during DNFB sensitization of WT mice markedly increased IL-12-producing hapten-primed dendritic cell numbers in the skin-draining lymph nodes. Sensitization of mice lacking the neutrophil serine protease cathepsin G (CG)-induced hapten-reactive CD4 and CD8 T cells producing IFN-γ and IL-17 with elevated and elongated CHS responses to DNFB challenge. Induction of CHS effector CD4 T cells producing IFN-γ in neutrophil-depleted WT mice was eliminated by s.c. injection of active, but not inactivated, CG during sensitization. Thus, hapten skin sensitization induces neutrophil release of CG that systemically inhibits hapten-presenting dendritic cell production of IL-12 and the development of hapten-reactive CD4 T cells to IFN-γ-producing CHS effector cells., (Copyright © 2019 by The American Association of Immunologists, Inc.)

Mutations in isocitrate dehydrogenase (IDH) or a reduced expression of L-2-hydroxyglutarate (HG)-dehydrogenase result in accumulation of D-2-HG or L-2-HG, respectively, in tumor tissues. D-2-HG and L-2-HG have been shown to affect T-cell differentiation and activation; however, effects on human myeloid cells have not been investigated so far. In this study we analyzed the impact of D-2-HG and L-2-HG on activation and maturation of human monocyte-derived dendritic cells (DCs). 2-HG was taken up by DCs and had no impact on cell viability but diminished CD83 expression after Lipopolysaccharides (LPS) stimulation. Furthermore, D-2-HG and L-2-HG significantly reduced IL-12 secretion but had no impact on other cytokines such as IL-6, IL-10 or TNF. Gene expression analyses of the IL-12 subunits p35/IL-12A and p40/IL-12B in DCs revealed decreased expression of both subunits. Signaling pathways involved in LPS-induced cytokine expression (NFkB, Akt, p38) were not altered by D-2-HG. However, 2-HG reprogrammed LPS-induced metabolic changes in DCs and increased oxygen consumption. Addition of the ATP synthase inhibitor oligomycin to DC cultures increased IL-12 secretion and was able to partially revert the effect of 2-HG. Our data show that both enantiomers of 2-HG can limit activation of DCs in the tumor environment.

Due to prolonged coevolution with the human being, Mycobacterium tuberculosis has acquired a sophisticated capacity to evade host immunity and persist in a latent state in the infected individual. As part of this evolutive process, mycobacteria have developed a highly complex cell wall that acts as a protective barrier. Herein we studied the effects of Di-O-acyl trehalose, a cell-wall glycolipid of virulent mycobacteria on murine bone marrow-derived dendritic cells. We have demonstrated that Di-O-Acyl-trehalose promotes a tolerogenic phenotype in bone marrow-derived murine DCs activated with mycobacterial antigens and Toll-like receptor agonists. This phenotype included low expression of antigen presentation and costimulatory molecules and altered cytokine production with downregulation of IL-12 and upregulation of IL-10, an anti-inflammatory cytokine. Additional markers of tolerogenicity were the expression of Indoleamine 2,3-dioxygenase and CD25. Furthermore, Di-O-Acyl-Trehalose promoted the expansion of FoxP3+ regulatory T lymphocytes. A better understanding of mycobacterial cell-wall components involved in the evasion of immunity is a prerequisite to designing better strategies to fight tuberculosis., Competing Interests: The authors have declared that no competing interest exist.

Early secretion of IL-12 by mouse dendritic cells (DCs) instructs T cells to make IFN-γ. However, only activated, but not naive T cells are able to license DCs for IL-12 production. We hypothesized that it might be due to different levels of CD40L expression on the surface of these cells, as CD40 signals are required for IL-12 production. Using quantitative cell-free systems incorporating CD40L in lipid bilayers combined with total internal reflection fluorescence microscopy and flow cytometry, we show that as low as ∼200 CD40L molecules/μm 2 in combination with IL-4 is sufficient to induce IL-12 production by DCs. Remarkably, CD40L alone is adequate to induce IL-23 secretion by DCs. Thus, although activated T cells have somewhat higher levels of CD40L, it is the combination of CD40L and the cytokines they secrete that licenses DCs and influences the effector class of the immune response.

Background: Mesenchymal stem cells (MSCs) have been demonstrated to be effective in treating autoimmune diseases including Sjögren's syndrome (SS). We aim to compare the effects of MSC transplantation (MSCT) and the role of serum interleukin-12 (IL-12) in SS., Methods: IL-12 levels were measured by ELISA. IL-12 mRNA transcripts in dendritic cells (DCs) were determined by RT-PCR. After co-culturing with MSCs, IL-12 mRNA transcripts in mouse and human DCs were detected. Non-obese diabetic (NOD) mice received MSCT, recombinant IL-12, or anti-IL-12 mAb treatment, respectively. Then, salivary flow rates, histopathology of salivary glands, and splenic lymphocyte subsets were examined in these mice., Results: IL-12 levels in the serum were significantly increased in SS patients and positively correlated with the EULAR 2010 Sjögren's syndrome disease activity index. DCs from SS patients produced more IL-12 than those from the control. Likewise, IL-12 treatment in NOD mice significantly decreased salivary flow rates and promoted lymphocyte infiltration in salivary glands. IL-12 antibodies downregulated Th1, Th17, and Tfh cell. MSCT enhanced salivary flow rates and decreased lymphocyte infiltrations in salivary glands of NOD mice. MSCT downregulated Th17 and Tfh cells but upregulated regulatory T cells. MSCT reduced IL-12 productions in both SS patients and mice., Conclusion: Our results indicate that MSCs ameliorate SS possibly via suppressing IL-12 production in DCs and that IL-12 could be a potential therapeutic target of SS., Trial Registration: NTC00953485 . Registered June 2009.

There has recently been a paradigm shift in the field of dendritic cell (DC)-based immunotherapy, where several clinical studies have confirmed the feasibility and advantageousness of using directly isolated human blood-derived DCs over in vitro differentiated subsets. There are two major DC subsets found in blood; plasmacytoid DCs (pDCs) and myeloid DCs (mDCs), and both have been tested clinically. CD1c + mDCs are highly efficient antigen-presenting cells that have the ability to secrete IL-12p70, while pDCs are professional IFN-α-secreting cells that are shown to induce innate immune responses in melanoma patients. Hence, combining mDCs and pDCs poses as an attractive, multi-functional vaccine approach. However, type I IFNs have been reported to inhibit IL-12p70 production and mDC-induced T-cell activation. In this study, we investigate the effect of IFN-α on mDC maturation and function. We demonstrate that both recombinant IFN-α and activated pDCs strongly enhance mDC maturation and increase IL-12p70 production. Co-cultured mDCs and pDCs additionally have beneficial effect on NK and NKT-cell activation and also enhances IFN-γ production by allogeneic T cells. In contrast, the presence of type I IFNs reduces the proliferative T-cell response. The mere presence of a small fraction of activated pDCs is sufficient for these effects and the required ratio between the subsets is non-stringent. Taken together, these results support the usage of mDCs and pDCs combined into one immunotherapeutic vaccine with broad immunostimulatory features.

