Structural,phenotypic and functional maturation of bone marrow dendritic cells (BMDCs) induced by Chitosan (CTS)

The objective of the present work was to explore the effect of CTS on structural, phenotypic and functional maturation of murine bone marrow derived dendritic cells (BMDCs). The maturity of BMDCs post treatment with CTS was evaluated using transmission electron microscopy (TEM) for structure changes, flow cytometry (FCM) for changes of key surface molecules, FITC-dextran bio-assay for phagocytosis, test of acid phosphatase activity (ACP) for biochemical changes and enzyme linked immunosorbent assay (ELISA) for cytokine level. We found that CTS downregulated the numbers of phagosomes inside the BMDCs, up-regulated the expression of MHC II, CD40, CD83, CD80 and CD86 molecules on BMDCs, decreased activity of ACP and phagocytosis by BMDCs, and induced production of higher levels of IL-12 and TNF-α. It was therefore confirmed that CTS could effectively promote the maturation of BMDCs. Our study provided more detailed evidence and rationale to support the application of CTS as an immune stimulator for enhancing host immunity and as an adjuvant in the design of DC-based vaccines.     

Functional modulation of the pathway between dendritic cells (DCs) and CD4+T cells by the neuropeptide: methionine enkephalin (MENK)

MENK, the endogenous neuropeptide, is suggested to be involved in the regulatory loop between the immune and neuroendocrine systems, with modulation of various functions of cells related to both the innate and adaptive immune systems. Our present research findings show that MENK serves as an immune modulator to the pathway between DCs and CD4+T cells. We studied changes of DCs in key surface molecules, the activity of acid phosphatases (ACPs), the production of IL-12, and the effects on murine CD4+T cell expansion and their cytokine production by MENK alone, and in combination with interkeukin-2 (IL-2) or interferon-γ (IFN-γ). In fact, we found that MENK could markedly induce the maturation of DCs through the addition of surface molecules such as MHC class II, CD86, and CD40 on murine DCs, the production of IL-12, and the down-regulation of ACP inside DCs, (which occurs when phagocytosis of DCs is decreased, and antigen presentation increased with maturation). We also found that MENK alone or in combination with IL-2 or IFN-γ, could markedly up-regulate both CD4+T cell expansion and the CD4 molecule expression in vivo and in vitro and that MENK alone, or MENK + IL-2, could enhance the production of interferon-γ from CD4+T cells. Moreover, MENK alone, or MENK + IFN-γ, could enhance the production of IL-2 from CD4+T cells. It is therefore concluded that MENK can exert positive modulation to the pathway between dendtritic cells and CD4+T cells.     

Ascaris lumbricoides pseudocoelomic body fluid induces a partially activated dendritic cell phenotype with Th2 promoting ability in vivo

Dendritic cells (DCs) matured with helminth-derived molecules that promote Th2 immune responses do not follow conventional definitions of DC maturation processes. While a number of models of DC maturation by Th2 stimuli are postulated, further studies are required if we are to clearly define DC maturation processes that lead to Th2 immune responses. In this study, we examine the interaction of Th2-inducing molecules from the parasitic helminth Ascaris lumbricoides with the maturation processes and function of DCs. Here we show that murine bone marrow-derived DCs are partially matured by A. lumbricoides pseudocoelomic body fluid (ABF) as characterised by the production of IL-6, IL-12p40 and macrophage inflammatory protein 2 (MIP-2) but no enhanced expression of cluster of differentiation (CD)-14, T-cell co-stimulatory markers CD80, CD86, CD40, OX40L and major histocompatibility complex class II was observed. Despite these phenotypic characteristics, ABF-stimulated DCs displayed the functional hallmarks of fully matured cells, enhancing DC phagocytosis and promoting Th2-type responses in skin-draining lymph node cells in vivo. ABF activated Th2-associated extracellular signal-regulated kinase-1 and nuclear factor-kB intracellular signalling pathways independently of toll-like receptor 4. Taken together, we believe this is the first paper to demonstrate A. lumbricoides murine DC-Th cell-driven responses shedding further light on DC maturation processes by helminth antigens.     

