TLR-ligand stimulated interleukin-23 subunit expression and assembly is regulated differentially in murine plasmacytoid and myeloid dendritic cells

An MVA-based vector expressing cell-free ISG15 increases IFN-I production and improves HIV-1-specific CD8 T cell immune responses

The human immunodeficiency virus (HIV), responsible of the Acquired Immune Deficiency Syndrome (AIDS), continues to be a major global public health issue with any cure or vaccine available. The Interferon-stimulated gene 15 (ISG15) encodes a ubiquitin-like protein that is induced by interferons and plays a critical role in the immune response. ISG15 is a modifier protein that covalently binds to its targets via a reversible bond, a process known as ISGylation, which is the best-characterized activity of this protein to date. However, ISG15 can also interact with intracellular proteins via non-covalent binding or act as a cytokine in the extracellular space after secretion. In previous studies we proved the adjuvant effect of ISG15 when delivered by a DNA-vector in heterologous prime-boost combination with a Modified Vaccinia virus Ankara (MVA)-based recombinant virus expressing HIV-1 antigens Env/Gag-Pol-Nef (MVA-B). Here we extended these results evaluating the adjuvant effect of ISG15 when expressed by an MVA vector. For this, we generated and characterized two novel MVA recombinants expressing different forms of ISG15, the wild-type ISG15GG (able to perform ISGylation) or the mutated ISG15AA (unable to perform ISGylation). In mice immunized with the heterologous DNA prime/MVA boost regimen, the expression of the mutant ISG15AA from MVA-Δ3-ISG15AA vector in combination with MVA-B induced an increase in the magnitude and quality of HIV-1-specific CD8 T cells as well as in the levels of IFN-I released, providing a better immunostimulatory activity than the wild-type ISG15GG. Our results confirm the importance of ISG15 as an immune adjuvant in the vaccine field and highlights its role as a potential relevant component in HIV-1 immunization protocols.

IL-17A activated by Toll-like receptor 9 contributes to the development of septic acute kidney injury

Toll-like receptor 9 (TLR9), which is activated by endogenously released mtDNA during sepsis, contributes to the development of polymicrobial septic acute kidney injury (AKI). However, downstream factors of TLR9 to AKI remain unknown. We hypothesized that IL-17A activated by TLR9 may play a critical role in septic AKI development. To determine the effects of TLR9 on IL-17A production in septic AKI, we used a cecal ligation and puncture (CLP) model in Tlr9 knockout (Tlr9KO) mice and wild-type (WT) littermates. We also investigated the pathway from TLR9 activation in dendritic cells (DCs) to IL-17A production by γδT cells in vitro. To elucidate the effects of IL-17A on septic AKI, Il-17a knockout (Il-17aKO) mice and WT littermates were subjected to CLP. We further investigated the relationship between the TLR9-IL-17A axis and septic AKI by intravenously administering recombinant IL-17A or vehicle into Tlr9KO mice and assessing kidney function. IL-17A levels in both plasma and the peritoneal cavity and mRNA levels of IL-23 in the spleen were significantly higher in WT mice after CLP than in Tlr9KO mice. Bone marrow-derived DCs activated by TLR9 induced IL-23 and consequently promoted IL-17A production in γδT cells in vitro. Knockout of Il-17a improved survival, functional and morphological aspects of AKI, and splenic apoptosis after CLP. Exogenous IL-17A administration aggravated CLP-induced AKI attenuated by knockout of Tlr9. TLR9 in DCs mediated IL-17A production in γδT cells during sepsis and contributed to the development of septic AKI.

Interleukin-12p40 variant form reduces Interleukin-12p80 secretion

IL-12 is a key cytokine for the promotion of CD4⁺ T cells differentiation to type 1 helper T cells. IL-12 is a heterodimer (IL-12p70) consisting of p40 and p35 subunits, and is mainly secreted from activated antigen-presenting cells, such as macrophages and dendritic cells (DCs). In this study, we found that activated mouse bone marrow-derived DCs (BMDCs) produced a p40 splice variant form mRNA in addition to the conventional p40 mRNA. This p40 variant mRNA was produced by alternative splicing in exon 5, and possessed a premature stop codon. As a result, the p40 variant protein contained 157 amino acids of the N-terminal part of p40 and an additional 10 novel amino acids. When the p40 variant was expressed in HEK-293T cells, it was not secreted from the cells. To investigate the function of the p40 variant, it was co-expressed with p40 and/or p35. The p40 variant did not affect the secretion of IL-12p40 or IL-12p70, or the function of the secreted p70. In contrast, the secretion of IL-12p80, a homodimeric IL-12 with two p40 subunits, was significantly decreased when the p40 variant was expressed. This new splicing variant p40 may act to fine-tune the function of IL-12p80.

