BCG Skin Infection Triggers IL-1R-MyD88-Dependent Migration of EpCAMlow CD11bhigh Skin Dendritic cells to Draining Lymph Node During CD4+ T-Cell Priming

The transport of antigen from the periphery to the draining lymph node (DLN) is critical for T-cell priming but remains poorly studied during infection with Mycobacterium bovis Bacille Calmette-Guérin (BCG). To address this we employed a mouse model to track the traffic of Dendritic cells (DCs) and mycobacteria from the BCG inoculation site in the skin to the DLN. Detection of BCG in the DLN was concomitant with the priming of antigen-specific CD4⁺ T cells at that site. We found EpCAM^low CD11b^high migratory skin DCs to be mobilized during the transport of BCG to the DLN. Migratory skin DCs distributed to the T-cell area of the LN, co-localized with BCG and were found in close apposition to antigen-specific CD4⁺ T cells. Consequently, blockade of skin DC traffic into DLN dramatically reduced mycobacterial entry into DLN and muted T-cell priming. Interestingly, DC and mycobacterial entry into the DLN was dependent on IL-1R-I, MyD88, TNFR-I and IL-12p40. In addition, we found using DC adoptive transfers that the requirement for MyD88 in BCG-triggered migration was not restricted to the migrating DC itself and that hematopoietic expression of MyD88 was needed in part for full-fledged migration. Our observations thus identify a population of DCs that contribute towards the priming of CD4⁺ T cells to BCG infection by transporting bacilli into the DLN in an IL-1R-MyD88-dependent manner and reveal both DC-intrinsic and -extrinsic requirements for MyD88 in DC migration.     

Airway eosinophils accumulate in the mediastinal lymph nodes but lack antigen-presenting potential for naive T cells

Asthma is characterized by infiltration of the airway wall with eosinophils. Although eosinophils are considered to be effector cells, recent studies have reported their ability to activate primed Th2 cells. In this study, we investigated whether eosinophils are capable of presenting Ag to unprimed T cells in draining lymph nodes (DLN) of the lung and compared this capacity with professional dendritic cells (DC). During development of eosinophilic airway inflammation in OVA-sensitized and challenged mice, CCR3(+) eosinophils accumulated in the DLN. To study their function, eosinophils were isolated from the bronchoalveolar lavage fluid of mice by sorting on CCR3(+)B220(-)CD3(-)CD11c(dim) low autofluorescent cells, avoiding contamination with other APCs, and were intratracheally injected into mice that previously received CFSE-labeled OVA TCR-transgenic T cells. Eosinophils did not induce divisions of T cells in the DLN, whereas DC induced on average 3.7 divisions in 45.7% of T cells. To circumvent the need for Ag processing or migration in vivo, eosinophils were pulsed with OVA peptide and were still not able to induce T cell priming in vitro, whereas DC induced vigorous proliferation. This lack of Ag-presenting ability was explained by the very weak expression of MHC class II on fresh eosinophils, despite expression of the costimulatory molecules CD80 and ICAM-1. This investigation does not support any role for airway eosinophils as APCs to naive T cells, despite their migration to the DLN at times of allergen exposure. DC are clearly superior in activating T cells in the DLN of the lung.     

Signal Relay by CC Chemokine Receptor 2 (CCR2) and Formylpeptide Receptor 2 (Fpr2) in the Recruitment of Monocyte-derived Dendritic Cells in Allergic Airway Inflammation

