A Th17- and Th2-skewed cytokine profile in cystic fibrosis lungs represents a potential risk factor for Pseudomonas aeruginosa infection

Reduced bone volumetric density and weak correlation between infection and bone markers in cystic fibrosis adult patients

In our current adult CF population, low BMD prevalence was only 20 %, lower than that historically described. We found a mild increase of serum RANK-L levels, independent from the bone resorption level. The increased fracture risk in CF may be explained by a lower tibial cortical thickness and total vBMD.

INTRODUCTION

Bone disease is now well described in cystic fibrosis (CF) adult patients. CF bone disease is multifactorial but many studies suggested the crucial role of inflammation. The objectives of this study were, in a current adult CF population, to assess the prevalence of bone disease, to examine its relationship with infections and inflammation, and to characterize the bone microarchitecture using high resolution peripheral scanner (HR-pQCT).

METHODS

Fifty-six patients (52 % men, 26 ± 7 years) were assessed in clinically stable period, during a respiratory infection, and finally 14 days after the end of antibiotic therapy. At each time points, we performed a clinical evaluation, lung function tests, and biochemical tests. Absorptiometry and dorso-lumbar radiographs were also performed. A subgroup of 40 CF patients (63 % men, 29 ± 6 years) underwent bone microarchitecture assessment and was age- and gender-matched with 80 healthy controls.

RESULTS

Among the 56 CF patients, the prevalence of low areal BMD (T-score < -2 at any site), was 20 % (95 % CI: [10.2 %; 32.4 %]). After infections, serum RANK-L (+24 %, p = 0.08) and OPG (+13 %, p = 0.04) were increased with a stable ratio. Microarchitectural differences were mostly observed at the distal tibia, with lower total and cortical vBMD and trabecular thickness (respectively -9.9, -3.0, and -5 %, p < 0.05) in CF patients compared to controls, after adjustment for age, gender, weight, and height.

CONCLUSIONS

In this study, bone disease among adult CF patients was less severe than that previously described with only 20 % of CF patients with low BMD. We found a mild increase of biological marker levels and an impaired volumetric density of the tibia that may explain the increased fracture risk in CF population.

Interleukin-17A Is Associated With Alveolar Inflammation and Poor Outcomes in Acute Respiratory Distress Syndrome

OBJECTIVE

Interleukin-17A is a proinflammatory cytokine known to play a role in host defense and pathologic inflammation in murine models of lung injury. The relationship between interleukin-17A and inflammation in human lung injury is unknown. Our primary objective was to determine whether interleukin-17A levels are associated with alveolar measures of inflammation and injury in patients with acute respiratory distress syndrome. Our secondary objective was to test whether interleukin-17A levels are associated with acute respiratory distress syndrome-related outcomes.

DESIGN

Observational study.

SETTING

Six North American medical centers.

PATIENTS

We studied two groups of patients with acute respiratory distress syndrome: 1) patients previously enrolled in a placebo-controlled clinical trial of omega-3 fatty acids performed at five North American medical centers (n = 86, acute respiratory distress syndrome 1), and 2) patients with systemic inflammatory response syndrome admitted to an ICU who developed acute respiratory distress syndrome (n = 140, acute respiratory distress syndrome 2). In acute respiratory distress syndrome 1, we used paired serum and bronchoalveolar lavage fluid samples obtained within 48 hours of acute respiratory distress syndrome onset, whereas in acute respiratory distress syndrome 2, we used plasma obtained within the first 24 hours of ICU admission.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We measured circulating interleukin-17A in acute respiratory distress syndrome 1 and acute respiratory distress syndrome 2. We also measured interleukin-17A, neutrophil counts, and total protein in bronchoalveolar lavage fluid from acute respiratory distress syndrome 1. We found that bronchoalveolar lavage interleukin-17A was strongly associated with higher bronchoalveolar lavage percent neutrophils (p < 0.001) and bronchoalveolar lavage total protein (p < 0.01) in acute respiratory distress syndrome1. In both acute respiratory distress syndrome 1 and acute respiratory distress syndrome 2, elevated interleukin-17A was associated with higher Sequential Organ Failure Assessment scores (p < 0.05).

CONCLUSIONS

Elevated circulating and alveolar levels of interleukin-17A are associated with increased percentage of alveolar neutrophils, alveolar permeability, and organ dysfunction in acute respiratory distress syndrome.

Immunity against Fungal Infections

Fungal diseases are major causes of morbidity and mortality among the immunocompromised, including HIV-infected individuals and patients with cancer. Individuals without a weakened immune system can also suffer from these infections. Not surprisingly, fungi are a major target for the immune system, rendered visible to it by expression of pathogen-associated molecular patterns/signatures. We now appreciate the roles of both innate and adaptive immunity in eliminating fungal infections, and how a disproportionate or inadequate immune response can diminish the host's capacity to eliminate fungi. This review focuses on our current understanding of the roles of innate and adaptive immunity in clearing common and emergent fungal pathogens. A clearer understanding of how the host's immune response tackles fungal infection may provide useful clues as to how we might develop new agents to treat those diseases in the future.

IL-17A impairs host tolerance during airway chronic infection by Pseudomonas aeruginosa

Resistance and tolerance mechanisms participate to the interplay between host and pathogens. IL-17-mediated response has been shown to be crucial for host resistance to respiratory infections, whereas its role in host tolerance during chronic airway colonization is still unclear. Here, we investigated whether IL-17-mediated response modulates mechanisms of host tolerance during airways chronic infection by P. aeruginosa. First, we found that IL-17A levels were sustained in mice at both early and advanced stages of P. aeruginosa chronic infection and confirmed these observations in human respiratory samples from cystic fibrosis patients infected by P. aeruginosa. Using IL-17a^−/− or IL-17ra^−/− mice, we found that the deficiency of IL-17A/IL-17RA axis was associated with: i) increased incidence of chronic infection and bacterial burden, indicating its role in the host resistance to P. aeruginosa; ii) reduced cytokine levels (KC), tissue innate immune cells and markers of tissue damage (pro-MMP-9, elastin degradation, TGF-β₁), proving alteration of host tolerance. Blockade of IL-17A activity by a monoclonal antibody, started when chronic infection is established, did not alter host resistance but increased tolerance. In conclusion, this study identifies IL-17-mediated response as a negative regulator of host tolerance during P. aeruginosa chronic airway infection.