Interleukin (IL)-12 and IL-23 and Their Conflicting Roles in Cancer

The balance of proinflammatory cytokines interleukin (IL)-12 and IL-23 plays a key role in shaping the development of antitumor or protumor immunity. In this review, we discuss the role IL-12 and IL-23 plays in tumor biology from preclinical and clinical data. In particular, we discuss the mechanism by which IL-23 promotes tumor growth and metastases and how the IL-12/IL-23 axis of inflammation can be targeted for cancer therapy.

Regulation of IL-10 and IL-12 production and function in macrophages and dendritic cells

Interleukin-10 and Interleukin-12 are produced primarily by pathogen-activated antigen-presenting cells, particularly macrophages and dendritic cells. IL-10 and IL-12 play very important immunoregulatory roles in host defense and immune homeostasis. Being anti- and pro-inflammatory in nature, respectively, their functions are antagonistically opposing. A comprehensive and in-depth understanding of their immunological properties and signaling mechanisms will help develop better clinical intervention strategies in therapy for a wide range of human disorders. Here, we provide an update on some emerging concepts, controversies, unanswered questions, and opinions regarding the immune signaling of IL-10 and IL-12.

Characterization of an IL-12 p40/p35 Truncated Fusion Protein That can Inhibit the Action of IL-12

Interleukin-12 (IL-12), a potent inducer of interferon gamma (IFNγ), is a heterodimeric protein consisting of p40 and p35 subunits whose expression is regulated independently. IL-12 is part of a cytokine family (currently consisting of IL-12, IL-23, IL-27, and IL-35) that can have profoundly different immunologic effects, despite sharing subunits. In constructing a single-chain fusion of p40 and p35, we discovered an insert corresponding to an intron in the gene encoding the p35 subunit that would result in a truncated form of p35 if translated. To test its possible role, we constructed, expressed, and analyzed fusions of p40 with the full-length or the truncated form of p35. The fusion protein containing the truncated p35 did not stimulate the proliferation of the IL-12-responsive cell line CTLL-2 nor did it induce IFNγ or the chemokine IFNγ-inducible protein 10 (IP-10, CXCL10) or monokine induced by IFNγ (MIG, CXCL9) from spleen cells. In striking contrast, the full-length IL-12 p40/p35 fusion induced robust responses in both assays. Moreover, the truncated IL-12 fusion protein inhibited the action of the full-length IL-12 p40/p35 fusion in the proliferation assay and also blocked the induction of IFNγ. These findings raise the possibility that alternative splicing may provide an additional regulatory mechanism for IL-12.

Combined anti-CD40 and anti-IL-23 monoclonal antibody therapy effectively suppresses tumor growth and metastases

Tumor-induced immunosuppression remains one of the major obstacles to many potentially effective cancer therapies and vaccines. Host interleukin (IL)-23 suppresses the immune response during tumor initiation, growth, and metastases, and neutralization of IL-23 causes IL-12-dependent antitumor effects. Here, we report that combining agonistic anti-CD40 monoclonal antibodies (mAb) to drive IL-12 production and anti-IL-23 mAbs to counter the tumor promoting effects of IL-23 has greater antitumor activity than either agent alone. This increased antitumor efficacy was observed in several experimental and spontaneous lung metastases models as well as in models of de novo carcinogenesis. The combination effects were dependent on host IL-12, perforin, IFN-γ, natural killer, and/or T cells and independent of host B cells and IFN-αβ sensitivity. Interestingly, in the experimental lung metastases tumor models, we observed that intracellular IL-23 production was specifically restricted to MHC-II(hi)CD11c(+)CD11b(+) cells. Furthermore, an increase in proportion of these IL-23-producing cells was detected only in tumor models where IL-23 neutralization was therapeutic. Overall, these data suggest the clinical potential of using anti-CD40 (push) and anti-IL-23 mAbs (pull) to tip the IL-12/23 balance in established tumors.