Bloodstream infections induce considerable morbidity, high mortality, and represent a significant burden of cost in health care; however, our understanding of the immune response to bacteremia is incomplete. Langerin + CD8α + dendritic cells (DCs), residing in the marginal zone of the murine spleen, have the capacity to cross-prime CD8 + T cells and produce IL-12, both of which are important components of antimicrobial immunity. Accordingly, we hypothesized that this DC subset may be a key promoter of adaptive immune responses to blood-borne bacterial infections. Utilizing mice that express the diphtheria toxin receptor under control of the langerin promoter, we investigated the impact of depleting langerin + CD8α + DCs in a murine model of intravenous infection with Mycobacterium bovis bacille Calmette-Guerin (BCG). In the absence of langerin + CD8α + DCs, the immune response to blood-borne BCG infection was diminished: bacterial numbers in the spleen increased, serum IL-12p40 decreased, and delayed CD8 + T cell activation, proliferation, and IFN-γ production was evident. Our data revealed that langerin + CD8α + DCs play a pivotal role in initiating CD8 + T cell responses and IL-12 production in response to bacteremia and may influence the early control of systemic bacterial infections.

For dendritic cells (DCs) to initiate an immune response, their ability to migrate and to produce interleukin-12 (IL-12) is crucial. It has been previously shown that low-dose radiation (LDR) promoted IL-12 production by DCs, resulting in increased DC activity that contributed to LDR hormesis in the immune system. However, the molecular mechanism of LDR-induced IL-12 production, as well as the effect of LDR on DC migration capacity require further elucidation. Using the JAWSII immortalized mouse dendritic cell line, we showed that in vitro X-ray irradiation (0.2 Gy) of DCs significantly increased DC migration and IL-12 production, and upregulated CCR7. The neutralizing antibody against CCR7 has been shown to abolish LDR-enhanced DC migration, demonstrating that CCR7 mediates LDR-promoting DC migration. We identified nuclear factor kappaB (NF-κB) as the central signaling pathway that mediated LDR-enhanced expression of IL-12 and CCR7 based on findings that 0.2 Gy X-ray irradiation activated NF-κB, showing increased nuclear p65 translocation and NF-κB DNA-binding activity, while an NF-κB inhibitor blocked LDR-enhanced expression of IL-12 and CCR7, as well as DC migration. Finally, we demonstrated that 0.2 Gy X-ray irradiation promoted ATM phosphorylation and reactive oxygen species generation; however, only the ATM inhibitor abolished the LDR-induced NF-κB-mediated expression of IL-12 and CCR7. Altogether, our data show that exposure to LDR resulted in a hormetic effect on DCs regarding CCR7-mediated migration and IL-12 production by activating the ATM/NF-κB pathway.

Golgi phosphoprotein 2 (GOLPH2), a widely expressed Golgi type II transmembrane protein, has been implicated in several important physiological and pathological processes, including virus infections, cancer cell proliferation, and metastasis. However, its biological functions and mechanisms, particularly in the immune system, remain highly obscure. In this study, we report the biochemical identification of GOLPH2 from B cell lymphoma culture supernatant and show that the secreted protein could inhibit IL-12 production by dendritic cells (DCs) and IL-12-induced IFN-γ production by activated T cells. Further molecular analysis revealed that GOLPH2's IL-12-inhibiting activity was mediated through a proximal IL12p35 promoter element involving a previously identified transcriptional repressor named GC-binding protein that is induced during phagocytosis of apoptotic cells by macrophages. We subsequently generated global golph2 knockout mice, which exhibited little developmental abnormality but were more susceptible to LPS-induced endotoxic shock than were wild-type mice with elevated serum IL-12 levels. Furthermore, we found that GOLPH2 played a regulatory role in macrophage polarization toward the M2 type. A comprehensive analysis of gene expression profiles of activated wild-type and GOLPH2-deficient DCs by RNA sequencing uncovered mechanistic insights into the way GOLPH2 potentially modulates DC function during inflammatory insults. Our functional study of GOLPH2 helps advance the scientific understanding of the biological and pathogenic roles of this novel and intriguing molecule with great potential as a diagnostic and prognostic marker as well as a therapeutic target in many acute and chronic inflammatory disorders., (Copyright © 2018 by The American Association of Immunologists, Inc.)

The advent of tyrosine kinase inhibitor (TKI) therapy markedly improved the outcome of patients with chronic-phase chronic myeloid leukemia (CML). However, the poor prognosis of patients with advanced-phase CML and the lifelong dependency on TKIs are remaining challenges; therefore, an effective therapeutic has been sought. The BCR-ABL p210 fusion protein's junction region represents a leukemia-specific neoantigen and is thus an attractive target for antigen-specific T-cell immunotherapy. BCR-ABL p210 fusion-region-specific CD4 + T-helper (Th) cells possess antileukemic potential, but their function remains unclear. In this study, we established a BCR-ABL p210 b3a2 fusion-region-specific CD4 + Th-cell clone (b3a2-specific Th clone) and examined its dendritic cell (DC)-mediated antileukemic potential. The b3a2-specific Th clone recognized the b3a2 peptide in the context of HLA-DRB1*09:01 and exhibited a Th1 profile. Activation of this clone through T-cell antigen receptor stimulation triggered DC maturation, as indicated by upregulated production of CD86 and IL-12p70 by DCs, which depended on CD40 ligation by CD40L expressed on b3a2-specific Th cells. Moreover, in the presence of HLA-A*24:02-restricted Wilms tumor 1 (WT1) 235-243 peptide, DCs conditioned by b3a2-specific Th cells efficiently stimulated the primary expansion of WTI-specific cytotoxic T lymphocytes (CTLs). The expanded CTLs were cytotoxic toward WT1 235-243 -peptide-loaded HLA-A*24:02-positive cell lines and exerted a potent antileukemic effect in vivo. However, the b3a2-specific Th-clone-mediated antileukemic CTL responses were strongly inhibited by both TKIs and interferon-α. Our findings indicate a crucial role of b3a2-specific Th cells in leukemia antigen-specific CTL-mediated immunity and provide an experimental basis for establishing novel CML immunotherapies.

Since 2010, the porcine epidemic diarrhea coronavirus (PEDV) has caused significant damage to the global pork industry. However, classical PEDV vaccine strains only provide limited protection against emerging strains. In this study, we successfully isolated and attenuated the PEDV epidemic strain Zhejiang08, which was characterized by good cell adaptation and high-titer production 48 h post infection in Vero E6 cells. The attenuated virus induced a high level of virus-specific neutralizing antibodies until 120 days after immunization in piglets and provided complete protection when challenged with an emerging virus strain on day 14 post immunization. Moreover, the capability to activate dendritic cells (DCs) of this isolate was identified. Higher expression levels of IL-12 and IFN-γ were recorded in DCs after treatment with Zhejiang08 for 24 h. Furthermore, genome sequencing and phylogenetic analysis revealed high homology between the main antigen epitopes of Zhejiang08 and PEDV pandemic isolates following 2011. Combining the glycosylation site prediction results and their distribution within the spatial structure of the S protein, led to the conclusion that the observed more effective host immune response of Zhejiang08 compared to CV777 was possibly associated with a lack of the potential glycosylation site in the 296 amino acids of the S protein. In summary, we illustrated that the attenuated virus represents a promising vaccine candidate., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

The objective of this study is to investigate the immunomodulatory activities of astragalus polysaccharide liposome (APSL) on murine peritoneal macrophages and bone marrow derived dendritic cells (DCs). The results showed that APSL not only significantly improved the phagocytosis of macrophages, the contents of IL-6 and IL-12, and the secretion of nitric oxide (NO) and inducible nitric oxide synthase (iNOS) in macrophages, but also promoted the proliferation of DCs precursor cells, enhanced the abilities of DCs on stimulating T-cell proliferation and presenting antigen, upregulated IFN-γ and IL-2 production of DCs, and improved the expression of CD80 and CD86 in DCs compared with astragalus polysaccharide (APS). These findings indicated that the immune-modulating activities of APS were remarkably enhanced after encapsulated with liposome, and liposome possessed the potential to act as effective drug delivery system. Moreover, it also provided the theoretical basis for further researching the mechanism of APSL on improving the immune response., (Copyright © 2017. Published by Elsevier B.V.)