Bone disease in cystic fibrosis: new pathogenic insights opening novel therapies

Mutations within the gene encoding for the chloride ion channel cystic fibrosis transmembrane conductance regulator (CFTR) results in cystic fibrosis (CF), the most common lethal autosomal recessive genetic disease that causes a number of long-term health problems, as the bone disease. Osteoporosis and increased vertebral fracture risk associated with CF disease are becoming more important as the life expectancy of patients continues to improve. The etiology of low bone density is multifactorial, most probably a combination of inadequate peak bone mass during puberty and increased bone losses in adults. Body mass index, male sex, advanced pulmonary disease, malnutrition and chronic therapies are established additional risk factors for CF-related bone disease (CFBD). Consistently, recent evidence has confirmed that CFTR plays a major role in the osteoprotegerin (OPG) and COX-2 metabolite prostaglandin E2 (PGE2) production, two key regulators in the bone formation and regeneration. Several others mechanisms were also recognized from animal and cell models contributing to malfunctions of osteoblast (cell that form bone) and indirectly of bone-resorpting osteoclasts. Understanding such mechanisms is crucial for the development of therapies in CFBD. Innovative therapeutic approaches using CFTR modulators such as C18 have recently shown in vitro capacity to enhance PGE2 production and normalized the RANKL-to-OPG ratio in human osteoblasts bearing the mutation F508del-CFTR and therefore potential clinical utility in CFBD. This review focuses on the recently identified pathogenic mechanisms leading to CFBD and potential future therapies for treating CFBD.

The IL-17A/IL-17RA axis in pulmonary defence and immunopathology

The interleukin (IL)-17A/IL-17 receptor A (IL-17RA) axis is emerging as a key player in host defence. Several studies have demonstrated that IL-17A-mediated responses play a critical role in both acute and chronic inflammation induced by infectious agents, environmental stimuli and genetic diseases in the airways. In this regard, it is becoming evident that IL-17A/IL-17RA signalling may have a protective and beneficial impact on health, but that it can also result in detrimental outcomes. On one hand, the IL-17A/IL-17RA axis can contribute to the elimination of noxious stimuli and to the resolution of acute inflammatory processes; on the other hand, it can exacerbate immunopathological responses, contributing to the development and progression of chronic respiratory illnesses. In addition, cellular and molecular signatures underlying IL-17A/IL-17RA signalling have been increasingly identified, although further studies are needed to clarify such complex responses. Here, we discuss the latest discoveries on the role of the IL-17A/IL-17RA axis in driving host pulmonary defence and immunopathology.

Modulating Innate and Adaptive Immunity by (R)-Roscovitine: Potential Therapeutic Opportunity in Cystic Fibrosis

(R)-Roscovitine, a pharmacological inhibitor of kinases, is currently in phase II clinical trial as a drug candidate for the treatment of cancers, Cushing's disease and rheumatoid arthritis. We here review the data that support the investigation of (R)-roscovitine as a potential therapeutic agent for the treatment of cystic fibrosis (CF). (R)-Roscovitine displays four independent properties that may favorably combine against CF: (1) it partially protects F508del-CFTR from proteolytic degradation and favors its trafficking to the plasma membrane; (2) by increasing membrane targeting of the TRPC6 ion channel, it rescues acidification in phagolysosomes of CF alveolar macrophages (which show abnormally high pH) and consequently restores their bactericidal activity; (3) its effects on neutrophils (induction of apoptosis), eosinophils (inhibition of degranulation/induction of apoptosis) and lymphocytes (modification of the Th17/Treg balance in favor of the differentiation of anti-inflammatory lymphocytes and reduced production of various interleukins, notably IL-17A) contribute to the resolution of inflammation and restoration of innate immunity, and (4) roscovitine displays analgesic properties in animal pain models. The fact that (R)-roscovitine has undergone extensive preclinical safety/pharmacology studies, and phase I and II clinical trials in cancer patients, encourages its repurposing as a CF drug candidate.

Bronchiectasis: Current Concepts in Pathogenesis, Immunology, and Microbiology

Bronchiectasis is a disorder of persistent lung inflammation and recurrent infection, defined by a common pathological end point: irreversible bronchial dilatation arrived at through diverse etiologies. This suggests an interplay between immunogenetic susceptibility, immune dysregulation, bacterial infection, and lung damage. The damaged epithelium impairs mucus removal and facilitates bacterial infection with increased cough, sputum production, and airflow obstruction. Lung infection is caused by respiratory bacterial and fungal pathogens, including Pseudomonas aeruginosa, Haemophilus, Aspergillus fumigatus, and nontuberculous mycobacteria. Recent studies have highlighted the relationship between the lung microbiota and microbial-pathogen niches. Disease may result from environments favoring interleukin-17-driven neutrophilia. Bronchiectasis may present in autoimmune disease, as well as conditions of immune dysregulation, such as combined variable immune deficiency, transporter associated with antigen processing-deficiency syndrome, and hyperimmunoglobulin E syndrome. Differences in prevalence across geography and ethnicity implicate an etiological mix of genetics and environment underpinning susceptibility.

Innate Immune Signaling Activated by MDR Bacteria in the Airway

Health care-associated bacterial pneumonias due to multiple-drug resistant (MDR) pathogens are an important public health problem and are major causes of morbidity and mortality worldwide. In addition to antimicrobial resistance, these organisms have adapted to the milieu of the human airway and have acquired resistance to the innate immune clearance mechanisms that normally prevent pneumonia. Given the limited efficacy of antibiotics, bacterial clearance from the airway requires an effective immune response. Understanding how specific airway pathogens initiate and regulate innate immune signaling, and whether this response is excessive, leading to host-induced pathology may guide future immunomodulatory therapy. We will focus on three of the most important causes of health care-associated pneumonia, Staphylococcus aureus, Pseudomonas aeruginosa, and Klebsiella pneumoniae, and review the mechanisms through which an inappropriate or damaging innate immune response is stimulated, as well as describe how airway pathogens cause persistent infection by evading immune activation.

Effect of treatment of cystic fibrosis pulmonary exacerbations on systemic inflammation

RATIONALE

In cystic fibrosis (CF), pulmonary exacerbations present an opportunity to define the effect of antibiotic therapy on systemic measures of inflammation.

OBJECTIVES

Investigate whether plasma inflammatory proteins demonstrate and predict a clinical response to antibiotic therapy and determine which proteins are associated with measures of clinical improvement.