Engagement of CD14 sensitizes primary monocytes to IFN-γ to produce IL-12/23p40 and IL-23 through p38 mitogen-activated protein kinase and independent of the janus kinase/signal transducers and activators of transcription signaling

Interferon (IFN)-γ is a potent stimulator of the IL-12 family Th1 cytokines, including IL-12/23p40 and IL-23, responsible for coordinating the innate and adaptive immune responses. Our results show that IFN-γ induced the production of IL-12/23p40 and IL-23p19 mRNA as well as IL-12p40 and IL-23 proteins in primary human monocytes isolated by positive selection through anti-CD14 microbeads. These results were confirmed by IFN-γ stimulation of CD14-activated monocytes resulting in IL-12/23p40 and IL-23 production. We investigated the signaling pathways governing the regulation of IL-23 and its subunits IL-23p40 and IL-23p19 following IFN-γ stimulation. We observed a differential regulation of IL-23p19, IL-12/23p40, and IL-23 following IFN-γ stimulation. IFN-γ-induced IL-23 and IL-12/23p40 expression was positively regulated by the p38 mitogen-activated protein kinases (MAPKs), independent of the Janus kinase (Jak)/signal transducers and activators of transcription (STAT) signaling. In contrast, IL-12 and IL-23 were negatively regulated by the Jak/STAT, phosphatidylinositol 3-kinase (PI3K), and the c-Jun-N-terminal kinase (JNK) MAPKs in IFN-γ-stimulated monocytes. Overall, our results suggest for the first time a differential positive regulation of IL-12p40 and IL-23 by p38 MAPKs independent of the Jak/STAT pathways and negative regulation by the Jak/STAT, JNK, and PI3K pathways in CD14-activated primary human monocytes stimulated with IFN-γ.

Mycophenolic acid derivative 118 improves outcome of skin grafts by suppressing IL-17 production

AIM

To investigate the effects and underlying mechanisms of 118, a novel derivative of mycophenolic acid, in a murine allogeneic skin graft model.

METHODS

Skin grafts were conducted by grafting BALB/c donor tail skin into C57BL/6 skin beds (allograft) or by grafting female C57BL/6 donor tail skin into female C57BL/6 skin beds (syngraft). The mice were treated with the derivative 118 (40 mg·kg(-1)·d(-1), po) for 13 d (3 d before and 10 d after transplantation). Skin grafts, splenocytes and graft-infiltrated lymphocytes were isolated and examined ex vivo. The effects of the derivative 118 on naive CD4(+) T cell differentiation were examined in vitro.

RESULTS

Treatment with the derivative 118 dramatically increased the survival rate of murine allogeneic skin grafts. Flow cytometric analysis and H&E staining showed that the derivative significantly decreased inflammatory cell infiltration into the grafts. The levels of the chemokines CXCL1, CXCL2, CCL7, and CCL2 were reduced in the derivative 118-treated grafts. Additionally, the derivative 118 significantly suppressed the IL-17 levels in the grafts but did not affect the differentiation of systemic helper T cells in the murine allogeneic skin graft model. Furthermore, IL-23p19 expression was suppressed in the grafts from the derivative 118-treated group, which might be due to decreases in TLR4 and MyD88 expression. Finally, the derivative 118 did not exert direct influences on helper T cell differentiation in vitro.

CONCLUSION

Treatment with the mycophenolic acid derivative 118 improves murine allogeneic skin grafts by decreasing IL-23 expression and suppressing local IL-17 secretion in the grafts, rather than directly inhibiting Th17 differentiation.