Chemoattractant receptors regulate leukocyte accumulation at sites of inflammation. In allergic airway inflammation, although a chemokine receptor CCR2 was implicated in mediating monocyte-derived dendritic cell (DC) recruitment into the lung, we previously also discovered reduced accumulation of DCs in the inflamed lung in mice deficient in formylpeptide receptor Fpr2 (Fpr2^−/−). We therefore investigated the role of Fpr2 in the trafficking of monocyte-derived DCs in allergic airway inflammation in cooperation with CCR2. We report that in allergic airway inflammation, CCR2 mediated the recruitment of monocyte-derived DCs to the perivascular region, and Fpr2 was required for further migration of the cells into the bronchiolar area. We additionally found that the bronchoalveolar lavage liquid from mice with airway inflammation contained both the CCR2 ligand CCL2 and an Fpr2 agonist CRAMP. Furthermore, similar to Fpr2^−/− mice, in the inflamed airway of CRAMP^−/− mice, DC trafficking into the peribronchiolar areas was diminished. Our study demonstrates that the interaction of CCR2 and Fpr2 with their endogenous ligands sequentially mediates the trafficking of DCs within the inflamed lung.     

Scavenger Receptors SR-AI/II and MARCO limit pulmonary dendritic cell migration and allergic airway inflammation

The class A scavenger receptors (SR-A) MARCO and SR-AI/II are expressed on lung macrophages (MPhis) and dendritic cells (DCs) and function in innate defenses against inhaled pathogens and particles. Increased expression of SR-As in the lungs of mice in an OVA-asthma model suggested an additional role in modulating responses to an inhaled allergen. After OVA sensitization and aerosol challenge, SR-AI/II and MARCO-deficient mice exhibited greater eosinophilic airway inflammation and airway hyperresponsiveness compared with wild-type mice. A role for simple SR-A-mediated Ag clearance ("scavenging") by lung MPhis was excluded by the observation of a comparable uptake of fluorescent OVA by wild-type and SR-A-deficient lung MPhis and DCs. In contrast, airway instillation of fluorescent Ag revealed a significantly higher traffic of labeled DCs to thoracic lymph nodes in SR-A-deficient mice than in controls. The increased migration of SR-A-deficient DCs was accompanied by the enhanced proliferation in thoracic lymph nodes of adoptively transferred OVA-specific T cells after airway OVA challenge. The data identify a novel role for SR-As expressed on lung DCs in the down-regulation of specific immune responses to aeroallergens by the reduction of DC migration from the site of Ag uptake to the draining lymph nodes.     

Mast cell-associated TNF promotes dendritic cell migration

Mast cells represent a potential source of TNF, a mediator which can enhance dendritic cell (DC) migration. Although the importance of mast cell-associated TNF in regulating DC migration in vivo is not clear, mast cells and mast cell-derived TNF can contribute to the expression of certain models of contact hypersensitivity (CHS). We found that CHS to FITC was significantly impaired in mast cell-deficient Kit(W-sh/W-sh) or TNF(-/)(-) mice. The reduced expression of CHS in Kit(W-sh/W-sh) mice was fully repaired by local transfer of wild-type bone marrow-derived cultured mast cells (BMCMCs), but was only partially repaired by transfer of TNF(-/)(-) BMCMCs. Thus, mast cells, and mast cell-derived TNF, were required for optimal expression of CHS to FITC. We found that the migration of FITC-bearing skin DCs into draining lymph nodes (LNs) 24 h after epicutaneous administration of FITC in naive mice was significantly reduced in mast cell-deficient or TNF(-/)(-) mice, but levels of DC migration in these mutant mice increased to greater than wild-type levels by 48 h after FITC sensitization. Mast cell-deficient or TNF(-/)(-) mice also exhibited significantly reduced migration of airway DCs to local LNs at 24 h after intranasal challenge with FITC-OVA. Migration of FITC-bearing DCs to LNs draining the skin or airways 24 h after sensitization was repaired in Kit(W-sh/W-sh) mice which had been engrafted with wild-type but not TNF(-/)(-) BMCMCs. Our findings indicate that mast cell-associated TNF can contribute significantly to the initial stages of FITC-induced migration of cutaneous or airway DCs.     

