17 Beta-estradiol (E2) plus tumor necrosis factor-alpha induces a distorted maturation of human monocyte-derived dendritic cells and promotes their capacity to initiate T-helper 2 responses

There is growing evidence that 17 beta-estradiol (E2) modulates immune function. Recent studies indicated that certain effects of E2 on in vivo immune function are not a result of a direct action on T cells, but rather an indirect action on antigen-presenting cells. This study demonstrates that the pregnancy-associated doses of E2 plus tumor necrosis factor-alpha (TauNuF alpha) induce distorted maturation of human dendritic cells (DCs) that result in an increased capacity to induce T helper (Th) 2 responses. E2 did not affect the expression of human leukocyte antigen class II and costimulatory molecules by DCs, but elicited the ability of DC to produce CC chemokine ligand 1, which can attract CCR8-expressing Th2 cells and regulatory T cells. In addition, E2/TNF alpha-matured DCs increased the production of IL-10 relative to the IL-12p70 on CD40 ligation, thereby inducing naive T-cell differentiation into a Th2. Moreover, the increased concentration of E2 in the route of maturation did indeed further enhance Th2 deviation. The dominant Th2 deviation was induced at a high E2 concentration typical during pregnancy. These findings demonstrate that the high physiological levels of E2 may be an important endogenous component for regulating the DC function and skewing the immune response toward Th2.     

Human cytomegalovirus-derived protein UL18 alters the phenotype and function of monocyte-derived dendritic cells

Human cytomegalovirus (HCMV) encodes the MHC class I-like molecule UL18, which binds with high affinity to the leukocyte Ig-like receptor-1 (LIR-1), an inhibitory receptor commonly expressed on myeloid cells and subsets of NK and T cells. The exact role of UL18 is not known, in particular in relation to its proposed role in HCMV immune escape. Given the ubiquitous expression of LIR-1 on dendritic cells (DCs), we hypothesized that UL18 may affect DC function. To study the effects of UL18 on DC, we made use of UL18 fusion proteins. We demonstrate that UL18 fusion proteins inhibit the chemotaxis of DCs. Furthermore, UL18 interfered with CD40 ligand-induced maturation of DCs, resulting in reduced allogeneic T cell proliferation. Finally, we demonstrate that UL18 proteins up-regulate the expression of the maturation marker CD83 on immature monocyte-derived DCs and induce cytokine production. The capacity of UL18 to affect the function and the phenotype of DCs suggests a novel role for this HCMV-derived protein.     

Galectin-9 induces maturation of human monocyte-derived dendritic cells]

We investigated the role of galectin-9 (Gal-9) in maturation of dendritic cells (DC). Culture of immature DCs with exogenous Gal-9 markedly increased the surface expression of CD40, CD54, CD80, CD83, CD86, and HLA-DR in a concentration-dependent manner, although Gal-9 had no effect on differentiation of human monocytes into immature DCs. Gal-9-treated DCs secreted IL-12 but not IL-10, and they elicited the production of Th1 cytokines (IFN-gamma and IL-2), but not that of the Th2 cytokines (IL-4 and IL-5) by allogeneic CD4(+) T cells. These effects of Gal-9 on immature DCs were not essentially dependent on its lectin properties, given that they were only slightly inhibited by lactose. We further found that a Gal-9 mutant that lacks beta-galactoside binding activity reproduced the above activities, and that an anti-Gal-9 mAb suppressed them. Gal-9 induced phosphorylation of the p38 MAPK and ERK1/2 in DCs, and an inhibitor of p38 signaling, but not inhibitors of signaling by either ERK1/2 or phosphatidylinositol 3-kinase, blocked Gal-9-induced up-regulation of costimulatory molecule expression and IL-12 production. These findings suggest that Gal-9 plays a role not only in innate immunity but also in acquired immunity by inducing DC maturation and promoting Th1 immune responses.     

