Inflammatory triggers associated with exacerbations of COPD orchestrate plasticity of group 2 innate lymphoid cells in the lungs.

Innate lymphoid cells (ILCs) are critical mediators of mucosal immunity, and group 1 ILCs (ILC1 cells) and group 3 ILCs (ILC3 cells) have been shown to be functionally plastic. Here we found that group 2 ILCs (ILC2 cells) also exhibited phenotypic plasticity in response to infectious or noxious agents, characterized by substantially lower expression of the transcription factor GATA-3 and a concomitant switch to being ILC1 cells that produced interferon-γ (IFN-γ). Interleukin 12 (IL-12) and IL-18 regulated this conversion, and during viral infection, ILC2 cells clustered within inflamed areas and acquired an ILC1-like phenotype. Mechanistically, these ILC1 cells augmented virus-induced inflammation in a manner dependent on the transcription factor T-bet. Notably, IL-12 converted human ILC2 cells into ILC1 cells, and the frequency of ILC1 cells in patients with chronic obstructive pulmonary disease (COPD) correlated with disease severity and susceptibility to exacerbations. Thus, functional plasticity of ILC2 cells exacerbates anti-viral immunity, which may have adverse consequences in respiratory diseases such as COPD.

IL-1ß, IL-4 and IL-12 control the fate of group 2 innate lymphoid cells in human airway inflammation in the lungs.

Group 2 innate lymphoid cells (ILC2s) secrete type 2 cytokines, which protect against parasites but can also contribute to a variety of inflammatory airway diseases. We report here that interleukin 1ß (IL-1ß) directly activated human ILC2s and that IL-12 induced the conversion of these activated ILC2s into interferon-γ (IFN-γ)-producing ILC1s, which was reversed by IL-4. The plasticity of ILCs was manifested in diseased tissues of patients with severe chronic obstructive pulmonary disease (COPD) or chronic rhinosinusitis with nasal polyps (CRSwNP), which displayed IL-12 or IL-4 signatures and the accumulation of ILC1s or ILC2s, respectively. Eosinophils were a major cellular source of IL-4, which revealed cross-talk between IL-5-producing ILC2s and IL-4-producing eosinophils. We propose that IL-12 and IL-4 govern ILC2 functional identity and that their imbalance results in the perpetuation of type 1 or type 2 inflammation.

Cigarette smoke silences innate lymphoid cell function and facilitates an exacerbated type I interleukin-33-dependent response to infection.

Cigarette smoking is a major risk factor for chronic obstructive pulmonary disease and is presumed to be central to the altered responsiveness to recurrent infection in these patients. We examined the effects of smoke priming underlying the exacerbated response to viral infection in mice. Lack of interleukin-33 (IL-33) signaling conferred complete protection during exacerbation and prevented enhanced inflammation and exaggerated weight loss. Mechanistically, smoke was required to upregulate epithelial-derived IL-33 and simultaneously alter the distribution of the IL-33 receptor ST2. Specifically, smoke decreased ST2 expression on group 2 innate lymphoid cells (ILC2s) while elevating ST2 expression on macrophages and natural killer (NK) cells, thus altering IL-33 responsiveness within the lung. Consequently, upon infection and release, increased local IL-33 significantly amplified type I proinflammatory responses via synergistic modulation of macrophage and NK cell function. Therefore, in COPD, smoke alters the lung microenvironment to facilitate an alternative IL-33-dependent exaggerated proinflammatory response to infection, exacerbating disease.

Oxidised IL-33 drives COPD epithelial pathogenesis via ST2-independent RAGE/EGFR signalling complex.

