Distribution Of Dendritic Cells Subsets Research Articles

Dendritic Cell Subsets and Effector Function in Idiopathic and Connective Tissue Disease-Associated Pulmonary Arterial Hypertension.

Pulmonary arterial hypertension (PAH) is a cardiopulmonary disease characterized by an incurable condition of the pulmonary vasculature, leading to increased pulmonary vascular resistance, elevated pulmonary arterial pressure resulting in progressive right ventricular failure and ultimately death. PAH has different underlying causes. In approximately 30–40% of the patients no underlying risk factor or cause can be found, so-called idiopathic PAH (IPAH). Patients with an autoimmune connective tissue disease (CTD) can develop PAH [CTD-associated PAH (CTD-PAH)], suggesting a prominent role of immune cell activation in PAH pathophysiology. This is further supported by the presence of tertiary lymphoid organs (TLOs) near pulmonary blood vessels in IPAH and CTD-PAH. TLOs consist of myeloid cells, like monocytes and dendritic cells (DCs), T-cells, and B-cells. Next to their T-cell activating function, DCs are crucial for the preservation of TLOs. Multiple DC subsets can be found in steady state, such as conventional DCs (cDCs), including type 1 cDCs (cDC1s), and type 2 cDCs (cDC2s), AXL+Siglec6+ DCs (AS-DCs), and plasmacytoid DCs (pDCs). Under inflammatory conditions monocytes can differentiate into monocyte-derived-DCs (mo-DCs). DC subset distribution and activation status play an important role in the pathobiology of autoimmune diseases and most likely in the development of IPAH and CTD-PAH. DCs can contribute to pathology by activating T-cells (production of pro-inflammatory cytokines) and B-cells (pathogenic antibody secretion). In this review we therefore describe the latest knowledge about DC subset distribution, activation status, and effector functions, and polymorphisms involved in DC function in IPAH and CTD-PAH to gain a better understanding of PAH pathology.

Protective Role of Myeloid Cells Expressing a G-CSF Receptor Polymorphism in an Induced Model of Lupus.

The genetic analysis of the lupus-prone NZM2410 mouse has identified a suppressor locus, Sle2c2, which confers resistance to spontaneous lupus in combination with NZM2410 susceptibility loci, or in the chronic graft-versus-host disease (cGVHD) induced model of lupus in the B6.Sle2c2 congenic strain. The candidate gene for Sle2c2, the Csf3r gene encoding the granulocyte colony-stimulating factor receptor (G-CSF-R/CD114), was validated when cGVHD was restored in B6.Sle2c2 mice after treatment with G-CSF. The goal of the project reported herein was to investigate the myeloid cells that confer resistance to cGVHD and to ascertain if the mechanism behind their suppression involves the G-CSF pathway. We showed that despite expressing the highest levels of G-CSF-R, neutrophils play only a modest role in the autoimmune activation induced by cGVHD. We also found reduced expression levels of G-CSF-R on the surface of dendritic cells (DCs) and a differential distribution of DC subsets in response to cGVHD in B6.Sle2c2 versus B6 mice. The CD8α+ DC subset, known for its tolerogenic phenotype, was expanded upon induction of cGVHD in B6.Sle2c2 mice. In addition, the deficiency of CD8α+ DC subset enhanced the severity of cGVHD in B6.Batf3−/− and B6.Sle2c2 mice, confirming their role in suppression of cGVHD. B6.Sle2c2DCs presented lowered activation and antigen presentation abilities and expressed lower levels of genes associated with DC activation and maturation. Exposure to exogenous G-CSF reversed the majority of these phenotypes, suggesting that tolerogenic DCs maintained through a defective G-CSF-R pathway mediated the resistance to cGVHD in B6.Sle2c2 mice.

Effect of dendritic cell immunotherapy on distribution of dendritic cell subsets in non-small cell lung cancer.