Response of human dendritic cells to different immunomodulatory polysaccharides derived from mushroom and barley

Polysaccharides derived from fungi and plants have been increasingly used as dietary supplement with therapeutic intention for cancer. However, whether these polysaccharides from different sources and structures can elicit similar immunological effects remain unknown. This study aims to investigate and compare the effects of selected groups of purified and crude polysaccharides on human dendritic cells (DCs), the most potent antigen-presenting cells. The selected polysaccharides were from Ganoderma lucidum [(GL) Lingzhi, Reishi], a medicinal mushroom commonly used by oriental; and barley glucan, a purified polysaccharide with known in vivo immunomodulating effect. We found that purified polysaccharides from GL mycelium could induce human PBMC proliferation and phenotypic and functional maturation of DCs with significant IL-12 and IL-10 production. Polysaccharides of GL spore and barley were both rather weak immunostimulator in vitro. In general, all these polysaccharides did not polarize T cells into either T(h)1 or T(h)2 or regulatory T cells, except for crude spore polysaccharides-treated DCs which could suppress T cell proliferation with IL-10 production. This study revealed the polysaccharides of different sources have different immune potency and effect on human immune cells including DCs. Our study also provides a reproducible biological platform for comparing the potential therapeutic effects of different herbal-derived polysaccharides in the future.     

Leptin deficiency impairs maturation of dendritic cells and enhances induction of regulatory T and Th17 cells

Leptin is an adipose‐secreted hormone that plays an important role in both metabolism and immunity. Leptin has been shown to induce Th1‐cell polarization and inhibit Th2‐cell responses. Additionally, leptin induces Th17‐cell responses, inhibits regulatory T (Treg) cells and modulates autoimmune diseases. Here, we investigated whether leptin mediates its activity on T cells by influencing dendritic cells (DCs) to promote Th17 and Treg‐cell immune responses in mice. We observed that leptin deficiency (i) reduced the expression of DC maturation markers, (ii) decreased DC production of IL‐12, TNF‐α, and IL‐6, (iii) increased DC production of TGF‐β, and (iv) limited the capacity of DCs to induce syngeneic CD4⁺ T‐cell proliferation. As a consequence of this unique phenotype, DCs generated under leptin‐free conditions induced Treg or T_H17 cells more efficiently than DCs generated in the presence of leptin. These data indicate important roles for leptin in DC homeostasis and the initiation and maintenance of inflammatory and regulatory immune responses by DCs.     

B7-H1阻断对未成熟树突状细胞免疫功能的影响

目的：探讨B7-H1阻断对未成熟树突状细胞(DCs)的免疫刺激活性的影响。 方法： 以细胞因子GM-CSF和IL-4体外诱导人单核细胞来源的树突状细胞，流式细胞仪检测在诱导过程中B7-H1的表达，并以B7-H1单抗阻断处理，分别以流式细胞仪、MTT法、ELISA、ELISPOT法检测B7-H1阻断对DCs的成熟和内吞能力、刺激淋巴细胞增殖、IL-12的分泌、诱导淋巴细胞分化的影响。 结果： DCs在诱导过程中B7-H1表达逐渐增强，第7 d时的阳性表达率为54.12％，以TNF-α诱导成熟后阳性表达率为83.64％；B7-H1阻断对DCs成熟和内吞能力无影响，但可使未成熟DCs刺激淋巴细胞增殖的能力和IL-12的分泌明显增强，并诱导淋巴细胞向分泌IFN-γ的Th1/Tc1的分化。 结论： B7-H1阻断可增强未成熟DCs的免疫刺激活性，利用B7-H1阻断的DCs瘤苗激发抗肿瘤免疫的方案值得进一步探讨。     

