Induction of antigen-specific regulatory T lymphocytes by human dendritic cells expressing the glucocorticoid-induced leucine zipper

Dendritic cells (DCs) determine whether antigen presentation leads to immune activation or to tolerance. Tolerance-inducing DCs (also called regulatory DCs) act partly by generating regulatory T lymphocytes (Tregs). The mechanism used by DCs to switch toward regulatory DCs during their differentiation is unclear. We show here that human DCs treated in vitro with glucocorticoids produce the glucocorticoid-induced leucine zipper (GILZ). Antigen presentation by GILZ-expressing DCs generates CD25(high)FOXP3(+)CTLA-4/CD152(+) and interleukin-10-producing Tregs inhibiting the response of CD4(+) and CD8(+) T lymphocytes. This inhibition is specific to the antigen presented, and only proliferating CD4(+) T lymphocytes express the Treg markers. Interleukin-10 is required for Treg induction by GILZ-expressing DCs. It is also needed for the suppressive function of Tregs. Antigen-presenting cells from patients treated with glucocorticoids generate interleukin-10-secreting Tregs ex vivo. These antigen-presenting cells produce GILZ, which is needed for Treg induction. Therefore, GILZ is critical for commitment of DCs to differentiate into regulatory DCs and to the generation of antigen-specific Tregs. This mechanism may contribute to the therapeutic effects of glucocorticoids.     

Opposing effects of dehydroepiandrosterone and dexamethasone on the generation of monocyte-derived dendritic cells

BACKGROUND: Dehydroepiandrosterone (DHEA) has been suggested as an immunostimulating steroid hormone, of which the effects on the development of dendritic cells (DC) are unknown. The effects of DHEA often oppose those of the other adrenal glucocorticoid, cortisol. Glucocorticoids (GC) are known to suppress the immune response at different levels and have recently been shown to modulate the development of DC, thereby influencing the initiation of the immune response. Variations in the duration of exposure to, and doses of, GC (particularly dexamethasone (DEX)) however, have resulted in conflicting effects on DC development. AIM: In this study, we describe the effects of a continuous high level of exposure to the adrenal steroid DHEA (10 M) on the generation of immature DC from monocytes, as well as the effects of the opposing steroid DEX on this development. RESULTS: The continuous presence of DHEA (10 M) in GM-CSF/IL-4-induced monocyte-derived DC cultures resulted in immature DC with a morphology and functional capabilities similar to those of typical immature DC (T cell stimulation, IL-12/IL-10 production), but with a slightly altered phenotype of increased CD80 and decreased CD43 expression (markers of maturity). The continuous presence of DEX at a concentration of 10 M in the monocyte/DC cultures resulted in the generation of plastic-adherent macrophage-like cells in place of typical immature DC, with increased CD14 expression, but decreased expression of the typical DC markers CD1a, CD40 and CD80. These cells were strongly reactive to acid phosphatase, but equally capable of stimulating T cell proliferation as immature DC. The production of IL-12 by these macrophage-like cells was virtually shut down, whereas the production of IL-10 was significantly higher than that of control immature DC. CONCLUSION: The continuous presence of a high level of GC during the generation of immature DC from monocytes can modulate this development away from DC towards a macrophage-like cell. The combination of a low CD80 expression and a shutdown of IL-12 production suggests the possibility of DEX-generated cells initiating a Th2-biased response. These effects by DEX on DC development contrast with those by DHEA, which resulted in a more typical DC although possessing a phenotype possibly indicating a more mature state of the cell.     

