Dendritic cells in chronic obstructive pulmonary disease: new players in an old game

Effect of cigarette smoke on mucosal vaccine response with activation of plasmacytoid dendritic cells: The outcomes of in vivo and in vitro experiments

Mucosal vaccines offer several advantages over transdermal vaccines, including the ability to acquire systemic and mucosal immunities. Smoking is a huge public health threat and major risk factor for various diseases that exacerbate or prolong respiratory symptoms and conditions. However, its impact on the efficacy of mucosal vaccines remains partially explored. Thus, this study investigates the effects of smoking on mucosal vaccine reactivity by assessing the induction of Th1 immunity, a vital response in infection defense. Cigarette smoke condensate was prepared as a substitute for mainstream smoke. We intranasally administered diphtheria toxoid as an antigen and natural CpG oligonucleotide G9.1, which enhances the Th1-type antibody (Ab) response in a plasmacytoid dendritic cells (pDCs) dependent manner, as an adjuvant to mice to assess the effect of cigarette smoke condensate on Ab responses. The mechanism of its effect was evaluated using human peripheral blood mononuclear cells and their pDC-rich fraction cultured with or without G9.1. In mice, cigarette smoke condensate tended to decrease diphtheria toxoid-specific Ab response, with a higher reduction in Th1-type IgG2 Ab response than in Th2-type IgG1 Ab response. In human peripheral blood mononuclear cells, cigarette smoke condensate significantly reduced the induction of IFN-α production by G9.1. Moreover, G9.1-induced increases in the CD83 expression in pDCs and the CD80 expression in DCs were suppressed via treatment with cigarette smoke condensate. Among the mechanisms suggested were decreased expression of toll-like receptor 9 mRNA, decreased expression of mRNA for IFN regulatory factor 7, and increased CpG methylation of its promoter region. The analysis of Tbet and GATA3 expressions revealed that cigarette smoke condensate exhibits Th1-directed immunostimulatory activity at a steady state but becomes more Th2-directed under G9.1 stimulation. In conclusion, smoking could reduce mucosal vaccine responses by decreasing pDC activation and, consequently, Th1-dominant immunity.

Airway microbiome-immune crosstalk in chronic obstructive pulmonary disease

Chronic Obstructive Pulmonary Disease (COPD) has significantly contributed to global mortality, with three million deaths reported annually. This impact is expected to increase over the next 40 years, with approximately 5 million people predicted to succumb to COPD-related deaths annually. Immune mechanisms driving disease progression have not been fully elucidated. Airway microbiota have been implicated. However, it is still unclear how changes in the airway microbiome drive persistent immune activation and consequent lung damage. Mechanisms mediating microbiome-immune crosstalk in the airways remain unclear. In this review, we examine how dysbiosis mediates airway inflammation in COPD. We give a detailed account of how airway commensal bacteria interact with the mucosal innate and adaptive immune system to regulate immune responses in healthy or diseased airways. Immune-phenotyping airway microbiota could advance COPD immunotherapeutics and identify key open questions that future research must address to further such translation.

The Role of CD40, CD86, and Glutathione S-Transferase Omega 1 in the Pathogenesis of Chronic Obstructive Pulmonary Disease

Objective. The aim of the study was to explore the relevance of CD40, CD86, and GSTO1 with the pathogenesis of COPD. Methods. Patients with acute exacerbation of COPD were contrasted with the healthy and nonsmoking ones and smoking but without COPD ones. The changes of CD40, CD86, and GSTO1 in the peripheral blood, collected from different groups, were detected by flow cytometry and western blotting, respectively. Results. Compared with the nonsmoking group and smoking but without the COPD group, the expression of CD40 and CD86 of the patients with COPD increased significantly, but the expression of GSTO1 decreased. CD40 and CD86 were negatively correlated with FEV1%, while GSTO1 was positively correlated with FEV1% and negatively correlated with CD40 and CD86. Conclusion. CD40, CD86, and GSTO1 may play a role in the pathogenesis of COPD, and they are related to the severity of COPD and the degree of changes in the lung function.

Does smoking habit affect dendritic cell expression in oral squamous cell carcinoma?

The aim of this study was to determine the presence of immature CD1a+ and mature CD83+ dendritic cells in oral squamous cell carcinoma, to compare immunoreactivity between smokers and nonsmokers, and to correlate the results with histopathological grading. In this observational study, twenty-eight paraffin-embedded biopsies of oral squamous cell carcinoma were retrospectively retrieved and submitted to immunohistochemistry for immature CD1a+ and mature CD83+. Descriptive and statistical analyses were performed. The sample consisted of 18 man (64.3%) and 10 women (35.7%), with a mean age of 64.6 years in the nonsmoker group and 53.2 years in the smoker group. The tongue (11 cases, 39.2%) was the most commonly affected anatomical site, followed by gingiva (6 cases, 21.4%). Histopathological grading revealed 7 low-grade and 7 high-grade malignancy cases in each group, and no correlation with the number of positive DCs. The number of immature CD1a+ was not significantly different between smoker and nonsmoker groups, while a lower number of mature CD83+ was detected in the smoker group (p = 0.001). Smoking changes the oral immune system and decreases the ability to activate and mature dendritic cells, which may influence the development and progression of oral squamous cell carcinoma.

MicroRNAs as Potential Regulators of Immune Response Networks in Asthma and Chronic Obstructive Pulmonary Disease

Chronic respiratory diseases (CRDs) are an important factor of morbidity and mortality, accounting for approximately 6% of total deaths worldwide. The main CRDs are asthma and chronic obstructive pulmonary disease (COPD). These complex diseases have different triggers including allergens, pollutants, tobacco smoke, and other risk factors. It is important to highlight that although CRDs are incurable, various forms of treatment improve shortness of breath and quality of life. The search for tools that can ensure accurate diagnosis and treatment is crucial. MicroRNAs (miRNAs) are small non-coding RNAs and have been described as promising diagnostic and therapeutic biomarkers for CRDs. They are implicated in multiple processes of asthma and COPD, regulating pathways associated with inflammation, thereby showing that miRNAs are critical regulators of the immune response. Indeed, miRNAs have been found to be deregulated in several biofluids (sputum, bronchoalveolar lavage, and serum) and in both structural lung and immune cells of patients in comparison to healthy subjects, showing their potential role as biomarkers. Also, miRNAs play a part in the development or termination of histopathological changes and comorbidities, revealing the complexity of miRNA regulation and opening up new treatment possibilities. Finally, miRNAs have been proposed as prognostic tools in response to both conventional and biologic treatments for asthma or COPD, and miRNA-based treatment has emerged as a potential approach for clinical intervention in these respiratory diseases; however, this field is still in development. The present review applies a systems biology approach to the understanding of miRNA regulatory networks in asthma and COPD, summarizing their roles in pathophysiology, diagnosis, and treatment.

