Rationale: Lower socioeconomic status (SES) confers a heightened risk of common cardiovascular and pulmonary diseases and increased mortality. The association of SES with outcomes in patients with pulmonary arterial hypertension (PAH) is less clear.
Objectives: To determine the association between SES and outcomes in patients with PAH.
Methods: We performed a prospective cohort study at a national referral center for patients with PAH in China. Two hundred sixty-two consecutive incident patients aged 18 to 65 years with a diagnosis of idiopathic PAH were recruited between January 2007 and June 2011 and followed up until November 2011. The primary endpoint was all-cause mortality. An SES score for each patient was derived from their educational level, annual household income, occupation, and medical reimbursement rate.
Measurements and Main Results: Patients with a lower SES had higher unadjusted mortality rates, with 3-year survival estimates of 50.1, 70.8, and 86.0% in increasing tertiles of SES (P for trend < 0.001). After adjustment for clinical features, hemodynamics, and type of PAH treatment, the hazard ratios for death were 2.98 (95% confidence interval, 1.51–5.89) in the lowest tertile of SES and 1.80 (95% confidence interval, 0.89–3.63) in the middle tertile of SES compared with the upper tertile (P for trend = 0.006).
Conclusions: A lower SES is strongly associated with a higher risk of death in idiopathic PAH. This association was independent of clinical characteristics, hemodynamics, and treatment. Addressing the health disparities associated with a lower SES may improve the outcomes of patients with PAH.
pulmonary arterial hypertension; socioeconomic status; survival
Rationale: Increasing body mass index (BMI) has been associated with less fractional exhaled nitric oxide (FeNO). This may be explained by an increase in the concentration of asymmetric dimethyl arginine (ADMA) relative to l-arginine, which can lead to greater nitric oxide synthase uncoupling.
Objectives: To compare this mechanism across age of asthma onset groups and determine its association with asthma morbidity and lung function.
Methods: Cross-sectional study of participants from the Severe Asthma Research Program, across early- (<12 yr) and late- (>12 yr) onset asthma phenotypes.
Measurements and Main Results: Subjects with late-onset asthma had a higher median plasma ADMA level (0.48 μM, [interquartile range (IQR), 0.35–0.7] compared with early onset, 0.37 μM [IQR, 0.29–0.59], P = 0.01) and lower median plasma l-arginine (late onset, 52.3 [IQR, 43–61] compared with early onset, 51 μM [IQR 39–66]; P = 0.02). The log of plasma l-arginine/ADMA was inversely correlated with BMI in the late- (r = −0.4, P = 0.0006) in contrast to the early-onset phenotype (r = −0.2, P = 0.07). Although FeNO was inversely associated with BMI in the late-onset phenotype (P = 0.02), the relationship was lost after adjusting for l-arginine/ADMA. Also in this phenotype, a reduced l-arginine/ADMA was associated with less IgE, increased respiratory symptoms, lower lung volumes, and worse asthma quality of life.
Conclusions: In late-onset asthma phenotype, plasma ratios of l-arginine to ADMA may explain the inverse relationship of BMI to FeNO. In addition, these lower l-arginine/ADMA ratios are associated with reduced lung function and increased respiratory symptom frequency, suggesting a role in the pathobiology of the late-onset phenotype.
asthma; obesity; age of asthma onset; ADMA; arginine
Rationale: Lymphocytes are increasingly associated with idiopathic pulmonary fibrosis (IPF). Semaphorin 7a (Sema 7a) participates in lymphocyte activation.
Objectives: To define the relationship between Sema 7a and lymphocytes in IPF.
Methods: We characterized the significance of Sema 7a+ lymphocytes in humans with IPF and in a mouse model of lung fibrosis caused by lung-targeted, transgenic overexpression of TGF-β1. We determined the site of Sema 7a expression in human and murine lungs and circulation and used adoptive transfer approaches to define the relevance of lymphocytes coexpressing Sema7a and the markers CD19, CD4, or CD4+CD25+FoxP3+ in TGF-β1–induced murine lung fibrosis.