Immunologic mechanisms of extracorporeal photochemotherapy in chronic graft-versus-host disease

Extracorporeal photochemotherapy (ECP) has been shown to be an effective therapy for patients with acute and chronic graft-versus-host disease (GVHD) following allogeneic bone marrow transplantation, but its biologic mechanism is not understood. We reported that clinical response to ECP was associated not only with normalization of skewed CD4/CD8 ratios but also with an increase in CD3(-)/CD56(+) natural killer cells and a decrease in the number of CD80(+) and CD123(+) circulating dendritic cells (DCs). To further elucidate the effects of ECP on activated lymphocyte subpopulations and the interaction between effector lymphocytes and antigen-presenting DCs, we isolated and characterized DC populations from patients with chronic GVHD undergoing ECP therapy. Antigen-presenting activity of DCs was measured as proliferation of antigen-stimulated autologous and allogeneic T cells by mixed-lymphocyte reaction (MLR). In MLR assays the proliferation of T cells was decreased in all 10 patients by a mean of 84% (range, 75%-95%; P < or =.002) after a 2-day cycle of ECP and longitudinally over the 12-month course of therapy. Immunophenotypic analysis of DC populations revealed a preponderance of DC1 monocytic dendritic cells in all patients before the initiation of ECP. Nine of 10 patients demonstrated a shift from DC1 to DC2 and as a concordant shift from a predominantly Th1 (interleukin-2 [IL-2], interferon-gamma) to Th2 (IL-4, IL-10) cytokine profile after ECP, and 8 of 10 had a clinical response to ECP. Our results suggest that ECP alters alloreactivity by affecting allo-targeted effector T cells and antigen-presenting DCs.     

Reduced expression and functional impairment of Toll-like receptor 2 on dendritic cells in chronic hepatitis C virus infection.

BACKGROUND: Dendritic cells (DCs) utilize Toll-like receptors (TLRs) to sense virus and initiate immune responses. We aimed at elucidating the roles of TLRs on DCs in hepatitis C virus (HCV) infection. METHODS: Monocyte-derived DCs were obtained from 32 healthy volunteers (HV) and 30 chronically HCV-infected patients (CH). TLR2, TLR3 and TLR4 expressions on immature DCs were quantified by real-time quantitative RT-PCR. We stimulated DCs with specific TLR ligands and examined DC maturation, cytokine production and ability to stimulate allogeneic CD4(+) T cells. RESULTS: TLR2 expression on immature DCs was lower in the CH group, whereas those of TLR3 or TLR4 were not different between the groups. Each TLR ligand induced DC maturation and stimulated them to release comparable levels of IL-12p70, IL-6, IL-10, TNF-alpha and IFN-beta between the groups. TLR2 and TLR4 ligands enhanced DC ability to stimulate T cell proliferation, with the degree due to the TLR2 ligand being lower in the CH group. CONCLUSIONS: In HCV infection, the TLR2 expression on DCs is reduced and TLR2-stimulated DCs show lesser ability to proliferate T cells than healthy counterparts, suggesting that the TLR2 system is involved in HCV-induced immunopathogenesis.     

ADMA对单核细胞来源的树突状细胞成熟和免疫的影响

目的:通过观察非对称性二甲基精氨酸(ADMA)对树突状细胞(dendritic cells,DCs)成熟及免疫的影响来探讨AS形成的可能机制。方法:贴壁法分离人外周血单核细胞,在含重组人粒-巨噬细胞集落刺激因子(rhGM-CSF 20ng/ml)和重组人白细胞介素-4(rhIL-4,10ng/ml)的完全培养基中培养,五天后收集imDC,用1、8、16umol/L的ADMA干预未成熟DC 24h。用流式细胞术检测DC细胞表面分子的表达、吞噬能力及DC的凋亡,用混合淋巴细胞反应检测成熟DC刺激T淋巴细胞增殖的能力,用ELISA检测DC细胞因子的分泌。结果:生理浓度ADMA并不刺激DC成熟及分化;但病理浓度ADMA抑制DC成熟;抑制DC诱导的T淋巴细胞增殖;诱导DC凋亡:抑制DC分泌IL-12细胞因子、TNF-α及IL-10细胞因子。结论:生理浓度ADMA并不刺激DC成熟及分化;但病理浓度AD-MA抑制DC成熟和免疫。     