Toxoplasma gondii-derived heat shock protein 70 stimulates the maturation of human monocyte-derived dendritic cells

We investigated the role of Toxoplasma gondii-derived heat shock protein 70 (TgHSP70) as a dendritic cell (DC) maturation-inducing molecule. TgHSP70 induced the maturation of human monocyte-derived dendritic cells as determined by increased levels of surface markers, namely, CD40, CD80, CD86, and HLA-DR. Moreover, TgHSP70 also reduced phagocytic activity and increased the allostimulatory capacity of DCs, suggesting the functional maturation of DCs by TgHSP70. Maturation of DCs by TgHSP70 also elicited a significant increase in IL-12 production in a polymyxin B-insensitive manner. TgHSP70 also stimulated extracellular signal-regulated kinase and p38 kinase pathways in DCs, and TgHSP70-induced IL-12 production was inhibited by SB203580 but not by PD98059, thus indicating the role of p38 kinase in the maturation of DCs by TgHSP70. This study demonstrates the role of TgHSP70 in the functional maturation of DCs and suggests TgHSP70 as a useful molecule for the development of a vaccine against T. gondii.     

Polysaccharide purified from Polyporus umbellatus (Per) Fr induces the activation and maturation of murine bone-derived dendritic cells via toll-like receptor 4

In this study, we report that a polysaccharide isolated from a Chinese medicinal herb, Zhu Ling (the sclerotium of Polyporus umbellatus (Per) Fr), induces phenotypic and functional maturation of murine bone-derived dendritic cells (BMDCs). Treatment of BMDCs with Polyporus polysaccharide (PPS) resulted in enhanced cell-surface expression of CD86, as well as enhanced production of both interleukin (IL)-12 p40 and IL-10 in a dose-dependent manner. In addition, treatment of BMDCs with PPS resulted in increased T cell-stimulatory capacity and decreased phagocytic ability. PPS-induced production of IL-12 p40 was inhibited by monoclonal antibodies to Toll-like receptor 4 (TLR4). Flow cytometric analysis showed that fluorescence-labeled PPS (f-PPS) bound specifically to BMDCs. This binding was blocked by both unlabeled PPS and anti-TLR4, but not by anti-TLR2 and anti-CR3 monoclonal antibodies. Taken together, our data show that PPS promotes the activation and maturation of murine BMDCs via TLR4.     

香菇多糖对小鼠骨髓树突状细胞表型和功能的影响

通过研究香菇多糖(Lentinan,LNT)对小鼠骨髓源树突状细胞(bone marrow dendritic cells,BMDCs)功能调节的机制,进一步阐明香菇多糖的免疫活性。本实验将BMDCs分成脂多糖(LPS)阳性对照组、LNT处理组和RPMI1640空白对照组,应用酸性磷酸酶活性检测、流式细胞仪检测技术、吞噬实验、酶联免疫吸附试验检测各组BMDCs表型和功能的各种指标。结果显示,LNT(50μg/mL)处理组BMDCs酸性磷酸酶活性降低;BMDCs吞噬能力比RPMI1640空白对照组明显下降;BMDCs表面MHCⅡ、CD40、CD83、CD80、CD86和DEC205的表达增加;BMDCs白细胞介素12(IL-12)、白细胞介素10(IL-10)和肿瘤坏死因子-α(TNF-α)的表达增加。证明了适宜浓度的LNT可以促进BMDCs表型及功能的成熟。     