METHODS

In this multicenter study, a panel of 15 plasma proteins was measured at the onset and end of treatment for pulmonary exacerbation and at a clinically stable visit in patients with CF who were 10 years of age or older.

MEASUREMENTS AND MAIN RESULTS

Significant reductions in 10 plasma proteins were observed in 103 patients who had paired blood collections during antibiotic treatment for pulmonary exacerbations. Plasma C-reactive protein, serum amyloid A, calprotectin, and neutrophil elastase antiprotease complexes correlated most strongly with clinical measures at exacerbation onset. Reductions in C-reactive protein, serum amyloid A, IL-1ra, and haptoglobin were most associated with improvements in lung function with antibiotic therapy. Having higher IL-6, IL-8, and α1-antitrypsin (α1AT) levels at exacerbation onset were associated with an increased risk of being a nonresponder (i.e., failing to recover to baseline FEV1). Baseline IL-8, neutrophil elastase antiprotease complexes, and α1AT along with changes in several plasma proteins with antibiotic treatment, in combination with FEV1 at exacerbation onset, were predictive of being a treatment responder.

CONCLUSIONS

Circulating inflammatory proteins demonstrate and predict a response to treatment of CF pulmonary exacerbations. A systemic biomarker panel could speed up drug discovery, leading to a quicker, more efficient drug development process for the CF community.

Streptomycin treatment alters the intestinal microbiome, pulmonary T cell profile and airway hyperresponsiveness in a cystic fibrosis mouse model

Cystic fibrosis transmembrane conductance regulator deficient mouse models develop phenotypes of relevance to clinical cystic fibrosis (CF) including airway hyperresponsiveness, small intestinal bacterial overgrowth and an altered intestinal microbiome. As dysbiosis of the intestinal microbiota has been recognized as an important contributor to many systemic diseases, herein we investigated whether altering the intestinal microbiome of BALB/c Cftr(tm1UNC) mice and wild-type littermates, through treatment with the antibiotic streptomycin, affects the CF lung, intestinal and bone disease. We demonstrate that streptomycin treatment reduced the intestinal bacterial overgrowth in Cftr(tm1UNC) mice and altered the intestinal microbiome similarly in Cftr(tm1UNC) and wild-type mice, principally by affecting Lactobacillus levels. Airway hyperresponsiveness of Cftr(tm1UNC) mice was ameliorated with streptomycin, and correlated with Lactobacillus abundance in the intestine. Additionally, streptomycin treated Cftr(tm1UNC) and wild-type mice displayed an increased percentage of pulmonary and mesenteric lymph node Th17, CD8 + IL-17+ and CD8 + IFNγ+ lymphocytes, while the CF-specific increase in respiratory IL-17 producing γδ T cells was decreased in streptomycin treated Cftr(tm1UNC) mice. Bone disease and intestinal phenotypes were not affected by streptomycin treatment. The airway hyperresponsiveness and lymphocyte profile of BALB/c Cftr(tm1UNC) mice were affected by streptomycin treatment, revealing a potential intestinal microbiome influence on lung response in BALB/c Cftr(tm1UNC) mice.

The neutrophil-recruiting chemokine GCP-2/CXCL6 is expressed in cystic fibrosis airways and retains its functional properties after binding to extracellular DNA

Infections in cystic fibrosis (CF), often involving Pseudomonas aeruginosa, result from a dysregulated airway immunity where one hallmark is the accumulation of necrotic and apoptotic immune cells, in particular neutrophils. In addition, neutrophils actively release DNA, forming neutrophil extracellular traps (NETs) that contain antimicrobial proteins. Altogether, free DNA in complex with actin accumulates in the airway lumen, resulting in highly viscous sputum that provides an anionic matrix, binding cationic antimicrobial proteins. In this study, granulocyte chemotactic protein 2 (GCP-2)/CXCL6, a neutrophil-activating chemokine with bactericidal properties, was detected in the airway epithelium of CF patients and was also present in azurophilic and specific granules of neutrophils. Elastase of neutrophils, but not of P. aeruginosa, completely degraded CXCL6 (chemokine (C-X-C motif) ligand 6). In addition, CXCL6 colocalized with extracellular DNA in both CF sputa and in in vitro-formed NETs. In vitro, CXCL6 bound DNA with a KD of 2,500 nM. Interestingly, both the bactericidal and the receptor-activating properties of CXCL6 (against neutrophils) remained largely unaffected in the presence of DNA. However, the chemotactic properties of CXCL6 were reduced by the presence of DNA. Taken together, CXCL6 is expressed in CF, retaining its functional properties even after binding to the anionic scaffold that extracellular DNA provides in CF.

Inflammation and its genesis in cystic fibrosis

The host inflammatory response in cystic fibrosis (CF) lung disease has long been recognized as a central pathological feature and an important therapeutic target. Indeed, many believe that bronchiectasis results largely from the oxidative and proteolytic damage comprised within an exuberant airway inflammatory response that is dominated by neutrophils. In this review, we address the longstanding argument of whether or not the inflammatory response is directly attributable to impairment of the cystic fibrosis transmembrane conductance regulator or only secondary to airway obstruction and chronic bacterial infection and challenge the importance of this distinction in the context of therapy. We also review the centrality of neutrophils in CF lung pathophysiology and highlight more recent data that suggest the importance of other cell types and signaling beyond NF-κB activation. We discuss how protease and redox imbalance are critical factors in CF airway inflammation and end by reviewing some of the more promising therapeutic approaches now under development.

Regulatory T-cell impairment in cystic fibrosis patients with chronic pseudomonas infection

RATIONALE

Patients with cystic fibrosis (CF) lung disease have chronic airway inflammation driven by disrupted balance of T-cell (Th17 and Th2) responses. Regulatory T cells (Tregs) dampen T-cell activation, but their role in CF is incompletely understood.

OBJECTIVES

To characterize numbers, function, and clinical impact of Tregs in CF lung disease.

METHODS

Tregs were quantified in peripheral blood and airway samples from patients with CF and from lung disease control patients without CF and healthy control subjects. The role of Pseudomonas aeruginosa and CF transmembrane conductance regulator (CFTR) in Treg regulation was analyzed by using in vitro and murine in vivo models.