Negative feedback on IL-23 exerted by IL-17A during pulmonary inflammation

It is now established that IL-17 has a broad pro-inflammatory potential in mammalian host defense, in inflammatory disease and in autoimmunity, whereas little is known about its anti-inflammatory potential and inhibitory feedback mechanisms. Here, we examined whether IL-17A can inhibit the extracellular release of IL-23 protein, the upstream regulator of IL-17A producing lymphocyte subsets, that is released from macrophages during pulmonary inflammation. We characterized the effect of IL-17A on IL-23 release in several models of pulmonary inflammation, evaluated the presence of IL-17 receptor A (RA) and C (RC) on human alveolar macrophages and assessed the role of the Rho family GTPase Rac1 as a mediator of the effect of IL-17A on the release of IL-23 protein. In a model of sepsis-induced pneumonia, intravenous exposure to Staphylococcus aureus caused higher IL-23 protein concentrations in cell-free bronchoalveolar lavage (BAL) samples from IL-17A knockout (KO) mice, compared with wild type (WT) control mice. In a model of Gram-negative airway infection, pre-treatment with a neutralizing anti-IL-17A Ab and subsequent intranasal (i.n.) exposure to LPS caused higher IL-23 and IL-17A protein concentrations in BAL samples compared with mice exposed to LPS, but pre-treated with an isotype control Ab. Moreover, i.n. exposure with IL-17A protein per se decreased IL- 23 protein concentrations in BAL samples. We detected IL-17RA and IL-17RC on human alveolar macrophages, and found that in vitro stimulation of these cells with IL-17A protein, after exposure to LPS, decreased IL-23 protein in conditioned medium, but not IL-23 p19 or p40 mRNA. This study indicates that IL-17A can partially inhibit the release of IL-23 protein during pulmonary inflammation, presumably by stimulating the here demonstrated receptor units IL-17RA and IL-17RC on alveolar macrophages. Hypothetically, the demonstrated mechanism may serve as negative feedback to protect from excessive IL-17A signaling and to control antibacterial host defense once it is activated.

Innate-adaptive crosstalk: how dendritic cells shape immune responses in the CNS

Dendritic cells (DCs) are a heterogeneous group of professional antigen presenting cells that lie in a nexus between innate and adaptive immunity because they recognize and respond to danger signals and subsequently initiate and regulate effector T-cell responses. Initially thought to be absent from the CNS, both plasmacytoid and conventional DCs as well as DC precursors have recently been detected in several CNS compartments where they are seemingly poised for responding to injury and pathogens. Additionally, monocyte-derived DCs rapidly accumulate in the inflamed CNS where they, along with other DC subsets, may function to locally regulate effector T-cells and/or carry antigens to CNS-draining cervical lymph nodes. In this review we highlight recent research showing that (a) distinct inflammatory stimuli differentially recruit DC subsets to the CNS; (b) DC recruitment across the blood-brain barrier (BBB) is regulated by adhesion molecules, growth factors, and chemokines; and (c) DCs positively or negatively regulate immune responses in the CNS.

Dexamethasone restrains ongoing expression of interleukin-23p19 in peripheral blood-derived human macrophages

Background

Since its recent discovery, interleukin-23 has been shown to be involved in the pathogenesis of autoimmune diseases favoring the development of a T cell subset referred to as T helper 17. Glucocorticoids are widely employed in inflammatory and autoimmune diseases as they inhibit pro-inflammatory signaling and prevent production of inflammation mediators. Very limited information is available about the efficacy of synthetic glucocorticoids in containing the expression of interleukin-23 under cell activation.

Results

We demonstrate here that the glucocorticoid analogue dexamethasone administered to human monocyte-derived macrophages is indeed able to restrain the expression of interleukin-23 once it has been triggered by a pro-inflammatory stimulus. This effect of dexamethasone is here demonstrated being secondary to suppression of p38 MAPK activity, and involving a protein phosphatase - likely MAPK phosphatase-1 (MKP-1).

Conclusions

Results reported in this paper show that a 10 nanomolar dose of dexamethasone not only prevents inflammatory activation but is also efficacious in confining active inflammation. This effect is here demonstrated not to occur through "canonical" inhibition of the NF-κB transcription factor but through a distinct cascade of down-modulation, that underlines the importance of the transactivating activity of glucocorticoid receptor in the context of its anti-inflammatory action.