青钱柳多糖对小鼠骨髓来源树突状细胞表面分子表达的影响

为探讨青钱柳多糖（CPC）对小鼠骨髓来源树突状细胞（BMDCs）细胞形态及表面分子的影响,首先采用细胞因子诱导法,以贴壁法获得贴壁单核细胞,添加重组粒细胞-巨噬细胞集落刺激因子（rmGM—CSF）和重组白细胞介素-4（rmIL-4）进行体外诱导,倒置显微镜及透射电镜观察细胞形态的变化;流式细胞术检测培养第6dDCs的表面标志CD80,CD86和MHCⅡ类分子的表达的变化。经CPC刺激24h后,采用流式细胞术检测DCs表面MHCⅡ类分子表达的变化。结果发现：经rmGM—CSF和traiL-4诱导获得的DCs随着培养时间的延长,细胞形态发生改变,逐渐变成具有树状突起的DCs。经LPS刺激后的DCs能够发生典型的DCs的成熟,而培养第6天的DCs具有典型的DCs表型特征,可用于后续进一步实验。与阴性对照相比,CPC显著促进树突状细胞表面MHCⅡ的表达,在浓度（10～200μg／mL）范围内呈现剂量依赖性。初步表明CPC可以促进树突状细胞的成熟。     

Inhibition of myeloid dendritic cell accessory cell function and induction of T cell anergy by alcohol correlates with decreased IL-12 production

Alcohol consumption inhibits accessory cell function and Ag-specific T cell responses. Myeloid dendritic cells (DCs) coordinate innate immune responses and T cell activation. In this report, we found that in vivo moderate alcohol intake (0.8 g/kg of body weight) in normal volunteers inhibited DC allostimulatory capacity. Furthermore, in vitro alcohol treatment during DC differentiation significantly reduced allostimulatory activity in a MLR using naive CD4(+) T cells, and inhibited tetanus toxoid Ag presentation by DCs. Alcohol-treated DCs showed reduced IL-12, increased IL-10 production, and a decrease in expression of the costimulatory molecules CD80 and CD86. Addition of exogenous IL-12 and IL-2, but not neutralization of IL-10, during MLR ameliorated the reduced allostimulatory capacity of alcohol-treated DCs. Naive CD4(+) T cells primed with alcohol-treated DCs showed decreased IFN-gamma production that was restored by exogenous IL-12, indicating inhibition of Th1 responses. Furthermore, CD4(+) T cells primed with alcohol-treated DCs were hyporesponsive to subsequent stimulation with the same donor-derived normal DCs, suggesting the ability of alcohol-treated DCs to induce T cell anergy. LPS-induced maturation of alcohol-treated immature DCs partially restored the reduced allostimulatory activity, whereas alcohol given only during DC maturation failed to inhibit DC functions, suggesting that alcohol primarily impairs DC differentiation rather than maturation. NFkappaB activation, a marker of DC maturation was not affected by alcohol. Taken together, alcohol both in vitro and in vivo can impair generation of Th1 immune responses via inhibition of DC differentiation and accessory cell function through mechanisms that involve decreased IL-12 induction.     

Different toll-like receptor stimuli have a profound impact on cytokines required to break tolerance and induce autoimmunity

Although toll-like receptor (TLR) signals are critical for promoting antigen presenting cell maturation, it remains unclear how stimulation via different TLRs influence dendritic cell (DC) function and the subsequent adaptive response in vivo. Furthermore, the relationship between TLR-induced cytokine production by DCs and the consequences on the induction of a functional immune response is not clear. We have established a murine model to examine whether TLR3 or TLR4 mediated DC maturation has an impact on the cytokines required to break tolerance and induce T-cell-mediated autoimmunity. Our study demonstrates that IL-12 is not absolutely required for the induction of a CD8 T-cell-mediated tissue specific immune response, but rather the requirement for IL-12 is determined by the stimuli used to mature the DCs. Furthermore, we found that IFNα is a critical pathogenic component of the cytokine milieu that circumvents the requirement for IL-12 in the induction of autoimmunity. These studies illustrate how different TLR stimuli have an impact on DC function and the induction of immunity.     

