Alteration of balance between myeloid dendritic cells and plasmacytoid dendritic cells in peripheral blood of patients with asthma

Asthma, a well-known helper T cell Type 2 (Th2)-mediated disease, has a polarized immune response toward a Th2 phenotype. However, the factors causing the Th2 polarization remain to be fully determined in this disease. Dendritic cells (DCs) are the most potent antigen-presenting cells that play a central role in initiating the primary immune response. In human blood, two functional distinct subsets of DCs, myeloid DCs and plasmacytoid DCs, have been identified. Myeloid DCs (mDCs) and plasmacytoid DCs (pDCs) are also called Type 1 DCs (DC1) and Type 2 DCs (DC2), respectively, because mDCs and pDCs were shown to preferentially differentiate naive T cells into Th1 and Th2 cells, respectively. In asthma, it can thus be speculated that an altered balance of mDCs to pDCs toward pDCs may contribute to the Th2 polarization. To clarify this, we examined the numbers of mDCs and pDCs in the peripheral blood of 44 patients with asthma and 38 normal subjects, using multicolor flow cytometry. We found that the patients with asthma had a significantly higher number of pDCs, resulting in a significant decrease in the ratio of mDCs to pDCs compared with normal subjects. These data indicate that the patients with asthma had a polarization of the mDC:pDC balance toward pDCs, which may be involved in producing the Th2-dominant immune phenotype in asthma.     

Role of mucosal dendritic cells in inflammatory bowel disease

The gastrointestinal innate and adaptive immune system continuously faces the challenge of potent stimuli from the commensal microflora and food constituents. These local immune responses require a tight control, the outcome of which is in most cases the induction of tolerance. Local T cell immunity is an important compartment of the specif ic intestinal immune system. T cell reactivity is programmed during the initial stage of its activation by professional presenting cells. Mucosal dendritic cells （DCs） are assumed to play key roles in regulating immune responses in the antigenrich gastrointestinal environment. Mucosal DCs are a heterogeneous population that can either initiate （innate and adaptive） immune responses, or control intestinal inflammation and maintain tolerance. Defects in this regulation are supposed to lead to the two major forms of inflammatory bowel disease （IBD）, Crohn＇s disease （CD） and ulcerative colitis （UC）. This review will discuss the emerging role of mucosal DCs in regulating intestinal inflammation and immune responses.     

树突状细胞与炎症性肠病

树突状细胞(DC)是体内功能最强的专职抗原提呈细胞,既能启动免疫应答,又能诱导免疫耐受。炎症性肠病可能是遗传和环境因素共同作用导致肠道黏膜对肠道正常菌群免疫反应失常引起的慢性非特异性炎症。DC可能参与了IBD的发生,对DC功能的进一步深入研究,有助于发现新的IBD治疗靶点。     

Dysfunction and infection of freshly isolated blood myeloid and plasmacytoid dendritic cells in patients infected with HIV-1

Recently it has been shown that the 2 populations of blood dendritic cells (DCs), termed plasmacytoid (pcDCs) and myeloid (myDCs), are reduced in HIV-1 infection. This study aimed to determine whether these 2 populations are targets for HIV-1 infection and whether their ability to stimulate T-lymphocyte proliferation is affected. Highly purified populations of myDCs and pcDCs were isolated from the blood of antiretroviral treatment-naive patients and assessed for the level of HIV provirus by polymerase chain reaction (PCR). We show that both populations are targets for HIV-1 infection as indicated by the presence of provirus in 12 of 14 pcDC and 13 of 14 myDC samples tested. A proportion of this provirus is integrated in myDCs. The ability of both myDCs and pcDCs from HIV-1-infected patients to stimulate allogeneic T-lymphocyte proliferation in a 6-day mixed leukocyte reaction was severely impaired, but was not mediated by secondary infection of T lymphocytes. Thus, in addition to depletion, both myeloid and plasmacytoid DCs are infected and show impaired functional capacity. These findings suggest that infection, depletion, and dysfunction of dendritic cells may contribute to the immunosuppression associated with HIV-1 disease.     

Intestinal dendritic cells in the pathogenesis of inflammatory bowel disease

The gastrointestinal tract harbors a large number and diverse array of commensal bacteria and is an important entry site for pathogens.For these reasons,the intestinal immune system is uniquely dedicated to protect against infections,while avoiding the development of destructive inflammatory responses to the microbiota.Several models have been proposed to explain how the immune system discriminates between,and appropriately responds to,commensal and pathogenic microorganisms.Dendritic cells(DCs)and regulato...     