Cell mediated immune responses through TLR4 prevents DMBA-induced mammary carcinogenesis in mice

Toll-like receptors (TLRs) activate signals that are critically involved in the initiation of adaptive immune responses and many tumorigenic chemicals have been associated with activation of those pathways. To determine the role of TLR-4 (TLR4) in mammary carcinogenesis, we subjected TLR4 deficient and wild type (WT) mice to oral gavage with carcinogenic polyaromatic hydrocarbon 7,12-dimethylbenz(a)anthracene (DMBA). TLR4 deficient mice developed more tumors relative to the WT mice. T cells of TLR4 deficient mice produced elevated levels of IL-17 and lower levels of IFN-γ relative to WT mice. IL-12 secreted by CD11c(+) cells was higher in WT mice, whereas greater amounts of IL-23 were produced by CD11c(+) cells from TLR4 deficient mice. Moreover, there was higher incidence of regulatory T cells in TLR4 deficient mice than WT mice. Similarly, various markers of angiogenesis [matrix metalloproteinases (MMP)-2 and MMP-9, CD31 and vascular endothelial growth factor] were highly expressed in tumors from TLR4 deficient mice than WT mice. The results of this study indicate that TLR4 plays an important role in the prevention of DMBA induced mouse mammary tumorigenesis and efforts to divert the cell-mediated immune response may, therefore, prove to be beneficial in the prevention of mammary tumors.

Differential roles of T-cell subsets in regulation of ultraviolet radiation induced cutaneous photocarcinogenesis

Ultraviolet (UV) radiation, in particular the midwavelength range (UVB; 290-320 nm), is one of the most significant risk factors for the development of nonmelanoma skin cancer. UVB radiation-induced immunosuppression, which occurs in both humans and laboratory animals, contributes to their pathogenesis. However, there are conflicting reports on the relative role of CD4(+) and CD8(+) T cells in UVB induced skin cancer. The purpose of this study was to delineate the contribution of these two cell subpopulations to UVB induced immunosuppression and tumor development using C3H/HeN (WT), CD4 knockout (CD4(-/-) ) and CD8 knockout (CD8(-/-) ) mice. We observed that UVB induced skin carcinogenesis was retarded in terms of number of tumors per group, tumor volume and percentage of mice with tumors, in mice deficient in CD4(+) T cells compared with wild-type mice, whereas significantly greater (P < 0.05) numbers of tumors occurred in CD8(-/-) mice. These results indicate that, CD4(+) T cells promote tumor development while CD8(+) T cells have the opposite effect. Further, we found that CD4(+) T cells from tumor-bearing mice produced interleukin (IL)-4, IL-10, and IL-17 whereas CD8(+) T cells produced interferon-γ. Manipulation of T-cell subpopulations that are induced by UVB radiation could be a means of preventing skin cancers caused by this agent.

CD40 ligand-triggered human dendritic cells mount interleukin-23 responses that are further enhanced by danger signals

Interleukin (IL)-23 is a heterodimeric cytokine composed of the IL-23-specific subunit p19 and the p40 subunit which also constitutes part of IL-12. IL-23 propagates development of Th17 cells, a novel T cell subset which produces IL-17 but no interferon-gamma or IL-4. For both, IL-23 and IL-23-driven IL-17, a crucial role in autoimmune diseases such as experimental autoimmune encephalomyelitis, collagen-induced arthritis, and colitis is well accepted. Recent studies indicate that there is also a role for IL-23 and IL-17 in tumorigenesis, promoting tumor growth and vascularization, and affecting tumor incidence. We show that human CD14(+) peripheral blood monocyte-derived dendritic cells (DC), as used for clinical applications in anti-tumor immunization strategies, produce high amounts of IL-23. CD40-triggering of immature and mature DC but not of primary monocytes induced a rapid expression of high levels of IL-23, free p40, and minor levels of IL-12. Upon stimulation of DC subsets with a variety of different danger signals such as single stranded and double stranded RNA, bacterial components or viral infections, IL-23 expression pattern was analyzed. Interestingly, co-stimulation with CD40L enabled IL-23 expression by DC subsets towards danger signals to which they have been unresponsive upon single stimulation. Furthermore, we detected two novel splice variants of the IL-23-specific subunit p19 that could be associated with the regulation of IL-23 expression. Data presented here might have an impact on DC-based cancer vaccination strategies and contribute to a better understanding of the complex regulation of the heterodimeric cytokine IL-23.