Interleukin-11 induces Th2 polarization of human CD4(+) T cells

Exploration of the immunomodulatory activities of the multifunctional cytokine interleukin-11 (IL-11) has prompted several therapeutic applications. The immunomodulatory effects of IL-11 on human antigen-presenting cells and on T cells were investigated. IL-11 inhibited IL-12 production by activated CD14(+) monocytes, but not by mature dendritic cells (DCs) stimulated via CD40 ligation. Moreover, IL-11 did not affect either DC maturation, as demonstrated by phenotypic analysis and evaluation of cytokine production, or DC generation from progenitor cells in the presence of specific growth factors. Molecular analysis demonstrated the expression of IL-11 receptor messenger RNA in highly purified CD14(+) monocytes, CD19(+) B cells, CD8(+), and CD4(+) T cells, and CD4(+)CD45RA(+) naive T lymphocytes. In keeping with this finding, IL-11 directly prevented Th1 polarization of highly purified CD4(+)CD45RA(+) naive T cells stimulated with anti-CD3/CD28 antibodies, as demonstrated by significant increases of IL-4 and IL-5, by significantly decreased interferon-gamma production and by flow cytometry intracellular staining of cytokines. Coincubation of naive T cells with DCs, the most potent stimulators of Th1 differentiation, did not revert IL-11-mediated Th2 polarization. Furthermore, parallel experiments demonstrated that the activity of IL-11 was comparable with that induced by IL-4, the most effective Th2-polarizing cytokine. Taken together, these findings show that IL-11 inhibits Th1 polarization by exerting a direct effect on human T lymphocytes and by reducing IL-12 production by macrophages. Conversely, IL-11 does not exert any activity on DCs. This suggests that IL-11 could have therapeutic potential for diseases where Th1 responses play a dominant pathogenic role.     

Dendritic-cell-associated C-type lectin 2 (DCAL-2) alters dendritic-cell maturation and cytokine production

Dendritic-cell (DC)-associated C-type lectin receptors (CLRs) take up antigens to present to T cells and regulate DC functions. DCAL-2 is a CLR with a cytosolic immunoreceptor tyrosine-based inhibitory motif (ITIM), which is restricted to immature DCs (iDCs), monocytes, and CD1a+ DCs. Cross-linking DCAL-2 on iDCs induced protein tyrosine phosphorylation and MAPK activation as well as receptor internalization. To test if DCAL-2 is involved in DC maturation and cytokine expression, we stimulated iDCs with anti-DCAL-2 mAb with or without LPS, zymosan, or CD40L. While anti-DCAL-2 did not induce iDCs to mature, it did up-regulate CCR7 expression and IL-6 and IL-10 production. DCAL-2 signals augmented DC maturation induced by LPS or zymosan, increasing both CCR7 and DC-LAMP expression. Of interest, DCAL-2 ligation had the opposite effects on TLR versus CD40L signaling: anti-DCAL-2 suppressed TLR-induced IL-12 expression, but significantly enhanced CD40L-induced IL-12 production. DCAL-2 ligation also suppressed the ability of TLR-matured DCs to induce IFN-gamma-secreting Th1 cells but augmented the capacity of CD40L-matured DCs to polarize naive T cells into Th1 cells. Thus, DCAL-2 may program DCs differently depending on whether DCs are signaled via TLRs or by T cells. DCAL-2 may be a potential immunotherapeutic target for modulating autoimmune diseases or for developing vaccines.     