T lymphocyte subsets in inflammatory bowel disease: peripheral blood

Peripheral blood T lymphocytes and T lymphocyte subsets have been quantified in 28 patients with ulcerative colitis and 26 with Crohn's disease by an indirect immunofluorescence technique using monoclonal antibodies: OKT3, which detects all peripheral blood T lymphocytes; OKT4 (T cells of helper phenotype); and OKT8 (T cells of supressor-cytotoxic phenotype). Eighteen normal subjects and 16 patients with a variety of non-inflammatory gastrointestinal disorders were studied as controls. No significant differences were found between patient and control groups in the proportions of circulating T lymphocytes or their subsets. When compared with normal subjects, absolute numbers of T lymphocytes were reduced in patients with active ulcerative colitis or Crohn's disease (p less than 0.05). OKT4+ T cell numbers were reduced in ulcerative colitis, whether active (p less than 0.02) or inactive (p less than 0.05) and in active Crohn's disease (p less than 0.05) Numbers of OKT8+ T cells were reduced in active Crohn's disease (p less than 0.01). There were no differences in T lymphocyte numbers between the patient groups and the disease control subjects. The OKT4+:OKT8+ ratio in patients with inflammatory bowel disease did not differ from that in controls. No relation was found between any of the parameters studied and disease activity, site, or extent of disease, or treatment with sulphasalazine or corticosteroids. The presence of Ia-like, HLA-DR antigens on T cells was detected using a double marker immunofluorescence technique. In control subjects up to 7% of OKT3+ cells were HLA-DR+. In only three patients was the proportion of HLA-DR+ cells greater than in controls. These results indicate that the pathogenesis of ulcerative colitis or Crohn's disease does not depend upon an alteration in the proportion of circulating T lymphocytes nor upon an imbalance of T lymphocyte subsets as defined by monoclonal antibodies. The reduction in T lymphocyte numbers may result from mucosal infiltration. The findings also suggest that circulating T lymphocytes are not activated.     

Mouse plasmacytoid dendritic cells derive exclusively from estrogen-resistant myeloid progenitors

Current models predict that mouse plasmacytoid dendritic cells (PDCs) derive from lymphoid progenitors. However, we show PDCs arise exclusively from common myeloid progenitors (CMPs) characterized by low-level expression of several lymphoid-associated genes, including a RAG2/GFP reporter transgene. This conclusion is supported by both adoptive transfer experiments and an estrogen treatment strategy that led to marked depletion of very early lymphoid progenitors without affecting RAG2/GFP(+) CMPs or the developmental kinetics, RAG-mediated recombinase activity, and cytokine production of PDCs. These data suggest that PDCs arise exclusively from early myeloid progenitors and that promiscuous low-level expression of lymphoid-associated genes is a general feature of PDC progenitors among CMPs.     

Differential requirement for DOCK2 in migration of plasmacytoid dendritic cells versus myeloid dendritic cells

The migratory properties of dendritic cells (DCs) are important for their functions. Although several chemokines and their receptors have been implicated in DC migration, the downstream signaling molecules are largely unknown. Here we show that DOCK2, a hematopoietic cell-specific CDM family protein, is indispensable for migration of plasmacytoid DCs (pDCs), but not myeloid DCs (mDCs). Although DOCK2-deficiency did not affect development of pDCs, DOCK2-deficient (DOCK2^–/–) mice exhibited a severe reduction of pDCs in the spleen and lymph nodes. Adoptive transfer experiments revealed that DOCK2^–/– pDCs failed to migrate into the periarteriolar lymphoid sheaths of the spleen. In DOCK2^–/– pDCs, chemokine-induced Rac activation was severely impaired, resulting in the reduction of motility and the loss of polarity during chemotaxis. In contrast, DOCK2^–/– mDCs did not show any defects in Rac activation and migration. These results indicate that pDCs and mDCs use distinct molecules to activate Rac during chemotaxis.     

Functional impairment of myeloid and plasmacytoid dendritic cells of patients with chronic hepatitis B

Dendritic cells (DC) play an important role in the induction of T-cell responses. We hypothesize that the hampered antiviral T-cell response in chronic hepatitis B patients is a result of impaired dendritic cell function. In this study, we compared the number, phenotype and functionality of two important blood precursor DC, myeloid DC (mDC) and plasmacytoid DC (pDC), of chronic hepatitis B patients with healthy volunteers. No differences in percentages of mDC and pDC in peripheral blood mononuclear cells were observed between chronic hepatitis B patients and healthy controls. The allostimulatory capacity of isolated and in vitro matured mDC, but not of pDC, was significantly decreased in patients compared to controls. Accordingly, a decreased percentage of mDC expressing CD80 and CD86 was observed after maturation, compared to controls. In addition, mDC of patients showed a reduced capacity to produce tumor necrosis factor alpha after a stimulus with synthetic double-stranded RNA and interferon gamma. Purified pDC from patients produced less interferon alpha, an important antiviral cytokine, in response to stimulation with Staphylococcus aureus Cowan strain I than pDC isolated from controls. In conclusion, mDC and pDC are functionally impaired in patients with chronic hepatitis B. This might be an important way by which hepatitis B virus evades an adequate immune response, leading to viral persistence and disease chronicity.     