MEASUREMENTS AND MAIN RESULTS

Tregs were decreased in peripheral blood and airways of patients with CF compared with healthy controls or lung disease patients without CF and correlated positively with lung function parameters. Patients with CF with chronic P. aeruginosa infection had lower Tregs compared with patients with CF without P. aeruginosa infection. Genetic knockout, pharmacological inhibition, and P. aeruginosa infection studies showed that both P. aeruginosa and CFTR contributed to Treg dysregulation in CF. Functionally, Tregs from patients with CF or from Cftr(-/-) mice were impaired in suppressing conventional T cells, an effect that was enhanced by P. aeruginosa infection. The loss of Tregs in CF affected memory, but not naive Tregs, and manifested gradually with disease progression.

CONCLUSIONS

Patients with CF who have chronic P. aeruginosa infection show an age-dependent, quantitative, and qualitative impairment of Tregs. Modulation of Tregs represents a novel strategy to rebalance T-cell responses, dampen inflammation, and ultimately improve outcomes for patients with infective CF lung disease.

Chronic Infection by Mucoid Pseudomonas aeruginosa Associated with Dysregulation in T-Cell Immunity to Outer Membrane Porin F

RATIONALE

Pseudomonas aeruginosa (PA) is an environmental pathogen that commonly infects individuals with cystic fibrosis (CF) and non-CF bronchiectasis, impacting morbidity and mortality. To understand the pathobiology of interactions between the bacterium and host adaptive immunity and to inform rational vaccine design, it is important to understand the adaptive immune correlates of disease.

OBJECTIVES

To characterize T-cell immunity to the PA antigen outer membrane porin F (OprF) by analyzing immunodominant epitopes in relation to infection status.

METHODS

Patients with non-CF bronchiectasis were stratified by frequency of PA isolation. T-cell IFN-γ immunity to OprF and its immunodominant epitopes was characterized. Patterns of human leukocyte antigen (HLA) restriction of immunodominant epitopes were defined using HLA class II transgenic mice. Immunity was characterized with respect to cytokine and chemokine secretion, antibody response, and T-cell activation transcripts.

MEASUREMENTS AND MAIN RESULTS

Patients were stratified according to whether PA was never, sometimes (<50%), or frequently (≥50%) isolated from sputum. Patients with frequent PA sputum-positive isolates were more likely to be infected by mucoid PA, and they showed a narrow T-cell epitope response and a relative reduction in Th1 polarizing transcription factors but enhanced immunity with respect to antibody production, innate cytokines, and chemokines.

CONCLUSIONS

We have defined the immunodominant, HLA-restricted T-cell epitopes of OprF. Our observation that chronic infection is associated with a response of narrowed specificity, despite strong innate and antibody immunity, may help to explain susceptibility in these individuals and pave the way for better vaccine design to achieve protective immunity.

Short-chain fatty acids affect cystic fibrosis airway inflammation and bacterial growth

The hypoxic environment of cystic fibrosis airways allows the persistence of facultative anaerobic bacteria, which can produce short-chain fatty acids (SCFAs) through fermentation. However, the relevance of SCFAs in cystic fibrosis lung disease is unknown. We show that SCFAs are present in sputum samples from cystic fibrosis patients in millimolar concentrations (mean±sem1.99±0.36 mM).

SCFAs positively correlated with sputum neutrophil count and higher SCFAs were predictive for impaired nitric oxide production. We studied the effects of the SCFAs acetate, propionate and butyrate on airway inflammatory responses using epithelial cell lines and primary cell cultures. SCFAs in concentrations present in cystic fibrosis airways (0.5–2.5 mM) affected the release of granulocyte-macrophage colony-stimulating factor, granulocyte colony-stimulating factor and interleukin (IL)-6. SCFAs also resulted in higher IL-8 release from stimulated cystic fibrosis transmembrane conductance regulator (CFTR) F508del-mutant compared to wild-type CFTR-corrected bronchial epithelial cells. At 25 mM propionate reduced IL-8 release in control but not primary cystic fibrosis epithelial cells. Low (0.5–2.5 mM) SCFA concentrations increased, while high (25–50 mM) concentrations decreased inducible nitric oxide synthase expression. In addition, SCFAs affected the growth ofPseudomonas aeruginosain a concentration- and pH-dependent manner.

Thus, our data suggest that SCFAs contribute to cystic fibrosis-specific alterations of responses to airway infection and inflammation.

Adult non-cystic fibrosis bronchiectasis is characterised by airway luminal Th17 pathway activation

BACKGROUND

Non-cystic fibrosis (CF) bronchiectasis is characterised by chronic airway infection and neutrophilic inflammation, which we hypothesised would be associated with Th17 pathway activation.

METHODS

Th17 pathway cytokines were quantified in bronchoalveolar lavage fluid (BALF), and gene expression of IL-17A, IL-1β, IL-8 and IL-23 determined from endobronchial biopsies (EBx) in 41 stable bronchiectasis subjects and 20 healthy controls. Relationships between IL-17A levels and infection status, important clinical measures and subsequent Pseudomonas aeruginosa infection were determined.

RESULTS

BALF levels of all Th17 cytokines (median (IQR) pg/mL) were significantly higher in bronchiectasis than control subjects, including IL-17A (1.73 (1.19, 3.23) vs. 0.27 (0.24, 0.35), 95% CI 1.05 to 2.21, p<0.0001) and IL-23 (9.48 (4.79, 15.75) vs. 0.70 (0.43, 1.79), 95% CI 4.68 to 11.21, p<0.0001). However, BALF IL-17A levels were not associated with clinical measures or airway microbiology, nor predictive of subsequent P. aeruginosa infection. Furthermore, gene expression of IL-17A in bronchiectasis EBx did not differ from control. In contrast, gene expression (relative to medians of controls) in bronchiectasis EBx was significantly higher than control for IL1β (4.12 (1.24, 8.05) vs 1 (0.13, 2.95), 95% CI 0.05 to 4.07, p = 0.04) and IL-8 (3.75 (1.64, 11.27) vs 1 (0.54, 3.89), 95% CI 0.32 to 4.87, p = 0.02) and BALF IL-8 and IL-1α levels showed significant relationships with clinical measures and airway microbiology. P. aeruginosa infection was associated with increased levels of IL-8 while Haemophilus influenzae was associated with increased IL-1α.

CONCLUSIONS AND CLINICAL RELEVANCE

Established adult non-CF bronchiectasis is characterised by luminal Th17 pathway activation, however this pathway may be relatively less important than activation of non-antigen-specific innate neutrophilic immunity.