Toll-like receptor 4 (TLR4) is essential for Hsp70-like protein 1 (HSP70L1) to activate dendritic cells and induce Th1 response

Toll-like receptors (TLRs) play important roles in initiation of innate and adaptive immune responses. Emerging evidence suggests that TLR agonists can serve as potential adjuvant for vaccination. Heat shock proteins (HSPs), functionally serving as TLR4 agonists, have been proposed to act as Th1 adjuvant. We have identified a novel Hsp70 family member, termed Hsp70-like protein 1 (Hsp70L1), shown that Hsp70L1 is a potent T helper cell (Th1) polarizing adjuvant that contributes to antitumor immune responses. However, the underlying mechanism for how Hsp70L1 exerts its Th1 adjuvant activity remains to be elucidated. In this study, we found that Hsp70L1 binds directly to TLR4 on the surface of DCs, activates MAPK and NF-κB pathways, up-regulates I-a(b), CD40, CD80, and CD86 expression and promotes production of TNF-α, IL-1β, and IL-12p70. Hsp70L1 failed to induce such phenotypic maturation and cytokine production in TLR4-deficient DCs, indicating a role for TLR4 in mediating Hsp70L1-induced DC activation. Furthermore, more efficient induction of carcinoembryonic antigen (CEA)-specific Th1 immune response was observed in mice immunized by wild-type DCs pulsed with Hsp70L1-CEA(576-669) fusion protein as compared with TLR4-deficient DCs pulsed with same fusion protein. In addition, TLR4 antagonist impaired induction of CEA-specific human Th1 immune response in a co-culture system of peripheral blood lymphocytes (PBLs) from HLA-A2.1(+) healthy donors and autologous DCs pulsed with Hsp70L1-CEA(576-669) in vitro. Taken together, these results demonstrate that TLR4 is a key receptor mediating the interaction of Hsp70L1 with DCs and subsequently enhancing the induction of Th1 immune response by Hsp70L1/antigen fusion protein.     

CD47 engagement inhibits cytokine production and maturation of human dendritic cells

Upon encounter with bacterial products, immature dendritic cells (iDCs) release proinflammatory cytokines and develop into highly stimulatory mature DCs. In the present study, we show that human monocyte-derived DCs functionally express the CD47 Ag, a thrombospondin receptor. Intact or F(ab')2 of CD47 mAb suppress bacteria-induced production of IL-12, TNF-alpha, GM-CSF, and IL-6 by iDCs. 4N1K, a peptide derived from the CD47-binding site of thrombospondin, also inhibits cytokine release. The inhibition of IL-12 and TNF-alpha is IL-10-independent inasmuch as IL-10 production is down-modulated by CD47 mAb and blocking IL-10 mAb fails to restore cytokine levels. CD47 ligation counteracts the phenotypic and functional maturation of iDCs in that it prevents the up-regulation of costimulatory molecules, the loss of endocytic activity, and the acquisition of an increased capacity to stimulate T cell proliferation and IFN-gamma production. Interestingly, regardless of CD47 mAb treatment during DC maturation, mature DC restimulated by soluble CD40 ligand and IFN-gamma, to mimic DC/T interaction, produce less IL-12 and more IL-18 than iDCs. Finally, CD47 ligation on iDCs does not impair their capacity to phagocytose apoptotic cells. We conclude that following exposure to microorganisms, CD47 ligation may limit the intensity and duration of the inflammatory response by preventing inflammatory cytokine production by iDCs and favoring their maintenance in an immature state.     

Double-stranded RNA stimulation or CD40 ligation of monocyte-derived dendritic cells as models to study their activation and maturation process

Monocyte-derived dendritic cells (DCs) were used as an in vitro model of myeloid DCs in order to determine a minimum marker pattern with which to characterize and distinguish different stages of DC activation and maturation. Phenotypic changes induced on immature DCs by two prototypic stimuli, poly I:C and CD40 ligation, were first examined. Both elicited HLA-DR, CD40, CD86 and CXCR4 upregulation, and CCR5 downregulation, but only CD40 ligand-stimulated DCs became CD83(+)\CCR7(+), whereas poly I:C-stimulated DCs expressed lower CD83 levels and were mostly CCR7(--). CD40 ligation and poly I:C elicited increased production of inflammatory cytokines interleukin (IL)-6 and tumor necrosis factor-alpha, of IL-10 and the CCL5 chemokine, but profiles differed as to higher IL-10, IL-12 and CCL22 (a CCR4 ligand important for T cell recruitment) levels for the former, and of CCL4 and CCL5 for the latter. Thus, a limited set of phenotypic markers, cytokine and chemokine production assays, may be used to distinguish the three stages in the life of DCs: immaturity, activation and full maturation. The ability of purified protein derivative-loaded DCs to stimulate autologous T cells to produce IL-2, IL-4 and interferon-gamma indeed depended on their activation stage and endocytic activity, which decreased upon maturation. We then examined whether ligation of CD4, CCR5 and\or CXCR4, the receptor and coreceptors of human immunodeficiency virus envelope gp120, respectively, affected DC activation or maturation, neither a monoclonal antibody to the gp120-binding site on CD4 nor CCL5 nor CXCL12, the natural ligands of CCR5 and CXCR4, respectively, nor gp120 altered the DC activation and maturation processes.     