Interferon-alpha2a is sufficient for promoting dendritic cell immunogenicity

Type I interferons (IFNs) are widely used therapeutically. IFN-alpha2a in particular is used as an antiviral agent, but its immunomodulatory properties are poorly understood. Dendritic cells (DCs) are the only antigen-presenting cells able to prime naive T cells and therefore play a crucial role in initiating the adaptive phase of the immune response. We studied the effects of IFN-alpha2a on DC maturation and its role in determining Th1/Th2 equilibrium. We found that IFN-alpha2a induced phenotypic maturation of DCs and increased their allostimulatory capacity. When dendritic cells were stimulated simultaneously by CD40 ligation and IFN-alpha2a, the production of interleukin (IL)-10 and IL-12 was increased. In contrast, lipopolysaccharide (LPS) stimulation in the presence of IFN-alpha2a mainly induced IL-10 release. The production of IFN-gamma and IL-5 by the responder naive T cells was also amplified in response to IFN-alpha2a-treated DCs. Furthermore, IL-12 production by IFN-alpha2a-treated DCs was enhanced further in the presence of anti-IL-10 antibody. Different results were obtained when DCs were treated simultaneously with IFN-alpha2a and other maturation factors, in particular LPS, and then stimulated by CD40 ligation 36 h later. Under these circumstances, IFN-alpha2a did not modify the DC phenotype, and the production of IL-10/IL-12 and IFN-gamma/IL-5 by DCs and by DC-stimulated naive T cells, respectively, was inhibited compared to the effects on DCs treated with maturation factors alone. Altogether, this work suggests that IFN-alpha2a in isolation is sufficient to promote DC activation, however, other concomitant events, such as exposure to LPS during a bacterial infection, can inhibit its effects. These results clarify some of the in vivo findings obtained with IFN-alpha2a and have direct implications for the design of IFN-alpha-based vaccines for immunotherapy.     

Cord blood dendritic cells prevent the differentiation of naïve T-helper cells towards Th1 irrespective of their subtype

Allogeneic cord blood transplantation is associated with a less severe graft-versus-host disease (GVHD). This observation is thought to be due to immaturity of cord blood cell immune capabilities. Dendritic cells (DCs) are the most potent antigen-presenting cells of the immune system capable of initiation and regulation of immune responses. In this investigation, we hypothesized that non-manipulated cord blood dendritic cells (CBDCs) not only differ in their functional maturity from adult peripheral blood DCs (PBDCs) but also differ in their subsets and their preference in promoting Th1 or Th2 immune responses. Non-manipulated fresh DCs were isolated from cord blood (CB) and adult peripheral blood (PB) mononuclear cells as lineage marker negative cells. The differences in expression of costimulatory molecules, the proportion of myeloid and lymphoid DCs subsets, their immunostimulatory characteristics and their influence on promoting the differentiation of naïve T cells towards Th1 or Th2 cells were then investigated in these two populations. Our results showed that freshly isolated CBDCs, similar to cord blood monocyte derived DCs, were poor inducers of IFN-γ secretion while they increased the induction of IL-4 production by T cells in comparison with PBDCs. CBDCs were also poor stimulators of allogenic T cells in mixed leukocyte reaction compared to adult peripheral blood dendritic cells. They also displayed decreased expression of HLA-DR and CD86 molecules. The ratio of lymphoid DCs (CD11c^?, CD123⁺) to myeloid DCs (CD11c⁺, CD123^?) was significantly higher in CB compared to PB. We conclude that CBDCs preferential priming of naive T cells towards Th2 population, seems to be an intrinsic property independent of their subtype. This property along with their functional immaturity should contribute to outcome of cord blood transplantation.     