High peripheral blood th17 percent associated with poor lung function in cystic fibrosis

People with cystic fibrosis (CF) have been reported to make lung T cell responses that are biased towards T helper (Th) 2 or Th17. We hypothesized that CF-related T cell regulatory defects could be detected by analyzing CD4⁺ lymphocyte subsets in peripheral blood. Peripheral blood mononuclear cells from 42 CF patients (6 months–53 years old) and 78 healthy controls (2–61 years old) were analyzed for Th1 (IFN-γ⁺), Th2 (IL-4⁺), Th17 (IL-17⁺), Treg (FOXP3⁺), IL-10⁺ and TGF-β⁺ CD4⁺ cells. We observed higher proportions of Treg, IL-10⁺ and TGF-β⁺ CD4⁺ cells in CF adults (≥ 18 years old), but not children/adolescents, compared with controls. Within the CF group, high TGF-β⁺% was associated with chronic Pseudomonas aeruginosa lung infection (p < 0.006). We observed no significant differences between control and CF groups in the proportions of Th1, Th2 or Th17 cells, and no association within the CF group of any subset with sex, CFTR genotype, or clinical exacerbation. However, high Th17% was strongly associated with poor lung function (FEV1 % predicted) (p = 0.0008), and this association was strongest when both lung function testing and blood sampling were performed within one week. Our results are consistent with reports of CF as a Th17 disease and suggest that peripheral blood Th17 levels may be a surrogate marker of lung function in CF.

Inflammation in cystic fibrosis lung disease: Pathogenesis and therapy

Lung disease is the major cause of morbidity and mortality in patients with cystic fibrosis (CF). Although CF lung disease is primarily an infectious disorder, the associated inflammation is both intense and ineffective at clearing pathogens. Persistent high-intensity inflammation leads to permanent structural damage of the CF airways and impaired lung function that eventually results in respiratory failure and death. Several defective inflammatory responses have been linked to cystic fibrosis transmembrane conductance regulator (CFTR) deficiency including innate and acquired immunity dysregulation, cell membrane lipid abnormalities, various transcription factor signaling defects, as well as altered kinase and toll-like receptor responses. The inflammation of the CF lung is dominated by neutrophils that release oxidants and proteases, particularly elastase. Neutrophil elastase in the CF airway secretions precedes the appearance of bronchiectasis, and correlates with lung function deterioration and respiratory exacerbations. Anti-inflammatory therapies are therefore of particular interest for CF lung disease but must be carefully studied to avoid suppressing critical elements of the inflammatory response and thus worsening infection. This review examines the role of inflammation in the pathogenesis of CF lung disease, summarizes the results of past clinical trials and explores promising new anti-inflammatory options.

Host-pathogen interplay in the respiratory environment of cystic fibrosis

Significant advances have been made in the understanding of disease progression in cystic fibrosis (CF), revealing a complex interplay between host and pathogenic organisms. The diverse CF microbiota within the airway activates an aberrant immune response that is ineffective in clearing infection. An appreciation of how the CF host immune system interacts with these organisms is crucial to understanding the pathogenesis of CF pulmonary disease. Here we discuss the microbial complexity present in the lungs of individuals with CF, review emerging concepts of innate and adaptive immune responses to pathogens that chronically inhabit the CF lung, and discuss therapies that target the aberrant inflammatory response that characterizes CF. A greater understanding of the underlying mechanisms will shed light on pathogenesis and guide more targeted therapies in the future that serve to reduce infection, minimize lung pathology, and improve the quality of life for patients with CF.

Granulocyte-macrophage colony stimulatory factor enhances the pro-inflammatory response of interferon-γ-treated macrophages to Pseudomonas aeruginosa infection

Pseudomonas aeruginosa is an opportunistic pathogen that can cause severe infections at compromised epithelial surfaces, such those found in burns, wounds, and in lungs damaged by mechanical ventilation or recurrent infections, particularly in cystic fibrosis (CF) patients. CF patients have been proposed to have a Th2 and Th17-biased immune response suggesting that the lack of Th1 and/or over exuberant Th17 responses could contribute to the establishment of chronic P. aeruginosa infection and deterioration of lung function. Accordingly, we have observed that interferon (IFN)-γ production by peripheral blood mononuclear cells from CF patients positively correlated with lung function, particularly in patients chronically infected with P. aeruginosa. In contrast, IL-17A levels tended to correlate negatively with lung function with this trend becoming significant in patients chronically infected with P. aeruginosa. These results are in agreement with IFN-γ and IL-17A playing protective and detrimental roles, respectively, in CF. In order to explore the protective effect of IFN-γ in CF, the effect of IFN-γ alone or in combination with granulocyte-macrophage colony-stimulating factor (GM-CSF), on the ability of human macrophages to control P. aeruginosa growth, resist the cytotoxicity induced by this bacterium or promote inflammation was investigated. Treatment of macrophages with IFN-γ, in the presence and absence of GM-CSF, failed to alter bacterial growth or macrophage survival upon P. aeruginosa infection, but changed the inflammatory potential of macrophages. IFN-γ caused up-regulation of monocyte chemoattractant protein-1 (MCP-1) and TNF-α and down-regulation of IL-10 expression by infected macrophages. GM-CSF in combination with IFN-γ promoted IL-6 production and further reduction of IL-10 synthesis. Comparison of TNF-α vs. IL-10 and IL-6 vs. IL-10 ratios revealed the following hierarchy in regard to the pro-inflammatory potential of human macrophages infected with P. aeruginosa: untreated < treated with GM-CSF < treated with IFN-γ < treated with GM-CSF and IFN-γ.

Reduced mucosal associated invariant T-cells are associated with increased disease severity and Pseudomonas aeruginosa infection in cystic fibrosis

Background

Primary defects in host immune responses have been hypothesised to contribute towards an inability of subjects with cystic fibrosis (CF) to effectively clear pulmonary infections. Innate T-lymphocytes provide rapid pathogen-specific responses prior to the development of classical MHC class I and II restricted T-cell responses and are essential to the initial control of pulmonary infection. We aimed to examine the relationship between peripheral blood lymphocyte phenotype and clinical outcomes in adults with CF.

Methods

We studied 41 subjects with CF and 22, age matched, non-smoking healthy control subjects. Lymphocytes were extracted from peripheral blood samples and phenotyped by flow-cytometry. Lymphocyte phenotype was correlated with sputum microbiology and clinical parameters.