BACKGROUND: Epithelial damage, repair and remodelling are critical features of chronic airway diseases including chronic obstructive pulmonary disease (COPD). Interleukin (IL)-33 released from damaged airway epithelia causes inflammation via its receptor, serum stimulation-2 (ST2). Oxidation of IL-33 to a non-ST2-binding form (IL-33ox) is thought to limit its activity. We investigated whether IL-33ox has functional activities that are independent of ST2 in the airway epithelium. METHODS: In vitro epithelial damage assays and three-dimensional, air-liquid interface (ALI) cell culture models of healthy and COPD epithelia were used to elucidate the functional role of IL-33ox. Transcriptomic changes occurring in healthy ALI cultures treated with IL-33ox and COPD ALI cultures treated with an IL-33-neutralising antibody were assessed with bulk and single-cell RNA sequencing analysis. RESULTS: We demonstrate that IL-33ox forms a complex with receptor for advanced glycation end products (RAGE) and epidermal growth factor receptor (EGFR) expressed on airway epithelium. Activation of this alternative, ST2-independent pathway impaired epithelial wound closure and induced airway epithelial remodelling in vitro. IL-33ox increased the proportion of mucus-producing cells and reduced epithelial defence functions, mimicking pathogenic traits of COPD. Neutralisation of the IL-33ox pathway reversed these deleterious traits in COPD epithelia. Gene signatures defining the pathogenic effects of IL-33ox were enriched in airway epithelia from patients with severe COPD. CONCLUSIONS: Our study reveals for the first time that IL-33, RAGE and EGFR act together in an ST2-independent pathway in the airway epithelium and govern abnormal epithelial remodelling and muco-obstructive features in COPD.

RORγt inhibitors block both IL-17 and IL-22 conferring a potential advantage over anti-IL-17 alone to treat severe asthma.

BACKGROUND: RORγt is a transcription factor that enables elaboration of Th17-associated cytokines (including IL-17 and IL-22) and is proposed as a pharmacological target for severe asthma. METHODS: IL-17 immunohistochemistry was performed in severe asthma bronchial biopsies (specificity confirmed with in situ hybridization). Primary human small airway epithelial cells in air liquid interface and primary bronchial smooth muscle cells were stimulated with recombinant human IL-17 and/or IL-22 and pro-inflammatory cytokines measured. Balb/c mice were challenged intratracheally with IL-17 and/or IL-22 and airway hyperreactivity, pro-inflammatory cytokines and airway neutrophilia measured. Balb/c mice were sensitized intraperitoneally and challenged intratracheally with house dust mite extract and the effect of either a RORγt inhibitor (BIX119) or an anti-IL-11 antibody assessed on airway hyperreactivity, pro-inflammatory cytokines and airway neutrophilia measured. RESULTS: We confirmed in severe asthma bronchial biopsies both the presence of IL-17-positive lymphocytes and that an IL-17 transcriptome profile in a severe asthma patient sub-population. Both IL-17 and IL-22 stimulated the release of pro-inflammatory cytokine and chemokine release from primary human lung cells and in mice. Furthermore, IL-22 in combination with IL-17, but neither alone, elicits airway hyperresponsiveness (AHR) in naïve mice. A RORγt inhibitor specifically blocked both IL-17 and IL-22, AHR and neutrophilia in a mouse house dust mite model unlike other registered or advanced pipeline modes of action. Full efficacy versus these parameters was associated with 90% inhibition of IL-17 and 50% inhibition of IL-22. In contrast, anti-IL-17 also blocked IL-17, but not IL-22, AHR or neutrophilia. Moreover, the deregulated genes in the lungs from these mice correlated well with deregulated genes from severe asthma biopsies suggesting that this model recapitulates significant severe asthma-relevant biology. Furthermore, these genes were reversed upon RORγt inhibition in the HDM model. Cell deconvolution suggested that the responsible cells were corticosteroid insensitive γδ-T-cells. CONCLUSION: These data strongly suggest that both IL-17 and IL-22 are required for Th2-low endotype associated biology and that a RORγt inhibitor may provide improved clinical benefit in a severe asthma sub-population of patients by blocking both IL-17 and IL-22 biology compared with blocking IL-17 alone.

Basophil sensitivity reflects long-term clinical outcome of subcutaneous immunotherapy in grass pollen-allergic patients.