The natural adjuvant properties of bacterial ghosts (BGs) lie within the presence of intact pathogen-associated molecular patterns on their surface. BGs can improve the direct delivery, natural processing and presentation of target antigens within dendritic cells (DCs). Moreover, sensitization of human DCs by cancer cell lysate (oncolysate)-loaded BGs in the presence of IFN-α and GM-CSF enhanced DC maturation as indicated by an increased expression of maturation markers and co-stimulatory molecules, higher production of IL-12p70 and stimulation of significantly increased proliferation of both autologous CD4 + and CD8 + T cells compared to DCs matured in the presence of purified lipopolysaccharide. The induced T cells efficiently recognized oncolysate-derived tumor-associated antigens expressed by cancer cells used for the production of oncolysate. Our optimized one-step simultaneous antigen delivery and DC maturation-inducing method emerges as a promising tool for the development and implementation of next-generation cellular cancer immunotherapies.

The extracellular matrix glycosaminoglycan, hyaluronan, has been described as a regulator of tissue inflammation, with hyaluronan fragments reported to stimulate innate immune cells. High molecular mass hyaluronan is normally present in tissues, but upon inflammation lower molecular mass fragments are generated. It is unclear if these hyaluronan fragments induce an inflammatory response or are a consequence of inflammation. In this study, mouse bone marrow derived macrophages and dendritic cells (DCs) were stimulated with various sizes of hyaluronan from different sources, fragmented hyaluronan, hyaluronidases and heavy chain modified-hyaluronan (HA-HC). Key pro-inflammatory molecules, tumour necrosis factor alpha, interleukin-1 beta, interleukin-12, CCL3, and the co-stimulatory molecules, CD40 and CD86 were measured. Only human umbilical cord hyaluronan, bovine testes and Streptomyces hyaluronlyticus hyaluronidase stimulated macrophages and DCs, however, these reagents were found to be contaminated with endotoxin, which was not fully removed by polymyxin B treatment. In contrast, pharmaceutical grade hyaluronan and hyaluronan fragments failed to stimulate in vitro-derived or ex vivo macrophages and DCs, and did not induce leukocyte recruitment after intratracheal instillation into mouse lungs. Hence, endotoxin-free pharmaceutical grade hyaluronan does not stimulate macrophages and DCs in our inflammatory models. These results emphasize the importance of ensuring hyaluronan preparations are endotoxin free.

Dendritic cells (DCs) are critical for defense against a variety of pathogens and the formation of adaptive immune responses. The transcription factor Batf3 is critical for the development of CD103(+)CD11b(-) DCs, which promote IL-12-dependent protective immunity during viral and parasitic infections, dampen Th2 immunity during helminthic infection, and exert detrimental effects during bacterial infection. Whether CD103(+) DCs modulate immunity during systemic or mucosal fungal disease remains unknown. Herein, we report that Batf3 is critical for accumulation of CD103(+) DCs in the kidney and tongue at steady state, for their expansion during systemic and oropharyngeal candidiasis, and for tissue-specific production of IL-12 in kidney but not tongue during systemic and oropharyngeal candidiasis, respectively. Importantly, deficiency of CD103(+) DCs does not impair survival or fungal clearance during systemic or oropharyngeal candidiasis, indicating that Batf3-dependent CD103(+) DC accumulation mediates pathogen- and tissue-specific immune effects.

Background: Dendritic cells (DCs) are key players in the induction and re-elicitation of TH2 responses to allergens. We have previously shown that different C-type lectin receptors on DCs play a major role in allergen recognition and uptake. In particular, mannose receptor (MR), through modulation of Toll-like receptor (TLR) 4 signaling, can regulate indoleamine 2,3-dioxygenase (IDO) activity, favoring TH2 responses. Interestingly, the aryl hydrocarbon receptor (AhR), a ligand-dependent transcription factor with an emerging role in immune modulation, has been implicated in IDO activation in response to TLR stimulation., Objective: Here we investigated how allergens and lectins modulate the TLR4-AhR-IDO axis in human monocyte-derived DCs., Methods: Using a combination of genomics, proteomics, and immunologic studies, we investigated the role of MR and AhR in IDO regulation and its effect on T helper cell differentiation., Results: We have demonstrated that LPS induces both IDO isoforms (IDO1 and IDO2) in DCs, with partial involvement of AhR. Additionally, we found that, like mannan, different airborne allergens can effectively downregulate TLR4-induced IDO1 and IDO2 expression, most likely through binding to the MR. Mannose-based ligands were also able to downregulate IL-12p70 production by DCs, affecting T helper cell polarization. Interestingly, AhR and some components of the noncanonical nuclear factor κB pathway were shown to be downregulated after MR engagement, which could explain the regulatory effects of MR on IDO expression., Conclusion: Our work demonstrates a key role for MR in the modulation of the TLR4-AhR-IDO axis, which has a significant effect on DC behavior and the development of immune responses against allergens., (Copyright © 2015 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)

Staphylococcus aureus is a major human pathogen that has evolved very efficient immune evading strategies leading to persistent colonization. During different stages of growth, S. aureus express various surface molecules, which may affect the immune stimulating properties, but very little is known about their role in immune stimulation and evasion. Depending on the growth phase, S. aureus may affect antigen presenting cells differently. Here, the impact of growth phases and the surface molecules lipoteichoic acid, peptidoglycan and poly-N-acetyl glucosamine on the induction of IL-12 imperative for an efficient clearance of S. aureus was studied in dendritic cells (DCs). Exponential phase (EP) S. aureus was superior to stationary phase (SP) bacteria in induction of IL-12, which required actin-mediated endocytosis and endosomal acidification. Moreover, addition of staphylococcal cell wall derived peptidoglycan to EP S. aureus stimulated cells increased bacterial uptake but abrogated IL-12 induction, while addition of lipoteichoic acid increased IL-12 production but had no effect on the bacterial uptake. Depletion of the capability to produce poly-N-acetyl glucosamine increased the IL-12 inducing activity of EP bacteria. Furthermore, the mutant dltA unable to produce D-alanylated teichoic acids failed to induce IL-12 but like peptidoglycan and the toll-like receptor (TLR) ligands LPS and Pam3CSK4 the mutant stimulated increased macropinocytosis. In conclusion, the IL-12 response by DCs against S. aureus is highly growth phase dependent, relies on cell wall D-alanylation, endocytosis and subsequent endosomal degradation, and is abrogated by receptor induced macropinocytosis.