The effect of dendritic cell (DC) immunotherapy on non-small cell lung cancer (NSCLC) and its influence on the distribution of DC subsets were studied. Peripheral blood was drawn from 55 patients, and DCs were cultured in vitro and injected into the patients three times. The changes in DC subsets in NSCLC patients before treatment and after three treatments were observed using a flow cytometer, and the difference in DC subsets between patients and healthy controls was compared. DC subsets in lung cancer tissues, para-carcinoma tissues and normal tissues were analyzed by indirect immunofluorescence and laser scanning confocal microscope (LSCM). The BDCA-1+ DC1 and BDCA-3+ DC2 in lung cancer tissues were significantly increased compared with those in para-carcinoma tissues and normal tissues (P<0.05). The number of DC1 and DC2 in para-carcinoma tissues were increased compared with those in normal tissues (P<0.05). The ratio of DC1 in peripheral blood in the normal control group was obviously higher than that in NSCLC patients (P<0.01). There were significant differences in DC1 and DC1/DC2 ratio in NSCLC patients with different tumor staging, and there were also obvious differences in patients with a different Karnofsky performance status (KPS) score. Moreover, compared with those before treatment, DC1 and DC1/DC2 ratio were significantly increased after three treatments, and there was a significant difference in the comparison of DC1/DC2 ratio between the NSCLC patients with survival time greater than and less than one year. The immune function of NSCLC patients was improved after DC immunotherapy. The survival time of NSCLC patients was closely associated with the DC1/DC2 ratio in peripheral blood. The detection of DC subsets in peripheral blood can help clinicians understand the immune function of NSCLC patients and provide a basis for the clinical judgment of prognosis of NSCLC patients.

Distribution of peripheral dendritic cells in patients with HBV infection or spleen and kidney deficiency

Spleen and kidney deficiency syndrome (SKD), a Traditional Chinese Medicine (TCM) syndrome, is the fundamental mechanisms of TCM. We aim to investigate the distribution of peripheral dendritic cells (DCs) in HBV patients with SKD or non-SKD. Peripheral venous blood from patients with HBV infection and healthy volunteers was collected to extract PBMC, and flow cytometry assay was used to measure the distribution of DCs subsets, including myeloid dendritic cells (mDCs) and plasmacytoid dendritic cells (pDCs). For the number of pDCs, it was higher in control group and non-SKD group, compared with HBV infection group and SKD group, respectively. For the number of mDCs, it was higher in control group and the non-SKD group compared to SKD group, while in control group it was higher than both HBeAg positive group and negative group. The number of pDCs in control group and chronic hepatitis B group were higher than HBVcarrier group, and it was higher in control group than both immune tolerance group and inactive group, while in immune clearance group it was higher than immune tolerance group and inactve group. The number of mDCs in control group and immune clearance group were higher than that of immune tolerance group. There was an obvious correlation between TCM syndromes and immune function in HBV infected patients, the number of pDCs and mDCs of the SKD group was lower than that in non-SKD group. These results provide a new insight into scientific evidence that TCM probably be based.

Dendritic cell subset positioning governs clonal diversity and magnitude of the CD8 T cell response

Abstract Although the molecular requirements for CD8 T cell responses have been well characterized, subunit vaccine formulations struggle to generate robust CD8 T cell immunity. One possible basis for this may be the relationship of dendritic cell (DC) subset topography to micro-anatomically dictated antigen dispersal and subsequent down-stream innate and adaptive cellular engagement. To address this issue directly in situ we utilized advanced quantitative imaging approaches (histo-cytometry) and found that protein immunization led to non-linear concentration gradients across draining lymph nodes. This graded distribution in turn affected which DC subset had access to high vs. low concentrations of antigen. Because DC subsets are specialized in MHC-I vs. MHC-II antigen processing and presentation, the result of this intersection of antigen dispersal and cell positioning was the predominant residence of MHC-I presenting DC in regions with lower antigen bioavailability. Modulating the antigen dose directly influenced the fraction of MHC-I presenting DC with access to sufficient antigen to activate T cells, allowing for direct control over the clonal diversity and magnitude of the response. These findings indicate that tissue microanatomy related to DC subset distribution and antigen dissemination within the lymph node is a critical regulator of CD8 T cell immunity. This research was supported by the Intramural Research Program of the NIH, NIAID.

Altered dendritic cell subset distribution in patients with Parkinson's disease: Impact of CMV serostatus

Parkinson's disease (PD) is characterised by low-level systemic inflammation, which may be at least partly due to pathophysiological activation of immunity. Here, the frequencies of different types of circulating dendritic cells (DCs) with and without a pro-inflammatory phenotype were determined in PD patients and controls. A high proportion of older people is infected with cytomegalovirus (CMV), which acts as a chronic antigenic stressor that could also contribute to increased inflammation. Following this idea, we found higher frequencies of myeloid DCs with a pro-inflammatory CD16+ILT2high phenotype in CMV-positive PD patients than controls, suggesting the potential involvement of CMV in exacerbating PD.