BACKGROUND: Allergic rhinoconjunctivitis is a public health problem. Allergen Immunotherapy is an effective and safe treatment, that modifies the natural course of allergic disease and induces long-term tolerance. OBJECTIVE: To correlate basophil and antibody biomarkers of subcutaneous immunotherapy to clinical outcomes and cellular changes in target tissue. METHODS: Adults suffering from allergic rhinoconjunctivitis due to grass pollen allergy were randomized to receive subcutaneous immunotherapy (n = 18) or to an open control group (n = 6). Patients reported daily symptom and medication scores and weekly rhinitis related quality of life scores during four pollen seasons. Biomarkers were measured every 3 months for three years treatment and every 6 months in the follow-up year. Nasal and cutaneous allergen challenge tests were performed annually. Leukocyte subsets were assessed in nasal mucosa biopsies at baseline and after treatment. RESULTS: Subcutaneous immunotherapy led to a 447-fold decrease in basophil sensitivity during the first treatment year. This remained 100-fold lower than baseline during the 3 year-treatment period and 10-fold lower during the follow-up year (n = 18, P = .03). Decrease in basophil sensitivity after three weeks of treatment predicted long-term improvement in seasonal combined symptom and medication scores (á¿¥=-0.69, P = .0027) during three years of treatment. AUC of IgE-blocking factor correlated to nasal allergen challenge (á¿¥ = 0.63, P = .0012) and SPT (á¿¥ = 0.45, P = .03). Plasma cell numbers in the nasal mucosa increased during treatment (P = .02). CONCLUSION: Decrease in basophil sensitivity after three weeks of subcutaneous allergen immunotherapy predicted the clinical outcome of this treatment.

Eosinophils, basophils and type 2 immune microenvironments in COPD-affected lung tissue.

Although elevated blood or sputum eosinophils are present in many patients with COPD, uncertainties remain regarding the anatomical distribution pattern of lung-infiltrating eosinophils. Basophils have remained virtually unexplored in COPD. This study mapped tissue-infiltrating eosinophils, basophils and eosinophil-promoting immune mechanisms in COPD-affected lungs.Surgical lung tissue and biopsies from major anatomical compartments were obtained from COPD patients with severity grades Global Initiative for Chronic Obstructive Lung Disease stages I-IV; never-smokers/smokers served as controls. Automated immunohistochemistry and in situ hybridisation identified immune cells, the type 2 immunity marker GATA3 and eotaxins (CCL11, CCL24).Eosinophils and basophils were present in all anatomical compartments of COPD-affected lungs and increased significantly in very severe COPD. The eosinophilia was strikingly patchy, and focal eosinophil-rich microenvironments were spatially linked with GATA3+ cells, including type 2 helper T-cell lymphocytes and type 2 innate lymphoid cells. A similarly localised and interleukin-33/ST2-dependent eosinophilia was demonstrated in influenza-infected mice. Both mice and patients displayed spatially confined eotaxin signatures with CCL11+ fibroblasts and CCL24+ macrophages.In addition to identifying tissue basophilia as a novel feature of advanced COPD, the identification of spatially confined eosinophil-rich type 2 microenvironments represents a novel type of heterogeneity in the immunopathology of COPD that is likely to have implications for personalised treatment.

IL-33 drives influenza-induced asthma exacerbations by halting innate and adaptive antiviral immunity.