MAPK mutations and cigarette smoke promote the pathogenesis of pulmonary Langerhans cell histiocytosis

Pulmonary Langerhans cell histiocytosis (PLCH) is a rare smoking-related lung disease characterized by dendritic cell (DC) accumulation, bronchiolocentric nodule formation, and cystic lung remodeling. Approximately 50% of patients with PLCH harbor somatic BRAF-V600E mutations in cells of the myeloid/monocyte lineage. However, the rarity of the disease and lack of animal models have impeded the study of PLCH pathogenesis. Here, we establish a cigarette smoke-exposed (CS-exposed) BRAF-V600E-mutant mouse model that recapitulates many hallmark characteristics of PLCH. We show that CD11c-targeted expression of BRAF-V600E increases DC responsiveness to stimuli, including the chemokine CCL20, and that mutant cell accumulation in the lungs of CS-exposed mice is due to both increased cellular viability and enhanced recruitment. Moreover, we report that the chemokine CCL7 is secreted from DCs and human peripheral blood monocytes in a BRAF-V600E-dependent manner, suggesting a possible mechanism for recruitment of cells known to dominate PLCH lesions. Inflammatory lesions and airspace dilation in BRAF-V600E mice in response to CS are attenuated by transitioning animals to filtered air and treatment with a BRAF-V600E inhibitor, PLX4720. Collectively, this model provides mechanistic insights into the role of myelomonocytic cells and the BRAF-V600E mutation and CS exposure in PLCH pathogenesis and provides a platform to develop biomarkers and therapeutic targets.

Sputum from chronic obstructive pulmonary disease patients inhibits T cell migration in a microfluidic device

Chronic obstructive pulmonary disease (COPD) is a common lung disease characterized by narrowed airways, resulting in serious breathing difficulty. Previous studies have demonstrated that inflammatory infiltration of leukocytes in the airway is associated with the pathogenesis of COPD. In the present study, we employed a microfluidic approach to assess the effect of COPD sputum on activated human peripheral blood T cell migration and chemotaxis under well-controlled gradient conditions. Our results showed considerable basal migration of T cells derived from peripheral blood of COPD patients and healthy controls in the medium control groups. By contrast, the migration of T cells from COPD patients and healthy controls was significantly inhibited in the presence of a gradient of sputum supernatant from COPD patients. Furthermore, chemotaxis of T cells from COPD patients or healthy subjects toward an SDF-1α gradient was clearly inhibited by sputum samples from the COPD patients. The inhibition effect revealed by the microfluidic cell migration experiments provides new information about the complex involvement of T cell trafficking in COPD.

The Th17/Treg Cytokine Imbalance in Chronic Obstructive Pulmonary Disease Exacerbation in an Animal Model of Cigarette Smoke Exposure and Lipopolysaccharide Challenge Association

We proposed an experimental model to verify the Th17/Treg cytokine imbalance in COPD exacerbation. Forty C57BL/6 mice were exposed to room air or cigarette smoke (CS) (12 ± 1 cigarettes, twice a day, 30 min/exposure and 5 days/week) and received saline (50 µl) or lipopolysaccharide (LPS) (1 mg/kg in 50 µl of saline) intratracheal instillations. We analyzed the mean linear intercept, epithelial thickness and inflammatory profiles of the bronchoalveolar lavage fluid and lungs. We evaluated macrophages, neutrophils, CD4⁺ and CD8⁺ T cells, Treg cells, and IL-10⁺ and IL-17⁺ cells, as well as STAT-3, STAT-5, phospho-STAT3 and phospho-STAT5 levels using immunohistochemistry and IL-17, IL-6, IL-10, INF-γ, CXCL1 and CXCL2 levels using ELISA. The study showed that CS exposure and LPS challenge increased the numbers of neutrophils, macrophages, and CD4⁺ and CD8⁺ T cells. Simultaneous exposure to CS/LPS intensified this response and lung parenchymal damage. The densities of Tregs and IL-17⁺ cells and levels of IL-17 and IL-6 were increased in both LPS groups, while IL-10 level was only increased in the Control/LPS group. The increased numbers of STAT-3, phospho-STAT3, STAT-5 and phospho-STAT5⁺ cells corroborated the increased numbers of IL-17⁺ and Treg cells. These findings point to simultaneous challenge with CS and LPS exacerbated the inflammatory response and induced diffuse structural changes in the alveolar parenchyma characterized by an increase in Th17 cytokine release. Although the Treg cell differentiation was observed, the lack of IL-10 expression and the decrease in the density of IL-10⁺ cells observed in the CS/LPS group suggest that a failure to release this cytokine plays a pivotal role in the exacerbated inflammatory response in this proposed model.

Cigarette Smoke-Induced Emphysema Exhausts Early Cytotoxic CD8+ T Cell Responses against Nascent Lung Cancer Cells

Chronic obstructive pulmonary disease is a chronic inflammatory disorder with an increased incidence of lung cancer. The emphysema component of chronic obstructive pulmonary disease confers the greatest proportion to lung cancer risk. Although tumors create inflammatory conditions to escape immunity, the immunological responses that control growth of nascent cancer cells in pre-established inflammatory microenvironments are unknown. In this study, we addressed this issue by implanting OVA-expressing cancer cells in the lungs of mice with cigarette smoke-induced emphysema. Emphysema augmented the growth of cancer cells, an effect that was dependent on T cytotoxic cells. OVA-specific OTI T cells showed early signs of exhaustion upon transfer in emphysema tumor hosts that was largely irreversible because sorting, expansion, and adoptive transfer failed to restore their antitumor activity. Increased numbers of PD-L1- and IDO-positive CD11c⁺ myeloid dendritic cells (DCs) infiltrated emphysema tumors, whereas sorted emphysema tumor DCs poorly stimulated OTI T cells. Upon adoptive transfer in immunocompetent hosts, T cells primed by emphysema tumor DCs were unable to halt tumor growth. DCs exposed to the emphysema tumor microenvironment downregulated MHC class II and costimulatory molecules, whereas they upregulated PD-L1/IDO via oxidative stress-dependent mechanisms. T cell activation increased upon PD-L1 blockade in emphysema DC-T cell cocultures and in emphysema tumor hosts in vivo. Analysis of the transcriptome of primary human lung tumors showed a strong association between computed tomography-based emphysema scoring and downregulation of immunogenic processes. Thus, suppression of adaptive immunity against lung cancer cells links a chronic inflammatory disorder, emphysema, to cancer, with clinical implications for emphysema patients to be considered optimal candidates for cancer immunotherapies.

Dendritic Cell Trafficking and Function in Rare Lung Diseases

Dendritic cells (DCs) are highly specialized immune cells that capture antigens and then migrate to lymphoid tissue and present antigen to T cells. This critical function of DCs is well defined, and recent studies further demonstrate that DCs are also key regulators of several innate immune responses. Studies focused on the roles of DCs in the pathogenesis of common lung diseases, such as asthma, infection, and cancer, have traditionally driven our mechanistic understanding of pulmonary DC biology. The emerging development of novel DC reagents, techniques, and genetically modified animal models has provided abundant data revealing distinct populations of DCs in the lung, and allow us to examine mechanisms of DC development, migration, and function in pulmonary disease with unprecedented detail. This enhanced understanding of DCs permits the examination of the potential role of DCs in diseases with known or suspected immunological underpinnings. Recent advances in the study of rare lung diseases, including pulmonary Langerhans cell histiocytosis, sarcoidosis, hypersensitivity pneumonitis, and pulmonary fibrosis, reveal expanding potential pathogenic roles for DCs. Here, we provide a review of DC development, trafficking, and effector functions in the lung, and discuss how alterations in these DC pathways contribute to the pathogenesis of rare lung diseases.