Impaired dendritic cell function in a spontaneous autoimmune polyneuropathy.

Spontaneous autoimmune polyneuropathy (SAP) in B7-2 knockout NOD mice mimics the progressive form of chronic inflammatory demyelinating polyradiculoneuropathy, and is mediated by myelin protein zero (P0)-reactive Th1 cells. In this study, we focused on the effect of B7-2 deletion on the function of dendritic cells (DCs) within the context of SAP. We found that development of SAP was associated with a preponderance or increase of CD11b(+) DCs in peripheral lymph nodes and sciatic nerves. B7-2 deletion led to altered immunophenotypic properties that differ between CD11b(+) DCs and CD8α(+) DCs. Both DC subsets from B7-2 knockout NOD mice exhibited impaired capacity to capture fluorophore-labeled myelin P0, but diminished Ag-presenting function was observed only in CD11b(+) DCs. Clinical assessment, electrophysiologic studies, and splenocyte proliferation studies revealed that absence of B7-2 on DCs was sufficient to cause impaired ability to induce tolerance to P0, which could be overcome by preconditioning with IL-10. Tolerance induction by Ag-pulsed wild-type NOD DCs was dependent on IL-10 and was associated with increased CD4(+) regulatory T cells, whereas tolerance induction by IL-10-conditioned B7-2-deficient DCs was associated with increased percentages of both regulatory T cells and B10 cells in the spleen. We conclude that B7-2 deletion has an impact on the distribution of DC subsets in lymphoid organs and alters the expression of costimulatory molecules, but functional consequences are not uniform across DC subsets. Defective tolerance induction in the absence of B7-2 can be restored by preconditioning of DCs with IL-10.

Respiratory tract dendritic cells in paediatric asthma.

Airway dendritic cells (DC) are critical mediators of lung inflammation in asthma, but the characteristics of DC in the airways of healthy children, and children with asthma, are currently unknown. We sought to identify changes in DC subset distribution and activation profile in paediatric asthma using flow cytometry to analyse induced sputum samples obtained from healthy and asthmatic children. Lung function and atopic status were determined by spirometry and skin prick testing. Induced sputum samples were analysed using 7-colour flow cytometry to identify airway DC populations (lineage(-) HLA-DR(+) sputum cells expressing either CD11c as conventional DC or CD123 as plasmacytoid DC). Sputum samples containing lower airway plugs were obtained from 10 healthy children and 8 children with asthma. Lineage(-) HLA-DR(+) DC were successfully identified in all samples, and DC comprised a significantly higher proportion of sputum cells in children with asthma compared with age-matched healthy controls (1.29% vs. 0.67%, P=0.02). DC expression of the costimulatory marker CD86 was significantly reduced in asthmatic children (73.4% vs. 59.7%, P=0.04). Sputum DC also included numerous CD1c(+) cells (mean 57% of the total DC population) and low frequencies of cells expressing the subset markers CD141 or CD123, although the proportions of these did not differ between groups. Airway DC can be identified and characterized non-invasively using flow cytometry to analyse paediatric sputum samples. Our data reveal that children with steroid-treated asthma exhibit increased frequency of airway DC with reduced expression of the costimulatory marker CD86, suggesting altered trafficking and/or maturation of these cells either due to asthma or steroid therapies.

Lymph node invasion by tumor cells modifies the distribution of dendritic cell subsets and memory T cell profiles in human cancer patients

Meeting abstracts In human breast cancer, the invasion of tumor-draining lymph nodes (TDLNs) is an important step in disease progression and has predictive value [[1][1]]. TDLN dendritic cells (DCs), which are comprised of lymphoid-organ-resident and skin-derived migratory DCs, present tumor

Interferon-α Production by Plasmacytoid Dendritic Cells Is Dispensable for an Effective Anti-Cytomegalovirus Response in Adaptor Protein-3-Deficient Mice