Immunosuppression in tumor microenvironments critically affects the success of cancer immunotherapy. Here, we focused on the role of interleukin (IL)-6/signal transducer and activator of transcription (STAT3) signaling cascade in immune regulation by human dendritic cells (DCs). IL-6-conditioned monocyte-derived DCs (MoDCs) impaired the presenting ability of cancer-related antigens. Interferon (IFN)-γ production attenuated by CD4(+) T cells co-cultured with IL-6-conditioned MoDCs corresponded with decreased DC IL-12p70 production. Human leukocyte antigen (HLA)-DR and CD86 expression was significantly reduced in CD11b(+)CD11c(+) cells obtained from peripheral blood mononuclear cells (PBMCs) of healthy donors by IL-6 treatment and was STAT3 dependent. Arginase-1 (ARG1), lysosomal protease, cathepsin L (CTSL), and cyclooxygenase-2 (COX2) were involved in the reduction of surface HLA-DR expression. Gene expressions of ARG1, CTSL, COX2, and IL6 were higher in tumor-infiltrating CD11b(+)CD11c(+) cells compared with PBMCs isolated from colorectal cancer patients. Expression of surface HLA-DR and CD86 on CD11b(+)CD11c(+) cells was down-regulated, and T cell-stimulating ability was attenuated compared with PBMCs, suggesting that an immunosuppressive phenotype might be induced by IL-6, ARG1, CTSL, and COX2 in tumor sites of colorectal cancer patients. There was a relationship between HLA-DR expression levels in tumor tissues and the size of CD4(+) T and CD8(+) T cell compartments. Our findings indicate that IL-6 causes a dysfunction in human DCs that activates cancer antigen-specific Th cells, suggesting that blocking the IL-6/STAT3 signaling pathway might be a promising strategy to improve cancer immunotherapy.

Introduction: Dendritic cells play a key role as initiators of T-cell responses, and even if tumour antigen-loaded dendritic cells can induce anti-tumour responses, their efficacy has been questioned, suggesting a need to enhance immunization strategies., Matherials & Methods: We focused on the characterization of bone marrow-derived dendritic cells pulsed with whole tumour lysate (TAA-DC), as a source of known and unknown antigens, in a mouse model of breast cancer (MMTV-Ras). Dendritic cells were evaluated for antigen uptake and for the expression of MHC class I/II and costimulatory molecules and markers associated with maturation., Results: Results showed that antigen-loaded dendritic cells are characterized by a phenotypically semi-mature/mature profile and by the upregulation of genes involved in antigen presentation and T-cell priming. Activated dendritic cells stimulated T-cell proliferation and induced the production of high concentrations of IL-12p70 and IFN-γ but only low levels of IL-10, indicating their ability to elicit a TH1-immune response. Furthermore, administration of Antigen loaded-Dendritic Cells in MMTV-Ras mice evoked a strong anti-tumour response in vivo as demonstrated by a general activation of immunocompetent cells and the release of TH1 cytokines., Conclusion: Data herein could be useful in the design of antitumoral DC-based therapies, showing a specific activation of immune system against breast cancer.

CD8α(+) and CD103(+) dendritic cells (DCs) play a central role in the development of type 1 immune responses. However, their role in type 2 immunity remains unclear. We examined this issue using Batf3(-/-) mice, in which both of these DC subsets are missing. We found that Th2 cell responses, and related events such as eosinophilia, alternative macrophage activation, and immunoglobulin class switching to IgG1, were enhanced in Batf3(-/-) mice responding to helminth parasites. This had beneficial or detrimental consequences depending on the context. For example, Batf3 deficiency converted a normally chronic intestinal infection with Heligmosomoides polygyrus into an infection that was rapidly controlled. However, liver fibrosis, an IL-13-mediated pathological consequence of wound healing in chronic schistosomiasis, was exacerbated in Batf3(-/-) mice infected with Schistosoma mansoni. Mechanistically, steady-state production of IL-12 by migratory CD103(+) DCs, independent of signals from commensals or TLR-initiated events, was necessary and sufficient to exert the suppressive effects on Th2 response development. These findings identify a previously unrecognized role for migratory CD103(+) DCs in antagonizing type 2 immune responses., (© 2016 Everts et al.)

Radiotherapy (RT) is a potent anti-tumor modality. However, unwanted effects including increased recurrence and metastasis that involve factors such as cytokines, which induce complex molecular mechanisms, have also been reported. In a previous study, we showed that interleukin (IL)-12 and radiotherapy combination treatment suppressed tumor growth and metastasis in a hepatoma mouse model. In this study, we investigated the mechanism underlying the IL-12 anti-tumor effect during radiotherapy. In tumor-bearing mice, irradiation decreased IL-12 expression in the tumors and spleens. However, a number of dendritic cells infiltrated into the tumors in which IL-12 expression did not decrease. To further study the underlying detailed mechanism for this decrease in IL-12, LPS-stimulated bone marrow-derived dendritic cells (BMDCs) were irradiated, and then IL-12- and IL-6-associated molecules were examined in irradiated tumors and BMDCs. Irradiation resulted in IL-12 suppression and IL-6 increase. IL-6 and signal transducer and activator of transcription 3 (STAT3) inhibitors restored the irradiation-induced IL-12 decrease via suppression of C-Rel activation. Taken together, our study suggests that irradiation-induced IL-6 can decrease IL-12 production through the inhibition of C-Rel phosphorylation by the IL-6/STAT3 signaling pathway.

Leishmania parasites and some molecules they secrete are known to modulate innate immune responses through effects on dendritic cells (DCs) and macrophages. Here, we characterized four Leishmania infantum potentially excreted/secreted recombinant proteins (LipESP) identified in our laboratory: Elongation Factor 1 alpha (LiEF-1α), a proteasome regulatory ATPase (LiAAA-ATPase) and two novel proteins with unknown functions, which we termed LiP15 and LiP23, by investigating their effect on in vitro differentiation and maturation of human DCs and on cytokine production by DCs and monocytes. During DCs differentiation, LipESP led to a significant decrease in CD1a. LiP23 and LiEF-1α, induced a decrease of HLA-DR and an increase of CD86 surface expression, respectively. During maturation, an up-regulation of HLA-DR and CD80 was found in response to LiP15, LiP23 and LiAAA-ATPase, while an increase of CD40 expression was only observed in response to LiP15. All LipESP induced an over-expression of CD86 with significant differences between proteins. These proteins also induced significant IL-12p70 levels in immature DCs but not in monocytes. The LipESP-induced IL-12p70 production was significantly enhanced by a co-treatment with IFN-γ in both cell populations. TNF-α and IL-10 were induced in DCs and monocytes with higher levels observed for LiP15 and LiAAA-ATPase. However, LPS-induced cytokine production during DC maturation or in monocyte cultures was significantly down regulated by LipESP co-treatment. Our findings suggest that LipESP strongly interfere with DCs differentiation suggesting a possible involvement in mechanisms established by the parasite for its survival. These proteins also induce DCs maturation by up-regulating several costimulatory molecules and by inducing the production of proinflammatory cytokines, which is a prerequisite for T cell activation. However, the reduced ability of LipESP-stimulated DCs and monocytes to respond to lipopolysaccharide (LPS) that can be observed during human leishmaniasis, suggests that under certain circumstances LipESP may play a role in disease progression.