Measurements and Main Results: Subjects with IPF show expression of Sema 7a on lung CD4+ cells and circulating CD4+ or CD19+ cells. Sema 7a expression is increased on CD4+ cells and CD4+CD25+FoxP3+ regulatory T cells, but not CD19+ cells, in subjects with progressive IPF. Sema 7a is expressed on lymphocytes expressing CD4 but not CD19 in the lungs and spleen of TGF-β1–transgenic mice. Sema 7a expressing bone marrow–derived cells induce lung fibrosis and alter the production of T-cell mediators, including IFN-γ, IL-4, IL-17A, and IL-10. These effects require CD4 but not CD19. In comparison to Sema 7a-CD4+CD25+FoxP3+ cells, Sema7a+CD4+CD25+FoxP3+ cells exhibit reduced expression of regulatory genes such as IL-10, and adoptive transfer of these cells induces fibrosis and remodeling in the TGF-β1–exposed murine lung.
Conclusions: Sema 7a+CD4+CD25+FoxP3+ regulatory T cells are associated with disease progression in subjects with IPF and induce fibrosis in the TGF-β1–exposed murine lung.
Semaphorin; lung; fibrosis; TGF-β1; regulatory T cells
Rationale: Although IFN-γ release assays (IGRAs) are widely used to screen for Mycobacterium tuberculosis infection in high-income countries, published data on repeatability are limited.
Objectives: To determine IGRA repeatability.
Methods: The study population included consecutive patients referred to The Methodist Hospital (Houston, TX) between August 1, 2010 and July 31, 2011 for latent tuberculosis (TB) infection screening with an IGRA (QuantiFERON-TB Gold In-Tube; Cellestis, Carnegie, Australia). We performed multiple IGRA tests using leftover stimulated plasma according to a prospectively formulated quality control protocol. We analyzed agreement in interpretation of test results classified according to manufacturer-recommended criteria and repeatability of quantitative TB response.
Measurements and Main Results: During the study period, 1,086 test results were obtained from 543 subjects. Per the manufacturer’s cut-point, the result of the second test was discordant from that of the first in 28 (8%) of 366 patients with valid test results, including 13 with an initial negative result and 15 with an initial positive result. Although agreement between repeat test results was high (κ = 0.84; 95% confidence interval, 0.79–0.90), the normal expected range of within-subject variability in TB response on retesting included differences of ± 0.60 IU/ml for all individuals (coefficient of variation, 14%), and ± 0.24 IU/ml (coefficient of variation, 27%) for individuals whose initial TB response was between 0.25 and 0.80 IU/ml.
Conclusions: There is substantial variability in TB response when IGRAs are repeated using the same patient sample. IGRA results should be interpreted cautiously when TB response is near interpretation cut-points.
interferon-γ release assay; QuantiFERON; repeatability; imprecision
Hepatopulmonary syndrome and portopulmonary hypertension are two pulmonary vascular complications of liver disease. The pathophysiology underlying each disorder is distinct, but patients with either condition may be limited by dyspnea. A careful evaluation of concomitant symptoms, the physical examination, pulmonary function testing and arterial blood gas analysis, and echocardiographic, imaging, and hemodynamic studies is crucial to establishing (and distinguishing) these diagnoses. Our understanding of the pathobiology, natural history, and treatment of these disorders has advanced considerably over the past decade; however, the presence of either still increases the risk of morbidity and mortality in patients with underlying liver disease. There is no effective medical treatment for hepatopulmonary syndrome. Although liver transplantation can resolve hepatopulmonary syndrome, there appears to be worse survival even with transplantation. Liver transplantation poses a very high risk of death in those with significant portopulmonary hypertension, where targeted medical therapies may improve functional status and allow successful transplantation in a small number of select patients.
hepatopulmonary syndrome; hypertension; pulmonary; liver cirrhosis; pulmonary circulation
Rationale: Nasal polyps (NPs) are characterized by intense edema or formation of pseudocysts filled with plasma proteins, mainly albumin. However, the mechanisms underlying NP retention of plasma proteins in their submucosa remain unclear.
Objectives: We hypothesized that formation of a fibrin mesh retains plasma proteins in NPs. We assessed the fibrin deposition and expression of the components of the fibrinolytic system in patients with chronic rhinosinusitis (CRS).
Methods: We assessed fibrin deposition in nasal tissue from patients with CRS and control subjects by means of immunofluorescence. Fibrinolytic components, d-dimer, and plasminogen activators were measured using ELISA, real-time PCR, and immunohistochemistry. We also performed gene expression and protein quantification analysis in cultured airway epithelial cells.