Adaptor protein-3 (AP-3) is a heterotetrameric complex, which regulates vesicular trafficking. Mutations of the β3A subunit cause the Hermansky-Pudlak syndrome type 2 (HPS-2), a rare genetic disease characterized by albinism, platelet defects, and recurrent infections. Likewise, pearl mice, which lack functional AP-3, show several HPS-2 defects. The AP-3 absence results in defective toll-like receptor trafficking and signaling in dendritic cells (DC), but its effect on the efficiency of the in vivo antiviral response is unclear. We evaluated the impact of AP-3 deficiency on the distribution of DC subsets, interferon (IFN) production, and the susceptibility to murine cytomegalovirus (MCMV) infection. Pearl mice showed a distribution and frequency of conventional (cDC) and plasmacytoid DC (pDC) similar to that of wild-type mice both before and after MCMV infection. Moreover, pearl mice controlled MCMV infection even at high virus doses and showed a normal production of IFN-α. Since pDC, but not cDC, from pearl mice showed an impaired IFN-α and tumor necrosis factor-α production in response to prototypic DNA (MCMV and Herpes Simplex virus) or RNA (Vesicular Stomatitis virus) viruses in vitro, it is likely that MCMV infection can be controlled in vivo independently of an efficient production of IFN-α by pDC, and that the AP-3 complex has a minimal impact on protective antiviral responses.

Neuroantigen-specific autoregulatory CD8+ T cells inhibit autoimmune demyelination through modulation of dendritic cell function.

Experimental autoimmune encephalomyelitis (EAE) is a well-established murine model of multiple sclerosis, an immune-mediated demyelinating disorder of the central nervous system (CNS). We have previously shown that CNS-specific CD8+ T cells (CNS-CD8+) ameliorate EAE, at least in part through modulation of CNS-specific CD4+ T cell responses. In this study, we show that CNS-CD8+ also modulate the function of CD11c+ dendritic cells (DC), but not other APCs such as CD11b+ monocytes or B220+ B cells. DC from mice receiving either myelin oligodendrocyte glycoprotein-specific CD8+ (MOG-CD8+) or proteolipid protein-specific CD8+ (PLP-CD8+) T cells were rendered inefficient in priming T cell responses from naïve CD4+ T cells (OT-II) or supporting recall responses from CNS-specific CD4+ T cells. CNS-CD8+ did not alter DC subset distribution or MHC class II and CD86 expression, suggesting that DC maturation was not affected. However, the cytokine profile of DC from CNS-CD8+ recipients showed lower IL-12 and higher IL-10 production. These functions were not modulated in the absence of immunization with CD8-cognate antigen, suggesting an antigen-specific mechanism likely requiring CNS-CD8-DC interaction. Interestingly, blockade of IL-10 in vitro rescued CD4+ proliferation and in vivo expression of IL-10 was necessary for the suppression of EAE by MOG-CD8+. These studies demonstrate a complex interplay between CNS-specific CD8+ T cells, DC and pathogenic CD4+ T cells, with important implications for therapeutic interventions in this disease.

Dysregulated cytokine production by dendritic cells modulates B cell responses in the NZM2410 mouse model of lupus.

The breakdown in tolerance of autoreactive B cells in the lupus-prone NZM2410-derived B6.Sle1.Sle2.Sle3 (TC) mice results in the secretion of autoantibodies. TC dendritic cells (DCs) enhance B cell proliferation and antibody secretion in a cytokine-dependent manner. However, the specific cytokine milieu by which TC DCs activate B cells was not known. In this study, we compared TC and C57BL/6 (B6) control for the distribution of DC subsets and for their production of cytokines affecting B cell responses. We show that TC DCs enhanced B cell proliferation through the production of IL-6 and IFN-γ, while antibody secretion was only dependent on IL-6. Pre-disease TC mice showed an expanded PDCA1+ cells prior to disease onset that was localized to the marginal zone and further expanded with age. The presence of PDCA1+ cells in the marginal zone correlated with a Type I Interferon (IFN) signature in marginal zone B cells, and this response was higher in TC than B6 mice. In vivo administration of anti-chromatin immune complexes upregulated IL-6 and IFN-γ production by splenic DCs from TC but not B6 mice. The production of BAFF and APRIL was decreased upon TC DC stimulation both in vitro and in vivo, indicating that these B cell survival factors do not play a role in B cell modulation by TC DCs. Finally, TC B cells were defective at downregulating IL-6 expression in response to anti-inflammatory apoptotic cell exposure. Overall, these results show that the TC autoimmune genetic background induces the production of B cell-modulating inflammatory cytokines by DCs, which are regulated by the microenvironment as well as the interplay between DC.