Mast cells promote Th1 and Th17 responses by modulating dendritic cell maturation and function

Mast cells (MCs) play an important role in the regulation of protective adaptive immune responses against pathogens. However, it is still unclear whether MCs promote such host defense responses via direct effects on T cells or rather by modifying the functions of antigen-presenting cells. To identify the underlying mechanisms of the immunoregulatory capacity of MCs, we investigated the impact of MCs on dendritic cell (DC) maturation and function. We found that murine peritoneal MCs underwent direct crosstalk with immature DCs that induced DC maturation as evidenced by enhanced expression of costimulatory molecules. Furthermore, the MC/DC interaction resulted in the release of the T-cell modulating cytokines IFN-γ, IL-2, IL-6 and TGF-β into coculture supernatants and increased the IL-12p70, IFN-γ, IL-6 and TGF-β secretion of LPS-matured DCs. Such MC-"primed" DCs subsequently induced efficient CD4+ T-cell proliferation. Surprisingly, we observed that MC-primed DCs stimulated CD4+ T cells to release high levels of IFN-γ and IL-17, demonstrating that MCs promote Th1 and Th17 responses. Confirming our in vitro findings, we found that the enhanced disease progression of MC-deficient mice in Leishmania major infection is correlated with impaired induction of both Th1 and Th17 cells.     

In vivo and in vitro effect of killed Propionibacterium acnes and its purified soluble polysaccharide on mouse bone marrow stem cells and dendritic cell differentiation

Among the effects exerted by Propionibacterium acnes, a most relevant one is its capacity to modulate the Th1/Th2 cellular immune response. This effect depends on the induction and activation of antigen presenting cells, mainly dendritic cells (DCs), whose number is increased in the peripheral blood of animals treated with this bacterium. A soluble P. acnes polysaccharide (PS) extract also acts on DCs, modulating a Th1 immune response. These data led us to investigate the role of P. acnes and its soluble PS on murine bone marrow (BM) DCs. Bone marrow cells were analyzed by flow cytometry, showing an increase of stem cells and DCs in P. acnes- or PS-treated animals. Culturing in the presence of granulocyte monocyte colony stimulating factor (GM-CSF) increased the in vitro differentiation and maturation of these cells into BM-derived DCs (CD11c⁺ and MHC class II⁺). Maturation of DCs was determined by increased CD80 and CD86 expression, IL-4 and IL-12 production, reduction in phagocytic capacity and increase in the antigen presenting ability to primed or naïve T lymphocytes. These data indicate that P. acnes as well as its PS can modulate BM stem cells, originating mature DCs, which are important mainly at the initial antigen contact.     

Complement C5a anaphylatoxin is an innate determinant of dendritic cell-induced Th1 immunity to Mycobacterium bovis BCG infection in mice

During acquired immunity to Mycobacterium bovis bacillus Calmette-Guerin (BCG) infection in mice, dendritic cells (DCs) present mycobacterial antigens to naive T cells to prime an immune response. Complement C5a (anaphylatoxin) secreted by mycobacteria-infected macrophages regulates IL-12p70 production. As IL-12p70 regulates Th1 immunity against mycobacteria in mice, we examined the effects of C5a on IL-12p70 secretion by murine DCs and Th1 immunity. DCs cultured from C5-deficient (C5(-/-)) and -sufficient (C5(+/+)) mice were infected with BCG in the presence or absence of the C5a peptide. ELISA showed that C5(-/-) DCs secreted less IL-12p70 (600 pg/mL vs. 100 pg/mL) than C5(+/+) DCs, and they secreted more IL-10. Using immunophenotyping, reduced CD40 expression was found on C5(-/-) DCs after BCG infection. BCG-primed DCs were then cocultured with naive or BCG-immune T cells to differentiate them into IFN-gamma-secreting Th1 T cells. Coincident with increased IL-12p70 levels, BCG-primed C5(+/+) DCs cocultured with naive or immune C5(+/+) T cells showed a larger increase in CD4+ IFN-gamma/CD8+ IFN-gamma+ T cells compared with cocultured DCs and T cells from C5(-/-) mice. Thus, BCG-primed C5(+/+) DCs were better able to drive a Th1 response. Furthermore, BCG aerosol-infected C5(-/-) mice showed reduced CD4 and CD8 IFN-gamma-secreting T cells in the lungs, concurrent with an increased growth of BCG. Thus, C5a, an innate peptide, appears to play an important role in the generation of acquired immune responses in mice by regulating the Th1 response through modulation of IL-12p70 secretion from DCs.     