Matrix metalloproteinase-9-mediated dendritic cell recruitment into the airways is a critical step in a mouse model of asthma

Dendritic cells (DCs) appear to be strategically implicated in allergic diseases, including asthma. Matrix metalloproteinase (MMP)-9 mediates transmigration of inflammatory leukocytes across basement membranes. This study investigated the role of MMP-9 in airway DC trafficking during allergen-induced airway inflammation. MMP-9 gene deletion affected the trafficking of pulmonary DCs in a specific way: only the inflammatory transmigration of DCs into the airway lumen was impaired, whereas DC-mediated transport of airway Ag to the thoracic lymph nodes remained unaffected. In parallel, the local production of the Th2-attracting chemokine CC chemokine ligand 17/thymus and activation-regulated chemokine, which was highly concentrated in purified lung DCs, fell short in the airways of allergen-exposed MMP-9(-/-) mice. This was accompanied by markedly reduced peribronchial eosinophilic infiltrates and impaired allergen-specific IgE production. We conclude that the specific absence of MMP-9 activity inhibits the development of allergic airway inflammation by impairing the recruitment of DCs into the airways and the local production of DC-derived proallergic chemokines.     

Involvement of intestinal epithelial cells in dendritic cell recruitment during C. parvum infection

Dendritic cells (DCs) play a key role in activating and orientating immune responses. Little is currently known about DC recruitment during Cryptosporidium parvum infection. In the intestine, epithelial cells act as sensors, providing the first signals in response to infection by enteric pathogens. We analyzed the contribution of these cells to the recruitment of DCs during cryptosporidiosis. We found that intestinal epithelial cells produced a broad range of DC-attracting chemokines in vitro in response to C. parvum infection. The supernatant of the infected cells induced the migration of both bone marrow-derived DCs (BMDC) and the SRDC lymphoid dendritic cell line. Chemokine neutralization abolished DC migration in these assays. We next analyzed chemokine mRNA expression in the mucosa of C. parvum-infected neonatal mice and recruitment of the various subsets of DCs. Myeloid (CD11c+ CD11b+) and double-negative DCs (CD11c+ CD11b- CD8alpha-) were the main subsets recruited in the ileum during C. parvum infection, via a mechanism involving IFNgamma. DCs were also recruited and activated in the draining lymph nodes during C. parvum infection, as shown by the upregulation of expression of MHC II and of the costimulation molecules CD40 and CD86.     

Analysis of Pulmonary Dendritic Cell Maturation and Migration during Allergic Airway Inflammation

Dendritic cells (DCs) are the key players involved in initiation of adaptive immune response by activating antigen-specific T cells. DCs are present in peripheral tissues in steady state; however in response to antigen stimulation, DCs take up the antigen and rapidly migrate to the draining lymph nodes where they initiate T cell response against the antigen^1,2. Additionally, DCs also play a key role in initiating autoimmune as well as allergic immune response³.DCs play an essential role in both initiation of immune response and induction of tolerance in the setting of lung environment⁴. Lung environment is largely tolerogenic, owing to the exposure to vast array of environmental antigens⁵. However, in some individuals there is a break in tolerance, which leads to induction of allergy and asthma. In this study, we describe a strategy, which can be used to monitor airway DC maturation and migration in response to the antigen used for sensitization. The measurement of airway DC maturation and migration allows for assessment of the kinetics of immune response during airway allergic inflammation and also assists in understanding the magnitude of the subsequent immune response along with the underlying mechanisms.Our strategy is based on the use of ovalbumin as a sensitizing agent. Ovalbumin-induced allergic asthma is a widely used model to reproduce the airway eosinophilia, pulmonary inflammation and elevated IgE levels found during asthma^6,7. After sensitization, mice are challenged by intranasal delivery of FITC labeled ovalbumin, which allows for specific labeling of airway DCs which uptake ovalbumin. Next, using several DC specific markers, we can assess the maturation of these DCs and can also assess their migration to the draining lymph nodes by employing flow cytometry.     