Suppression of ongoing experimental autoimmune myasthenia gravis by transfer of RelB-silenced bone marrow dentritic cells is associated with a change from a T helper Th17/Th1 to a Th2 and FoxP3+ regulatory T-cell profile

OBJECTIVE

To observe the therapeutic effect of RelB-silenced dendritic cells (DCs) in experimental autoimmune myasthenia gravis (EAMG), and further to investigate the mechanism of this immune system therapeutic.

METHODS

(1) RelB-silenced DCs and control DCs were prepared and the supernatants were collected for IL-12p70, IL-6, and IL-23 measurement by ELISA. (2) RelB-silenced DCs and control DCs were co-cultured with AChR-specific T cells, and the supernatant was collected to observe the IL-17, IFN-gamma, IL-4 production. (3) EAMG mice with clinical scores of 1 to 2 were collected and enrolled randomly into the RelB-silenced DC group or the control DC group. RelB-silenced DCs or an equal amount of control DCs were injected intravenously on days 0, 7, and 14 after enrollment. Clinical scores were evaluated every other day. Twenty days after allotment, serum from individual mice was collected to detect serum concentrations of anti-mouse AChR IgG, IgG1, IgG2b, and IgG2c. The splenocytes were isolated for analysis of lymphocyte proliferative responses, cytokine (IL-17, IFN-gamma, IL-4) production, and protein levels of RORgammat, T-bet, GATA-3, and FoxP3 (the special transcription factors of Th17, Th1, Th2, and Treg, respectively).

RESULTS

(1) RelB-silenced DCs produced significantly reduced amounts of IL-12p70, IL-6, and IL-23, as compared with control DCs. (2) RelB-silenced DCs spurred on the CD4(+) T cells from Th1/Th17 to the Th2 cell subset in the co-culture system. (3) Treatment with RelB-silenced DCs effectively reduced myasthenic symptoms and levels of serum anti-acetylcholine receptor autoantibody in mice with ongoing EAMG. Th17-related markers (RORgammat, IL-17) and Th1-related markers (T-bet, IFN-gamma) were downregulated, whereas Th2 markers (IL-4 and GATA3) and Treg marker (FoxP3) were upregulated.

CONCLUSIONS

RelB-silenced DCs were able to create a particular cytokine environment that was absent of inflammatory cytokines. RelB-silenced DCs provide a practical means to normalize the differentiation of the four T-cell subsets (Th17, Th1, Th2, and Treg) in vivo, and thus possess therapeutic potential in Th1/Th17-dominant autoimmune disorders such as myasthenia gravis.

Interleukin-23/Th17 pathways and inflammatory bowel disease

The IL-23/Th17 pathway has recently been identified to play a critical role in a number of chronic inflammatory diseases including inflammatory bowel disease (IBD). The identification in IBD patients of associations in IL23R and regions that include other genes in the IL-23/Th17 pathway has highlighted the importance of proper IL-23/Th17 pathway regulation in intestinal immune homeostasis. IL-23 plays a role in CD4+ Th17 lineage cells, characterized by IL-17 secretion and the expression of the transcription factor retinoic acid-related orphan receptor (ROR)gamma tau, and in other immune and nonimmune cells. The balance between effector T cell subsets, such as Th17 cells, and CD4+ T regulatory subsets is finely regulated; dysregulation of this balance can lead to inflammation and autoimmunity. As such, the IL-23/Th17 pathway contributes to immune responses that play a role in defenses to microbial infection, as well as in the intestinal inflammation observed in both animal models of colitis and human IBD.