Measurements and Main Results: Immunofluorescence data showed profound fibrin deposition in NP compared with uncinate tissue (UT) from patients with CRS and control subjects. Levels of the cross-linked fibrin cleavage product protein, d-dimer, were significantly decreased in NP compared with UT from patients with CRS and control subjects, suggesting reduced fibrinolysis (P < 0.05). Expression levels of tissue plasminogen activator (t-PA) mRNA and protein were significantly decreased in NP compared with UT from patients with CRS and control subjects (P < 0.01). Immunohistochemistry demonstrated clear reduction of t-PA in NP, primarily in the epithelium and glands. Th2 cytokine–stimulated cultured airway epithelial cells showed down-regulation of t-PA, suggesting a potential Th2 mechanism in NP.
Conclusions: A Th2-mediated reduction of t-PA might lead to excessive fibrin deposition in the submucosa of NP, which might contribute to the tissue remodeling and pathogenesis of CRS with nasal polyps.
chronic rhinosinusitis; nasal polyps; tissue plasminogen activator; fibrin; fibrinolysis
Rationale: The function of the P2X7 nucleotide receptor protects against exacerbation in people with mild-intermittent asthma during viral illnesses, but the impact of disease severity and maintenance therapy has not been studied.
Objectives: To evaluate the association between P2X7, asthma exacerbations, and incomplete symptom control in a more diverse population.
Methods: A matched P2RX7 genetic case-control was performed with samples from Asthma Clinical Research Network trial participants enrolled before July 2006, and P2X7 pore activity was determined in whole blood samples as an ancillary study to two trials completed subsequently.
Measurements and Main Results: A total of 187 exacerbations were studied in 742 subjects, and the change in asthma symptom burden was studied in an additional 110 subjects during a trial of inhaled corticosteroids (ICS) dose optimization. African American carriers of the minor G allele of the rs2230911 loss-of-function single nucleotide polymorphism were more likely to have a history of prednisone use in the previous 12 months, with adjustment for ICS and long-acting β2-agonists use (odds ratio, 2.7; 95% confidence interval, 1.2–6.2; P = 0.018). Despite medium-dose ICS, attenuated pore function predicted earlier exacerbations in incompletely controlled patients with moderate asthma (hazard ratio, 3.2; confidence interval, 1.1–9.3; P = 0.033). After establishing control with low-dose ICS in patients with mild asthma, those with attenuated pore function had more asthma symptoms, rescue albuterol use, and FEV1 reversal (P < 0.001, 0.03, and 0.03, respectively) during the ICS adjustment phase.
Conclusions: P2X7 pore function protects against exacerbations of asthma and loss of control, independent of baseline severity and the maintenance therapy.
asthma; P2X7; exacerbation; Asthma Clinical Research Network; corticosteroids
Rationale: Asthma is a heterogeneous lung disorder characterized by airway inflammation and airway dysfunction, manifesting as hyperresponsiveness and obstruction. Glutathione S-transferase M1 (GSTM1) is a multifunctional phase II enzyme and regulator of stress-activated cellular signaling relevant to asthma pathobiology. A common homozygous deletion polymorphism of the GSTM1 gene eliminates enzyme activity.
Objectives: To determine the effect of GSTM1 on airway inflammation and reactivity in adults with established atopic asthma in vivo.
Methods: Nineteen GSTM1 wild-type and eighteen GSTM1-null individuals with mild atopic asthma underwent methacholine and inhaled allergen challenges, and endobronchial allergen provocations through a bronchoscope.
Measurements and Main Results: The influx of inflammatory cells, panels of cytokines and chemokines linked to asthmatic inflammation, F2-isoprostanes (markers of oxidative stress), and IgE were measured in bronchoalveolar lavage fluid at baseline and 24 hours after allergen instillation. Individuals with asthma with the GSTM1 wild-type genotype had greater baseline and allergen-provoked airway neutrophilia and concentrations of myeloperoxidase than GSTM1-null patients. In contrast, the eosinophilic inflammation was unaffected by GSTM1. The allergen-stimulated generation of acute-stress and proneutrophilic mediators, tumor necrosis factor-α, CXCL-8, IL-1β, and IL-6, was also greater in the GSTM1 wild-type patients. Moreover, post-allergen airway concentrations of IgE and neutrophil-generated mediators, matrix metalloproteinase-9, B-cell activating factor, transforming growth factor-β1, and elastase were higher in GSTM1 wild-type individuals with asthma. Total airway IgE correlated with B-cell activating factor concentrations. In contrast, levels of F2-isoprostane were comparable in both groups. Finally, GSTM1 wild-type individuals with asthma required lower threshold concentrations of allergen to produce bronchoconstriction.