Adenosine affects expression of membrane molecules,cytokine and chemokine release,and the T-cell stimulatory capacity of human dendritic cells

Dendritic cells (DCs) express functional purinergic type 1 receptors, but the effects of adenosine in these antigen-presenting cells have been only marginally investigated. Here, we further characterized the biologic activity of adenosine in immature DCs (iDCs) and lipopolysaccharide (LPS)-matured DCs (mDCs). Chronic stimulation with adenosine enhanced the macropinocytotic activity and the membrane expression of CD80, CD86, major histocompatibility complex (MHC) class I, and HLA-DR molecules on iDCs. Adenosine also increased LPS-induced CD54, CD80, MHC class I, and HLA-DR molecule expression in mDCs. In addition, adenosine dose-dependently inhibited tumor necrosis factor alpha and interleukin-12 (IL-12) release, whereas it enhanced the secretion of IL-10 from mDCs. The use of selective receptor agonists revealed that the modulation of the cytokine and cell-surface marker profile was due to activation of A(2) adenosine receptor. Functionally, adenosine reduced the allostimulatory capacity of iDCs, but not of mDCs. More important, DCs matured in the presence of adenosine had a reduced capacity to induce T helper 1 (Th1) polarization of naive CD4(+) T lymphocytes. Finally, adenosine augmented the release of the chemokine CCL17 and inhibited CXCL10 production by mDCs. In aggregate, the results provide initial evidence that adenosine diminishes the capacity of DCs to initiate and amplify Th1 immune responses.     

Subset of DC-SIGN(+) dendritic cells in human blood transmits HIV-1 to T lymphocytes

The dendritic cell (DC)-specific molecule DC-SIGN is a receptor for the HIV-1 envelope glycoprotein gp120 and is essential for the dissemination of HIV-1. DC-SIGN is expressed by DCs, both monocyte-derived DCs and DCs in several tissues, including mucosa and lymph nodes. To identify a DC-SIGN(+) DC in blood that may be involved in HIV-1 infection through blood, we have analyzed the expression of DC-SIGN in human blood cells. Here we describe the characterization of a subset of DCs in human blood, isolated from T-/NK-/B-cell-depleted peripheral blood mononuclear cells (PBMCs) on the basis of expression of DC-SIGN. This subset coexpresses CD14, CD16, and CD33 and is thus of myeloid origin. In contrast to CD14(+) monocytes, DC-SIGN(+) blood cells display a DC-like morphology and express markers of antigen-presenting cells, including CD1c, CD11b, CD11c, CD86, and high levels of major histocompatibility complex (MHC) class I and II molecules. This DC population differs from other described CD14(-) blood DC subsets. Functionally, DC-SIGN(+) blood DCs are able to stimulate proliferation of allogeneic T cells and can produce tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) upon activation with lipopolysaccharide (LPS). When they encounter HIV-1, low amounts of these blood DC-SIGN(+) DCs enhance infection of T lymphocytes in trans, whereas blood monocytes and CD14(-) blood DCs are not capable of transmitting HIV-1. Therefore DC-SIGN(+) blood DCs can be the first target for HIV-1 upon transmission via blood; they can capture minute amounts of HIV-1 through DC-SIGN and transfer HIV-1 to infect target T cells in trans.     

来氟米特对狼疮患者树突状细胞作用机制的初探

目的　探讨来氟米特(LEF)处理前后系统性红斑狼疮(SLE)患者树突状细胞(DC)表面标志及功能的改变,揭示LEF治疗SLE的作用机制,为开展“抑制性DCs”治疗SLE奠定实验基础。方法　(1)分离SLE患者外周血单核细胞,用细胞因子诱导DC成熟, LEF组再加入A7717262(来氟米特的活性代谢产物)培养。第9天收集DC细胞,流式细胞仪检测CD80、CD83、CD86和HLA DR的表达。(2)分别将A771726处理或不处理的第9天DC和T细胞进行培养, 72h后用MTT法检测DC刺激淋巴细胞增殖的能力,FACS检测T细胞亚群和ELISA检测培养上清中IL 10和IFNγ水平。结果A771726处理后虽DC形态无改变,但DC表达CD83、CD86和HLA DR百分数较对照组均明显降低(72 70±1 77vs 79 36±4 80, 63 50±14 06vs. 83 91±9 81, 80 44±12 56vs. 90 51±8 63,P值均<0 01)。A771726处理后的DC,其刺激T细胞增殖相应的吸光度值明显降低,混合培养的上清液中IL 10水平较无A771726处理的DC与T细胞的混合培养上清液明显降低,而IFNγ两者间无显著差异;但见CD 4 CD 25CTLA 4 T细胞百分比增高。结论　LEF在体外可抑制SLE患者外周血DC的成熟;未成熟DC能抑制T细胞增殖及T细胞向Th2 细胞转化,诱导CD 4 CD 25CTLA 4 T细胞产生,从而纠正SLE患者的部分免疫紊乱。     