Results

In comparison to healthy control subjects, mucosal associated invariant T (MAIT)-lymphocytes were significantly reduced in the peripheral blood of subjects with CF (1.1% versus 2.0% of T-lymphocytes, P = 0.002). MAIT cell concentration was lowest in CF subjects infected with P. aeruginosa and in subjects receiving treatment for a pulmonary exacerbation. Furthermore a reduced MAIT cell concentration correlated with severity of lung disease.

Conclusion

Reduced numbers of MAIT cells in subjects with CF were associated with P. aeruginosa pulmonary infection, pulmonary exacerbations and more severe lung disease. These findings provide the impetus for future studies examining the utility of MAIT cells in immunotherapies and vaccine development. Longitudinal studies of MAIT cells as biomarkers of CF pulmonary infection are awaited.

IL-17A induces Pendrin expression and chloride-bicarbonate exchange in human bronchial epithelial cells

The epithelium plays an active role in the response to inhaled pathogens in part by responding to signals from the immune system. Epithelial responses may include changes in chemokine expression, increased mucin production and antimicrobial peptide secretion, and changes in ion transport. We previously demonstrated that interleukin-17A (IL-17A), which is critical for lung host defense against extracellular bacteria, significantly raised airway surface pH in vitro, a finding that is common to a number of inflammatory diseases. Using microarray analysis of normal human bronchial epithelial (HBE) cells treated with IL-17A, we identified the electroneutral chloride-bicarbonate exchanger Pendrin (SLC26A4) as a potential mediator of this effect. These data were verified by real-time, quantitative PCR that demonstrated a time-dependent increase in Pendrin mRNA expression in HBE cells treated with IL-17A up to 48 h. Using immunoblotting and immunofluorescence, we confirmed that Pendrin protein expression is increased in IL-17 treated HBE cells and that it is primarily localized to the mucosal surface of the cells. Functional studies using live-cell fluorescence to measure intracellular pH demonstrated that IL-17A induced chloride-bicarbonate exchange in HBE cells that was not present in the absence of IL-17A. Furthermore, HBE cells treated with short interfering RNA against Pendrin showed substantially reduced chloride-bicarbonate exchange. These data suggest that Pendrin is part of IL-17A-dependent epithelial changes and that Pendrin may therefore be a therapeutic target in IL-17A-dependent lung disease.

Expression of MIG/CXCL9 in cystic fibrosis and modulation of its activities by elastase of Pseudomonas aeruginosa

In cystic fibrosis (CF), colonization of the airways with Pseudomonas aeruginosa is associated with disease deterioration. The mechanism behind the disease progression is not fully understood. The present work shows that the antibacterial chemokine MIG/CXCL9 is present in the airways and in sputum of CF patients. MIG/CXCL9 showed high bactericidal activity against. P. aeruginosa, including some strains from the airways of CF patients. Full-length MIG/CXCL9 was detected in sputum from healthy controls and CF patients colonized with P. aeruginosa. However, degraded MIG/CXCL9 was only found in CF sputum. In vitro, elastase of P. aeruginosa cleaved off a fragment of similar size and two additional fragments from MIG/CXCL9. The fragments showed less bactericidal activity against P. aeruginosa compared with the full-length protein. The fragments did not activate the MIG/CXCL9 receptor CXCR3 (expressed e.g. by NK cells, mast cells, and activated T cells) but instead displayed noncompetitive inhibition. In vitro, a decrease in CXCR3-bearing cells was found within and in the proximity of the bronchial epithelium of CF lung tissue compared with controls. Taken together, both bactericidal and cell-recruiting activities of MIG/CXCL9 are corrupted by P. aeruginosa through release of elastase, and this may contribute to impaired airway host defense in CF.

Could T cells be involved in lung deterioration and hyperglycemia in cystic fibrosis?

Cystic fibrosis-related diabetes (CFRD) is the most frequent complication of cystic fibrosis (CF) and associated with increased mortality. Why patients have an accelerated loss of lung function before the diagnosis of CFRD remains poorly understood. We reported that patients with or without CFRD had increased glucose excursions when compared to healthy peers. Studies have demonstrated that patients with CF have increased glucose fluctuations and hyperglycemia and that this may affect the clinical course of CF and lead to lymphocyte dysfunction. T-helper 17 (Th17) lymphocytes produce and secrete the pro-inflammatory cytokine IL-17. The Th17 pathway is involved in CF lung inflammation, β-cell destruction in type 1 diabetes (T1D) and Th17 cells of patients with type 2 diabetes have increased production of IL-17 when compared to healthy peers. Also, regulatory T-cells (Tregs) have been shown to be dysfunctional and produce IL-17 in T1D. Furthermore, vitamin D can affect inflammation in CF, diabetes and the differentiation of lymphocytes. In this review, we discuss the potential roles of hyperglycemia on Th17 cells, Tregs and IL-17 as a potential cause for accelerated lung function decline before CFRD and how this could be modulated by vitamin D or by directly intervening in the IL-17A pathway.

Differential responses to rhinovirus- and influenza-associated pulmonary exacerbations in patients with cystic fibrosis

RATIONALE

The mechanism by which viruses cause exacerbations of chronic airway disease and the capacity of patients with cystic fibrosis (CF) to respond to viral infection are not precisely known.

OBJECTIVES

To determine the antiviral response to infection in patients with CF.

METHODS

Sputum was collected from patients with CF with respiratory exacerbation. Viruses were detected in multiplex polymerase chain reaction (PCR)-based assays. Gene expression of 84 antiviral response genes was measured, using a focused quantitative PCR gene array.

MEASUREMENTS AND MAIN RESULTS

We examined 36 samples from 23 patients with respiratory exacerbation. Fourteen samples tested virus-positive and 22 virus-negative. When we compared exacerbations associated with rhinovirus (RV, n = 9) and influenza (n = 5) with virus-negative specimens, we found distinct patterns of antiviral gene expression. RV was associated with greater than twofold induction of five genes, including those encoding the monocyte-attracting chemokines CXCL10, CXCL11, and CXCL9. Influenza was associated with overexpression of 20 genes, including those encoding the cytokines tumor necrosis factor and IL-12; the kinases MEK, TBK-1, and STAT-1; the apoptosis proteins caspase-8 and caspase-10; the influenza double-stranded RNA receptor RIG-I and its downstream effector MAVS; and pyrin, an IFN-stimulated protein involved in influenza resistance.