Interleukin-12 is one of the cytokines that induce acquired immunity by progressing the differentiation of T cells. When antigens are presented by APCs, including macrophages and DCs, T cells are activated and produce the Th1 cytokines IL-2 and IFN-γ. We have previously reported greater IL-12 production from macrophages infected with early-shared BCG sub-strains (ex. BCG-Japan, -Sweden) than from those infected with late-shared BCG (ex. BCG-Pasteur and -Connaught) . In this study, we investigated the Th1 cytokine-inducing activity of splenocytes co-cultured with BCG-infected DCs. Early-shared BCG-infected DCs produced IL-12 and TNF-α⋅ Furthermore, when they were co-cultured with purified protein derivative-stimulated DCs, the splenocytes of mice immunized with BCG-Tokyo/Japan produced more Th1 cytokine than did those of mice immunized with BCG-Connaught. In conclusion, early-shared BCG sub-strains more strongly induce Th1 cytokine production in vivo. This study provides basic information to inform the selection of candidates for primary vaccination., (© 2015 The Societies and Wiley Publishing Asia Pty Ltd.)

Inorganic arsenic, a well-known Nrf2 inducer, exerts immunosuppressive properties. In this context, we recently reported that the differentiation of human blood monocytes into immature dendritic cells (DCs), in the presence of low and noncytotoxic concentrations of arsenic, represses the ability of DCs to release key cytokines in response to different stimulating agents. Particularly, arsenic inhibits the expression of human interleukin-12 (IL-12, also named IL-12p70), a major proinflammatory cytokine that controls the differentiation of Th1 lymphocytes. In the present study, we determined if Nrf2 could contribute to these arsenic immunotoxic effects. To this goal, human monocyte-derived DCs were first differentiated in the absence of metalloid and then pretreated with arsenic just before DC stimulation with lipopolysaccharide (LPS). Under these experimental conditions, arsenic rapidly and stably activates Nrf2 and increases the expression of Nrf2 target genes. It also significantly inhibits IL-12 expression in activated DCs, at both mRNA and protein levels. Particularly, arsenic reduces mRNA levels of IL12A and IL12B genes which encodes the p35 and p40 subunits of IL-12p70, respectively. tert-Butylhydroquinone (tBHQ), a reference Nrf2 inducer, mimics arsenic effects and potently inhibits IL-12 expression. Genetic inhibition of Nrf2 expression markedly prevents the repression of both IL12 mRNA and IL-12 protein levels triggered by arsenic and tBHQ in human LPS-stimulated DCs. In addition, arsenic significantly reduces IL-12 mRNA levels in LPS-activated bone marrow-derived DCs from Nrf2+/+ mice but not in DCs from Nrf2-/- mice. Finally, we show that, besides IL-12, arsenic significantly reduces the expression of IL-23, another heterodimer containing the p40 subunit. In conclusion, our study demonstrated that arsenic represses IL-12 expression in human-activated DCs by specifically stimulating Nrf2 activity., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Why and when the immune system skews to Th2 mediated allergic immune responses is still poorly characterized. With two homologous lipocalins, the major respiratory dog allergen Can f 1 and the human endogenous, non-allergenic Lipocalin-1, we investigated their impact on human monocyte-derived dendritic cells (DC). The two lipocalins had differential effects on DC according to their allergenic potential. Compared to Lipocalin-1, Can f 1 persistently induced lower levels of the Th1 skewing maturation marker expression, tryptophan breakdown and interleukin (IL)-12 production in DC. As a consequence, T cells stimulated by DC treated with Can f 1 produced more of the Th2 signature cytokine IL-13 and lower levels of the Th1 signature cytokine interferon-γ than T cells stimulated by Lipocalin-1 treated DC. These data were partially verified by a second pair of homologous lipocalins, the cat allergen Fel d 4 and its putative human homologue major urinary protein. Our data indicate that the crosstalk of DC with lipocalins alone has the potential to direct the type of immune response to these particular antigens. A global gene expression analysis further supported these results and indicated significant differences in intracellular trafficking, sorting and antigen presentation pathways when comparing Can f 1 and Lipocalin-1 stimulated DC. With this study we contribute to a better understanding of the induction phase of a Th2 immune response., (© 2015 The Authors. Journal of Cellular and Molecular Medicine published by John Wiley & Sons Ltd and Foundation for Cellular and Molecular Medicine.)

Impaired T cell responses are a defining characteristic of HIV infection, but the extent to which altered mononuclear phagocyte function contributes to this defect is unclear. We show that mononuclear phagocytes enriched from rhesus macaque lymph nodes have suppressed ability to stimulate CD4 T cell proliferation and IFN-γ release after acute SIV infection. When individual populations were isolated, myeloid dendritic cells (mDC) and macrophages but not plasmacytoid DC (pDC) had suppressed capacity to stimulate CD4 T cell proliferation, with macrophage function declining as infection progressed. Macrophages, but not pDC or mDC, had suppressed capacity to induce IFN-γ release from CD4 T cells in acute infection, even after stimulation with virus-encoded TLR7/8 ligand. Changes in expression of costimulatory molecules did not explain loss of function postinfection. Conversely, pDC and mDC had marked loss of IFN-α and IL-12 production, respectively, and macrophages lost production of both cytokines. In T cell cocultures without TLR7/8 ligand, macrophages were the primary source of IL-12, which was profoundly suppressed postinfection and correlated with loss of IFN-γ release by T cells. TLR7/8-stimulated pDC, mDC and macrophages all produced IL-12 in T cell cocultures, which was suppressed in chronic infection. Supplementing IL-12 enhanced mDC-driven IFN-γ release from T cells, and IL-12 and IFN-α together restored function in TLR7/8-activated macrophages. These findings reveal loss of macrophage and mDC T cell-stimulating function in lymph nodes of SIV-infected rhesus macaques associated with diminished IL-12 and IFN-α production that may be a factor in AIDS immunopathogenesis., (Copyright © 2015 by The American Association of Immunologists, Inc.)

During late gestation the bovine immune system is less capable of eliciting inflammatory responses and eliminating invading pathogens. The maternal immune system is directed toward tolerance in order to prevent fetal rejection due to recognition of paternal antigens. In humans and mice, dendritic cell (DC) populations maintain a tolerogenic phenotype essential in the generation and preservation of maternal immune tolerance throughout pregnancy. However, the primary mechanisms which facilitate maternal immune tolerance involved in bovine gestation remain poorly understood. In order to determine if DC phenotype and function were regulated toward tolerance during bovine gestation, we compared in vitro generated monocyte-derived DC (mo-DC) from monocytes isolated from cows in late gestation (LG) to those from non-pregnant (NP) cows in their ability to mature following stimulation with UV irradiated Escherichia coli. Our results show mo-DC from LG cows have an impaired ability to mature in response to E. coli stimulation in a receptor and cytokine-mediated fashion in comparison to those from NP cows. Specifically, mo-DC from LG cows were unable to upregulate MHC II and maintained high expression of CD14, both indicative of an immature phenotype following E. coli-stimulation. Only mo-DC from LG showed significant increase in IL-10 production and had a significantly lower ratio of production of the Th1-polarizing cytokine IL-12 to regulatory cytokine IL-10 following E. coli stimulation compared to mo-DC from NP cows. Our findings demonstrate mo-DC from LG cows have a stifled capacity to develop a mature phenotype and drive pro-inflammatory Th1-type responses to E. coli stimulation. Results from this study provide insight into DC immune modulation in bovine pregnancy and elucidate host factors which may contribute to the heightened susceptibility to infection in late gestation., (Copyright © 2015 Elsevier B.V. All rights reserved.)