Enhancement of CTLs induced by DCs loaded with ubiquitinated hepatitis B virus core antigen

AIM: To investigate whether hepatitis B virus (HBV) could induce a hepatitis B virus core antigen (HBcAg)-specific cytotoxic T lymphocyte (CTL) response in vitro by dendritic cells (DCs) transduced with lentiviral vector-encoding ubiquitinated hepatitis B virus core antigen (LV-Ub-HBcAg).METHODS: Recombinant LV-Ub-HBcAg were transfected into highly susceptible 293 T cells to obtain high virus titres. Bone marrow-derived DCs isolated from BALB/c mice were cultured with recombinant granulocyte-macrophage colony-stimulating factor and recombinant interleukin (IL)-4. LV-Ub-HBcAg, lentiviral vector-encoding hepatitis B virus core antigen (LV-HBcAg), lentiviral vector (LV) or lipopolysaccharide were added to induce DC maturation, and the DC phenotypes were analyzed by flow cytometry. The level of IL-12 in the supernatant was detected by enzyme-linked immunosorbent assay (ELISA). T lymphocytes were proliferated using Cell Counting Kit-8. DCs were cultured and induced to mature using different LVs, and co-cultured with allogeneic T cells to detect the secretion levels of IL-2, IL-4, IL-10 and interferon-γ in the supernatants of T cells by ELISA. Intracellular cytokines of proliferative T cells were analyzed by flow cytometry, and specific CTL activity was measured by a lactate dehydrogenase release assay.RESULTS: LV-Ub-HBcAg-induced DCs secreted more IL-12 and upregulated the expression of CD80, CD86 and major histocompatibility class II. DCs sensitised by different LVs effectively promoted cytokine secretion; the levels of IL-2 and interferon-γ induced by LV-Ub-HBcAg were higher than those induced by LV-HBcAg. Compared with LV-HBcAg-transduced DCs, LV-Ub-HBcAg-transduced DCs more efficiently stimulated the proliferation of T lymphocytes and generated HBcAg-specific cytotoxic T lymphocytes.CONCLUSION: LV-Ub-HBcAg effectively induced DC maturation. The mature DCs efficiently induced T cell polarisation to Th1 and generated HBcAg-specific CTLs.     

Glucocorticoids transform CD40-triggering of dendritic cells into an alternative activation pathway resulting in antigen-presenting cells that secrete IL-10

Dendritic cell (DC) activation through CD40-CD40 ligand interactions is a key regulatory step for the development of protective T-cell immunity and also plays an important role in the initiation of T-cell responses involved in autoimmune diseases and allograft rejection. In contrast to previous reports, we show that the immunosuppressive drug dexamethasone (DEX) redirects rather than simply blocks this DC activation process. We found that DCs triggered through CD40 in the presence of DEX were unable to acquire high levels of costimulatory, adhesion, and major histocompatibility complex class I and II molecules and failed to express the maturation marker CD83, whereas antigen uptake was not affected. Moreover, DEX strikingly modified the CD40-activated DC cytokine secretion profile by suppressing the production of the proinflammatory cytokine interleukin (IL)-12 and potentiating the secretion of the anti-inflammatory cytokine IL-10. Accordingly, DEX-exposed CD40-triggered DCs displayed a decreased T-cell allostimulatory potential and a dramatically impaired ability to activate cloned CD4(+) T helper 1 (Th1) cells. Moreover, interaction between Th1 cells and these DCs rendered the T cells hyporesponsive to further antigen-specific restimulation. Collectively, our results demonstrate that DEX profoundly modulates CD40-dependent DC activation and suggest that the resulting alternatively activated DCs can be exploited for suppression of unwanted T-cell responses in vivo.     