碳纳米管对树突状细胞成熟和T细胞分化作用研究

Th分化在免疫应答过程中起着关键性的作用,主要由树突状细胞来调控。碳纳米管是由碳元素组成的空心管状纳米材料,可作为抗原载体。碳纳米管对树突状细胞和Th分化的影响是决定其免疫响应的关键因素。分析氧化多壁碳纳米管(CNT)对小鼠骨髓来源的树突状细胞(BMDCs)功能的影响,以及对过敏抗原多肽OVA_323-339的 Th1和Th2免疫反应的影响。实验结果显示,BMDCs大量吞噬CNT,但对其细胞表面活化标志分子CD86、MHCII以及细胞因子TNF-α表达没有明显变化。CNT/抗原复合物可促进BMDCs表面MHCII的表达和CD8⁺T细胞增殖,增殖细胞的比例由28.7%分别增加到40.6%、41.3%和29.6%。Th2型细胞因子IL-4、IL-13和IL-10的表达和CD4⁺T的增殖受到抑制,增殖细胞的比例由54.4%减少到38.9%、46.6%和39.8%。研究结果提示,CNT不影响DCs的成熟和活化,但CNT可以影响过敏抗原的Th分化平衡,可抑制Th2型细胞因子的表达,促进Th1型免疫响应。     

Effects of DKK-3, a Wnt signaling inhibitor,on dendritic cell phenotype and T cell polarization

Abstract

Wnt signaling plays crucial roles in regulation of a wide range of processes in different cell types including immune cells and, in particular, dendritic cells and T cells. Growing indications point out that Wnt pathway components modulate the both innate and adaptive immune responses through regulating DC functions. We investigated the effects of recombinant DKK-3 protein on the phenotype and biological functions of bone marrow-derived DCs (BM-DCs) as well as T cell polarization. The phenotype and the cytokine production of BM-derived DCs in the presence DKK-3 were analyzed using flow cytometry and ELISA, respectively. Also, capability of DCs to activate T cells was evaluated by CFSE-labeled splenocytes. Regulatory T cell induction, T cell polarization, and cytokine secretion were assessed by flow cytometry and ELISA in splenocytes cultured in the presence of DKK-3. Our results showed that the expression of CD86 and CD40 increased in the DKK-3-treated DC, while the expression of PDL-1 and PDL-2 diminished. Furthermore, the presence of DKK-3 decreased IL-10 and IL-4 production and increased IFN-gamma production by treated DCs.DKK-3. Moreover, DKK-3 shifted naive CD4 T cells towards T_H1 cells through up-regulation of T-bet and down-regulation of GATA-3. Our results, therefore, suggest that DKK-3 protein has the ability to promote the generation of Th1-immunostimulatory DCs from its precursors.     

CD1-dependent dendritic cell instruction

Both microbial products and T cell factors influence dendritic cell (DC) maturation. However, it is not known which T cells are capable of interacting with DCs at the initiation of adaptive immunity, when foreign antigen-specific T cells are rare. We show here that self-reactive CD1-restricted T cells can promote DC maturation by recognizing CD1 in the absence of foreign antigens. T cell recognition of all four CD1 isoforms can trigger DC maturation, but their distinct mechanisms of costimulation lead to profound differences in concomitant interleukin 12 p70 production. Distinct CD1-reactive T cells may thus differentially direct DC development early in the immune response, thereby controlling subsequent polarization of acquired immunity.     