BACKGROUND: Influenza virus triggers severe asthma exacerbations for which no adequate treatment is available. It is known that IL-33 levels correlate with exacerbation severity, but its role in the immunopathogenesis of exacerbations has remained elusive. OBJECTIVE: We hypothesized that IL-33 is necessary to drive asthma exacerbations. We intervened with the IL-33 cascade and sought to dissect its role, also in synergy with thymic stromal lymphopoietin (TSLP), in airway inflammation, antiviral activity, and lung function. We aimed to unveil the major source of IL-33 in the airways and IL-33-dependent mechanisms that underlie severe asthma exacerbations. METHODS: Patients with mild asthma were experimentally infected with rhinovirus. Mice were chronically exposed to house dust mite extract and then infected with influenza to resemble key features of exacerbations in human subjects. Interventions included the anti-IL-33 receptor ST2, anti-TSLP, or both. RESULTS: We identified bronchial ciliated cells and type II alveolar cells as a major local source of IL-33 during virus-driven exacerbation in human subjects and mice, respectively. By blocking ST2, we demonstrated that IL-33 and not TSLP was necessary to drive exacerbations. IL-33 enhanced airway hyperresponsiveness and airway inflammation by suppressing innate and adaptive antiviral responses and by instructing epithelial cells and dendritic cells of house dust mite-sensitized mice to dampen IFN-ß expression and prevent the TH1-promoting dendritic cell phenotype. IL-33 also boosted luminal NETosis and halted cytolytic antiviral activities but did not affect the TH2 response. CONCLUSION: Interventions targeting the IL-33/ST2 axis could prove an effective acute short-term therapy for virus-induced asthma exacerbations.

IL-33 blockade affects mediators of persistence and exacerbation in a model of chronic airway inflammation.

BACKGROUND: Severe inflammatory airway diseases are associated with inflammation that does not resolve, leading to structural changes and an overall environment primed for exacerbations. OBJECTIVE: We sought to identify and inhibit pathways that perpetuate this heightened inflammatory state because this could lead to therapies that allow for a more quiescent lung that is less predisposed to symptoms and exacerbations. METHODS: Using prolonged exposure to house dust mite in mice, we developed a mouse model of persistent and exacerbating airway disease characterized by a mixed inflammatory phenotype. RESULTS: We show that lung IL-33 drives inflammation and remodeling beyond the type 2 response classically associated with IL-33 signaling. IL-33 blockade with an IL-33 neutralizing antibody normalized established inflammation and improved remodeling of both the lung epithelium and lung parenchyma. Specifically, IL-33 blockade normalized persisting and exacerbating inflammatory end points, including eosinophilic, neutrophilic, and ST2+CD4+ T-cell infiltration. Importantly, we identified a key role for IL-33 in driving lung remodeling because anti-IL-33 also re-established the presence of ciliated cells over mucus-producing cells and decreased myofibroblast numbers, even in the context of continuous allergen exposure, resulting in improved lung function. CONCLUSION: Overall, this study shows that increased IL-33 levels drive a self-perpetuating amplification loop that maintains the lung in a state of lasting inflammation and remodeled tissue primed for exacerbations. Thus IL-33 blockade might ameliorate symptoms and prevent exacerbations by quelling persistent inflammation and airway remodeling.

Bronchoscopic mucosal cryobiopsies as a method for studying airway disease.

BACKGROUND: Investigating disease mechanisms and treatment responses in obstructive airway diseases with invasive sampling are hampered by the small size and mechanical artefacts that conventional forceps biopsies suffer from. Endoscopic cryobiopsies are larger and more intact and are being increasingly used. However, the technique has not yet been explored for obtaining mucosa biopsies. OBJECTIVE: To investigate differences in size and quality of endobronchial mucosal biopsies obtained with cryotechnique and forceps. Further, to check for eligibility of cryobiopsies to be evaluated with immunohistochemistry and in situ hybridization and to investigate tolerability and safety of the technique. METHODS: Endobronchial mucosal biopsies were obtained with cryotechnique and forceps from patients with haemoptysis undergoing bronchoscopy and evaluated by quantitative morphometry, automated immunohistochemistry and in situ hybridization. RESULTS: A total of 40 biopsies were obtained from 10 patients. Cross-sectional areas were threefold larger in cryobiopsies (median: 3.08 mm2 (IQR: 1.79) vs 1.03 mm2 (IQR: 1.10), P < 0.001). Stretches of intact epithelium were 8-fold longer (median: 4.61 mm (IQR: 4.50) vs 0.55 mm (IQR: 1.23), P = 0.001). Content of glands (median: 0.095 mm2 (IQR: 0.30) vs 0.00 mm2 (IQR: 0.01), P = 0.002) and airway smooth muscle (median: 0.25 mm2 (IQR: 0.30) vs 0.060 mm2 (IQR: 0.11), P = 0.02) was higher in the cryobiopsies compared with forceps biopsies. Further, the cryobiopsies had well-preserved protein antigens and mRNA. Mild to moderate bleeding was the only complication observed. CONCLUSION AND CLINICAL RELEVANCE: By yielding significantly larger and more intact biopsies, the cryotechnique represents a valuable new research tool to explore the bronchi in airway disease. Ultimately with the potential to create better understanding of underlying disease mechanisms and improvement of treatments.