Conclusions: The functional GSTM1 genotype promotes neutrophilic airway inflammation in humans with atopic asthma in vivo.
atopic asthma; GSTM1 polymorphism; inflammatory asthma phenotypes; neutrophilic airway inflammation
Rationale: Patients who developed acute respiratory distress syndrome (ARDS) after infection with severe respiratory viruses (e.g., severe acute respiratory syndrome–coronavirus, H5N1 avian influenza virus), exhibited unusually high levels of CXCL10, which belongs to the non-ELR (glutamic-leucine-arginine) CXC chemokine superfamily. CXCL10 may not be a bystander to the severe virus infection but may directly contribute to the pathogenesis of neutrophil-mediated, excessive pulmonary inflammation.
Objectives: We investigated the contribution of CXCL10 and its receptor CXCR3 axis to the pathogenesis of ARDS with nonviral and viral origins.
Methods: We induced nonviral ARDS by acid aspiration and viral ARDS by intratracheal influenza virus infection in wild-type mice and mice deficient in CXCL10, CXCR3, IFNAR1 (IFN-α/β receptor 1), or TIR domain-containing adaptor inducing IFN-β (TRIF).
Measurements and Main Results: We found that the mice lacking CXCL10 or CXCR3 demonstrated improved severity and survival of nonviral and viral ARDS, whereas mice that lack IFNAR1 did not control the severity of ARDS in vivo. The increased levels of CXCL10 in lungs with ARDS originate to a large extent from infiltrated pulmonary neutrophils, which express a unique CXCR3 receptor via TRIF. CXCL10-CXCR3 acts in an autocrine fashion on the oxidative burst and chemotaxis in the inflamed neutrophils, leading to fulminant pulmonary inflammation.
Conclusions: CXCL10-CXCR3 signaling appears to be a critical factor for the exacerbation of the pathology of ARDS. Thus, the CXCL10-CXCR3 axis could represent a prime therapeutic target in the treatment of the acute phase of ARDS of nonviral and viral origins.
CXCL10; CXCR3; ARDS
Rationale: A genome-wide association study (GWAS) for circulating chronic obstructive pulmonary disease (COPD) biomarkers could identify genetic determinants of biomarker levels and COPD susceptibility.
Objectives: To identify genetic variants of circulating protein biomarkers and novel genetic determinants of COPD.
Methods: GWAS was performed for two pneumoproteins, Clara cell secretory protein (CC16) and surfactant protein D (SP-D), and five systemic inflammatory markers (C-reactive protein, fibrinogen, IL-6, IL-8, and tumor necrosis factor-α) in 1,951 subjects with COPD. For genome-wide significant single nucleotide polymorphisms (SNPs) (P < 1 × 10−8), association with COPD susceptibility was tested in 2,939 cases with COPD and 1,380 smoking control subjects. The association of candidate SNPs with mRNA expression in induced sputum was also elucidated.
Measurements and Main Results: Genome-wide significant susceptibility loci affecting biomarker levels were found only for the two pneumoproteins. Two discrete loci affecting CC16, one region near the CC16 coding gene (SCGB1A1) on chromosome 11 and another locus approximately 25 Mb away from SCGB1A1, were identified, whereas multiple SNPs on chromosomes 6 and 16, in addition to SNPs near SFTPD, had genome-wide significant associations with SP-D levels. Several SNPs affecting circulating CC16 levels were significantly associated with sputum mRNA expression of SCGB1A1 (P = 0.009–0.03). Several SNPs highly associated with CC16 or SP-D levels were nominally associated with COPD in a collaborative GWAS (P = 0.001–0.049), although these COPD associations were not replicated in two additional cohorts.
Conclusions: Distant genetic loci and biomarker-coding genes affect circulating levels of COPD-related pneumoproteins. A subset of these protein quantitative trait loci may influence their gene expression in the lung and/or COPD susceptibility.