Characterization of plasmacytoid dendritic cells in inflammatory arthritis synovial fluid

OBJECTIVE: To examine the phenotype of dendritic cell subsets in synovial fluid and peripheral blood from patients with rheumatoid arthritis (RA) or spondyloarthropathy (SpA). METHODS: Multiparameter flow cytometry was used to identify and characterize dendritic cells in mononuclear cell populations isolated from synovial fluid and peripheral blood. RESULTS: Synovial fluid contained two subsets of dendritic cells (DC), myeloid and plasmacytoid. These subsets could also be identified in peripheral blood, but there were lower numbers of DC in peripheral blood compared with synovial fluid. Plasmacytoid DC were distinguished from the myeloid subset by high expression of CD123 and lack of expression of CD11c. In comparison with myeloid dendritic cells, the plasmacytoid subset were less mature, similar to those in peripheral blood. They failed to express CD83 and DC-LAMP, and had relatively low levels of CD40 and CD86. Comparison of dendritic cells in synovial fluid from RA and SpA patients showed increased numbers of the plasmacytoid subset in SpA. CONCLUSIONS: This is the first demonstration of the plasmacytoid subset of dendritic cells in synovial fluid. Since these cells are major producers of type I interferons, their increased numbers in SpA might be relevant to pathogenesis, but the immature phenotype in SpA synovial fluid may also indicate that conditions for maturation of this subset do not pertain in SpA synovium.     

Antigen induced suppression in peripheral blood and lamina propria mononuclear cells in inflammatory bowel disease.

Using an autologous system, suppressor cell function to a range of mycobacterial antigens and Kunin antigen of peripheral blood mononuclear cells and lamina propria lymphocytes has been investigated in normal subjects and patients with inflammatory bowel disease. In the peripheral blood there was reduced antigen induced suppression in patients with Crohn's disease in remission to Mycobacterium paratuberculosis, purified protein derivative (PPD), M fortuitum, and Kunin antigens (p less than 0.05). In patients with ulcerative colitis in remission there was reduced antigen induced suppression in the peripheral blood to Kunin antigen (p less than 0.001), M avium (p less than 0.01), M nonchromogenecin, and M fortuitum (p less than 0.05). The phenomenon of antigen induced suppression was largely CD8 dependent, as depleting CD8+ cells reduced the effect and the concentration of soluble CD8 in the culture supernatant was directly related to the suppressor index (r = 0.25, p less than 0.05). These results are likely to be a true reflection of the cell mediated response to antigen as patients with a positive Mantoux skin test have a significantly higher suppressor index to PPD than Mantoux negative subjects (p less than 0.05). These findings may have significance in the aetiopathogenesis of inflammatory bowel disease. However, a similar effect could not be shown in the lamina propria lymphocytes of patients having colectomy for active disease.     

Increased production of vascular endothelial growth factor by peripheral blood mononuclear cells in patients with inflammatory bowel disease

BACKGROUND: Vascular endothelial growth factor (VEGF) is a potent angiogenic, vascular permeability-enhancing cytokine with overexpression in various pathological disorders, including tumour growth, chronic inflammation and tissue repair. Recent studies have shown significantly increased serum levels of VEGF in patients with inflammatory bowel disease. The origin of the circulating VEGF is still unknown. The present investigation examines the VEGF production by peripheral blood mononuclear cells (PBMCs) in patients with inflammatory bowel disease. METHODS: VEGF levels were measured in culture supernatants of unstimulated PBMCs of 27 patients with inflammatory bowel disease and 10 healthy volunteers using a solid phase ELISA. In addition, VEGF serum levels were determined. RESULTS: PBMCs of both active Crohn's disease patients (1142.6+/-483.9 pg/ml, P < 0.001, n = 12) and active ulcerative colitis patients (748.0+/-637.6 pg/ml, P = 0.006, n = 4) produced significantly higher amounts of VEGF compared with PBMCs of healthy volunteers (113.4+/-101.8 pg/ml, n = 10). In addition, there was a significantly increased VEGF production by PBMCs of patients with active disease compared with PBMCs of patients with quiescent Crohn's disease (261.6+/-254.8 pg/ml, P < 0.001, n = 7) and inactive ulcerative colitis (147.7+/-100.3 pg/ml, P = 0.02, n = 4). There was no significant difference in VEGF release between patients with inactive inflammatory bowel disease and healthy controls. CONCLUSIONS: Significantly increased VEGF production by PBMCs was found in patients with active Crohn's disease and active ulcerative colitis. The study helps to clarify one of the origins of the significantly enhanced VEGF serum levels in patients with active inflammatory bowel disease observed in recent studies.     