The cellular and molecular determinants of emphysematous destruction in COPD

The introduction of microCT has made it possible to show that the terminal bronchioles are narrowed and destroyed before the onset of emphysematous destruction in COPD. This report extends those observations to the cellular and molecular level in the centrilobular phenotype of emphysematous destruction in lungs donated by persons with very severe COPD (n = 4) treated by lung transplantation with unused donor lungs (n = 4) serving as controls. These lung specimens provided companion samples to those previously examined by microCT (n = 61) that we examined using quantitative histology (n = 61) and gene expression profiling (n = 48). The histological analysis showed that remodeling and destruction of the bronchiolar and alveolar tissue is associated with macrophage, CD4, CD8, and B cell infiltration with increased formation of tertiary lymphoid organs. Moreover, gene set enrichment analysis showed that genes known to be expressed by natural killer (NK), lymphoid tissue inducer (LTi), and innate lymphoid cell 1 (ILC1) cells, but not ILC2 or ILC3 cells, were enriched in the expression profiles associated with CD4, CD8, and B cell infiltration. Based on these findings, we postulate that the centrilobular phenotype of emphysematous destruction COPD is driven by a Th1 response activated by infiltrating ILC1, NK, and LTi cells.

Regulatory T-Cell Distribution within Lung Compartments in COPD

The importance of the adaptive immune response, specifically the role of regulatory T (Treg) cells in controlling the obstruction progression in smokers, has been highlighted. To quantify the adaptive immune cells in different lung compartments, we used lung tissues from 21 never-smokers without lung disease, 22 current and/or ex-smokers without lung disease (NOS) and 13 current and/or ex-smokers with chronic obstructive pulmonary disease (COPD) for histological analysis. We observed increased T, B, IL-17 and BAFF⁺ cells in small and large airways of COPD individuals; however, in the NOS, we only observed increase in T and IL-17⁺ cells only in small airways. A decrease in the density of Treg⁺, TGF-β⁺ and IL-10⁺ in small and large airways was observed only in COPD individuals. In the lymphoid tissues, Treg, T,B-cells and BAFF⁺ cells were also increased in COPD; however, changes in Treg inhibitory associated cytokines were not observed in this compartment. Therefore, our results suggest that difference in Treg⁺ cell distributions in lung compartments and the decrease in TGF-β⁺ and IL-10⁺ cells in the airways may lead to the obstruction in smokers.

The dendritic cell high-affinity IgE receptor is overexpressed in both asthma and severe COPD

BACKGROUND

The reduction of asthma exacerbations following omalizumab treatment has been related to the suppression of the high-affinity IgE receptor (FcεRI) on plasmacytoid dendritic cells (DCs). However, the FcεRI expression on DCs in chronic obstructive pulmonary disease (COPD) is unknown.

OBJECTIVE

To compare FcεRI expression on DCs in COPD with patients with allergic asthma and healthy controls, and to relate the findings to clinical parameters, blood eosinophil concentrations and serum immunoglobin E (IgE) concentrations.

METHODS

Using four-colour flow cytometry, FcεRI expression on blood myeloid DCs and plasmacytoid DCs was analyzed in 64 patients with COPD, 20 patients with allergic asthma, 41 asymptomatic never smokers and 21 asymptomatic current smokers.

RESULTS

As compared with never smokers, current smokers displayed an increased expression of the FcεRI on myeloid and plasmacytoid DCs. In patients with COPD, the expression of the FcεRI on plasmacytoid DCs, but not myeloid DCs, increased from spirometric GOLD stage 2 to GOLD stage 4, and was correlated with several lung function parameters. Patients with severe COPD and patients with allergic asthma displayed a similar FcεRI overexpression on plasmacytoid DCs. In all groups, there was a positive correlation between total IgE serum concentrations and the FcεRI expression on plasmacytoid DCs.

CONCLUSIONS AND CLINICAL RELEVANCE

Severe COPD and allergic asthma are characterized by a similar overexpression of the high-affinity IgE receptor on plasmacytoid DCs. In view of the effect of anti-IgE on exacerbations in asthma, trials investigating the effect of anti-IgE on exacerbations in severe COPD appear to be warranted.

Cigarette smoke-induced chronic obstructive pulmonary disease is attenuated by CCL20-blocker: a rat model

AIM

To evaluate whether the effect of dendritic cells (DCs) on chronic obstructive pulmonary disease (COPD) can be relieved by blocking CCL20.

METHODS

30 Wistar rats were randomly divided into three groups: control, COPD, and COPD treated with CCL20 monoclonal antibody. In the latter two groups, COPD was induced by four-week cigarette smoke exposure and trachea injection of lipopolysaccharide solution on two occasions. CCL20 monoclonal antibody was injected intraperitoneally on the first day. All animals were sacrificed on the 29th day. Pathomorphology of the lung and bronchiole was analyzed using hematoxylin and eosin staining. The CCR6 content in the bronchoalveolar lavage fluid was detected using ELISA. DC distribution in the lung was examined by immunohistochemistry for OX62.

RESULTS

COPD rat models showed pathological alterations similar to those in COPD patients. DCs, CCR6, and the severity of emphysema were significantly increased in the COPD group than in controls (all P values <0.001), and they were significantly reduced after anti-CCL20 treatment compared with the COPD group (all P values <0.05).

CONCLUSION

The interaction between CCR6 and its ligand CCL20 promotes the effect of DCs in the COPD pathogenesis, which can be reduced by blocking CCL20.

[COPD: An early disease]

This general review deals with the mechanisms which underlie the genetic factors in COPD. Many cellular and biochemical mechanisms occur in bronchial inflammation. We present the experimental models of COPD, insisting on the importance of oxydative stress, and on recent knowledge about the lung microbiome. Starting from this pathophysiology basis, we show how various genetic targets are able to interfere with the disease model. Thanks to these genetic targets, new markers in exhaled breath condensates and new drug targets are rising.

IL-22 Defect During Streptococcus pneumoniae Infection Triggers Exacerbation of Chronic Obstructive Pulmonary Disease

Progression of chronic obstructive pulmonary disease (COPD) is linked to episodes of exacerbations caused by bacterial infections due to Streptococcus pneumoniae. Our objective was to identify during COPD, factors of susceptibility to bacterial infections among cytokine network and their role in COPD exacerbations. S. pneumoniae was used to sub-lethally challenge mice chronically exposed to air or cigarette smoke (CS) and to stimulate peripheral blood mononuclear cells (PBMC) from non-smokers, smokers and COPD patients. The immune response and the cytokine production were evaluated. Delayed clearance of the bacteria and stronger lung inflammation observed in infected CS-exposed mice were associated with an altered production of IL-17 and IL-22 by innate immune cells. This defect was related to a reduced production of IL-1β and IL-23 by antigen presenting cells. Importantly, supplementation with recombinant IL-22 restored bacterial clearance in CS-exposed mice and limited lung alteration. In contrast with non-smokers, blood NK and NKT cells from COPD patients failed to increase IL-17 and IL-22 levels in response to S. pneumoniae, in association with a defect in IL-1β and IL-23 secretion. This study identified IL-17 and IL-22 as susceptibility factors in COPD exacerbation. Therefore targeting such cytokines could represent a potent strategy to control COPD exacerbation.

Imbalance of dendritic cell co-stimulation in COPD

Background

Dendritic cells (DCs) control immunity and play a role in the pathogenesis of chronic obstructive pulmonary disease (COPD). However, the expression of function-associated surface molecules on circulating DCs in COPD is unknown.