The function of dendritic cells (DCs) can be modulated through multiple signals, including recognition of pathogen-associated molecular patterns, as well as signals provided by rapidly activated leukocytes in the local environment, such as innate-like T cells. In this article, we addressed the possibility that the roles of different murine DC subsets in cross-priming CD8(+) T cells can change with the nature and timing of activatory stimuli. We show that CD8α(+) DCs play a critical role in cross-priming CD8(+) T cell responses to circulating proteins that enter the spleen in close temporal association with ligands for TLRs and/or compounds that activate NKT cells. However, if NKT cells are activated first, then CD8α(-) DCs become conditioned to respond more vigorously to TLR ligation, and if triggered directly, these cells can also contribute to priming of CD8(+) T cell responses. In fact, the initial activation of NKT cells can condition multiple DC subsets to respond more effectively to TLR ligation, with plasmacytoid DCs making more IFN-α and both CD8α(+) and CD8α(-) DCs manufacturing more IL-12. These results suggest that different DC subsets can contribute to T cell priming if provided appropriately phased activatory stimuli, an observation that could be factored into the design of more effective vaccines., (Copyright © 2015 by The American Association of Immunologists, Inc.)

Inhibition of Janus-activated kinase-1 (JAK1) is a promising clinical concept for post-transplant immunosuppression and autoimmunity. However, it also raises concerns regarding possible immunosuppressive side effects. Our study investigates JAK1 signalling in the context of CD40L and bacterially activated human MoDC using siRNA and biological inhibitors. We demonstrate that strong stimuli (e.g. intact Escherichia coli or LPS in addition to IL-1β) induce IL-12p70 via a ROS/RELA/CDK9 pathway that is inhibited by simultaneous JAK1/STAT3 signalling. Transcription is effective if RELA recruits the positive transcription elongation factor b (P-TEFb) component CDK9 to a combined RELA/STAT3 binding site -50 to -20bp upstream of the start site of the IL-12p35 promoter. STAT3 simultaneously attaches to this site and inhibits CDK9 binding. In the presence of IFNγ, JAK1/2 inhibitors block STAT1/IRF1/IRF8-dependent activation and simultaneously enhance CDK9-dependent activation signals. This inverse regulation of IFNγ- vs. E. coli-induced cytokine production by JAK inhibitors including Ruxolitinib was similarly observed for IL-6 and TNF-α production, but not for IL-10 production. Thus, JAK1 inhibition enhances IL-12p70 production in this context by increased DNA binding of CDK9. In contrast, weak RELA-activation signals (CD40L, LPS) depended on IFN-γ induced STAT1/IRF1/IRF8 co-signalling, which was completely blocked by JAK inhibitors as reported before. Our results suggest a novel molecular mechanism of how cytokine responses to invading pathogens are separable from IFNγ-dependent autoimmunity by targeting JAK1/STAT3 activation., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Recent studies have indicated that different strains of Lactobacilli differ in their ability to regulate IL-12 production by dendritic cells (DCs), as some strains are stronger inducer of IL-12 while other are not and can even inhibit IL-12 production stimulated by IL-12-inducer Lactobacilli. In this report we demonstrate that Lactobacillus reuteri 5289, as previously described for other strains of L. reuteri, can inhibit DC production of IL-12 induced by Lactobacilllus acidophilus NCFM. Remarkably, L. reuteri 5289 was able to inhibit IL-12 production induced not only by Lactobacilli, as so far reported, but also by bacteria of different genera, including pathogens. We investigated in human DCs the signal transduction pathways involved in the inhibition of IL-12 production induced by L. reuteri 5289, showing that this potential anti-inflammatory activity, which is also accompanied by an elevated IL-10 production, is associated to a prolonged phosphorilation of ERK1/2 MAP kinase pathway. Improved understanding of the immune regulatory mechanisms exerted by Lactobacilli is crucial for a more precise employment of these commensal bacteria as probiotics in human immune-mediated pathologies, such as allergies or inflammatory bowel diseases., (Copyright © 2015 European Federation of Immunological Societies. Published by Elsevier B.V. All rights reserved.)

This study aimed to examine anti-prostate cancer immune response induced by dendritic cells (DCs) transduced with PSMA/4-1BBL recombinant adenoviruses in vitro. Ad-PSMA, Ad-4-1BBL, and Ad-GFP were transfected into DCs derived from peripheral blood of healthy volunteers. Ad-PSMA/4-1BBL-DC, Ad-PSMA-DC, Ad-4-1BBL-DC, Ad-GFP-DC, and normal-DC, PSMA and 4-1BBL protein levels in DCs were detected by western blot. IL-12, IFN-γ and IL-10 were measured by ELISA. Mixed lymphocyte reaction and the cytotoxicity of each group targeted to LNCap, Du145, and 22RV prostate cancer cells were determined by CCK-8 assay. PSMA and 4-1BBL protein could express on DC successfully, the IL-12 supernatant content (134.29 ± 2.22 pg) was higher than others (P < 0.05). The ability to stimulate autologous T lymphocyte proliferation in the co-transfection group was higher than others (P < 0.05). When the DCs were co-cultured with CTLs, the PSMA/4-1BBL-DC-CTL group showed the highest content of IFN-γ (1176.10 ± 14.37pg/5 x 10(6) cells), but the lowest IL-10 content (75.14 ± 2.01 pg/5 x 10(6) cells) (P < 0.05), and the strongest anti-tumor effect when the effector to target ratio was 40:1, along with a higher killing ratio of LNCap cells than others (P < 0.05). Overall, Mature DCs transfected with Ad-PSMA/4- 1BBL not only showed high secretion of IL-12, but also induced CTLs to stimulate and enhance the killing effect of PSMA specific effector cells to PSMA positively expressing prostate cancer cells. Furthermore, the DCs infected with two kinds of tumor-associated antigens would induce more effective tumor-specific CTL induction.