Dendritic cells differentiated in the presence of a single-stranded viral RNA sequence conserve their ability to activate CD4 T lymphocytes but lose their capacity for Th1 polarization

Monocyte-derived dendritic cells (DCs) differentiate in the presence of Toll-like-receptor (TLR) ligands in the course of ongoing infections. A single-stranded RNA (ssRNA) sequence, corresponding to the sequence of the U5 region of human immunodeficiency virus type 1 RNA, was used to mimic viral activation of TLR7 in human DCs. We determined the effector potential of DCs differentiated in the presence of this ssRNA molecule (ssRNA-DCs). ssRNA-DCs phenotypically resembled mature DCs. In contrast, their capacity to allostimulate naive CD4(+) T cells resembled that of conventional immature DCs and could be increased by TLR4 stimulation. Th1 polarization of CD4(+) T cells and production of interleukin 12p70 (IL-12p70) by ssRNA-DCs were selectively abrogated in response to a late TLR4, but not in response to a CD40, maturation signal. Inhibition of p38 mitogen-activated protein kinase partially restored IL-12p70 secretion but did not restore Th1 polarization, whereas addition of exogenous IL-12 led to recovery of Th1 polarization. In contrast to lipopolysaccharide, ssRNA induced IL-12p70 production at the very earliest stages of DC differentiation, indicating a particular role for TLR7 in monocyte-derived DCs recently engaged in differentiation. These data demonstrate generation of phenotypically mature DCs with the ability to expand CD4(+) T lymphocytes lacking Th1/2-polarizing capacity.     

CD8alpha(-) and CD8alpha(+) subclasses of dendritic cells undergo phenotypic and functional maturation in vitro and in vivo

Dendritic cells (DCs) are essential for the priming of immune responses. This antigen-presenting function of DCs develops in sequence in a process called maturation, during which they become potent sensitizers of na?ve T cells but reduce their ability to capture and process antigens. Some heterogeneity exists in mouse-DC populations, and two distinct subsets of DCs expressing high levels of CD11c can be identified on the basis of CD8alpha expression. We have studied the phenotype and maturation state of mouse splenic CD8alpha(-) and CD8alpha(+) DCs. Both subsets were found to reside in the spleen as immature cells and to undergo a phenotypic maturation upon culture in vitro in GM-CSF-containing medium or in vivo in response to lipopolysaccharide. In vitro and in vivo analyses showed that this maturation process is an absolute requisite for DCs to acquire their T-cell priming capacity, transforming CD8alpha(-) and CD8alpha(+) DCs into potent and equally efficient activators of na?ve CD4(+) and CD8(+) T cells. Furthermore, these results highlight the importance that environmental factors may have on the ability of DC subsets to influence Th responses qualitatively; i.e., the ability to drive Th1 versus Th2 differentiation may not be fixed immutably for each DC subset.     

Complement protein C1q induces maturation of human dendritic cells

Maturation of dendritic cells (DCs) is known to be induced by several stimuli, including microbial products, inflammatory cytokines and immobilized IgG, as demonstrated recently. Since immune complexes formed in vivo also contain C1q, moreover apoptotic cells and several pathogens fix C1q in the absence of antibodies, we undertook to investigate whether this complement protein has an impact on various functions of human DCs. Maturation of monocyte-derived immature DCs (imMDCs) cultured on immobilized C1q was followed by monitoring expression of CD80, CD83, CD86, MHCII and CCR7. The functional activity of the cells was assessed by measuring cytokine secretion and their ability to activate allogeneic T lymphocytes. Cytokine production by T cells co-cultured with C1q-matured DCs was also investigated. C1q, but not the structurally related mannose-binding lectin was found to bind to imMDC in a dose-dependent manner and induced NF-kappaB translocation to the nucleus. Immobilized C1q induced maturation of MDCs and enhanced secretion of IL-12 and TNF-alpha, moreover, elevated their T-cell stimulating capacity. As IFN-gamma levels were increased in supernatants of MDC-T cell co-cultures, our data suggest that C1q-induced DC maturation generates a Th1-type response. Interestingly, IL-10 levels were elevated by C1q-treated MDCs but not in the supernatant of their co-cultures with allogeneic T cells. Taken together, these results indicate that C1q-opsonized antigens may play a role in the induction and regulation of immune response. Moreover our data are relevant in view of the role of C1q in removal of apoptotic cells and the association between C1q-deficiency and autoimmunity.     