Methods

Four-colour flow cytometry was used to compare blood DC surface molecules of 54 patients with COPD (median age: 59 years; median FEV₁: 38% predicted, median CAT score: 24) with two age-matched control groups with normal lung function: 21 current smokers and 21 never-smokers.

Results

Concentrations of plasmacytoid DCs (pDCs) and myeloid DCs (mDCs) and the mDC/pDC ratio did not differ between the groups. The increased expression of BDCA-1, BDCA-3, CD86 and CCR5 on mDCs in patients with COPD did not significantly differ from smokers with normal lung function. In contrast, COPD was specifically characterised by a decreased expression of the anti-inflammatory co-stimulatory molecule PD-L1 on pDCs and an increased expression of the pro-inflammatory co-stimulatory molecule OX40 ligand (OX40L) on mDCs. These changes were not confined to patients with elevated systemic inflammation markers (leukocytes, c-reactive protein, interleukin-6, fibrinogen). The ratio of OX40L to PD-L1 expression (OX40L/PD-L1 ratio), a quantitative measure of imbalanced DC co-stimulation, correlated with the severity of pulmonary emphysema in patients with COPD.

Conclusion

An imbalance of DC co-stimulation might contribute to the pathogenesis of COPD.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-015-0174-x) contains supplementary material, which is available to authorized users.

Cigarette smoke affects dendritic cell maturation in the small airways of patients with chronic obstructive pulmonary disease

The aim of the present study was to characterize and quantify the numbers and expression levels of cells markers associated with dendritic cell (DC) maturation in small airways in current smokers and non-smokers with or without chronic obstructive pulmonary disease (COPD). Lung tissues from the following 32 patients were obtained during resection for lung cancer: Eight smokers with COPD, eight non-smokers with COPD, eight current smokers without COPD and eight non-smokers without COPD, serving as a control. The tissue sections were immunostained for cluster of differentiation (CD)83+ and CD1a+ to delineate mature and immature DCs, and chemokine receptor type 7 (CCR7+) to detect DC migratory ability. Myeloid DCs were collected from the lung tissues, and subsequently the CD83+ and CCR7+ expression levels in the lung myeloid DCs were detected using flow cytometry. The expression levels of CD83+, CD1a+ and CCR7+ mRNA in total lung RNA were evaluated by reverse transcription quantitative polymerase chain reaction (RT-qPCR). Evident chronic bronchitis and emphysema pathological changes were observed in the lung tissues of patients with COPD. The results revealed that the numbers of CD83+ and CCR7+ DCs were reduced but the numbers of CD1a+ DCs were significantly increased in the COPD group as compared with the control group (P<0.05, respectively). Using RT-qPCR, the expression levels of CCR7+ and CD83+ mRNA were found to be reduced in the smokers with COPD as compared with the non-smokers without COPD group (P<0.05, respectively). Excessive local adaptive immune responses are key elements in the pathogenesis of COPD. Cigarette smoke may stimulate immune responses by impairing the homing of airway DCs to the lymph nodes and reduce the migratory potential of DCs. The present study revealed that COPD is associated with reduced numbers of mature CD83+ DCs and lower CCR7+ expression levels in small airways.

T-regulatory cells and programmed death 1+ T cells contribute to effector T-cell dysfunction in patients with chronic obstructive pulmonary disease

RATIONALE

Previous studies from our laboratory have shown that peripheral blood mononuclear cells (PBMCs) from patients with chronic obstructive pulmonary disease (COPD) prone to exacerbations with nontypeable Haemophilus influenzae have impaired responses to lipoprotein P6. We hypothesized that an underlying immunosuppressive network could be responsible for the defective antibacterial immunity observed in these patients. We evaluated T regulatory cells (Tregs), myeloid-derived suppressor cells (MDSC), and exhausted T effector cells (programmed death 1 [PD-1](+)) in patients with COPD, because these cells are known to play a pivotal role in suppressing immune responses.

OBJECTIVES

We performed an in-depth characterization of Tregs, T effector cells, and MDSC in COPD and correlated their levels and function with disease severity.

METHODS

Treg, effector T cell, and MDSC frequency from patients with COPD and healthy subjects' PBMCs were analyzed by flow cytometry. Treg immunosuppressive capacity was measured by in vitro suppression assay. The frequency of interferon-γ producing T cells and T-cell proliferation were measured after blocking CTLA-4 and PD-1. Plasma proinflammatory and immunosuppressive cytokine levels were measured.

MEASUREMENTS AND MAIN RESULTS

Significantly increased levels of Tregs, MDSC, and PD-1(+) exhausted effector T cells were present in patients with COPD compared with healthy subjects. Tregs from patients with COPD suppressed P6-specific T-cell proliferation to a greater extent than Tregs from healthy subjects. Plasma levels of Treg-generated cytokines, IL-10, and transforming growth factor-β were elevated. Blockade of CTLA-4 resulted in significant augmentation of T-cell IFN-γ production in patients with COPD.

CONCLUSIONS

Functionally suppressive Tregs, MDSCs, and exhausted PD-1(+) T cells contribute to effector T-cell dysfunction in COPD.

Tolerogenic signaling by pulmonary CD1c+ dendritic cells induces regulatory T cells in patients with chronic obstructive pulmonary disease by IL-27/IL-10/inducible costimulator ligand

BACKGROUND

Increased mortality rates in patients with chronic obstructive pulmonary disease (COPD) are largely due to severe infectious exacerbations. Impaired respiratory immunity is linked to the enhanced susceptibility to infections. Dendritic cells (DCs) direct host immune responses toward immunity or tolerance. Pulmonary CD1c(+) DCs elicit robust antiviral immune responses in healthy subjects. Nevertheless, their functional specialization in patients with COPD remains unexplored.

OBJECTIVE

We sought to better understand the mechanisms that suppress respiratory immunity in patients with COPD by examining the immunostimulatory and tolerogenic properties of pulmonary CD1c(+) DCs.

METHODS

We analyzed the expression of costimulatory and tolerogenic molecules by pulmonary CD1c(+) DCs from patients with COPD (CD1c(+)DCCOPD) and former smokers without COPD. We isolated lung CD1c(+) DCs and determined their ability to stimulate allogeneic T-cell responses. The suppressive effects of lung CD1c(+) DCs and CD1c(+) DC-primed T cells on mixed leukocyte reactions were examined. An experimental human model of COPD exacerbation was used to investigate the levels of critical immunosuppressive molecules in vivo.

RESULTS

CD1c(+) DCs from patients with COPD hinder T-cell effector functions and favor the generation of suppressive IL-10-secreting CD4(+) T cells that function through IL-10 and TGF-β. IL-27, IL-10, and inducible T-cell costimulator ligand signaling are essential for CD1c(+)DCCOPD-mediated differentiation of IL-10-producing suppressive T cells. Exposure of lung CD1c(+) DCs from nonobstructed subjects to lungs of patients with COPD confers tolerogenic properties. IL-27 and IL-10 levels are increased in the lung microenvironment on rhinovirus-induced COPD exacerbation in vivo.

CONCLUSION

We identify a novel tolerogenic circuit encompassing suppressive CD1c(+) DCs and regulatory T cells in patients with COPD that might be implicated in impaired respiratory immunity and further highlight IL-10 and IL-27 as potent therapeutic targets.