Purpose: Dendritic cells (DCs) play critical roles in promoting innate and adaptive immunity in microbial infection. Functional impairment of DCs may mediate the suppression of viral-specific T-cell immune response in chronic hepatitis B (CHB) patients. Osteopontin (OPN) is involved in several liver diseases and infectious diseases. However, whether OPN affects DC function in hepatitis B virus (HBV) infection is unknown., Methods: Twenty CHB patients and 20 healthy volunteers were recruited. OPN secreted by DCs was compared. Peripheral blood mononuclear cells cultured with OPN antibody were examined to study the costimulatory molecular expression and interleukin (IL)-12 production of DCs after HBV antigenic stimulation. OPN-deficient mice were used to investigate the influence of OPN on DC maturation and function after HBV antigenic stimulation in vitro and in vivo. Exogenous OPN was administrated to further verify the functioning of DCs from CHB patients upon HBV antigenic stimulation., Results: We found that OPN production of DCs from CHB patients was significantly lower than those from healthy volunteers. The absence of OPN impaired IL-12 production and costimulatory molecular expression of DCs upon stimulation with HBV antigens. Defective DC function led to reduced activation of Th1 response to HBV antigens. In addition, OPN deficiency in DCs reduced the HBV antigen-induced inflammatory response in the liver of mice. Importantly, OPN administration significantly promoted the maturation of DCs from CHB patients in vitro., Conclusion: These findings suggested that OPN could improve the maturation and functioning of DCs in the immune response to HBV antigens, which might be useful to further improve the effect of DC vaccine.

Cystic echinococcosis is a chronic infectious disease that results from a host/parasite interaction. Vaccination with ferritin derived from Echinococcus granulosus is a potential preventative treatment. To understand whether ferritin is capable of inducing a host immune response, we investigated the response of dendritic cells (DCs) to both recombinant ferritin protein and the hydatid fluid (HF) of E. granulosus. We evaluated the immunomodulatory potential of these antigens by performing, immunocytochemistry, electron microscopy and in vivo imaging of monocyte-derived murine DCs. During antigen stimulation of DCs, ferritin cause DCs maturation and induced higher levels of surface marker expression and activated T-cell proliferation and migration. On contrary, HF failed to induce surface marker expression and to stimulate T-cell proliferation. In response to HF, DCs produced interleukin-6 (IL-6), but no IL-12 and IL-10. DCs stimulated with ferritin produced high levels of cytokines. Overall, HF appears to induce host immunosuppression in order to ensure parasite survival via inhibits DC maturation and promotes Th2-dependent secretion of cytokines. Although ferritin also promoted DC maturation and cytokine release, it also activates CD4+T-cell proliferation, but regard of the mechanism of the Eg.ferritin induce host to eradicate E. granulosus were not clear.

IL-35 is a cytokine of the IL-12 family, existing as a heterodimer of IL-12p35 and Ebi3. IL-35 has anti-inflammatory properties and is produced by regulatory T cells in humans and mice, where it is required for optimal suppression of immune responses. Distinct from other IL-12 cytokines, the expression of IL-35 has not been described in antigen-presenting cells. In view of the immune-regulatory properties of IL-35, we investigated the expression, regulation, and function of IL-12p35 and Ebi3 in human monocyte-derived dendritic cells and tolerogenic DCs (tolDCs). These tolDCs do not produce IL-12p70 or the homodimer IL-12p40. We demonstrate that tolDCs completely lack transcriptional expression of IL-12p40. However, tolDCs maintain mRNA expression of IL-12p35 and Ebi3. Using intracellular flow cytometry and Western blot analysis, we show that tolDCs produce Ebi3 and IL-12p35, and both can be enhanced upon stimulation with IFN-γ, LPS, or CD40L. tolDCs supernatants have the capacity to suppress T-cell activation. Using IL12A silencing, we demonstrate that IL-12p35 is required for tolDCs to reach their full suppressive potential. Taken together, our results indicate that tolDCs produce IL-35, providing an additional novel mechanism by which tolDCs elicit their tolerogenic potential., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The innate immune system utilizes pattern recognition receptors (PRRs) to recognize microbes. Pathogens contain various molecules with diverse effects on immune response. In this study, we evaluated the effect of DNA and protein components derived from two intracellular microorganisms including Listeria monocytogenes (L. monocytogenes) and Toxoplasma gondii (T. gondii) on dendritic cells (DCs) activation and ensuing adaptive immune responses. DNA and protein components of L. monocytogenes and T. gondii were prepared using relevant kits. DNA and protein components of these two pathogens were added to immature DCs (iDCs). Subsequently, co-stimulatory expression and cytokine production by DCs were measured. Finally, we evaluated the stimulatory capacity of mature DCs (mDCs) in DC-T cells co-culture. The results showed that protein matured-DCs produced higher level of IL (Interleukin)-12p70. There was also a significant increase in Interferon-Gamma (IFN-γ) production and proliferative capacity in T cells co-cultured with protein matured-DCs. On the other hand, DNA matured-DCs produced significantly higher amounts of Transforming growth factor-beta (TGF-β). Collectively, these results imply a regulatory nature for DNA and potent stimulatory character for protein components of these two intracellular microorganisms.

Dendritic cells (DCs) comprise two functionally distinct subsets: plasmacytoid DCs (pDCs) and myeloid DCs (mDCs). pDCs are specialized in rapid and massive secretion of type I interferon (IFN-I) in response to nucleic acids through Toll like receptor (TLR)-7 or TLR-9. In this report, we characterized a CD56(+) DC population that express typical pDC markers including CD123 and BDCA2 but produce much less IFN-I comparing with pDCs. In addition, CD56(+) DCs cluster together with mDCs but not pDCs by genome-wide transcriptional profiling. Accordingly, CD56(+) DCs functionally resemble mDCs by producing IL-12 upon TLR4 stimulation and priming naïve T cells without prior activation. These data suggest that the CD56(+) DCs represent a novel mDC subset mixed with some pDC features. A CD4(+)CD56(+) hematological malignancy was classified as blastic plasmacytoid dendritic cell neoplasm (BPDCN) due to its expression of characteristic molecules of pDCs. However, we demonstrated that BPDCN is closer to CD56(+) DCs than pDCs by global gene-expression profiling. Thus, we propose that the CD4(+)CD56(+) neoplasm may be a tumor counterpart of CD56(+) mDCs but not pDCs.

Beta-catenin signaling has recently been tied to the emergence of tolerogenic dendritic cells (DCs). In this article, we demonstrate a novel role for beta-catenin in directing DC subset development through IFN regulatory factor 8 (IRF8) activation. We found that splenic DC precursors express beta-catenin, and DCs from mice with CD11c-specific constitutive beta-catenin activation upregulated IRF8 through targeting of the Irf8 promoter, leading to in vivo expansion of IRF8-dependent CD8a+, plasmacytoid, and CD103+ CD11b2 DCs. beta-catenin–stabilized CD8a+ DCs secreted elevated IL-12 upon in vitro microbial stimulation, and pharmacological beta-catenin inhibition blocked this response in wild-type cells. Upon infections with Toxoplasma gondii and vaccinia virus, mice with stabilized DC beta-catenin displayed abnormally high Th1 and CD8+ T lymphocyte responses, respectively. Collectively, these results reveal a novel and unexpected function for beta-catenin in programming DC differentiation toward subsets that orchestrate proinflammatory immunity to infection.