N-3-(oxododecanoyl)-L-homoserine lactone promotes the induction of regulatory T-cells by preventing human dendritic cell maturation

N-3-(Oxododecanoyl)-L-homoserine lactone (C12) is a small bacterial signaling molecule secreted by Pseudomonas aeruginosa (PA), which activates mammalian cells through TLR4-independent mechanisms. C12 acts as an immunosuppressant and it has been shown to modulate murine bone marrow-derived dendritic cell-mediated T-helper 2 (Th2) cell polarizations in vitro. In the present study, we initially examined the impact of C12 on the maturation of human monocyte-derived dendritic cells (Mo-DCs) and the induction of regulatory T-cells (iTregs) in culture. Our findings demonstrate that C12-treated Mo-DCs failed to undergo lipopolysaccharide (LPS)-induced maturation. At the molecular level, C12 blocked the upregulation of surface molecules, including CD11c, HLA-DR, CD40, and CD80, and it switched to an interleukin (IL)-10^high, IL-12p70^low phenotype. Moreover, C12 selectively inhibited the capacity of Mo-DCs to stimulate the proliferation of allogeneic CD4⁺ T-cells. Otherwise, the C12-treated Mo-DCs promoted the generation of CD4⁺CD25⁺Foxp3⁺-induced regulatory T-cells (iTregs) and enhanced their IL-10 and transforming growth factor (TGF)-β production associated with reduced interferon (IFN)-γ and IL-12p70 production. These findings provide new insights towards understanding the persistence of chronic inflammation in PA infection.     

Cestode antigens induce a tolerogenic-like phenotype and inhibit LPS inflammatory responses in human dendritic cells

Pathogens have developed strategies to modify Dendritic Cells (DCs) phenotypes and impair their functions in order to create a safer environment for their survival. DCs responses to helminths and their derivatives vary among different studies. Here we show that excretory/secretory products of the cestode Taenia crassiceps (TcES) do not induce the maturation of human DCs judged by a lack of increment in the expression of CD83, HLA-DR, CD80 and CD86 molecules but enhanced the production of IL-10 and positively modulated the expression of the C-type lectin receptor MGL and negatively modulated the expression of DC-SIGN. Additionally, these antigens were capable of down-modulating the inflammatory response induced by LPS in these cells by reducing the expression of the maturation markers and the production of the inflammatory cytokines IL-1β, TNF, IL-12 and IL-6. The effects of TcES upon the DCs responses to LPS were stronger if cells were exposed during their differentiation to the helminth antigens. All together, these findings suggest the ability of TcES to induce the differentiation of human DCs into a tolerogenic-like phenotype and to inhibit the effects of inflammatory stimuli.     