UV照射与非UV照射FITC致敏小鼠淋巴结树突状细胞的光电镜免疫组织化学特性

本工作观察了小鼠淋巴结树突状细胞（ＤＣ）的光、电镜免疫组织化学特性,并探讨其功能。从ＦＩＴＩＣ致敏小鼠淋巴结分离的ＤＣ在体外可刺激ＦＩＴＣ特异性Ｔ－细胞株增殖。注射经ＵＶ照射、ＦＩＴＣ致敏的小鼠淋巴结细胞（ＤＬＮＣ）至受体小鼠,可导致该小鼠的免疫耐受;这些细胞在体外仍可促进ＦＩＴＣ特异性Ｔ－细胞株增殖,但明显弱于非ＵＶ照射小鼠ＤＬＮＣ的作用。免疫光镜下显示ＵＶ－ＦＩＴＣ致敏小鼠淋巴结的ＦＩＴＣ阳性ＤＣ与非ＵＶ照射ＦＩＴＣ致敏组一样也表达了ＭＡＣ－１、２、３和Ｆ４／８０等巨噬细胞标志,唯其ＦＩＴＣ阳性细胞率明显高于非照射ＦＩＴＣ致敏组动物。免疫电镜下显示这些细胞呈Ｉａ阳性和ＦＩＴＣ阳性,ＦＩＴＣ主要定位于线粒体和溶酶体结构等处。研究表明这些与ＦＩＴＣ致敏小鼠ＤＬＮＣ有关的细胞活性的差异与Ｉａ阳性ＤＣ数量减少、表面Ｉａ的表达、ＦＩＴＣ在ＤＣ内的分布变化无关。某些Ｉａ阳性ＤＣ胞质内可见Ｂｉｒｂｅｃｋ颗粒样结构,提示Ｉａ阳性ＤＣ的不同群体可迁移至ＵＶ照射小鼠的淋巴结。     

The leukotriene C(4) transporter MRP1 regulates CCL19 (MIP-3beta, ELC)-dependent mobilization of dendritic cells to lymph nodes

Adaptive immune responses begin after antigen-bearing dendritic cells (DCs) traffic from peripheral tissues to lymph nodes. Here, we show that DC migration from skin to lymph nodes utilizes the leukotriene C(4) (LTC(4)) transporter multidrug resistance-associated protein 1 (MRP1). DC mobilization from the epidermis and trafficking into lymphatic vessels was greatly reduced in MRP1(-/-) mice, but migration was restored by exogenous cysteinyl leukotrienes LTC(4) or LTD(4). In vitro, these cysteinyl leukotrienes promoted optimal chemotaxis to the chemokine CCL19, but not to other related chemokines. Antagonism of CCL19 in vivo prevented DC migration out of the epidermis. Thus, MRP-1 regulates DC migration to lymph nodes, apparently by transporting LTC(4), which in turn promotes chemotaxis to CCL19 and mobilization of DCs from the epidermis.     

α-1 antitrypsin promotes semimature, IL-10-producing and readily migrating tolerogenic dendritic cells

Tolerogenic IL-10-positive CCR7-positive dendritic cells (DC) promote T regulatory (Treg) cell differentiation upon CCR7-dependent migration to draining lymph nodes (DLN). Indeed, in human DC deficiencies, Treg levels are low. α-1 antitrypsin (AAT) has been shown to reduce inflammatory markers, promote a semimature LPS-induced DC phenotype, facilitate Treg expansion, and protect pancreatic islets from alloimmune and autoimmune responses in mice. However, the mechanism behind these activities of AAT is poorly understood. In this study, we examine interactions among DC, CD4(+) T cells, and AAT in vitro and in vivo. IL-1β/IFN-γ-mediated DC maturation and effect on Treg development were examined using OT-II cells and human AAT (0.5 mg/ml). CCL19/21-dependent migration of isolated DC and resident islet DC was assessed, and CCR7 surface levels were examined. Migration toward DLN was evaluated by FITC skin painting, transgenic GFP skin tissue grafting, and footpad DC injection. AAT-treated stimulated DC displayed reduced MHC class II, CD40, CD86, and IL-6, but produced more IL-10 and maintained inducible CCR7. Upon exposure of CD4(+) T cells to OVA-loaded AAT-treated DC, 2.7-fold more Foxp3(+) Treg cells were obtained. AAT-treated cells displayed enhanced chemokine-dependent migration and low surface CD40. Under AAT treatment (60 mg/kg), DLN contained twice more fluorescence after FITC skin painting and twice more donor DC after footpad injection, whereas migrating DC expressed less CD40, MHC class II, and CD86. Intracellular DC IL-10 was 2-fold higher in the AAT group. Taken together, these results suggest that inducible functional CCR7 is maintained during AAT-mediated anti-inflammatory conditions. Further studies are required to elucidate the mechanism behind the favorable tolerogenic activities of AAT.     