Lower number of plasmacytoid dendritic cells in peripheral blood of children with bronchiolitis following respiratory syncytial virus infection

Objectives

Dendritic cells (DCs) are key mediators of allergic airway inflammation. Thus, it is important to understand the relationship between respiratory syncytial virus (RSV) infection and DCs, especially in children with RSV bronchiolitis.

Methods

We collected peripheral blood from 71 children with RSV bronchiolitis at the time of admission and 28 children who were followed up 3 months following admission. Flow cytometry was performed to detect dendritic cell immunophenotypes.

Results

Patients with RSV bronchiolitis exhibited significantly higher number of myeloid DCs and lower number of plasmacytoid DCs at the time of admission and 3 months following discharge, compared with healthy controls. These children had a significantly higher myeloid/plasmacytoid ratio 3 months after discharge compared with healthy controls.

Conclusions

Among children with RSV bronchiolitis, there is an imbalance in peripheral blood myeloid/plasmacytoid ratio. The low number of plasmacytoid DCs in peripheral blood indicates the development of bronchiolitis due to RSV infection.     

The importance of peripheral immune cells in inflammatory bowel disease.

Background/aims: Inappropriate down regulation of an activated immune system is considered as the main pathogenetic mechanism in inflammatory bowel disease. Migration of circulating cells to a diseased intestine is considered as an important factor in the pathogenesis of inflammatory bowel disease. We aimed to evaluate some features of circulating immune cells in inflammatory bowel disease. Methods: Twenty-two control, 29 Crohn's disease and 17 ulcerative colitis patients were studied. CD2, CD3, CD4, CD8, CD11b, CD11c, CD25, CD45RA, CD45RO, CD54 and HLA DR on the surface of peripheral blood lymphocytes and CD11b, CD11c, CD45RA and CD45RO on the phagocytes were researched with two-color immunofluorescence flow cytometry. Results: The percentages of CD2+ and CD4+ lymphocytes were found significantly reduced in ulcerative colitis. CD3+ and CD8+ lymphocytes in inflammatory bowel disease were higher than in controls. CD45RA+ lymphocytes were found significantly decreased in ulcerative colitis and active Crohn's disease. CD45RO+ lymphocytes and CD45RO+, CD11b+ and CD11c+ phagocytes were significantly increased in Crohn's disease. Conclusions: We demonstrated that there were significant differences between ulcerative colitis and Crohn's disease in the expression of some important surface markers on the peripheral blood immune cells. It seems that circulating CD11b-CD11c and CD45RA-CD45RO expressing phagocytes are important in inflammatory bowel disease and may be useful in distinguishing Crohn's disease from ulcerative colitis. These findings may give us some clues about the immunopathogenesis of inflammatory bowel disease.     

Normal functional capacity in circulating myeloid and plasmacytoid dendritic cells in patients with chronic hepatitis C

Initial reports analyzing dendritic cell (DC) function in patients with hepatitis C virus (HCV) infection have been controversial. Here, we enumerate and characterize the function of circulating myeloid and plasmacytoid DCs. The results show lower percentages of myeloid DCs (0.62 vs. 0.83; P = .05) and plasmacytoid DCs (0.11 vs. 0.34; P = .004) in patients with chronic HCV infection than in healthy, non-HCV-infected individuals. Despite the lower numbers of circulating myeloid DCs present, no phenotypic or functional defects were identified. The lower percentage of plasmacytoid DCs resulted in decreased absolute interferon (IFN)-alpha production; however, when analyzed on a per-cell basis, plasmacytoid DCs from HCV-infected patients generated levels of IFN-alpha equivalent to those generated by DCs from healthy, non-HCV-infected individuals. Contrary to data from previous models (which attributed HCV pathogenesis to defects in the DC compartment), our data reveal functional DC subsets in patients with chronic HCV infection. These results are encouraging for DC-based HCV immunotherapy trials.