Unravelling the complexity of tissue inflammation in uncontrolled and severe asthma.

PURPOSE OF REVIEW: The clinical and inflammatory heterogeneity in asthma constitutes a major challenge for improved treatment. This review describes the nature of the inflammatory complexity and how it can be decoded to yield improved disease understanding and personalized treatment. The focus is on the difficult task of revealing the immunological complexity as it occurs inside diseased patient tissues. RECENT FINDINGS: The inflammatory heterogeneity in asthma stretches beyond the classical division into allergic Th2 eosinophilic versus Th1 and/or Th17 neutrophilic (or paucigranulocytic) phenotypes. Rather than having one distinct type of inflammation, many patients display a patchwork of overlapping immune signatures. The patient diversity is further increased by differences in regard of distal lung involvement. Faced with this staggering complexity, calls have been made for a pragmatic biomarker-guided identification of treatable traits. In parallel, novel high-dimensional analyses and multiplex imaging aid the long-term goal of decoding the underlying molecular endotypes. SUMMARY: Asthma is vastly heterogeneous with multiple and superimposed inflammatory and anatomical phenotypes. Despite the intensive research and introduction of highly immune-selective dugs, basic questions remain; especially as still too many of today's uncontrolled patients remain poorly understood. Here, pragmatic biomarker strategies, combined with novel methodological approaches that ultimately reveal the complete immunological complexity, will pave the way for improved differential diagnosis and personalized medication.

Composition and functionality of the intrahepatic innate lymphoid cell-compartment in human nonfibrotic and fibrotic livers.

Human innate lymphoid cells have been described to exist in different organs, with functional deregulation of these cells contributing to several disease states. Here, we performed the first detailed characterization of the phenotype, tissue-residency properties, and functionality of ILC1s, ILC2s, and ILC3s in the human adult and fetal liver. In addition, we investigated changes in the ILC compartment in liver fibrosis. A unique composition of tissue-resident ILCs was observed in nonfibrotic livers as compared with that in mucosal tissues, with NKp44- ILC3s accounting for the majority of total intrahepatic ILCs. The frequency of ILC2s, representing a small fraction of ILCs in nonfibrotic livers, increased in liver fibrosis and correlated directly with the severity of the disease. Notably, intrahepatic ILC2s secreted the profibrotic cytokine IL-13 when exposed to IL-33 and thymic stromal lymphopoetin (TSLP); these cytokines were produced by hepatocytes, hepatic stellate cells (HSCs), and Kupffer cells in response to TLR-3 stimulation. In summary, the present results provide the first detailed characterization of intrahepatic ILCs in human adult and fetal liver. The results indicate a role for ILC2s in human liver fibrosis, implying that targeting ILC2s might be a novel therapeutic strategy for its treatment.

Intratumoural leukocyte infiltration is a prognostic indicator among pancreatic cancer patients with type 2 diabetes.