Clinical trial registered with www.clinicaltrials.gov (NCT 00292552).
biomarker; chronic obstructive pulmonary disease; genome-wide association study
Rationale: Systemic glucocorticoids are used therapeutically to treat a variety of medical conditions. Epigenetic processes such as DNA methylation may reflect exposure to glucocorticoids and may be involved in mediating the responses and side effects associated with these medications.
Objectives: To test the hypothesis that differences in DNA methylation are associated with current systemic steroid use.
Methods: We obtained DNA methylation data at 27,578 CpG sites in 14,475 genes throughout the genome in two large, independent cohorts: the International COPD Genetics Network (ndiscovery = 1,085) and the Boston Early Onset COPD study (nreplication = 369). Sites were tested for association with current systemic steroid use using generalized linear mixed models.
Measurements and Main Results: A total of 511 sites demonstrated significant differential methylation by systemic corticosteroid use in all three of our primary models. Pyrosequencing validation confirmed robust differential methylation at CpG sites annotated to genes such as SLC22A18, LRP3, HIPK3, SCNN1A, FXYD1, IRF7, AZU1, SIT1, GPR97, ABHD16B, and RABGEF1. Functional annotation clustering demonstrated significant enrichment in intrinsic membrane components, hemostasis and coagulation, cellular ion homeostasis, leukocyte and lymphocyte activation and chemotaxis, protein transport, and responses to nutrients.
Conclusions: Our analyses suggest that systemic steroid use is associated with site-specific differential methylation throughout the genome. Differentially methylated CpG sites were found in biologically plausible and previously unsuspected pathways; these genes and pathways may be relevant in the development of novel targeted therapies.
DNA methylation; glucocorticoids; chronic obstructive pulmonary disease
Rationale: Severe sepsis is common and highly morbid, yet the epidemiology of severe sepsis at the frontier of the health care system—pre-hospital emergency care—is unknown.
Objectives: We examined the epidemiology of pre-hospital severe sepsis among emergency medical services (EMS) encounters, relative to acute myocardial infarction and stroke.
Methods: Retrospective study using a community-based cohort of all nonarrest, nontrauma King County EMS encounters from 2000 to 2009 who were transported to a hospital.
Measurements and Main Results: Overall incidence rate of hospitalization with severe sepsis among EMS encounters, as well as pre-hospital characteristics, admission diagnosis, and outcomes. Among 407,176 EMS encounters, we identified 13,249 hospitalizations for severe sepsis, of whom 2,596 died in the hospital (19.6%). The crude incidence rate of severe sepsis was 3.3 per 100 EMS encounters, greater than for acute myocardial infarction or stroke (2.3 per 100 and 2.2 per 100 EMS encounters, respectively). More than 40% of all severe sepsis hospitalizations arrived at the emergency department after EMS transport, and 80% of cases were diagnosed on admission. Pre-hospital care intervals, on average, exceeded 45 minutes for those hospitalized with severe sepsis. One-half or fewer of patients with severe sepsis were transported by paramedics (n = 7,114; 54%) or received pre-hospital intravenous access (n = 4,842; 37%).
Conclusions: EMS personnel care for a substantial and increasing number of patients with severe sepsis, and spend considerable time on scene and during transport. Given the emphasis on rapid diagnosis and intervention for sepsis, the pre-hospital interval may represent an important opportunity for recognition and care of sepsis.
sepsis; emergency medical services; epidemiology
Ventilatory instability may play an important role in the pathogenesis of obstructive sleep apnea. We hypothesized that the influence of ventilatory instability in this disorder would vary depending on the underlying collapsibility of the upper airway. To test this hypothesis, we correlated loop gain with apnea–hypopnea index during supine, nonrapid eye movement sleep in three groups of patients with obstructive sleep apnea based on pharyngeal closing pressure: negative pressure group (pharyngeal closing pressure less than –1 cm H2O), atmospheric pressure group (between –1 and +1 cm H2O), and positive pressure group (greater than +1 cm H2O). Loop gain was measured by sequentially increasing proportional assist ventilation until periodic breathing developed, which occurred in 24 of 25 subjects. Mean loop gain for all three groups was 0.37 ± 0.11. A significant correlation was found between loop gain and apnea–hypopnea index in the atmospheric group only (r = 0.88, p = 0.0016). We conclude that loop gain has a substantial impact on apnea severity in certain patients with sleep apnea, particularly those with a pharyngeal closing pressure near atmospheric.