Chemokine-mediated distribution of dendritic cell subsets in renal cell carcinoma

BackgroundRenal cell carcinoma (RCC) represents one of the most immunoresponsive cancers. Antigen-specific vaccination with dendritic cells (DCs) in patients with metastatic RCC has been shown to induce cytotoxic T-cell responses associated with objective clinical responses. Thus, clinical trials utilizing DCs for immunotherapy of advanced RCCs appear to be promising; however, detailed analyses concerning the distribution and function of DC subsets in RCCs are lacking.MethodsWe characterized the distribution of the different immature and mature myeloid DC subsets in RCC tumour tissue and the corresponding normal kidney tissues. In further analyses, the expression of various chemokines and chemokine receptors controlling the migration of DC subsets was investigated.ResultsThe highest numbers of immature CD1a+ DCs were found within RCC tumour tissue. In contrast, the accumulation of mature CD83+/DC-LAMP+ DCs were restricted to the invasive margin of the RCCs. The mature DCs formed clusters with proliferating T-cells. Furthermore, a close association was observed between MIP-3α-producing tumour cells and immature CCR6+ DC recruitment to the tumour bed. Conversely, MIP-3β and SLC expression was only detected at the tumour border, where CCR7-expressing T-cells and mature DCs formed clusters.ConclusionIncreased numbers of immature DCs were observed within the tumour tissue of RCCs, whereas mature DCs were found in increased numbers at the tumour margin. Our results strongly implicate that the distribution of DC subsets is controlled by local lymphoid chemokine expression. Thus, increased expression of MIP-3α favours recruitment of immature DCs to the tumour bed, whereas de novo local expression of SLC and MIP-3β induces accumulation of mature DCs at the tumour margin forming clusters with proliferating T-cells reflecting a local anti-tumour immune response.

Aging is associated with altered dendritic cells subset distribution and impaired proinflammatory cytokine production

Aging is characterized by the gradual decline in immune function. Dendritic cells (DC) are potent antigen-presenting cells that regulate the balance between immunity and tolerance. The reduction in immune responsiveness and increased susceptibility to infections observed in the aged population could be due to age-related defects in DC differentiation and function. In this study, we examined the effects of aging on DC subset frequency, antigen-presenting function, and activation using physiologically relevant, ex vivo splenic DC isolated from young (8 wk) and aged (26 mo) C57Bl/6 mice. Splenic DC isolated from aged mice had reduced frequency of plasmacytoid DC (CD11 lowPDCA-1 +) and CD11c +CD8 + DC, and an increase in CD11c +CD8 − DC. Plasmacytoid DC from aged mice had similar IFNα production upon CpG stimulation compared to young mice, and the ability of splenic DC to stimulate T cells was not affected by age. In contrast, aged splenic DC had markedly decreased production of TNFα upon LPS stimulation. Reduced splenic DC activation in aged mice was not due to altered TLR4 expression, but was associated with reduced phosphorylation of STAT1 and STAT3 proteins. Taken together, our results suggested that aging was associated with dysregulation in splenic DC activation and subset differentiation, and may represent one of the factors contributing to the decline in immune function with age.

Effect of sialic acid loss on dendritic cell maturation

Sialic acids are key structural determinants and contribute to the functionality of a number of immune cell receptors. Previously, we demonstrated that differentiation of human dendritic cells (DCs) is accompanied by an increased expression of sialylated cell surface structures, putatively through the activity of the ST3Gal.I and ST6Gal.I sialyltransferases. Furthermore, DC endocytosis was reduced upon removal of the cell surface sialic acid residues by neuraminidase. In the present work, we evaluate the contribution of the sialic acid modifications in DC maturation. We demonstrate that neuraminidase-treated human DCs have increased expression of major histocompatibility complex (MHC) and costimulatory molecules, increased gene expression of specific cytokines and induce a higher proliferative response of T lymphocytes. Together, the data suggest that clearance of cell surface sialic acids contributes to the development of a T helper type 1 proinflammatory response. This postulate is supported by mouse models, where elevated MHC class II and increased maturation of specific DC subsets were observed in DCs harvested from ST3Gal.I(-/-) and ST6Gal.I(-/-) mice. Moreover, important qualitative differences, particularly in the extent of reduced endocytosis and in the peripheral distribution of DC subsets, existed between the ST3Gal.I(-/-) and ST6Gal.I(-/-) strains. Together, the data strongly suggest not only a role of cell surface sialic acid modifications in maturation and functionality of DCs, but also that the sialic acid linkages created by different sialyltransferases are functionally distinct. Consequently, with particular relevance to DC-based therapies, cell surface sialylation, mediated by individual sialyltransferases, can influence the immunogenicity of DCs upon antigen loading.