Prostaglandin D2 inhibits airway dendritic cell migration and function in steady state conditions by selective activation of the D prostanoid receptor 1

PGD(2) is the major mediator released by mast cells during allergic responses, and it acts through two different receptors, the D prostanoid receptor 1 (DP1) and DP2, also known as CRTH2. Recently, it has been shown that PGD(2) inhibits the migration of epidermal Langerhans cells to the skin draining lymph nodes (LNs) and affects the subsequent cutaneous inflammatory reaction. However, the role of PGD(2) in the pulmonary immune response remains unclear. Here, we show that the intratracheal instillation of FITC-OVA together with PGD(2) inhibits the migration of FITC(+) lung DC to draining LNs. This process is mimicked by the DP1 agonist BW245C, but not by the DP2 agonist DK-PGD(2). The ligation of DP1 inhibits the migration of FITC-OVA(+) DCs only temporarily, but still inhibits the proliferation of adoptively transferred, OVA-specific, CFSE-labeled, naive T cells in draining LNs. These T cells produced lower amounts of the T cell cytokines IL-4, IL-10, and IFN-gamma compared with T cells from mice that received FITC-OVA alone. Taken together, our data suggest that the activation of DP receptor by PGD(2) may represent a pathway to control airway DC migration and to limit the activation of T cells in the LNs under steady state conditions, possibly contributing to homeostasis in the lung.     

Tracking the 'general': tagging skin-derived dendritic cells

Dendritic cells (DCs) are the sentinels of the immune system; their migration, maturation and mobilization are fundamental to immunity and tolerance. The recent tracking of DCs from the skin to lymph node (LN) and their enumeration using a Cre/loxP system demonstrate the recruitment of a higher than expected number of DCs to the draining LN after cutaneous administration of DNA-coated gold particles. The longevity of the migrated DCs was also longer than previously reported.     

Visualizing dendritic cell migration within the skin

Dendritic cells (DCs) within the skin are a heterogeneous population of cells, including Langerhans cells of the epidermis and at least three subsets of dermal DCs. Collectively, these DCs play important roles in the initiation of adaptive immune responses following antigen challenge of the skin as well as being mediators of tolerance to self-antigen. A key functional aspect of cutaneous DCs is their migration both within the skin and into lymphatic vessels, resulting in their emigration to draining lymph nodes. Here, we discuss our current understanding of the requirements for successful DC migration in and from the skin, and introduce some of the microscopic techniques developed in our laboratory to facilitate a better understanding of this process. In particular, we detail our current use of multi-photon excitation (MPE) microscopy of murine skin to dissect the migratory behavior of DCs in vivo. B. Roediger and L. G. Ng contributed equally to this work.     

Differential expression of cell surface markers by ovine respiratory tract dendritic cells.

Dendritic cells (DCs) are key antigen-presenting cells central to the induction of primary immune responses. Despite the prevalence of respiratory disease in sheep and the increasing use of the ovine lung as a model for human disease, ovine respiratory tract DCs (RTDCs) have not yet been characterized. Using single and double immunocytochemical staining, expression of a number of potential DC markers (MHC class II, CD1b, SIRPalpha, and CD205) by ovine RTDC populations has been determined. MHC class II staining revealed widespread populations of DCs either adjacent to respiratory airway epithelium or within the lung parenchyma. CD1b was expressed by a small subpopulation of both airway and parenchymal RTDCs. Expression of SIRPalpha was limited to a small subpopulation of airway RTDCs but was absent from the lung parenchyma. CD205 was widely expressed by airway RTDCs but expressed only by a small subpopulation of parenchymal RTDCs. In addition, the majority (87%) of parenchymal CD205+ cells exhibited a non-DC-like morphology and did not express MHC class II, suggesting that these single CD205+ cells were not DCs. Phenotypic differences between airway and parenchymal RTDCs may be related to functional differences between the two populations.     