Accumulation of BDCA1⁺ dendritic cells in interstitial fibrotic lung diseases and Th2-high asthma

Dendritic cells (DCs) significantly contribute to the pathology of several mouse lung disease models. However, little is known of the contribution of DCs to human lung diseases. In this study, we examined infiltration with BDCA1⁺ DCs of human lungs in patients with interstitial lung diseases or asthma. Using flow cytometry, we found that these DCs increased by 5∼6 fold in the lungs of patients with idiopathic pulmonary fibrosis or hypersensitivity pneumonitis, which are both characterized by extensive fibrosis in parenchyma. The same DC subset also significantly increased in the lung parenchyma of patients with chronic obstructive pulmonary disease, although the degree of increase was relatively modest. By employing immunofluorescence microscopy using FcεRI and MHCII as the specific markers for BDCA1⁺ DCs, we found that the numbers of BDCA1⁺ DCs also significantly increased in the airway epithelium of Th2 inflammation-associated asthma. These findings suggest a potential contribution of BDCA1⁺ DCs in human lung diseases associated with interstitial fibrosis or Th2 airway inflammation.

Impact of smoking on dendritic cell phenotypes in the airway lumen of patients with COPD

Background

Myeloid dendritic cells (DCs) are increased in the airway wall of patients with chronic obstructive pulmonary disease (COPD), and postulated to play a crucial role in COPD. However, DC phenotypes in COPD are poorly understood.

Methods

Function-associated surface molecules on bronchoalveolar lavage fluid (BALF) DCs were analyzed using flow cytometry in current smokers with COPD, in former smokers with COPD and in never-smoking controls.

Results

Myeloid DCs of current smokers with COPD displayed a significantly increased expression of receptors for antigen recognition such as BDCA-1 or Langerin, as compared with never-smoking controls. In contrast, former smokers with COPD displayed a significantly decreased expression of these receptors, as compared with never-smoking controls. A significantly reduced expression of the maturation marker CD83 on myeloid DCs was found in current smokers with COPD, but not in former smokers with COPD. The chemokine receptor CCR5 on myeloid DCs, which is also important for the uptake and procession of microbial antigens, was strongly reduced in all patients with COPD, independently of the smoking status.

Conclusion

COPD is characterized by a strongly reduced CCR5 expression on myeloid DCs in the airway lumen, which might hamper DC interactions with microbial antigens. Further studies are needed to better understand the role of CCR5 in the pathophysiology and microbiology of COPD.

Decreased maturation of dendritic cells in the central airways of COPD patients is associated with VEGF, TGF-β and vascularity

BACKGROUND

Dendritic cells (DCs) have a pivotal role in the onset and regulation of innate and adaptive immune responses. Moreover, DCs can interact with angiogenic modulators, resulting in modification of their biology and participation in angiogenesis.

OBJECTIVES

This study was designed to evaluate the relationship between the density of DCs, vascularity and expression of angiogenic factors [vascular endothelial growth factor (VEGF), transforming growth factor (TGF)-β and basic fibroblast growth factor (bFGF)] in the central airways of chronic obstructive pulmonary disease (COPD) patients.

METHODS

The study included 20 patients with moderate/severe COPD and 8 healthy control subjects. Bronchial biopsies were evaluated by immunohistochemistry. Specimens were examined for CD83 and CD207 to mark mature and immature DCs, respectively, for collagen IV to evaluate vascularity, and for VEGF, TGF-β and bFGF.

RESULTS

Compared to controls, COPD patients had a significant reduction of CD83+ cells and an increased CD207/CD83 ratio (p < 0.05). Vascularity, VEGF, TGF-β and bFGF were also significantly increased in COPD patients as compared to controls (p < 0.01). In COPD patients, CD83+ cells were inversely related to VEGF and TGF-β expression (p < 0.05). Moreover, the CD207/CD83 ratio was positively related to VEGF, TGF-β and vascularity (p < 0.05). Finally, CD207+ cells were inversely related to FEV1 (p < 0.05).

CONCLUSION

Our results show a reduced maturation of DCs in COPD that was related to airway vascularity and angiogenic factors (VEGF and TGF-β). Additionally, immature DCs were significantly related to disease severity. We propose that the interplay between airway vascular changes, on one hand, and DCs maturation on the other, may play a key role in the pathogenetic mechanisms of COPD.

Fluticasone impact on airway dendritic cells in smokers: a randomized controlled trial

Background

Myeloid Dendritic cells are key drivers of inflammation in smoke-related lung diseases, whereas plasmacytoid DCs play a crucial role in the defense against infections. Effects of inhaled corticosteroids (ICS) on airway DCs in smokers are unknown.

Methods

In this randomized, double-blind, placebo-controlled clinical trial, 45 active cigarette smokers inhaled placebo, fluticasone or fluticasone plus salmeterol twice daily for 4 weeks. Bronchoalveolar lavage fluid DCs were analyzed using four-color flow cytometry before and after the inhalation period. In addition, fluticasone effects were tested on T-cell proliferation in co-cultures with blood myeloid DCs from smokers.

Results

Inhalation of fluticasone plus salmeterol, but not fluticasone alone or placebo, reduced endobronchial concentrations of myeloid DCs (median decrease: 24%), macrophages (median decrease: 26%) and neutrophils (median decrease: 76%). In contrast, fluticasone reduced plasmacytoid DC concentrations independently of salmeterol. There were no changes in the expression of function-associated surface molecules on myeloid DC (such as CD1a, Langerin, BDCA-1, CD83 or CCR5) in all groups after treatment. Fluticasone (either alone or in combination with salmeterol) suppressed T-cell proliferation in co-cultures with blood myeloid DCs from smokers.

Conclusions

Resistance to ICS monotherapy in smokers might in part be due to lacking effects on airway myeloid DCs, whereas the increased risk for infections during ICS therapy could be attributable to a reduction in plasmacytoid DCs. Combination therapy of fluticasone with salmeterol is associated with a reduction in airway myeloid DCs, but also airway macrophages and neutrophils.

Trial registration

Registered at ClinicalTrials.gov (identifier: NCT00908362) and the European Clinical Trial Database, EudraCT (identifier: 2009-009459-40).

The role of dendritic cells in the pathogenesis of cigarette smoke-induced emphysema in mice

Chronic Obstructive Pulmonary Disease (COPD) is an important lung and airway disease which affects the lives of around 200 million people worldwide. The pathological hallmark of COPD is emphysema and bronchiolitis and is based on the inflammatory response of the innate and adaptive immune system to the inhalation of toxic particles and gases. The inflamed airways of COPD patients contain several inflammatory cells including neutrophils, macrophages, T lymphocytes, and dendritic cells (DC). The potential role of DCs as mediators of inflammation in the airways of smokers and COPD patients is poorly understood. The current study investigated the role of DC subsets in an animal model of cigarette smoke-induced lung emphysema through the expansion or depletion of DC subsets. Expansion of both myeloid DC (mDC) and plasmacytoid DC (pDC) by Flt3L treatment induced a decline in macrophage numbers and increased the levels of fibroblast growth factor (FGF) and vascular endothelial growth factor (VEGF) in the bronchoalveolar lavage (BAL) fluid of smoke-exposed animals. The increase in the mean linear intercept (Lm) following Flt3L treatment was decreased by pDC depletion. In conclusion, pharmacological modulation of DC subsets may have an effect on the development of airway responses and emphysema as indicated by the decline in macrophage numbers and the increase in FGF and VEGF levels in the bronchoalveolar lavage fluid. Moreover, the depletion of pDCs decreased the Lm which might suggest a role for pDC in the pathogenesis of lung emphysema.