control of breathing; loop gain; pharyngeal closing pressure; pharyngeal collapsibility; ventilatory stability
Common genetic risk variants identified by genome-wide association studies have explained a small portion of disease heritability in complex diseases. It is becoming apparent that each gene/locus is heterogeneous and that multiple rare independent risk alleles across the population contribute to disease risk. Next-generation sequencing technologies have reached the maturity and low cost necessary to perform whole genome, whole exome, and targeted region sequencing to identify all rare risk alleles across a population, a task that is not possible to achieve by genotyping. Design of whole genome, whole exome, and targeted sequencing projects to identify disease variants for complex lung diseases requires four main steps: library preparation, sequencing, sequence data analysis, and statistical analysis. Although data analysis approaches are still evolving, a number of published studies have successfully identified rare variants associated with complex disease. Despite many challenges that lie ahead in applying these technologies to lung disease, rare variants are likely to be a critical piece of the puzzle that needs to be solved to understand the genetic basis of complex lung disease and to use this information to develop better therapies.
genetic variants; rare variants; next-generation sequencing; complex lung disease; disease risk alleles
Rationale: Unprecedented pollution control actions during the Beijing Olympics provided a quasi-experimental opportunity to examine biologic responses to drastic changes in air pollution levels.
Objectives: To determine whether changes in levels of biomarkers reflecting pulmonary inflammation and pulmonary and systemic oxidative stress were associated with changes in air pollution levels in healthy young adults.
Methods: We measured fractional exhaled nitric oxide, a number of exhaled breath condensate markers (H+, nitrite, nitrate, and 8-isoprostane), and urinary 8-hydroxy-2-deoxyguanosine in 125 participants twice in each of the pre- (high pollution), during- (low pollution), and post-Olympic (high pollution) periods. We measured concentrations of air pollutants near where the participants lived and worked. We used mixed-effects models to estimate changes in biomarker levels across the three periods and to examine whether changes in biomarker levels were associated with changes in pollutant concentrations, adjusting for meteorologic parameters.
Measurements and Main Results: From the pre- to the during-Olympic period, we observed significant and often large decreases (ranging from −4.5% to −72.5%) in levels of all the biomarkers. From the during-Olympic to the post-Olympic period, we observed significant and larger increases (48–360%) in levels of these same biomarkers. Moreover, increased pollutant concentrations were consistently associated with statistically significant increases in biomarker levels.
Conclusions: These findings support the important role of oxidative stress and that of pulmonary inflammation in mediating air pollution health effects. The findings demonstrate the utility of novel and noninvasive biomarkers in the general population consisting largely of healthy individuals.
air pollution; inflammation; oxidative stress; respiratory health; the Beijing Olympics
Rationale: Activation of the adenosine A2B receptor (A2BR) promotes antiinflammatory effects in diverse biological settings, but the role of this receptor in antimicrobial host defense in the lung has not been established. Gram-negative bacillary pneumonia is a common and serious illness associated with high morbidity and mortality, the treatment of which is complicated by increasing rates of antibiotic resistance.
Objectives: To test the hypothesis that absence of adenosine A2B receptor signaling promotes host defense against bacterial pneumonia.
Methods: We used a model of Klebsiella pneumoniae pneumonia in wild-type mice and mice with targeted deletion of the A2BR. Host responses were compared in vivo and leukocyte responses to the bacteria were examined in vitro.
Measurements and Main Results: A2BR–/– mice demonstrated enhanced bacterial clearance from the lung and improved survival after infection with K. pneumoniae compared with wild-type controls, an effect that was mediated by bone marrow–derived cells. Leukocyte recruitment to the lungs and expression of inflammatory cytokines did not differ between A2BR–/– and wild-type mice, but A2BR–/– neutrophils exhibited sixfold greater bactericidal activity and enhanced production of neutrophil extracellular traps compared with wild-type neutrophils when incubated with K. pneumoniae. Consistent with this finding, bronchoalveolar lavage fluid from A2BR–/– mice with Klebsiella pneumonia contained more extracellular DNA compared with wild-type mice with pneumonia.
Conclusions: These data suggest that the absence of A2BR signaling enhances antimicrobial activity in gram-negative bacterial pneumonia.
neutrophil; extracellular traps; pneumonia; adenosine