Retrovirus-mediated IL-7 expression in leukemic dendritic cells generated from primary acute myelogenous leukemias enhances their functional properties

Myeloid lineage-derived dendritic cells (DCs) are considered the professional antigen-presenting cell type responsible for eliciting T-cell-mediated immune responses. Acute myelogenous leukemia (AML) is a disease in which tumor antigens are expressed by the malignant clone that also has the potential to differentiate into DC-like cells (leukemic DCs) with antigen-presenting capacity. This study investigated whether the constitutive expression of the cytokine interleukin-7 (IL-7) in primary AML cells during their differentiation toward leukemic DCs results in superior antigen-presenting cells. A bicistronic retroviral vector encoding the IL-7 cytokine and the surface immunoselectable low-affinity nerve growth factor receptor (LNGFr) gene was constructed and used for transduction experiments. A serum-free system was used to transduce and differentiate leukemic cells toward leukemic DCs. The study included 8 patients with AML. The transduction efficiency with the cytokine vector varied among patients, ranging from 5% to 30% as judged by LNGFr expression. The leukemic origin of the transduced cells was confirmed in a patient with a chromosomal translocation t(9:11) by fluorescence in situ hybridization analysis. Cytokine modified-cells consistently secreted IL-7 (mean, 415 pg +/- 190/10(6) cells/48 hours; n = 5). We demonstrate that IL-7-transduced cells are included in the differentiated leukemic DC subset, and, as shown in a particular case, that about half of the mature CD80(+) and CD83(+) populations coexpress the LNGFr transgene. In addition, IL-7-modified leukemic cells induce stronger allo-T-cell stimulation and higher amounts of IL-2 production in T cells compared with control groups. Finally, cytokine-transduced leukemic DCs can effectively prime and generate cytotoxic T lymphocytes against autologous leukemic blasts.     

Defective costimulatory function is a striking feature of antigen-presenting cells in an HLA-B27-transgenic rat model of spondylarthropathy

OBJECTIVE: A disease resembling the human spondylarthropathies develops in HLA-B27-transgenic rats. This disease in rats is mediated by CD4+ T cells, but antigen-presenting cells (APCs) may also play a role. Dendritic cells (DCs) have been reported to be defective in allogeneic mixed lymphocyte culture in this model. Here, we further investigated the functional defect of APCs. METHODS: DCs and B cells from nontransgenic, HLA-B27 (33-3)-transgenic, and HLA-B7 (120-4)-transgenic rats were used to stimulate T cells. Surface expression of HLA-B transgene and rat molecules on APCs and the formation of conjugates between DCs and T cells were monitored by flow cytometry. RESULTS: We observed a strikingly defective stimulation of allogeneic and syngeneic T lymphocytes by APCs from HLA-B27 but not HLA-B7 rats, even if stimulation was driven in the presence of anti-T cell receptor (TCR) antibody. We found no evidence that HLA-B27 DCs were immature, lacked production of some diffusible factor, or produced an inhibitory factor for T cells. When comparing the levels of expression of class II major histocompatibility complex, CD2, intercellular adhesion molecule 1, lymphocyte function-associated antigen 1, B7, and CD40 molecules at the surface of DCs from 33-3, 120-4, and nontransgenic rats, we found little difference. However, HLA-B27-transgenic DCs formed fewer conjugates with T cells than did nontransgenic DCs. Furthermore, the proportion of conjugates formed between DCs and T cells, as well as the difference between nontransgenic and HLA-B27-transgenic DCs, were in large part reduced by blocking CD86 on DCs. CONCLUSION: We confirmed defective stimulation of T cells by APCs in HLA-B27 rats, the mechanism of which appears to implicate APC/T cell contact, independent of TCR engagement. In addition, decreased use of the CD86 costimulatory molecule by B27 DCs was observed. Impaired costimulatory function could result in a loss of tolerance toward microbial flora in this model.     