The Fasciola hepatica tegumental antigen suppresses dendritic cell maturation and function

Parasitic worms and molecules derived from them have powerful anti-inflammatory properties and are shown to have therapeutic effects on inflammatory diseases. The helminth Fasciola hepatica has been reported to suppress antigen-specific Th1 responses in concurrent bacterial infections, thus demonstrating its anti-inflammatory ability in vivo. Here, F. hepatica tegumental antigen (Teg) was shown to significantly suppress serum levels of gamma interferon (IFN-gamma) and interleukin-12p70 (IL-12p70) in a model of septic shock. Since dendritic cells (DCs) are a good source of IL-12p70 and critical in driving adaptive immunity, we investigated the effects of F. hepatica Teg on the activation and function of murine DCs. While Teg alone did not induce cytokine production or cell surface marker expression on DCs, it significantly suppressed cytokine production (IL-12p70, IL-6, IL-10, tumor necrosis factor alpha, and nitrite) and cell surface marker expression (CD80, CD86, and CD40) in DCs matured with a range of Toll-like receptor (TLR) and non-TLR ligands. Teg works independently of the TLR4 pathway, since it still functioned in DCs generated from TLR4 mutant and knockout mice. It impaired DC function by inhibiting their phagocytic capacity and their ability to prime T cells. It does not appear to target the common components (extracellular signal-regulated kinase, Jun N-terminal protein kinase, or p38) of the TLR pathways; however, it suppressed the active p65 subunit of the transcription factor NF-kappaB in mature DCs, which could explain the impairment of proinflammatory cytokine production. Overall, our results demonstrate the potent anti-inflammatory properties of F. hepatica Teg and its therapeutic potential as an anti-inflammatory agent.

Differential capability of human cutaneous dendritic cell subsets to initiate Th17 responses

Human skin-migratory dendritic cells (DCs) have the ability to prime and bias Th1 and Th2 CD4+ T lymphocytes. However, whether human cutaneous DCs are capable of initiating proinflammatory Th17 responses remains undetermined. We report that skin-migratory DCs stimulate allogeneic naive CD4+ T cells that differentiate simultaneously into two distinct effector Th17 and Th1 populations capable of homing to the skin, where they induce severe cutaneous damage. Skin-migratory Langerhans cells (smiLCs) were the main cutaneous DC subset capable of inducing Th17 responses dependent on the combined effects of IL-15 and stabilized IL-6, which resulted in IL-6 trans-signaling of naive CD4+ T cells. Different from smiLCs, purified skin-migratory dermal DCs did not synthesize IL-15 and were unable to bias Th17 responses. Nevertheless, these dermal DCs were capable of differentiating Th17 cells in mixed leukocyte cultures supplemented with IL-15 and stabilized IL-6. Overall, our data demonstrate that human epidermal smiLCs induce Th17 responses by mechanisms different from those previously described and highlight the need to target clinical treatments based on these variations.

LPS and poly I:C induce chromatin modifications at a novel upstream region of the IL-23 p19 promoter

IL-23, a heterodimer of IL-12 p40 and IL-23 p19, is critical for an effective immune response to many infections and has been implicated in several autoimmune diseases, however, little is known about the regulation of IL-23 gene expression in monocytes. We found that poly I:C, LPS, flagellin, and zymogen activated significant IL-23 production in primary human monocytes. Using chromatin immunoprecipitation, we found that a distal upstream region of the IL-23 p19 promoter at -601 to -521 underwent extensive histone modifications in response to stimuli. This distal region of the promoter is not highly conserved between species and has not been previously implicated in the regulation of IL-23 expression. Knockdown of CBP markedly decreased IL-23 p19 responses to poly I:C but had a less dramatic effect on LPS responses, confirming different chromatin responses to these two stimuli. Our data suggest that one of the mechanisms regulating IL-23 expression is the regulation of histone modifications at this distal upstream region of the promoter.

Toll-like receptor ligand activation of murine bone marrow-derived dendritic cells