BACKGROUND: The life expectancy of pancreatic cancer patients remains minimal. The disease progression may be influenced by type 2 diabetes (T2D) and inflammatory status, although important gaps persist around their joint effects on disease outcome. The aim of this study was to investigate the clinical significance of the tumour immune microenvironment on pancreatic cancer prognosis in relation to T2D status. METHOD: Tumour-infiltrating macrophages, neutrophils and eosinophils were studied in primary pancreatic tumours and paired lymph node metastases in relation to patient and tumour characteristics, T2D status and overall survival in a retrospective cohort of patients with resectable pancreatic cancer in Sweden. RESULTS: Of the 80 included pancreatic cancer patients, 22 (27.2%) had T2D. The diabetic pancreatic cancer patients had significantly higher systemic high white blood cell count than those without diabetes (P = 0.028). Macrophage infiltration levels were higher in lymph node metastases compared with primary tumours (P = 0.040) among pancreatic cancer patients with diabetes. Type 2 diabetes or intra-tumoural leukocyte (macrophage, neutrophil or eosinophil) infiltration alone did not significantly influence pancreatic cancer prognosis. However, among cancer patients with T2D high macrophage or neutrophil tumour-infiltration was associated with a significant reduction in overall survival (adjusted hazard ratio [HR] 7.2; 95% CI 1.5-35.0 and HR 5.4; 95% CI 1.1-26.3, respectively). CONCLUSION: These results demonstrate associations between T2D and enhanced inflammatory processes with significant implications on survival among pancreatic cancer patients with T2D. Validation in larger independent patient cohorts may identify additional prognostic tools and improved treatment strategies for specific patient subsets.

Eosinophilic airway inflammation in asthmatic patients is associated with an altered airway microbiome.

BACKGROUND: Asthmatic patients have higher microbiome diversity and an altered composition, with more Proteobacteria and less Bacteroidetes compared with healthy control subjects. Studies comparing airway inflammation and the airway microbiome are sparse, especially in subjects not receiving anti-inflammatory treatment. OBJECTIVE: We sought to describe the relationship between the airway microbiome and patterns of airway inflammation in steroid-free patients with asthma and healthy control subjects. METHODS: Bronchoalveolar lavage fluid was collected from 23 steroid-free nonsmoking patients with asthma and 10 healthy control subjects. Bacterial DNA was extracted from and subjected to Illumina MiSeq sequencing of the 16S rDNA V4 region. Eosinophils and neutrophils in the submucosa were quantified by means of immunohistochemical identification and computerized image analysis. Induced sputum was obtained, and airway hyperresponsiveness to mannitol and fraction of exhaled nitric oxide values were measured. Relationships between airway microbial diversity and composition and inflammatory profiles were analyzed. RESULTS: In asthmatic patients airway microbial composition was associated with airway eosinophilia and AHR to mannitol but not airway neutrophilia. The overall composition of the airway microbiome of asthmatic patients with the lowest levels of eosinophils but not asthmatic patients with the highest levels of eosinophils deviated significantly from that of healthy subjects. Asthmatic patients with the lowest levels of eosinophils had an altered bacterial abundance profile, with more Neisseria, Bacteroides, and Rothia species and less Sphingomonas, Halomonas, and Aeribacillus species compared with asthmatic patients with more eosinophils and healthy control subjects. CONCLUSION: The level of eosinophilic airway inflammation correlates with variations in the microbiome across asthmatic patients, whereas neutrophilic airway inflammation does not. This warrants further investigation on molecular pathways involved in both patients with eosinophilic and those with noneosinophilic asthma.

Effectiveness of bronchial thermoplasty in patients with severe refractory asthma: Clinical and histopathologic correlations.