Glycolipid presentation to natural killer T cells differs in an organ-dependent fashion

It has been shown that dendritic cells (DCs) are able to present glycolipids to natural killer (NK) T cells in vivo. However, the essential role of DCs, as well as the role of other cells in glycolipid presentation, is unknown. Here, we show that DCs are the crucial antigen-presenting cells (APCs) for splenic NK T cells, whereas Kupffer cells are the key APCs for hepatic NK T cells. Both cell types stimulate cytokine production by NK T cells within 2 h of glycolipid administration, but only DCs are involved in the systemic, downstream responses to glycolipid administration. More specifically, CD8alpha+ DCs produce IL-12 in response to glycolipid presentation, which stimulates secondary IFN-gamma production by NK cells in different organs. Different APCs participate in glycolipid presentation to NK T cells in vivo but differ in their involvement in the overall glycolipid response.     

miR-221 and miR-155 regulate human dendritic cell development, apoptosis, and IL-12 production through targeting of p27kip1, KPC1, and SOCS-1

Dendritic cells (DCs) are potent antigen-presenting cells derived from hematopoietic progenitor cells and circulating monocytes. To investigate the role of microRNAs (miRNAs) during DC differentiation, maturation, and function, we profiled miRNA expression in human monocytes, immature DCs (imDCs), and mature DCs (mDCs). Stage-specific, differential expression of 27 miRNAs was found during monocyte differentiation into imDCs and mDCs. Among them, decreased miR-221 and increased miR-155 expression correlated with p27(kip1) accumulation in DCs. Silencing of miR-221 or overexpressing of miR-155 in DCs resulted in p27(kip1) protein increase and DC apoptosis. Moreover, mDCs from miR-155(-/-) mice were less apoptotic than those from wild-type mice. Silencing of miR-155 expression had little effect on DC maturation but reduced IL-12p70 production, whereas miR-155 overexpression in mDCs enhanced IL-12p70 production. Kip1 ubiquitination-promoting complex 1, suppressor of cytokine signaling 1, and CD115 (M-CSFR) were functional targets of miR-155. Furthermore, we provide evidence that miR-155 indirectly regulated p27(kip1) protein level by targeting Kip1 ubiquitination-promoting complex 1. Thus, our study uncovered miRNA signatures during monocyte differentiation into DCs and the new regulatory role of miR-221 and miR-155 in DC apoptosis and IL-12p70 production.     

Fusion of dendritic cells with multiple myeloma cells results in maturation and enhanced antigen presentation

Dendritic cells (DCs) are potent antigen-presenting cells that are uniquely capable of inducing primary immune responses. Although tumour cells may directly inhibit DC maturation, exposure to tumour products may also result in their activation. Fusions of cancer cells and DCs are being explored as cancer vaccines. The effect of tumour cell fusion on DC maturation and their functional characteristics has not been defined. In the present study, immature and mature DC generated from human CD34+ and peripheral blood precursors were fused to multiple myeloma cells in the presence of polyethylene glycol. Fusion of both immature and mature DCs with tumour cells resulted in an activated phenotype. In this regard, fusion cells expressed interleukin-12, a cytokine essential for the induction of T-helper cell type 1 immunity. In contrast to immature DCs, fusion cells also strongly expressed CC-chemokine receptor R7, which is responsible for DC migration to draining lymph nodes. Fusions generated with both immature and mature DCs also potently stimulated T-cell expression of gamma-interferon and cytotoxic T lymphocyte killing of tumour targets. These findings demonstrate that tumour cell fusion induces DC maturation and the development of an activated phenotype necessary for their effectiveness as cancer vaccines.     