The dendritic cell niche in chronic obstructive pulmonary disease

The pulmonary innate immune system is heavily implicated in the perpetual airway inflammation and impaired host defense characterizing Chronic Obstructive Pulmonary Disease (COPD). The airways of patients suffering from COPD are infiltrated by various immune and inflammatory cells including macrophages, neutrophils, T lymphocytes, and dendritic cells. While the role of macrophages, neutrophils and T lymphocytes is well characterized, the contribution of dendritic cells to COPD pathogenesis is still the subject of emerging research. A paper by Botelho and colleagues in the current issue of Respiratory Research investigates the importance of dendritic cell recruitment in cigarette-smoke induced acute and chronic inflammation in mice. Dendritic cells of the healthy lung parenchyma and airways perform an important sentinel function and regulate immune homeostasis. During inflammatory responses the function and migration pattern of these cells is dramatically altered but the underlying mechanisms are incompletely understood. Botelho and colleagues demonstrate here the importance of IL-1R1/IL-1α related mechanisms including CCL20 production in cigarette-smoke induced recruitment of dendritic cells and T cell activation in the mouse lung.

Cigarette smoke-induced accumulation of lung dendritic cells is interleukin-1α-dependent in mice

Background

Evidence suggests that dendritic cells accumulate in the lungs of COPD patients and correlate with disease severity. We investigated the importance of IL-1R1 and its ligands IL-1α and β to dendritic cell accumulation and maturation in response to cigarette smoke exposure.

Methods

Mice were exposed to cigarette smoke using a whole body smoke exposure system. IL-1R1-, TLR4-, and IL-1α-deficient mice, as well as anti-IL-1α and anti-IL-1β blocking antibodies were used to study the importance of IL-1R1 and TLR4 to dendritic cell accumulation and activation.

Results

Acute and chronic cigarette smoke exposure led to increased frequency of lung dendritic cells. Accumulation and activation of dendritic cells was IL-1R1/IL-1α dependent, but TLR4- and IL-1β-independent. Corroborating the cellular data, expression of CCL20, a potent dendritic cells chemoattractant, was IL-1R1/IL-1α-dependent. Studies using IL-1R1 bone marrow-chimeric mice revealed the importance of IL-1R1 signaling on lung structural cells for CCL20 expression. Consistent with the importance of dendritic cells in T cell activation, we observed decreased CD4⁺ and CD8⁺ T cell activation in cigarette smoke-exposed IL-1R1-deficient mice.

Conclusion

Our findings convey the importance of IL-1R1/IL-1α to the recruitment and activation of dendritic cells in response to cigarette smoke exposure.

[Chronic obstructive pulmonary disease: an autoimmune disease?]

Chronic obstructive pulmonary disease (COPD) is an important cause of morbidity and mortality characterized by irreversible airflow limitation involving a reduced caliber of distal airways (less than 2mm) and alveolar destruction. Exposure to tobacco is a major risk factor for COPD, but all smokers do not develop the disease. In addition, there is continued progression of the disease several years after cessation of the exposure. To explain these phenomena, factors involving innate immunity including the release of neutrophil elastase, macrophage metalloproteases, in combination with pro-apoptotic factors, involved in the worsening of the lesions of emphysema and fibrosis of small airways have been described for many years. More recently, it has been proposed at an advanced stage of the disease that an autoimmune reaction directed mainly at elastin could participate to the pathogenesis of the disease. We here review the immunological processes and currently available data on autoimmunity in COPD.

[Structural abnormalities and inflammation in COPD: a focus on small airways]

Chronic obstructive pulmonary disease (COPD) is characterized by poorly reversible airflow limitation associated with airway remodelling and inflammation of both large and small airways. The site of airflow obstruction in COPD is located in the small airways, justifying a focus on this compartment. The structural abnormalities that are found in bronchioles with a diameter less than 2mm are characterized by increased airway wall thickness with peribronchial fibrosis, and by luminal obstruction by mucous exudates. Destruction of alveolar walls, the hallmark of emphysema, may be related to protease-antiprotease imbalance, and to mechanisms involving apoptosis, senescence, and autoimmunity. Cigarette smoke inhalation triggers the recruitment of innate immune cells (neutrophils and macrophages) and putatively adaptive immunity mediated via T and B lymphocytes and lymphoid follicles in the small airways. These data suggest a potential role for therapies that can target remodelling and inflammation in the small airways of patients with COPD.

Impact of smoking on inflammation: overview of molecular mechanisms

BACKGROUND

Inflammation is a critical component of normal tissue repair, as well as being fundamental to the body's defense against infection. Environmental factors, such as smoking, have been reported to modify the host response and hence modify inflammation progression, severity and outcome. Therefore, a comprehensive understanding of the molecular mechanisms by which smoking affects inflammation is vital for preventive and therapeutic strategies on a clinical level.

AIM

The purpose of the present article is to review the potential biological mechanisms by which smoking affects inflammation, emphasizing recent developments.

RESULTS

Smoking is reported to effect a number of biological mediators of inflammation through its effect on immune-inflammatory cells, leading to an immunosuppressant state. Recent evidence strongly suggests that the molecular mechanisms behind the modulation of inflammation by smoking mainly involve the nuclear factor-kappa B (NF-kB) family, through the activation of both an inhibitor of IkB kinase (IKK)-dependent and -independent pathway. In addition to NF-kB activation, a number of transcriptional factors including GATA, PAX5 and Smad 3/4, have also been implicated.

CONCLUSION

Multiple mechanisms may be responsible for the association of smoking and inflammation, and the identification of potential therapeutic targets should guide future research.

Current concepts on oxidative/carbonyl stress, inflammation and epigenetics in pathogenesis of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a global health problem. The current therapies for COPD are poorly effective and the mainstays of pharmacotherapy are bronchodilators. A better understanding of the pathobiology of COPD is critical for the development of novel therapies. In the present review, we have discussed the roles of oxidative/aldehyde stress, inflammation/immunity, and chromatin remodeling in the pathogenesis of COPD. An imbalance of oxidants/antioxidants caused by cigarette smoke and other pollutants/biomass fuels plays an important role in the pathogenesis of COPD by regulating redox-sensitive transcription factors (e.g., NF-κB), autophagy and unfolded protein response leading to chronic lung inflammatory response. Cigarette smoke also activates canonical/alternative NF-κB pathways and their upstream kinases leading to sustained inflammatory response in lungs. Recently, epigenetic regulation has been shown to be critical for the development of COPD because the expression/activity of enzymes that regulate these epigenetic modifications have been reported to be abnormal in airways of COPD patients. Hence, the significant advances made in understanding the pathophysiology of COPD as described herein will identify novel therapeutic targets for intervention in COPD.