BACKGROUND: The effectiveness of bronchial thermoplasty (BT) has been reported in patients with severe asthma, yet its effect on different bronchial structures remains unknown. OBJECTIVE: We sought to examine the effect of BT on bronchial structures and to explore the association with clinical outcome in patients with severe refractory asthma. METHODS: Bronchial biopsy specimens (n = 300) were collected from 15 patients with severe uncontrolled asthma before and 3 months after BT. Immunostained sections were assessed for airway smooth muscle (ASM) area, subepithelial basement membrane thickness, nerve fibers, and epithelial neuroendocrine cells. Histopathologic findings were correlated with clinical parameters. RESULTS: BT significantly improved asthma control and quality of life at both 3 and 12 months and decreased the numbers of severe exacerbations and the dose of oral corticosteroids. At 3 months, this clinical benefit was accompanied by a reduction in ASM area (median values before and after BT, respectively: 19.7% [25th-75th interquartile range (IQR), 15.9% to 22.4%] and 5.3% [25th-75th IQR], 3.5% to 10.1%, P < .001), subepithelial basement membrane thickening (4.4 µm [25th-75th IQR, 4.0-4.7 µm] and 3.9 µm [25th-75th IQR, 3.7-4.6 µm], P = 0.02), submucosal nerves (1.0 ‰ [25th-75th IQR, 0.7-1.3 ‰] immunoreactivity and 0.3 ‰ [25th-75th IQR, 0.1-0.5 ‰] immunoreactivity, P < .001), ASM-associated nerves (452.6 [25th-75th IQR, 196.0-811.2] immunoreactive pixels per mm2 and 62.7 [25th-75th IQR, 0.0-230.3] immunoreactive pixels per mm2, P = .02), and epithelial neuroendocrine cells (4.9/mm2 [25th-75th IQR, 0-16.4/mm2] and 0.0/mm2 [25th-75th IQR, 0-0/mm2], P = .02). Histopathologic parameters were associated based on Asthma Control Test scores, numbers of exacerbations, and visits to the emergency department (all P ≤ .02) 3 and 12 months after BT. CONCLUSION: BT is a treatment option in patients with severe therapy-refractory asthma that downregulates selectively structural abnormalities involved in airway narrowing and bronchial reactivity, particularly ASM, neuroendocrine epithelial cells, and bronchial nerve endings.

IL-18 associated with lung lymphoid aggregates drives IFNγ production in severe COPD.

BACKGROUND: Increased interferon gamma (IFNγ) release occurs in Chronic Obstructive Pulmonary Disease (COPD) lungs. IFNγ supports optimal viral clearance, but if dysregulated could increase lung tissue destruction. METHODS: The present study investigates which mediators most closely correlate with IFNγ in sputum in stable and exacerbating disease, and seeks to shed light on the spatial requirements for innate production of IFNγ, as reported in mouse lymph nodes, to observe whether such microenvironmental cellular organisation is relevant to IFNγ production in COPD lung. RESULTS: We show tertiary follicle formation in severe disease alters the dominant mechanistic drivers of IFNγ production, because cells producing interleukin-18, a key regulator of IFNγ, are highly associated with such structures. Interleukin-1 family cytokines correlated with IFNγ in COPD sputum. We observed that the primary source of IL-18 in COPD lungs was myeloid cells within lymphoid aggregates and IL-18 was increased in severe disease. IL-18 released from infected epithelium or from activated myeloid cells, was more dominant in driving IFNγ when IL-18-producing and responder cells were in close proximity. CONCLUSIONS: Unlike tight regulation to control infection spread in lymphoid organs, this local interface between IL-18-expressing and responder cell is increasingly supported in lung as disease progresses, increasing its potential to increase tissue damage via IFNγ.

Increased IL-17RA and IL-17RC in End-Stage COPD and the Contribution to Mast Cell Secretion of FGF-2 and VEGF.

Mast cells are accumulated in advanced chronic obstructive pulmonary disease (COPD), and interleukin (IL)-17 signaling plays a role in disease progression. The expression, localization and functional relevance of IL-17 receptor (R)A and IL-17RC was explored in COPD by immunodetection, and functional assays.IL-17RA and IL-17RC was increased in very severe COPD, and expressed by mast cells. Increased secretion of the pro-angiogenic basic fibroblast growth factor and vascular endothelial growth factor was observed in vitro-maintained mast cells stimulated with IL-17A. Expression of these mediators was confirmed in end-stage COPD. Thus, accumulation of mast cells in COPD may contribute to vascular remodeling.