CONCLUSIONS

We conclude that virus-induced exacerbations of CF are associated with immune responses tailored to specific infections. Influenza induced a more potent response consisting of inflammation, whereas RV infection had a pronounced effect on chemokine expression. As far as we are aware, this study is the first to compare specific responses to different viruses in live patients with chronic airway disease.

Due diligence in the characterization of matrix effects in a total IL-13 Singulex™ method

After obtaining her PhD in Cellular and Molecular biology from the University of Nevada, Reno, Stephanie has spent the last 15 years in the field of bioanalysis. She has held positions in academia, biotech, contract research and large pharma where she has managed ligand binding assay (discovery to Phase IIb clinical) and flow cytometry (preclinical) laboratories as well as taken the lead on implementing new/emergent technologies. Currently Stephanie leads Pfizer’s Regulated Bioanalysis Ligand Binding Assay group, focusing on early clinical biomarker support.

Interleukin (IL)-13, a Th2 cytokine, drives a range of physiological responses associated with the induction of allergic airway diseases and inflammatory bowel diseases. Analysis of IL-13 as a biomarker has provided insight into its role in disease mechanisms and progression. Serum IL-13 concentrations are often too low to be measured by standard enzyme-linked immunosorbent assay techniques, necessitating the implementation of a highly sensitive assay. Previously, the validation of a Singulex™ Erenna® assay for the quantitation of IL-13 was reported. Herein we describe refinement of this validation; defining the impact of matrix interference on the lower limit of quantification, adding spiked matrix QC samples, and extending endogenous IL-13 stability. A fit-for-purpose validation was conducted and the assay was used to support a Phase II clinical trial.

Vaccines for Pseudomonas aeruginosa: a long and winding road

Despite the recognition of Pseudomonas aeruginosa as an opportunistic pathogen, no vaccine against this bacteria has come to market. This review describes the current state-of-the-art in vaccinology for this bacterium. This includes a discussion of those at risk for infection, the types of vaccines and the approaches for empirical and targeted antigen selection under development, as well as a perspective on where the field should go. In addition, the challenges in developing a vaccine for those individuals at risk are discussed.

Phagocytic and signaling innate immune receptors: are they dysregulated in cystic fibrosis in the fight against Pseudomonas aeruginosa?

Cystic fibrosis (CF) is a genetic disease that affects mainly the lung and the digestive system, causing progressive disability and organ failure. The most prevalent CFTR mutation dF508 (which constitutes 70% of all mutations) results in an incorrect targeting of the CFTR molecule to the membrane. It is now a well-accepted concept that mucosal innate immune responses are dysregulated in cystic fibrosis through a cycle of infectious and inflammatory episodes. However, although much work has focused on the late consequences of chronic lung inflammation in CF, very little is known on the early events leading to infection and colonization, such as that of Pseudomonas aeruginosa (P.a). We review here the involvement of a range of innate phagocytic/signaling receptors in the control of this pathogen (mannose receptor, complement receptor-3, Toll-like receptors, etc.) and evaluate the possibility that the activity of some of these receptors may be dysregulated in cystic fibrosis, potentially explaining the florid infections encountered in this disease.

A tale of two cytokines: IL-17 and IL-22 in asthma and infection

The Th17 pathway has recently been shown to play a critical role in host defense, allergic responses and autoimmune inflammation. Th17 cells predominantly produce IL-17 and IL-22, which are two cytokines with broad effects in the lung and other tissues. This review summarizes not only what is currently known about the molecular regulation of this pathway and Th17-related cytokine signaling, but also the roles of these cytokines in pathogen immunity and asthma. In the last 5 years, the Th17 field has rapidly grown and research has revealed that the Th17 pathway is essential in lung pathogenesis in response to exogenous stimuli. As work in the field continues, it is expected that many exciting therapeutic advances will be made for a broad range of diseases.

T cell unresponsiveness in a pediatric cystic fibrosis patient: a case report

A girl was diagnosed with cystic fibrosis (CF) at birth, with repeatedly positive sweat tests and homozygous F508del mutations of her CF transmembrane conductance regulator (CFTR) gene. From an early age, her lung disease was more severe than her birth cohort peers despite aggressive treatment. At the age of 16 she was listed for lung transplantation, but prior to transplant was not on systemic corticosteroids or other immunosuppressive agents. In response to ex vivo stimulation, her pre-transplant peripheral blood T cells unexpectedly failed to produce detectable levels of IFN-γ, unlike cells from healthy controls or from another girl with CF and lung disease of comparable severity. Furthermore, naïve T cells freshly isolated from her peripheral blood showed a complete block of T cell differentiation into Th1, Th17 and Treg lineages, even in the presence of cytokines known to promote differentiation into the respective lineages. Her serology has been remarkably devoid of evidence of exposure to viruses that have been associated with T cell exhaustion. However, her freshly isolated naïve T cells showed sustained expression of markers of T cell exhaustion, which were further induced upon ex vivo stimulation, pointing to T cell exhaustion as the cause of the failure of naïve T cells to undergo differentiation in response to cytokine stimulation. Although excessive inflammation in CF lung can be both ineffective at clearing certain pathogens as well as destructive to the lung tissue itself, adequate inflammation is a component of an effective overall immune response to microbial pathogens. Our present findings suggest that intrinsic impairment of T cell differentiation may have contributed to the greater severity and more rapid progression of her CF lung disease than of the lung disease of most of her peers.

Intrinsic predisposition of naïve cystic fibrosis T cells to differentiate towards a Th17 phenotype

Background

Cystic fibrosis (CF) is a complex, multi-system, life-shortening, autosomal recessive disease most common among Caucasians. Pulmonary pathology, the major cause of morbidity and mortality in CF, is characterized by dysregulation of cytokines and a vicious cycle of infection and inflammation. This cycle causes a progressive decline in lung function, eventually resulting in respiratory failure and death. The Th17 immune response plays an active role in the pathogenesis of CF pulmonary pathology, but it is not known whether the pathophysiology of CF disease contributes to a heightened Th17 response or whether CF naïve CD4+ T lymphocytes (Th0 cells) intrinsically have a heightened predisposition to Th17 differentiation.

Methods

To address this question, Th0 cells were isolated from the peripheral blood of CF mice, human CF subjects and corresponding controls. Murine Th0 cells were isolated from single spleen cell suspensions using fluorescence-activated cell sorting. Lymphocytes from human buffy coats were isolated by gradient centrifugation and Th0 cells were further isolated using a human naïve T cell isolation kit. Th0 cells were then assessed for their capacity to differentiate along Th17, Th1 or Treg lineages in response to corresponding cytokine stimulation. The T cell responses of human peripheral blood cells were also assessed ex vivo using flow cytometry.