Lung myeloid dendritic cells coordinately induce TH1 and TH17 responses in human emphysema

Exposure to tobacco smoke activates innate and adaptive immune responses that in long-term smokers have been linked to diseases of the lungs, cardiovascular system, joints, and other organs. The destruction of lung tissue that underlies smoking-induced emphysema has been associated with T helper 1 cells that recognize the matrix protein elastin. Factors that result in the development of such autoreactive T cells in smokers remain unknown but are crucial for further understanding the pathogenesis of systemic inflammatory diseases in smokers. Here, we show that lung myeloid dendritic cells were sufficient to induce T helper 1 and T helper 17 responses in CD4 T cells. T helper 1 and 17 cells are invariably present in lungs from patients with emphysema but not in lungs from normal individuals. Interleukin-17A, a canonical T helper 17 cytokine, enhanced secretion of CCL20, a chemoattractant for dendritic cells, and matrix metalloproteinase 12, a potent elastolytic proteinase, from lung macrophages. Thus, although diverse lung factors potentially contribute to T helper effector differentiation in vivo, lung myeloid dendritic cells direct the generation of pathogenic T cells and support a feedback mechanism that sustains both inflammatory cell recruitment and lung destruction. This mechanism may underlie disease in other elastin-rich organs and tissues.

Janus kinase-3 dependent inflammatory responses in allergic asthma

Allergic asthma is a chronic inflammatory condition of the lung characterized by reversible airway obstruction, high serum immunoglobulin (Ig) E levels, and chronic airway inflammation. A number of cells including mast cells, T cells, macrophages and dendritic cells play a role in the pathogenesis of the disease. Janus kinase (JAK)-3, a non-receptor protein tyrosine kinase, traditionally known to mediate cytokine signaling, also regulates functional responses of these cells. In this review the role of JAK-3 in regulating various pathogenic processes in allergic asthma is discussed. We propose that targeting JAK-3 is a rationale approach to control the inflammatory responses of multiple cell types responsible for the pathogenesis of allergic asthma.

Cigarette smoke promotes dendritic cell accumulation in COPD; a Lung Tissue Research Consortium study

BACKGROUND

Abnormal immune responses are believed to be highly relevant in the pathogenesis of chronic obstructive pulmonary disease (COPD). Dendritic cells provide a critical checkpoint for immunity by their capacity to both induce and suppress immunity. Although evident that cigarette smoke, the primary cause of COPD, significantly influences dendritic cell functions, little is known about the roles of dendritic cells in the pathogenesis of COPD.

METHODS

The extent of dendritic cell infiltration in COPD tissue specimens was determined using immunohistochemical localization of CD83+ cells (marker of matured myeloid dendritic cells), and CD1a+ cells (Langerhans cells). The extent of tissue infiltration with Langerhans cells was also determined by the relative expression of the CD207 gene in COPD versus control tissues. To determine mechanisms by which dendritic cells accumulate in COPD, complimentary studies were conducted using monocyte-derived human dendritic cells exposed to cigarette smoke extract (CSE), and dendritic cells extracted from mice chronically exposed to cigarette smoke.

RESULTS

In human COPD lung tissue, we detected a significant increase in the total number of CD83+ cells, and significantly higher amounts of CD207 mRNA when compared with control tissue. Human monocyte-derived dendritic cells exposed to CSE (0.1-2%) exhibited enhanced survival in vitro when compared with control dendritic cells. Murine dendritic cells extracted from mice exposed to cigarette smoke for 4 weeks, also demonstrated enhanced survival compared to dendritic cells extracted from control mice. Acute exposure of human dendritic cells to CSE induced the cellular pro-survival proteins heme-oxygenase-1 (HO-1), and B cell lymphoma leukemia-x(L) (Bcl-xL), predominantly through oxidative stress. Although activated human dendritic cells conditioned with CSE expressed diminished migratory CCR7 expression, their migration towards the CCR7 ligand CCL21 was not impaired.

CONCLUSIONS

These data indicate that COPD is associated with increased numbers of cells bearing markers associated with Langerhans cells and mature dendritic cells, and that cigarette smoke promotes survival signals and augments survival of dendritic cells. Although CSE suppressed dendritic cell CCR7 expression, migration towards a CCR7 ligand was not diminished, suggesting that reduced CCR7-dependent migration is unlikely to be an important mechanism for dendritic cell retention in the lungs of smokers with COPD.

Chronic cigarette smoke exposure primes NK cell activation in a mouse model of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a debilitating, progressive lung disease punctuated by exacerbations of symptoms. COPD exacerbations are most often associated with viral infections, and exposure to cigarette smoke (CS) followed by viral infection has been shown experimentally to enhance lung inflammation, tissue destruction, and airway fibrosis. Despite this, however, the cellular mechanisms responsible for this effect are unknown. In this study, we examined NK cell function in a mouse model of COPD given the vital role of NK cells following viral infection. Ex vivo stimulation of lung leukocytes with poly(I:C), ssRNA40, or ODN1826 enhanced production of NK cell-derived IFN-gamma in CS-exposed mice. NK cells from CS-exposed mice exhibited a novel form of priming; highly purified NK cells from CS-exposed mice, relative to NK cells from filtered air-exposed mice, produced more IFN-gamma following stimulation with IL-12, IL-18, or both. Further, NK cell priming was lost following smoking cessation. NKG2D stimulation through overexpression of Raet1 on the lung epithelium primed NK cell responsiveness to poly(I:C), ssRNA40, or ODN1826 stimulation, but not cytokine stimulation. In addition, NK cells from CS-exposed mice expressed more cell surface CD107a upon stimulation, demonstrating that the NK cell degranulation response was also primed. Together, these results reveal a novel mechanism of activation of the innate immune system and highlight NK cells as important cellular targets in controlling COPD exacerbations.

Lung dendritic cell expression of maturation molecules increases with worsening chronic obstructive pulmonary disease

RATIONALE

Dendritic cells (DCs) have not been well studied in chronic obstructive pulmonary disease (COPD), yet their integral role in activating and differentiating T cells makes them potential participants in COPD pathogenesis.

OBJECTIVES

To determine the expression of maturation molecules by individual DC subsets in relationship to COPD stage and to expression of the acute activation marker CD69 by lung CD4(+) T cells.

METHODS

We nonenzymatically released lung leukocytes from human surgical specimens (n = 42) and used flow cytometry to identify three DC subsets (mDC1, mDC2, and pDC) and to measure their expression of three costimulatory molecules (CD40, CD80 and CD86) and of CD83, the definitive marker of DC maturation. Spearman nonparametric correlation analysis was used to identify significant correlations between expression of DC maturation molecules and COPD severity.

MEASUREMENTS AND MAIN RESULTS

Expression of CD40 by mDC1 and mDC2 and of CD86 by mDC2 was high regardless of GOLD stage, but CD80 and CD83 on these two DC subsets increased with disease progression. pDC also showed significant increases in expression of CD40 and CD80. Expression of all but one of the DC molecules that increased with COPD severity also correlated with CD69 expression on lung CD4(+) T cells from the same patients, with the exception of CD83 on mDC2.

CONCLUSIONS

This cross-sectional study implies that COPD progression is associated with significant increases in costimulatory molecule expression by multiple lung DC subsets. Interactions with lung DCs may contribute to the immunophenotype of CD4(+) T cells in advanced COPD. Clinical trial registered with www.clinicaltrials.gov (NCT00281229).

Decreased small airway and alveolar CD83+ dendritic cells in COPD

BACKGROUND

Dendritic cells (DCs) have been reported to be increased in the small airways of patients with COPD, but the maturity status of these cells is unclear. We have quantified the numbers of cells expressing markers associated with DC maturation.