Hepatitis C virus (HCV) infection is a global health problem characterized by a high rate of chronic infection, which may in part be due to a defect in myeloid dendritic cells (mDCs). This defect appears to be remedied by treatment with interferon-α (IFN-α) -based antiviral therapies; however, the molecular mechanisms underlying mDC dysfunction in HCV infection and restoration by IFN-α treatment are unclear. The ubiquitin-editing protein A20 plays a crucial role in controlling the maturation, cytokine production and immunostimulatory function of mDCs. We propose that the expression of A20 correlates with the function of mDCs during HCV infection and IFN-α therapy. In this study, we observed that A20 expression in mDCs isolated from chronically HCV-infected subjects was significantly higher than healthy subjects or subjects achieving sustained virological responses (SVR) following antiviral treatment. Notably, A20 expression in mDCs from HCV patients during IFN-α treatment was significantly lower than for untreated patients, SVR patients, or healthy subjects. Besides, A20 expression in mDCs stimulated by polyI:C differed between HCV patients and healthy subjects, and this difference could be abrogated by the treatment with IFN-α in vitro. Additionally, A20 expression by polyI:C-activated mDCs, with or without IFN-α treatment, negatively correlated with the expression of HLA-DR, CD86 and CCR7, and the secretion of interleukin-12 (IL-12), but positively associated with the production of IL-10. Importantly, silencing A20 expression using small interfering RNAs increased the production of IL-12 in mDCs of chronically HCV-infected individuals. These findings suggest that A20 plays a crucial role in negative regulation of innate immune responses during chronic viral infection., (© 2014 John Wiley & Sons Ltd.)

Trichinella spiralis muscle larvae excretory-secretory antigens (ES L1) are most likely responsible for the induction of immune response during infection by this parasitic. The antigens bear carbohydrate structures that may contribute to immune system activation resulting in a Th2/anti-inflammatory immune response. We show that T. spiralis glycans affect the expression and the production of IL-4 and IL-10 in vivo. Alteration of carbohydrate structures on ES L1 altered dendritic cell (DC) maturation. Periodate treatment of ES L1 led to the reduction in both ERK and p38 phosphorylation which may be the cause of reduced IL-10 and IL-12p70 production. In vitro priming of naïve T cells with DCs stimulated with native and periodate-treated ES L1 emphasized the importance of intact glycans for IL-10 production. We conclude that T. spiralis glycans affect the anti-inflammatory environment and can interfere with the development of inflammatory diseases., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Understanding the signaling that governs the immunogenicity of human dendritic cells (DCs) is a prerequisite for improving DC-based therapeutic vaccination strategies, in which the ability of DCs to induce robust and lasting Ag-specific CTL responses is of critical importance. Cytokine-matured DCs are regularly used, but to induce memory-type CTLs, they require additional activation stimuli, such as CD4+ T-cell help or TLR activation. One common denominator of these stimuli is the activation of NF-κB. Here, we show that human monocyte-derived, cytokine cocktail-matured DCs transfected with constitutively active mutants of IκB kinases (caIKKs) by mRNA electroporation, further upregulated maturation markers, and secreted enhanced amounts of cytokines, including IL-12p70, which was produced for more than 48 h after transfection. Most importantly, cytotoxic T cells induced by caIKK-transfected DCs combined high CD27 expression, indicating a more memory-like phenotype, and a markedly enhanced secondary expandability with a high lytic capacity. In contrast, CTLs primed and expanded with unmodified cytokine cocktail-matured DCs did not maintain their proliferative capacity upon repetitive stimulations. We hypothesize that "designer" DCs expressing constitutively active IκB kinases will prove highly immunogenic also in vivo and possibly emerge as a new strategy to improve the clinical efficacy of therapeutic vaccinations against cancer and other chronic diseases., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Wnt5a is a secreted pleiotropic glycoprotein produced in an inflammatory state by a wide spectrum of ubiquitous cell populations. Recently, we demonstrated that Wnt5a skews the differentiation of human monocyte derived dendritic cells (moDCs) to a tolerogenic functional state. In this study we focus our interest on the role of this Wnt ligand after DC differentiation, during their maturation and function. We show that the expression of Wnt receptors is tightly regulated during the life cycle of DCs suggesting a differential responsiveness to Wnt signaling conditioned by their differentiation stage and the maturational stimuli. Furthermore, we confirm that Wnt5a is the main non-canonical Wnt protein expressed by DCs and its production increases upon specific stimuli. Exogenous Wnt5a improved the endocytic capacity of immature DCs but it is not a stimulatory signal on its own, slightly affecting the maturation and function of DCs. However, knocking down Wnt5a gene expression in maturing DCs demonstrates that DC-derived Wnt5a is necessary for normal IL-12 secretion and plays a positive role during the development of Th1 responses. Wnt5a acts both in autocrine and paracrine ways. Thus, human naive CD4(+) T cells express Wnt receptors and, the addition of Wnt5a during CD3/CD28 stimulation enhances IL-2 and IFN-γ production. Taken together these results suggest a time-dependent role for Wnt5a during inflammatory responses conditioned by the differentiation stage of cellular targets., (Copyright © 2014 Elsevier B.V. All rights reserved.)

MicroRNAs (miRNAs) are aberrant in many human tumors which can be transferred to immune cells by tumor-derived exosomes. Dendritic cells (DCs) play an important role in activation of immune response. However, the effect of tumor-derived exosomes on toll-like receptor (TLR) in DCs remains unclear. We investigated the influence of pancreatic cancer derived exosomes on TLR4, and downstream cytokines via miR-203. Our results showed that miR-203 expressed in panc-1 cells and exosomes, and upregulated in exosomes-treated DCs. TLR4 decreased after treatment of exosomes and miR-203 mimics, while increased in exosomes-treated DCs by miR-203 inhibitors. But the mRNA level of TLR4 was not significantly different between DCs and exosomes-treated DCs. Tumor necrosis factor-α (TNF-α) and interleukin-12 (IL-12) also decreased under treatment of exosomes and miR-203 mimics, both of which increased in exosomes-treated DCs by miR-203 inhibitors. Collectively, pancreatic cancer derived exosomes downregulate TLR4 and downstream cytokines in DCs via miR-203., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Sepsis-induced immune reactions are reduced in TNF receptor 2 (TNFR2)-deficient mice as previously shown. In order to elucidate the underlying mechanisms, the functional integrity of myeloid cells of TNFR2-deficient mice was analyzed and compared to wild type (WT) mice. The capacity of dendritic cells to produce IL-12 was strongly impaired in TNF-deficient mice, mirroring impaired production of IL-12 by WT dendritic cells in sepsis or after LPS or TNF pre-treatment. In addition, TNFR2-deficient mice were refractory to LPS pre-treatment and also to hyper-sensitization by inactivated Propionibacterium acnes, indicating habituation to inflammatory stimuli by the immune response when TNFR2 is lacking. Constitutive expression of TNF mRNA in kidney, liver, spleen, colon and lung tissue, and the presence of soluble TNFR2 in urine of healthy WT mice supported the conclusion that TNF is continuously present in naïve mice and controlled by soluble TNFR2. In TNFR2-deficient mice endogenous TNF levels cannot be balanced and the continuous exposure to enhanced TNF levels impairs dendritic cell function. In conclusion, TNF pre-exposure suppresses secondary inflammatory reactions of myeloid cells; therefore, continuous control of endogenous TNF by soluble TNFR2 seems to be essential for the maintenance of adequate sensitivity to inflammatory stimuli., (© The Author(s) 2013 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.)