HIV-1 Nef induces dendritic cell differentiation: a possible mechanism of uninfected CD4(+) T cell activation

Human immunodeficiency virus (HIV)-1 Nef protein is an essential modulator of AIDS pathogenesis and we have previously demonstrated that rNef enters uninfected human monocytes and induces T cells bystander activation, up-regulating IL-15 production. Since dendritic cells (DCs) play a central role in HIV-1 primary infection we investigated whether rNef affects DCs phenotypic and functional maturation in order to define its role in the immunopathogenesis of AIDS. We found that rNef up-regulates the expression on immature DCs of surface molecules known to be critical for their APC function. These molecules include CD1a, HLA-DR, CD40, CD83, CXCR4, and to a lower extent CD80 and CD86. On the other hand, rNef down-regulates surface expression of HLA-ABC and mannose receptor. The functional consequence of rNef treatment of immature DCs is a decrease in their endocytic and phagocytic activities and an increase in cytokine (IL-1beta, IL-12, IL-15, TNF-alpha) and chemokine (MIP-1alpha, MIP-1beta, IL-8) production as well as in their stimulatory capacity. These results indicate that rNef induces a coordinate series of phenotypic and functional changes promoting DC differentiation and making them more competent APCs. Indeed, Nef induces CD4(+) T cell bystander activation by a novel mechanism involving DCs, thus promoting virus dissemination.     

Bursopentin (BP5) from chicken bursa of fabricius attenuates the immune function of dendritic cells

Bursopentine (BP5), a novel pentapeptide isolated from chicken bursa of fabricius, has been proved to have immunomodulatory effects on B and T lymphocytes, anti-oxidative stress on macrophages, and antiproliferation on tumor cells. However, the effects of BP5 on the immune function exhibited by dendritic cells (DCs), which are regarded as a major target for immunomodulators, remain unknown. In this study, we examined the effects of BP5 on the activation and maturation of murine bone marrow-derived DCs. Our results showed that BP5 significantly suppressed the secretion of lipopolysaccharide (LPS)-induced pro-inflammatory (TNF-α, IL-1β, IL-6 and IL-12p70) and anti-inflammatory (IL-10) cytokines by DCs, and this impact was not due to its cytotoxicity. Besides, BP5 reversed the morphological changes and attenuated the expression of phenotypic markers (MHC II, CD40, CD80 and CD86 molecules) in LPS-induced DCs. Furthermore, BP5 restored the decreased FITC-dextran uptake in LPS-treated DCs, arrested the LPS-induced migration of DCs and abrogated the promoting ability of LPS-induced DCs for allogeneic T cell proliferation. These findings show a new immunopharmacological capability of BP5 and provide a novel approach in the prevention and therapy of chronic inflammation and autoimmunity via abolishing the immune function of DCs.     

MIF synergizes with Trypanosoma cruzi antigens to promote efficient dendritic cell maturation and IL-12 production via p38 MAPK

Macrophage migration inhibitory factor (MIF) has been found to be involved in host resistance to several parasitic infections. To determine the mechanisms of the MIF-dependent responses to Trypanosoma cruzi, we investigated host resistance in MIF-/- mice (on the BALB/c background) during an intraperitoneal infection. We focused on the potential involvement of MIF in dendritic cell (DC) maturation and cytokine production. Following a challenge with 5 x 10³ T. cruzi parasites, wild type (WT) mice developed a strong IL-12 response and adequate maturation of the draining mesenteric lymph node DCs and were resistant to infection. In contrast, similarly infected MIF^-/- mice mounted a weak IL-12 response, displayed immature DCs in the early phases of infection and rapidly succumbed to T. cruzi infection. The lack of maturation and IL-12 production by the DCs in response to total T. cruzi antigen (TcAg) was confirmed by in vitro studies. These effects were reversed following treatment with recombinant MIF. Interestingly, TcAg-stimulated bone marrow-derived DCs from both WT and MIF^-/- mice had increased ERK1/2 MAPK phosphorylation. In contrast, p38 phosphorylation was only upregulated in WT DCs. Reconstitution of MIF to MIF^-/- DCs upregulated p38 phosphorylation. The MIF-p38 pathway affected MHC-II and CD86 expression as well as IL-12 production. These findings demonstrate that the MIF-induced early DC maturation and IL-12 production mediates resistance to T. cruzi infection, probably by activating the p38 pathway.     