METHODS

Lung tissue was obtained at resection for lung cancer from 41 patients with COPD (30 current smokers and 11 ex-smokers; 32 steroid-treated patients and 9 steroid-naïve patients), 19 ex-smokers without COPD and 9 never-smokers without COPD. Tissue sections were immunostained for CD1a to mark immature DCs, and for CD83, fascin, and DC-lysosome-associated membrane protein (DC-LAMP) to delineate mature DCs.

RESULTS

The volume density (ie, the volume of DCs as the percentage volume of the airway wall) comprising CD83+ DCs was significantly reduced in patients with COPD (median, 0; range, 0 to 5.1%) vs smokers (median, 2.8%; range, 0 to 10.2%) and never-smokers (median, 1.9%; range, 0.8 to 5.1%) without COPD (p = 0.000 and 0.012, respectively). Using a semiquantitative score for the alveolar wall, CD83+ DCs also were decreased in patients with COPD (median, 0; range, 0 to 2%) vs smokers (median, 1%; range, 0 to 2%) and never-smokers (median, 1%; range, 0.7 to 2%) without COPD (p = 0.004 and 0.04, respectively). No differences were detected in CD83+ DCs between current smokers and ex-smokers with COPD or between steroid-treated and steroid-naive patients. No differences were detected in CD1a+ DCs. Fascin and DC-LAMP were found to have poor specificity for mature DCs.

CONCLUSIONS

COPD is associated with decreased numbers of (mature) CD83+ DCs in small airways and alveoli. The relevance of such a reduction on pulmonary immune responses requires further investigation.

The cytokine network in chronic obstructive pulmonary disease

Multiple cytokines play a role in the orchestration of inflammation in inflammatory airway diseases, such as chronic obstructive pulmonary disease, through the recruitment, activation and survival of inflammatory cells. Lymphokines secreted from T cells regulate the pattern of inflammation, whereas proinflammatory cytokines amplify and perpetuate the inflammatory response. Multiple chemokines recruit inflammatory cells from the circulation into the lungs and many growth factors maintain this inflammation and lead to characteristic structural changes in the airways. There are several therapeutic approaches that target cytokine-mediated inflammation in chronic obstructive pulmonary disease, but blocking specific cytokines may not provide clinical benefit, whereas broad-spectrum anti-inflammatory approaches are more likely to be clinically effective.

Organic dust exposure alters monocyte-derived dendritic cell differentiation and maturation

Organic dust exposure in agricultural animal environments results in airway diseases. Dendritic cells (DCs) orchestrate inflammatory immune response in the airways, but little is known about how organic dust affects differentiation and maturation of monocyte-derived immature and mature DCs (iDCs, mDCs). Peripheral blood monocytes were differentiated in vitro into iDCs with granulocyte-macrophage colony stimulating factor + IL-4 (6 days) with and without swine facility organic dust extract (ODE, 0.1%). Unlike control iDCs, ODE-conditioned iDCs maintained key monocyte properties (increased mCD14, increased phagocytic ability) while expressing DC features [increased mCD83, HLA-DR, CD80, CD86, diminished cytokine (TNF-alpha, IL-6) responsiveness]. At day 6, iDCs were cultured for an additional 48 h (days 7 and 8) with lipopolysaccharide (LPS) to induce mDCs. ODE-conditioned mDCs maintained high expression of mCD14(+) and elevated phagocytosis while their DC features weakened as evidenced by decreased CD11c, CD83, HLA-DR, CD86, and CCR7 expression and reduced lymphocyte-stimulating capacity. Similar results were observed when monocytes were exposed to ODE for only the first 48 h and with ODE depleted of endotoxin. Control iDCs exposed to ODE during the final 2 days of iDC maturation (days 7 and 8) did not differ from control (no ODE) iDCs in surface marker expression and phagocytic ability, but exhibited enhanced lymphocyte-stimulating capacity. Dust exposure alters monocyte differentiation to iDCs and prevents maturation of iDC to mDCs. The first 48 h of monocyte differentiation appears to be the susceptible period to exposure. Environmental exposures present during early monocyte differentiation may impact the critical balance of DCs in the lung.

Innate immune processes are sufficient for driving cigarette smoke-induced inflammation in mice

The objective of this study was to characterize the impact of cigarette smoke exposure on lung immune and inflammatory processes. BALB/c and C57BL/6 mice were exposed to cigarette smoke for 4 days (acute) or at least 5 weeks (prolonged). Both mouse strains manifested an inflammatory response after acute smoke exposure, characterized by an influx of neutrophils and mononuclear cells. Multiplex analysis revealed a greater than twofold increase of the cytokines IL-1alpha, -5, -6, and -18, as well as the chemokines monocyte chemotactic protein-1 and -3, macrophage inflammatory protein-1alpha, -beta, and -gamma, -2, -3beta, macrophage defined chemokine, granulocyte chemotactic protein-2, and interferon-gamma-inducible protein-10. In BALB/c mice, neutrophilia persisted after prolonged exposure, whereas C57BL/6 showed evidence of attenuated neutrophilia both in the bronchoalveolar lavage and the lungs. In both mouse strains, cigarette smoke exposure was associated with an expansion of mature (CD11c(hi)/major histocompatibility complex class II(hi)) myeloid dendritic cells; we observed no changes in plasmacytoid dendritic cells. Lymphocytes in the lungs displayed an activated phenotype that persisted for CD4 T cells only after prolonged exposure. In BALB/c mice, T cells acquired T helper (Th) 1 and Th2 effector function after 5 weeks of smoke exposure, whereas, in C57BL/6 mice, neither Th1 nor Th2 cells were detected. In both mouse strains, cigarette smoke exposure led to an accumulation of FoxP3+ T regulatory cells in the lungs. Studies in RAG1 knockout mice suggest that these regulatory cells may participate in controlling smoke-induced inflammation. Acute and prolonged cigarette smoke exposure was associated with inflammation, activation of the adaptive immune system, and expansion of T regulatory cells in the lungs.

How cigarette smoke skews immune responses to promote infection, lung disease and cancer

A complex and multilayered immune defence system protects the host against harmful agents and maintains tissue homeostasis. Cigarette smoke exposure markedly impacts the immune system, compromising the host's ability to mount appropriate immune and inflammatory responses and contributing to smoking-related pathologies. These adverse effects on the immune system not only occur in active smokers, but also in those exposed to smoke passively in contaminated environments, and may persist for decades after exposure has ended.

Between a cough and a wheeze: dendritic cells at the nexus of tobacco smoke-induced allergic airway sensitization

Exposure to cigarette smoke represents a major risk factor for the development of asthma. Enhanced sensitization toward allergens has been observed in humans and laboratory animals exposed to cigarette smoke. Pulmonary dendritic cells (DCs) are crucially involved in sensitization toward allergens and play an important role in the development of T helper (Th)2-mediated allergic airway inflammation. We propose the concept that aberrant DC activation forms the basis for the deviation of the lung's default tolerogenic response toward allergic inflammation when harmless antigens are concomittantly inhaled with tobacco smoke. This review will summarize evidence suggesting that tobacco smoke can achieve this effect by providing numerous triggers of innate immunity, which can profoundly modulate airway DC biology. Tobacco smoke can affect the airway DC network either directly or indirectly by causing the release of DC-targeted mediators from the pulmonary tissue environment, resulting in the induction of a Th2-oriented pathological immune response. A thorough knowledge of the molecular pathways involved may open the door to novel approaches in the treatment of asthma.