香加皮羽扇豆烷乙酸酯(CPLA)对树突状细胞分化成熟的影响

目的：探讨香加皮羽扇豆烷乙酸酯（CPLA）对人外周血单个核细胞（PBMC）来源的树突状细胞（DC）在体外分化成熟及免疫活性的影响。方法：从人外周血分离单个核细胞，与细胞因子GM—CSF、IL-4共培养，于第5天加入DC的促成熟刺激剂TNF-α（阳性对照组）或CPLA。倒置显微镜和透射电镜下观察DC的形态；应用流式细胞术检测成熟DC的表面标志CD1a、CD83、CD80和CD86的表达情况；用ELISA检测DC培养上清中IL-12和IFN-γ的含量；用MTT法测定DC刺激T细胞增殖的能力。结果：培养10d后，经CPLA刺激的PBMC呈现出典型DC的形态学特征；成熟DC的特征性表面分子CD1a、CD83、CD80和CD86表达水平均明显上调（P〈0．05）；细胞培养上清中IL-12和IFN-γ含量明显增高（P〈0．05）；刺激T细胞增殖的能力明显增强（P〈0．05）。结论：CPLA可诱导PBMC来源的DC分化成熟，并可促进其细胞因子的分泌，增强DC的免疫调节活性。     

Respiratory syncytial virus differentially activates murine myeloid and plasmacytoid dendritic cells

Respiratory syncytial virus (RSV) is the primary cause of bronchiolitis in young children. Upon infection both T helper 1 (Th1) and Th2 cytokines are produced. Because RSV-induced Th2 responses have been associated with severe immunopathology and aggravation of allergic reactions, the regulation of the immune response following RSV infection is crucial. In this study we examined the influence of RSV on the activation and function of murine bone marrow-derived dendritic cells (DCs). RSV induced the expression of maturation markers on myeloid DCs (mDCs) in vitro. The mDCs stimulated with RSV and ovalbumin (OVA) enhanced proliferation of OVA-specific T cells, which produced both Th1 and Th2 cytokines. In contrast to mDCs, RSV did not induce the expression of maturation markers on plasmacytoid DCs (pDCs), not did it enhance the proliferation of OVA-specific T cells that were cocultured with pDCs. However, RSV stimulated the production of interferon-alpha (IFN-alpha) by pDCs. Our findings indicate a clear difference in the functional activation of DC subsets. RSV-stimulated mDCs may have immunostimulatory effects on both Th1 and Th2 responses, while RSV-stimulated pDCs have direct antiviral activity through the release of IFN-alpha.     

Characterization and functional study of five novel monoclonal antibodies against human OX40L highlight reverse signalling: enhancement of IgG production of B cells and promotion of maturation of DCs

OX40 ligand (OX40L), a molecule originally identified as human gp34, is an important co-stimulatory molecule during immune response. In this study, we report on five functional mouse anti-human OX40L monoclonal antibodies named as 9H10, 4C12, 8D10, 4H4 and 1G1, characterized by means of flow cytometry, Western blot and competition assay. These monoclonal antibodies bound to distinct OX40L epitopes on activated B cells and dendritic cells (DCs) and two of them could suppress the proliferation of T lymphocytes co-stimulated by mature DCs. Furthermore, we demonstrated that our monoclonal antibodies, such as 9H10 and 4C12, could trigger OX40L reverse signal that enhanced IgG production of B cells and promoted maturation of DCs as evidenced by the upexpression of CD80, CD86, CD83 and CXCR4 and monoclonal antibody 9H10 could also promote anti-CD40 monoclonal-antibody-stimulated DCs in order to induce T cells to secrete more interleukin-2 and interferon-gamma, which suggested that OX40L signals could strengthen the effect of CD40 signals on promoting Th1 differentiation.