Extracellular ATP induces a distorted maturation of dendritic cells and inhibits their capacity to initiate Th1 responses

Dendritic cells (DCs) express functional purinergic receptors, but the effects of purine nucleotides on DC functions have been marginally investigated. In this study, we report on the ability of micromolar concentrations of ATP to affect the maturation and Ag-presenting function of monocyte-derived DCs in vitro. Chronic stimulation (24 h) of DCs with low, noncytotoxic ATP doses increased membrane expression of CD54, CD80, CD86, and CD83, slightly reduced the endocytic activity of DCs, and augmented their capacity to promote proliferation of allogeneic naive T lymphocytes. Moreover, ATP enhanced LPS- and soluble CD40 ligand-induced CD54, CD86, and CD83 expression. On the other hand, ATP markedly and dose-dependently inhibited LPS- and soluble CD40 ligand-dependent production of IL-1alpha, IL-1beta, TNF-alpha, IL-6, and IL-12, whereas IL-1 receptor antagonist and IL-10 production was not affected. As a result, T cell lines generated from allogeneic naive CD45RA(+) T cells primed with DCs matured in the presence of ATP produced lower amounts of IFN-gamma and higher levels of IL-4, IL-5, and IL-10 compared with T cell lines obtained with LPS-stimulated DCs. ATP inhibition of TNF-alpha and IL-12 production by mature DCs was not mediated by PGs or elevation of intracellular cAMP and did not require ATP degradation. The inability of UTP and the similar potency of ADP to reproduce ATP effects indicated that ATP could function through the P2X receptor family. These results suggest that extracellular ATP may serve as an important regulatory signal to dampen IL-12 production by DCs and thus prevent exaggerated and harmful immune responses.     

Oncostatin M induces dendritic cell maturation and Th1 polarization

Oncostatin M (OSM) is a pleiotropic cytokine and a member of the gp130/IL-6 cytokine family that has been found to be involved in both pro- and anti-inflammatory responses in cell-mediated immunity. Maturation of dendritic cells (DCs) is crucial for initiation of primary immune responses and is regulated by several stimuli. In this study, the role of OSM in the phenotypic and functional maturation of DCs was evaluated in vitro. Stimulation with OSM upregulated the expression of CD80, CD86, MHC class I and MHC class II and reduced the endocytic capacity of immature DCs. Moreover, OSM induced the allogeneic immunostimulatory capacity of DCs by stimulating the production of the Th1-promoting cytokine IL-12. OSM also increased the production of IFN-γ by T cells in mixed-lymphocyte reactions, which would be expected to contribute to the Th1 polarization of the immune response. The expression of surface markers and cytokine production in DCs was mediated by both the MAPK and NF-κB pathways. Taken together, these results indicate that OSM may play a role in innate immunity and in acquired immunity by enhancing DCs maturation and promoting Th1 immune responses.     

Cytokine production by dendritic cells genetically engineered to express IL-4: induction of Th2 responses and differential regulation of IL-12 and IL-23 synthesis

Dendritic cells (DCs) retrovirally transduced with IL-4 have recently been shown to inhibit murine collagen-induced arthritis and associated Th1 immune responses in vivo, but the mechanisms that underly these effects are not yet understood. In this report we demonstrate that IL-4-transduced DCs loaded with antigen led to lower T cell production of IFN-gamma, increased production of IL-4, and an attenuated, delayed type hypersensitivity response. We hypothesized that the ability of such DCs to regulate the Th1 immune response in vivo depends in part on their capacity to produce IL-12 and IL-23. Quantitative mRNA analysis revealed that IL-4-transduced DCs stimulated with CD40 ligand expressed higher levels of IL-12p35 mRNA, but lower levels of mRNA for IL-23p19 and the common subunit p40 found in both IL-12 and IL-23, compared with control DCs. These results, which indicate that expression of the IL-12 and IL-23 subunits is differentially regulated in IL-4-transduced DCs, were confirmed by ELISA of the IL-12 and IL-23 heterodimers. Thus, therapeutic suppression of Th1 -mediated autoimmunity (as recently shown in murine collagen-induced arthritis) and induction of Th2 responses in vivo by IL-4-transduced DCs occurs despite their potential to produce increased levels of IL-12, but could reflect, in part, decreased production of IL-23.