Plasmacytoid Dendritic Cells Are Proportionally Expanded at Diagnosis of Type 1 Diabetes and Enhance Islet Autoantigen Presentation to T-Cells Through Immune Complex Capture

OBJECTIVE—Immune-mediated destruction of β-cells resulting in type 1 diabetes involves activation of proinflammatory, islet autoreactive T-cells, a process under the control of dendritic cells of the innate immune system. We tested the hypothesis that type 1 diabetes development is associated with disturbance of blood dendritic cell subsets that could enhance islet-specific autoimmunity.RESEARCH DESIGN AND METHODS—We examined blood dendritic cells (plasmacytoid and myeloid) in 40 patients with recent-onset diabetes (median duration 28 days) and matched control subjects. We also examined the relative ability of different dendritic cell subsets to process and present soluble or immune complexed islet cell autoantigen (the islet tyrosine phosphatase IA-2) to responder CD4 T-cells.RESULTS—The balance of blood dendritic cells was profoundly disturbed at diabetes diagnosis, with a significantly elevated proportion of plasmacytoid and reduction of myeloid cells compared with control subjects. Dendritic cell subset distribution was normal in long-standing disease and in patients with type 2 diabetes. Both dendritic cell subsets processed and presented soluble IA-2 to CD4 T-cells after short-term culture, but only plasmacytoid dendritic cells enhanced (by as much as 100%) autoantigen presentation in the presence of IA-2+ autoantibody patient serum.CONCLUSIONS—The plasmacytoid subset of dendritic cells is overrepresented in the blood close to diabetes onset and shows a distinctive ability to capture islet autoantigenic immune complexes and enhance autoantigen-driven CD4 T-cell activation. This suggests a synergistic proinflammatory role for plasmacytoid dendritic cells and islet cell autoantibodies in type 1 diabetes.

Recruitment of dendritic cells in human liver with metastases

Dendritic cells (DCs) play a key role in the generation of antitumor immune responses as the most potent professional antigen-presenting cells. In this study we examined the distribution of DCs subsets in selected areas of liver metastases and adjacent liver tissue of 74 patients with gastrointestinal cancers (14 gastric, 47 colon, and 13 rectal) using immunohistochemistry for the DCs markers S-100 protein, HLA-DR, CD1a, and CD83. S-100 protein-positive DCs were localized mainly in clusters in metastases and at the tumor border with the surrounding liver tissue, while HLA-DR-positive DCs were significantly more in number (P<0.0001) and were diffusely distributed in metastasis stroma and at the tumor border. S-100 protein-positive DCs with mature phenotype were presented around metastases and in the sinusoidal lumena, whereas S-100 protein-positive DCs with less mature phenotype based on their ultrastructure were scattered in the tumor stroma. CD1a- and CD83-positive DCs were observed predominantly in small groups or as single cells in the tumor stroma and in the invasive margin. The numbers of CD1a-positive DCs (immature) and CD83-positive DCs (mature) were comparable, but significantly lower than that of S-100 protein-positive (P<0.0001) and HLA-DR-positive cells (P<0.0001).We observed more S-100 protein-positive DCs and HLA-DR-expressing cells in the sinusoids and portal tracts of the liver tissue, surrounding metastases, than in control liver tissue. In conclusion, this study provides additional information on the functional subtypes and distribution of DCs infiltrating metastatic tissue and local liver environment in patients with liver metastases from gastrointestinal cancers.