Dendritic cells of mucosa and skin: "recruited for vaccination"

Mucosae and skin are exposed to environmental antigens and are natural entry routes for most infectious agents. To maintain immunological tolerance and ensure protective immunity against pathogens, epithelial surfaces are surveyed permanently by antigen-presenting dendritic cells (DCs). Many DC subsets have been described in epithelial tissues, depending on the inflammatory state and the type of epithelium. Identification of the DC subset able to induce cytotoxic CD8+ T cells against antigens delivered via mucosae or skin, is a major issue for the development of efficient anti-infectious and anti-tumoral vaccines. Until recently, it was commonly accepted that Langerhans cells (LC), the prototype of immature DCs residing in skin and certain mucosae, can capture and process antigens and, in response to danger signals, undergo a maturation program allowing their migration to the draining lymph nodes for priming of na?ve T cells. This concept likely needs to be revisited. Recent evidence from animal models revealed that resident epithelial tissue DCs, including LCs, do not play a direct role in T cell priming, but may contribute to maintenance of peripheral tolerance. Alternatively, DCs newly recruited into muco-cutaneous tissues exposed to pro-inflammatory stimuli are responsible for efficient priming and differentiation of CD8+ T cells into cytolytic effectors. These DC originate from blood monocytes and can cross-present protein antigens to CD8+ T cells, which subsequently give rise to specific CTL effectors. Remarkably, components derived from bacteria, virus and chemicals capable to enhance CCL20 production in epithelia, promote CCR6-dependent DC recruitment and behave as adjuvants allowing for cross-primed CD8+ CTL. These advances in the dynamic and function of epithelial tissue DC provide a rationale for the screening of novel CD8+ T cell adjuvants and the design of novel mucosal and skin vaccines.     

Airway activation of formyl peptide receptors inhibits Th1 and Th17 cell responses via inhibition of mediator release from immune and inflammatory cells and maturation of dendritic cells

Formyl peptide receptors (FPRs) are chemoattractant receptors that mediate inflammatory cell responses to infection. Recent evidence indicates that noneosinophilic asthma phenotypes can be developed by both Th1 and Th17 cell responses when exposed to LPS-containing allergens. In this study, we evaluated the effects of airway activation of FPRs by their synthetic agonist, Trp-Lys-Tyr-Met-Val-D-Met (W-peptide), on the development of Th1 and Th17 cell responses in a noneosinophilic asthma mouse model. A noneosinophilic asthma mouse model was generated by intranasal sensitization with 10 μg of LPS plus 75 μg of OVA on days 0, 1, 2, and 7. Mice were then challenged with 50 μg of OVA alone on days 14, 15, 21, and 22. W-peptide was administered during the sensitization period, and immune and inflammatory responses were evaluated after OVA challenge. Lung inflammation after OVA challenge was partly abolished by airway activation of FPRs during sensitization. Maturation of dendritic cells (DCs) and migration of DCs from the lung to lung-draining lymph nodes were inhibited by FPR activation. In addition, airway activation of FPRs inhibited allergen-specific T cell proliferation in the lymph nodes. Production of IL-12 and IL-6 (Th1- and Th17-polarizing cytokines) from lung DCs was decreased by airway activation of FPRs. This effect resulted in the inhibition of allergen-specific Th1 and Th17 cell responses. Airway activation of FPRs during sensitization effectively prevents the development of Th1 and Th17 cell responses induced by LPS-containing allergens via multiple mechanisms, such as inhibition of DC maturation and migration and the production of Th1- and Th7-polarizing cytokines.     