IL-17A Is Elevated in End-Stage Chronic Obstructive Pulmonary Disease and Contributes to Cigarette Smoke-induced Lymphoid Neogenesis.

RATIONALE: End-stage chronic obstructive pulmonary disease (COPD) is associated with an accumulation of pulmonary lymphoid follicles. IL-17A is implicated in COPD and pulmonary lymphoid neogenesis in response to microbial stimuli. We hypothesized that IL-17A is increased in peripheral lung tissue during end-stage COPD and also directly contributes to cigarette smoke-induced lymphoid neogenesis. OBJECTIVES: To characterize the tissue expression and functional role of IL-17A in end-stage COPD. METHODS: Automated immune detection of IL-17A and IL-17F was performed in lung tissue specimens collected from patients with Global Initiative for Chronic Obstructive Lung Disease stage I-IV COPD, and smoking and never-smoking control subjects. In parallel, Il17a(-/-) mice and wild-type control animals were exposed to cigarette smoke for 24 weeks, and pulmonary lymphoid neogenesis was assessed. MEASUREMENTS AND MAIN RESULTS: Tissue expression of IL-17A and IL-17F was increased in COPD and correlated with lung function decline. IL-17A was significantly elevated in severe to very severe COPD (Global Initiative for Chronic Obstructive Lung Disease III/IV) compared with both smokers and never-smokers without COPD. Although CD3(+) T cells expressed IL-17A in very severe COPD, most IL-17A(+) cells were identified as tryptase-positive mast cells. Attenuated lymphoid neogenesis and reduced expression of the B-cell attracting chemokine C-X-C motif ligand (CXCL) 12 was observed in cigarette smoke-exposed Il17a(-/-) mice. CXCL12 was also highly expressed in lymphoid follicles in COPD lungs, and the pulmonary expression was significantly elevated in end-stage COPD. CONCLUSIONS: IL-17A in the peripheral lung of patients with severe to very severe COPD may contribute to disease progression and development of lymphoid follicles via activation of CXCL12.

IL-17A and the Promotion of Neutrophilia in Acute Exacerbation of Chronic Obstructive Pulmonary Disease.

RATIONALE: Nontypeable Haemophilus influenzae (NTHi) causes acute exacerbation of chronic obstructive pulmonary disease (AECOPD). IL-17A is central for neutrophilic inflammation and has been linked to COPD pathogenesis. OBJECTIVES: We investigated whether IL-17A is elevated in NTHi-associated AECOPD and required for NTHi-exacerbated pulmonary neutrophilia induced by cigarette smoke. METHODS: Experimental studies with cigarette smoke and NTHi infection were pursued in gene-targeted mice and using antibody intervention. IL-17A was measured in sputum collected from patients with COPD at baseline, during, and after AECOPD. MEASUREMENTS AND MAIN RESULTS: Exacerbated airway neutrophilia in cigarette smoke-exposed mice infected with NTHi was associated with an induction of IL-17A. In agreement, elevated IL-17A was observed in sputum collected during NTHi-associated AECOPD, compared with samples collected before or after the event. NTHi-exacerbated neutrophilia and induction of neutrophil chemoattractants over the background of cigarette smoke, as observed in wild-type mice, was absent in Il17a(-/-) mice and in mice treated with a neutralizing anti-IL-17A antibody. Further studies revealed that IL-1 receptor (R)1 signaling was required for IL-17A-dependent neutrophilia. Moreover, deficiency or therapeutic neutralization of IL-17A did not increase bacterial burden or delay bacterial clearance. CONCLUSIONS: IL-17A is induced during NTHi-associated AECOPD. Functionally, IL-1R1-dependent IL-17A is required for NTHi-exacerbated pulmonary neutrophilia induced by cigarette smoke. Targeting IL-17A in AECOPD may thus be beneficial to reduce neutrophil recruitment to the airways.