Differences in circulating dendritic cell subtypes in peripheral, placental and cord blood in African pregnant women

Dendritic cells (DC) are important for induction of primary immune responses and immunological tolerance. Changes in the frequency of DC subsets were analyzed in peripheral blood from pregnant women (mPB) and compared to placental blood (PB) and cord blood (CB). DCs were identified by flow cytometry in whole blood as lineage negative and HLA-DR-positive cells. Different DC subtypes were identified with CD123 and CD11c markers. In these data, the percentage of DC was significantly lower in mPB, PB and CB than in control women, but the absolute number of DC was higher in CB, suggesting that numbers of DC in CB do not explain the decrease of the immune response in newborn infants. Myeloid DCs (MDC) decreased in all compartments of pregnant women compared to control women, especially in mPB where MDC became lower than lymphoid DCs. An increase of less differentiated DC was observed in mPB and CB from pregnant women. DCs in pregnant women were mainly immature DC with a proportion of CD83-positive DC, identical as control women. The levels of IFNγ, TNFα, IL-2, IL-4, IL-5 and IL-10 were not different in the three compartments (mPB, PB, CB). In conclusion, the phenotype and subset of DCs were different in pregnant women than in control women, suggesting a role in maintenance of immune tolerance against the fetus. The distribution of DC subsets was different in mPB, PB and CB. Their role in the regulation of immune response remains to be elicited.

Glucocorticoids severely impair differentiation and antigen presenting function of dendritic cells despite upregulation of Toll-like receptors

Glucocorticoids (GCs) are widely used as anti-inflammatory and immunosuppressive agents. Effects of GC have mainly been attributed to the suppression of T cells. Recently, several studies have indicated the role of dendritic cells (DC) in GC-mediated immunosuppression. We investigated the effect of GC on characteristics of DC. Given the crucial role of Toll-like receptor (TLR) triggering for the initiation of DC maturation program, we analyzed the expression of TLR2, 3, 4 by GC-treated DC. To extend our in vitro findings, we analyzed the distribution of DC subsets in the blood of patients treated with high-dose corticosteroids. DC differentiation in presence of GC was skewed to a qualitatively distinct population incapable of inducing an efficient immune response, whereas GC presence during the process of maturation significantly reduced DC IL-12 p70 and TNF production and T cell stimulatory function. Despite the fact that GC increased expression of TLR2, 3 and 4 on DC, their stimulation with TLR-derived signals did not induce maturation. Administration of high-dose GC to the patients with systemic autoimmunity induced a decrease of circulating myeloid DC and abrogated plasmacytoid DC. These findings provide further insights into the mechanisms of GC immunosuppressive functions and reveal additional mechanisms of their therapeutic efficiency.

Plasmacytoid Dendritic Cells Induce CD8+ Regulatory T Cells In Human Ovarian Carcinoma

To directly dissect the role of each immune component in human tumor immunopathogenesis, we have studied the interaction between dendritic cells and T cells in the tumor environment of patients with ovarian carcinoma. We previously reported that functional plasmacytoid dendritic cells, but not functionally mature myeloid dendritic cells, accumulated in tumor microenvironments. We now show that tumor ascites macrophage-derived dendritic cells induced tumor-associated antigen-specific CD8+ T cells with effector functions. Strikingly, tumor ascites plasmacytoid dendritic cells induced interleukin-10+ CCR7+ CD45RO+ CD8+ regulatory T cells. Four characteristics have been identified in tumor plasmacytoid dendritic cell-induced CD8+ regulatory T cells: (a) induction of CD8+ regulatory T cells is independent of CD4+ CD25+ T cells; (b) CD8+ regulatory T cells significantly suppress myeloid dendritic cell-mediated tumor-associated antigen-specific T cell effector functions through interleukin-10; (c) repetitive myeloid dendritic cell stimulation can recover CD8+ regulatory T cell-mediated poor T cell proliferation, but not T cell effector function; (d) CD8+ regulatory T cells express functional CCR7, and efficiently migrate with lymphoid homing chemokine MIP-3beta. Primary suppressive CCR7+ CD45RO+ CD8+ T cells are found in the tumor environment of patients with ovarian cancers. Thus, tumor-associated plasmacytoid dendritic cells contribute to the tumor environmental immunosuppressive network. Collectively, tumors manipulate tumor microenvironmental dendritic cell subset distribution and function to subvert tumor immunity. The data are relevant to understanding tumor immunopathology as well as reevaluating tumor immunotherapeutic strategies.