Chemokine receptor CCR2 but not CCR5 or CCR6 mediates the increase in pulmonary dendritic cells during allergic airway inflammation

Increased numbers of pulmonary dendritic cells (DCs) are recruited to the lungs during allergic airway inflammation and contribute to the maintenance of the inflammatory immune response. The chemokine receptors that directly control DC accumulation into the lungs are largely unknown. To explore this issue, we generated mixed bone marrow chimeric mice containing both wild-type and knockout cells for a given chemokine receptor. After induction of allergic airway inflammation, we specifically tracked and compared chemokine receptor knockout vs wild-type DC populations through various lung compartments. Using this approach, we show that CCR2, but not CCR5 or CCR6, directly controls the accumulation of DCs into allergic lungs. Furthermore, the size of inflammatory monocyte populations in peripheral blood was strikingly CCR2 dependent, suggesting that CCR2 primarily mediates the release of monocytic DC precursors into the bloodstream.     

Dynamics of dendritic cell phenotype and interactions with CD4+ T cells in airway inflammation and tolerance

An emerging concept is that different types of dendritic cells (DCs) initiate different immune outcomes, such as tolerance vs inflammation. In this study, we have characterized the DCs from the lung draining lymph nodes of mice immunized for allergic airway inflammation or tolerance and examined their interactions with CD4(+) T cells. The DC population derived from tolerized mice was predominantly CD11c(+), B220(+), Gr-1(+), CD11b(-), and MHC class II(low), which resembled plasmacytoid-type DCs whereas DCs from the inflammatory condition were largely CD11c(+), B220(-), Gr-1(-), CD11b(+), and MHC class II(high) resembling myeloid-type DCs. The DCs from the tolerogenic condition were poor inducers of T cell proliferation. DCs from both conditions induced T cell IL-4 production but the T cells cultured with tolerogenic DCs were unresponsive to IL-4 as indicated by inhibition of STAT6 activation and expression of growth factor-independent 1, which has been recently shown to be important for STAT6-activated Th2 cell expansion. Our data suggest that airway tolerance vs inflammation is determined by the DC phenotype in lung draining lymph nodes.     

Cysteinyl leukotrienes regulate dendritic cell functions in a murine model of asthma

Dendritic cells (DCs) act as APCs in the airway and play a critical role in allergy. Cysteinyl leukotrienes (cysLTs) synthesized from arachidonic acid are primary mediators of immediate asthmatic reaction. The aim of this study was to investigate the effects of cysLTs on Dermatophagoides farinae (Der f)-pulsed mouse myeloid DCs in inducing allergic airway inflammation in vitro and in vivo. Control DC (medium-pulsed), Der f-pulsed DC, cysLT-pulsed DC, Der f- and cysLT-pulsed DC, and Der f-pulsed and cysLT receptor antagonist (LTRA)-treated DC were prepared from murine bone marrow, and the production of cytokines ws compared. Subsequently, these DCs were intranasally instilled into another group of naive mice, followed by intranasal Der f challenge to induce allergic airway inflammation in vivo. Der f-pulsed DC produced significantly higher amounts of IL-10 and IL-12 compared with control DC. Der f- and cysLT-pulsed DC further increased IL-10 production compared with Der f-pulsed DC. In contrast, treatment of Der f-pulsed DC with LTRA increased IL-12 and decreased IL-10. Intranasal instillation of Der f-pulsed DC resulted in airway eosinophilia associated with a significant rise in IL-5 levels in the airway compared with control DC. Pulmonary eosinophilia and excess IL-5 were further enhanced in Der f- and cysLT-pulsed DC-harboring mice. In contrast, Der f-pulsed and LTRA-treated DC significantly inhibited airway eosinophilia, reduced IL-5, and increased IFN-gamma in the airway. Our results suggest that cysLTs play an important role in the development of allergic airway inflammation by regulating the immunomodulatory functions of DCs.