Results

Here we identify in both mouse and human CF an intrinsically enhanced predisposition of Th0 cells to differentiate towards a Th17 phenotype, while having a normal propensity for differentiation into Th1 and Treg lineages. Furthermore, we identify an active Th17 response in the peripheral blood of human CF subjects.

Conclusions

We propose that these novel observations offer an explanation, at least in part, for the known increased Th17-associated inflammation of CF and the early signs of inflammation in CF lungs before any evidence of infection. Moreover, these findings point towards direct modulation of T cell responses as a novel potential therapeutic strategy for combating excessive inflammation in CF.

Roles of TGF-beta and periostin in fibrosclerosis in patients with IgG4-related diseases

CONCLUSION

These results suggest that transforming growth factor (TGF)-beta and periostin could be useful as novel biomarkers and therapeutic targets in IgG4-related disease.

OBJECTIVES

IgG4-related disease is an uncommon fibrosclerosing and inflammatory mass-forming disease that can be systemic or can affect single organs. To clarify the roles of TGF-beta, periostin, and interleukin (IL)-13 in the pathogenesis of IgG4-related disease, we studied a total of 36 serum and 11 tissue samples from patients with IgG4-related disease.

METHODS

This was a retrospective clinical study. The patient group consisted of six females and seven males (average age 60 years, range 38-74 years). Serum IgG4 levels, the tissue density of IgG4-positive plasmacytes, and the expression of TGF-beta and periostin in the affected tissues were examined immunohistochemically.

RESULTS

Serum IgG4 levels were elevated in all patients (mean 776.6, range 185-2820 mg/dl), and IgG4-positive plasmacytes were observed in the affected salivary glands. Seven patients with prominent infiltration of the involved glands with IgG4-positive plasmacytes had fatal systemic complications, including pancreatitis, after swelling of the salivary glands. Overexpression of TGF-beta and periostin was observed in affected tissues obtained from these patients.

Impaired functions of macrophage from cystic fibrosis patients: CD11b, TLR-5 decrease and sCD14, inflammatory cytokines increase

BACKGROUND

Early in life, cystic fibrosis (CF) patients are infected with microorganisms. The role of macrophages has largely been underestimated in literature, whereas the focus being mostly on neutrophils and epithelial cells. Macrophages may however play a significant role in the initiating stages of this disease, via an inability to act as a suppressor cell. Yet macrophage dysfunction may be the first step in cascade of events leading to chronic inflammation/infection in CF. Moreover, reports have suggested that CFTR contribute to altered inflammatory response in CF by modification of normal macrophage functions.

OBJECTIVES

In order to highlight possible intrinsic macrophage defects due to impaired CFTR, we have studied inflammatory cytokines secretions, recognition of pathogens and phagocytosis in peripheral blood monocyte-derived macrophages from stable adult CF patients and healthy subjects (non-CF).

RESULTS

In CF macrophage supernatants, concentrations of sCD14, IL-1β, IL-6, TNF-α and IL-10 were strongly raised. Furthermore expression of CD11b and TLR-5 were sorely decreased on CF macrophages. Beside, no difference was observed for mCD14, CD16, CD64, TLR-4 and TLR1/TLR-2 expressions. Moreover, a strong inhibition of phagocytosis was observed for CF macrophages. Elsewhere CFTR inhibition in non-CF macrophages also led to alterations of phagocytosis function as well as CD11b expression.

CONCLUSIONS

Altogether, these findings demonstrate excessive inflammation in CF macrophages, characterized by overproduction of sCD14 and inflammatory cytokines, with decreased expression of CD11b and TLR-5, and impaired phagocytosis. This leads to altered clearance of pathogens and non-resolution of infection by CF macrophages, thereby inducing an exaggerated pro-inflammatory response.

Intracellular secretory leukoprotease inhibitor modulates inositol 1,4,5-triphosphate generation and exerts an anti-inflammatory effect on neutrophils of individuals with cystic fibrosis and chronic obstructive pulmonary disease

Secretory leukoprotease inhibitor (SLPI) is an anti-inflammatory protein present in respiratory secretions. Whilst epithelial cell SLPI is extensively studied, neutrophil associated SLPI is poorly characterised. Neutrophil function including chemotaxis and degranulation of proteolytic enzymes involves changes in cytosolic calcium (Ca²⁺) levels which is mediated by production of inositol 1,4,5-triphosphate (IP₃) in response to G-protein-coupled receptor (GPCR) stimuli. The aim of this study was to investigate the intracellular function of SLPI and the mechanism-based modulation of neutrophil function by this antiprotease. Neutrophils were isolated from healthy controls (n = 10), individuals with cystic fibrosis (CF) (n = 5) or chronic obstructive pulmonary disease (COPD) (n = 5). Recombinant human SLPI significantly inhibited fMet-Leu-Phe (fMLP) and interleukin(IL)-8 induced neutrophil chemotaxis (P < 0.05) and decreased degranulation of matrix metalloprotease-9 (MMP-9), hCAP-18, and myeloperoxidase (MPO) (P < 0.05). The mechanism of inhibition involved modulation of cytosolic IP₃ production and downstream Ca²⁺ flux. The described attenuation of Ca²⁺ flux was overcome by inclusion of exogenous IP₃ in electropermeabilized cells. Inhibition of IP₃ generation and Ca²⁺ flux by SLPI may represent a novel anti-inflammatory mechanism, thus strengthening the attractiveness of SLPI as a potential therapeutic molecule in inflammatory airway disease associated with excessive neutrophil influx including CF, non-CF bronchiectasis, and COPD.

IL-17 in lung disease: friend or foe?

Interleukin 17 (IL-17) is a key proinflammatory cytokine in the T helper 17 pathway. While it is important in the clearance of certain pathogens, IL-17 has been shown to contribute to the pathogenesis of such inflammatory diseases as rheumatoid arthritis and psoriasis. In the lung, it has been postulated to be involved in the neutrophilic inflammation and airway remodelling of chronic respiratory conditions but the situation is increasingly complex. This review summarises the evidence for its role in several chronic inflammatory lung diseases: asthma, obliterative bronchiolitis, chronic obstructive pulmonary disease, sarcoidosis and cystic fibrosis.