Dendritic cells (DCs) are required for the initiation of primary immune responses. The pattern of Toll-like receptor (TLR) expression on various subsets of these cells has been shown to differ, suggestive of distinct roles in influencing immune responses. We have examined here the responses of immature DCs derived from murine bone marrow (BMDCs) to a range of TLR ligands. BMDCs cultured for 6 days in the presence of granulocyte-macrophage colony-stimulating factor were stimulated for 24 hr with ligands to TLR1-2 [Pam(3)Cys-Ser-(Lys)(4) (PAM)], TLR2-6 (macrophage-activating lipopeptide-2 (MALP-2); zymosan or peptidoglycan (PG)], TLR3 (polyinosinic-polycytidylic acid), TLR4 [lipopolysaccharide R515 (LPS)], TLR5 (flagellin), TLR7 (polyuridylic acid) and TLR9 [CpG ODN2395 (CpG)]. DC activation was monitored using membrane marker expression and analysis of culture supernatants for cytokine/chemokine release. Ligands to TLR3 and TLR7 failed to activate BMDCs. All other TLR ligands caused elevated expression of membrane markers. PAM, MALP-2 and LPS induced high-level expression of proinflammatory cytokines and chemokines. Treatment with CpG was associated with a preferential type 1 cytokine and chemokine profile. Zymosan and PG were proinflammatory but also skewed towards a type 2 pattern of cytokines and chemokines. In contrast, flagellin did not cause marked secretion by BMDCs of cytokines or chemokines. These data for BMDCs are largely consistent with the reported TLR repertoire of freshly isolated murine Langerhans cells. In addition, murine BMDCs show selective responses to TLR ligands with respect to general activation, with differentiated cytokine patterns suggestive of potential priming for divergent immune responses.

Immune response profiles in human skin

In addition to the function as a physical barrier human skin has been shown to be an important immune organ displaying various defense mechanisms, which can be divided into three major functional compartments: (i) Epithelial defense, which is characterized by antimicrobial peptides and proteins (AP) and which can be induced in inflammatory lesions but also in the absence of inflammation. (ii) Innate-inflammatory immunity, which involves recognition of microbial compounds by particular receptors like Toll-like receptors (TLR) and subsequent activation of signalling pathways resulting in expression of pro-inflammatory cytokines and interferons, as well as genes of adaptive immunity. Interferon alpha (IFNalpha) produced by plasmacytoid dendritic cells (DC) may stimulate myeloid DC to produce IL-12 resulting in classical T-cell activation or to produce IL-23 activating IL-17 producing T-cells (IL-23/IL-17 pathway). (iii) Adaptive immunity, which is based on antigen presenting cells, T-cells and B-cells and which is characterized by specificity and memory. In contrast to epithelial defense and innate-inflammatory immunity, adaptive immune functions provide slowly reacting protection. Recent improvements of our knowledge of dysregulated immune pathways associated with inflammatory skin diseases represent an important basis of novel immunomodulatory treatment modalities.

rs1004819 is the main disease-associated IL23R variant in German Crohn's disease patients: combined analysis of IL23R, CARD15, and OCTN1/2 variants

Background

The IL23R gene has been identified as a susceptibility gene for inflammatory bowel disease (IBD) in the North American population. The aim of our study was to test this association in a large German IBD cohort and to elucidate potential interactions with other IBD genes as well as phenotypic consequences of IL23R variants.

Methods

Genomic DNA from 2670 Caucasian individuals including 833 patients with Crohn's disease (CD), 456 patients with ulcerative colitis (UC), and 1381 healthy unrelated controls was analyzed for 10 IL23R SNPs. Genotyping included the NOD2 variants p.Arg702Trp, p.Gly908Arg, and p.Leu1007fsX1008 and polymorphisms in SLC22A4/OCTN1 (1672 C→T) and SLC22A5/OCTN2 (–207 G→C).

Results

All IL23R gene variants analyzed displayed highly significant associations with CD. The strongest association was found for the SNP rs1004819 [P = 1.92×10⁻¹¹; OR 1.56; 95 % CI (1.37–1.78)]. 93.2% of the rs1004819 TT homozygous carriers as compared to 78% of CC wildtype carriers had ileal involvement [P = 0.004; OR 4.24; CI (1.46–12.34)]. The coding SNP rs11209026 (p.Arg381Gln) was protective for CD [P = 8.04×10⁻⁸; OR 0.43; CI (0.31–0.59)]. Similar, but weaker associations were found in UC. There was no evidence for epistasis between the IL23R gene and the CD susceptibility genes CARD15 and SLC22A4/5.

Conclusion

IL23R is an IBD susceptibility gene, but has no epistatic interaction with CARD15 and SLC22A4/5. rs1004819 is the major IL23R variant associated with CD in the German population, while the p.Arg381Gln IL23R variant is a protective marker for CD and UC.