1,25-Dihydroxyvitamin D(3) inhibits dendritic cell differentiation and maturation in vitro

OBJECTIVE: Because of its potent immunosuppressive properties in vitro as well as in vivo, we studied the effect of 1,25-dihydroxyvitamin D(3) (calcitriol) on differentiation, maturation, and function of dendritic cells (DC). MATERIALS AND METHODS: Monocyte-derived DCs were generated with GM-CSF plus IL-4, and maturation was induced by a 2-day exposure to TNFalpha. DCs were derived from CD34(+) progenitors using SCF plus GM-CSF plus TNFalpha. For differentiation studies, cells were exposed to calcitriol at concentrations of 10(-)(9)- 10(-7) M at days 0, 6, and 8, respectively. The obtained cell populations were evaluated by morphology, phenotype, and function. RESULTS: When added at day 0, calcitriol blocked DC differentiation from monocytes and inhibited the generation of CD1a(+) cells from progenitor cells while increasing CD14(+) cells. Exposure of immature DCs to calcitriol at day 6 resulted in a loss of the DC-characteristic surface molecule CD1a, downregulation of the costimulatory molecules CD40 and CD80, and MHC class II expression, whereas the monocyte/macrophage marker CD14 was clearly reinduced. In addition, calcitriol hindered TNFalpha-induced DC maturation, which is usually accompanied with induction of CD83 expression and upregulation of costimulatory molecules. In contrast, the mature CD83(+) DCs remained CD1a(+)CD14(-) when exposed to calcitriol. The capacity of cytokine-treated cells to stimulate allogeneic and autologous T cells and to take up soluble antigen was inhibited by calcitriol. CONCLUSION: The potent suppression of DC differentiation, the reversal of DC phenotype, and function in immature DCs, as well as the inhibition of DC maturation by calcitriol, may explain some of its immunosuppressive properties.     

Dysfunction of peripheral blood dendritic cells from patients with chronic hepatitis B virus infection

AIM: To identify the property of dendritic cells (DCs) of peripheral blood monocytes (PBMC) in patients with chronic HBV infection. METHODS: Twenty patients with persistent HBV infection were included in this study, 10 healthy subjects being used as a control group. The peripheral blood mononuclear cells (PBMC) of T cell-depleted populations were incubated and induced into mature dendritic cells in the RPMI-1640 medium in the presence of cytokines GM-CSF, IL-4, FLt-3,TNF-alpha and 100mL.L(-1 )of fetal calf serum for a total of 10-12 days. The expressions of surface markers on DCs were evaluated using flow cytometric analysis. ELISA method was used to determine the cytokine levels of interleukin-12 (IL-12) and IL-10 in the supernatant produced by DCs. For detection of the stimulatory capacity of DCs to T cell proliferation, mytomycin C-treated DC were incubated with allogenic T cells. RESULTS: A typical morphology of mature DCs from healthy subjects and HBV-infected patients was induced in in vitro incubation, but the proliferation ability and cellular number of DCs from HBV-infected patients significantly decreased compared with healthy individuals. In particular, the expression levels of HLA-DR, CD80 (B7-1) and CD86 (B7-2) on DC surface from patients were also lower than that from healthy individuals (0.46 vs 0.92 for HLA-DR, 0.44 vs 0.88 for CD80 and 0.44 vs 0.84 for CD86,P<0.05). The stimulatory capacity and production of IL-12 of DCs from patients in allogenic mixed lymphocyte reaction (AMLR) significantly decreased, but the production level of nitric oxide (NO) by DCs simultaneously increased compared with healthy subjects (86 +/- 15 vs 170 +/- 22 micromol.L(-1), P <0.05). CONCLUSION: The patients with chronic HBV infection have the defective function and immature phenotype of dendritic cells, which may be associated with the inability of efficient presentation of HBV antigens to host immune system for the clearance of HBV.