IL-3 up-regulates and activates human eosinophil CD32 and αMß2 integrin causing degranulation.

BACKGROUND: Eosinophils contribute to the pathogenesis of multiple diseases, including asthma. Treatment with antibodies targeting IL-5 or IL-5 receptor α reduces the frequency of asthma exacerbations. Eosinophil receptors for IL-5 share a common ß-chain with IL-3 and GM-CSF receptors. We recently reported that IL-3 is more potent than IL-5 or GM-CSF in maintaining the ERK/p90S6K/RPS6 ribosome-directed signaling pathway, leading to increased protein translation. OBJECTIVE: We aimed to determine disease-relevant consequences of prolonged eosinophil stimulation with IL-3. RESULTS: Human blood eosinophils were used to establish the impact of activation with IL-3 on IgG-driven eosinophil degranulation. When compared to IL-5, continuing exposure to IL-3 further induced degranulation of eosinophils on aggregated IgG via increased production and activation of both CD32 (low affinity IgG receptor) and αMß2 integrin. In addition, unlike IL-5 or GM-CSF, IL-3 induced expression of CD32B/C (FCGRIIB/C) subtype proteins, without changing CD32A (FCGRIIA) protein and CD32B/C mRNA expression levels. Importantly, these in vitro IL-3-induced modifications were recapitulated in vivo on airway eosinophils. CONCLUSIONS AND CLINICAL RELEVANCE: We observed for the first time upregulation of CD32B/C on eosinophils, and identified IL-3 as a potent inducer of CD32- and αMß2-mediated eosinophil degranulation.

Nasal lavage VEGF and TNF-α levels during a natural cold predict asthma exacerbations.

BACKGROUND: Asthma exacerbations contribute to significant morbidity, mortality and healthcare utilization. Furthermore, viral infections are associated with asthma exacerbations by mechanisms that are not fully understood. OBJECTIVE: The aim of this analysis was to determine whether cytokine patterns in patients with colds could identify risks for subsequent asthma exacerbations. METHODS: We analysed cytokine levels in nasal lavage fluid (NLF) in 59 subjects (46 with asthma) with acute upper respiratory symptoms and after symptomatic resolution. Analyte choice was based on potential relevance to asthma exacerbations: antiviral (IFN-α, IFN-ß, IFN-γ, IFN-λ1, IP-10, TRAIL), cell recruiting (G-CSF, IL-1ß, IL-8, MCP-1, MCP-3, TNF-α), polarizing (CXCL13, IL-10, IL-13, IL-17, TSLP), and injury remodelling (fibronectin, IL-33, MMP-9, VEGF). RESULTS: The overall cytokine response induced during viral infections was not different between asthmatic and non-asthmatic individuals for a wide array of cytokines. However, mean levels of VEGF, TNF-α and IL-1ß were 1.7-, 5.1- and 4.7-fold higher in samples from asthma subjects who exacerbated in the first 3 weeks of the cold compared with those who did not exacerbate (P = 0.006, 0.01, 0.048, respectively). Using receiver operating characteristic curve-defined thresholds, high VEGF and TNF-α levels predicted a shorter time-to-exacerbation after NLF sampling (25% exacerbation rate: 3 vs. 45 days, and 3 vs. 26 days; P = 0.03, 0.04, respectively). CONCLUSION AND CLINICAL RELEVANCE: Although they produce similar cytokine responses to viral infection as non-asthmatics, asthmatics with higher levels of VEGF and TNF-α in NLF obtained during acute cold phases predicted subsequent asthma exacerbations in this cohort of patients with mild-to-moderate disease. In the future, stratifying the risk of an asthma exacerbation by cytokine profile may aid the targeting of personalized treatment and intervention strategies.

Interferon gene expression in sputum cells correlates with the Asthma Index Score during virus-induced exacerbations.

BACKGROUND: The majority of asthma exacerbations are related to viral respiratory infections. Some, but not all, previous studies have reported that low interferon responses in patients with asthma increase the risk for virus-induced exacerbations. OBJECTIVE: We sought to determine the relationship between lower airway inflammatory biomarkers, specifically interferon gene expression, and the severity or presence of an exacerbation in asthmatics experiencing a naturally occurring viral infection. METHODS: Sputum samples were analysed from subjects in an asthma exacerbation study who experienced a confirmed viral infection. Subjects were monitored for daily symptoms, medication use and peak expiratory flow rate until baseline. Sputum samples were assessed for cell counts and gene expression. RESULTS: Interferon gamma expression was significantly greater in patients with asthma exacerbations compared to non-exacerbating patients (P = 0.002). IFN-α1, IFN-ß1 and IFN-γ mRNA levels correlated with the peak Asthma Index (r = 0.58, P < 0.001; r = 0.57, P = 0.001; and r = 0.51, P = 0.004, respectively). Additionally, IL-13, IL-10 and eosinophil major basic protein mRNA levels were greater in patients with asthma exacerbations compared to non-exacerbating patients (P = 0.03, P = 0.06 and P = 0.02, respectively), and IL-13 mRNA correlated with the peak Asthma Index (P = 0.006). CONCLUSIONS: Our findings indicate that asthma exacerbations are associated with increased rather than decreased expression of interferons early in the course of infection. These findings raise the possibility that excessive virus-induced interferon production during acute infections can contribute to airway inflammation and exacerbations of asthma.

The effects of lebrikizumab in patients with mild asthma following whole lung allergen challenge.

BACKGROUND: Interleukin 13 (IL13) is a T-helper type 2 (Th2) cytokine associated with inflammation and pathology in allergic diseases such as bronchial asthma. We have shown that treatment with lebrikizumab, an anti-IL13 monoclonal antibody, significantly improves prebronchodilator forced expiratory volume in 1 s (FEV(1)) in a subset of subjects with uncontrolled asthma. OBJECTIVE: To evaluate efficacy and safety of lebrikizumab in subjects with mild asthma who underwent bronchial allergen challenge. METHODS: Twenty-nine subjects were randomized 1 : 1-5 mg/kg lebrikizumab (n = 13) or placebo (n = 16) administered subcutaneously every 4 weeks over 12 weeks, a total of four doses. Primary efficacy outcome was late asthmatic response (LAR) at Week 13, defined as area under the curve of FEV1 measured 2-8 h following inhaled allergen challenge. Serum biomarkers were measured to verify IL13 pathway inhibition and identify patients with an increased response to lebrikizumab. RESULTS: At Week 13, the LAR in lebrikizumab subjects was reduced by 48% compared with placebo subjects, although this was not statistically significant (95% confidence interval, -19%, 90%). Exploratory analysis indicated that lebrikizumab-treated subjects with elevated baseline levels of peripheral blood eosinophils, serum IgE, or periostin exhibited a greater reduction in LAR compared with subjects with lower baseline levels of these biomarkers. Lebrikizumab exerted systemic effects on markers of Th2 inflammation, reducing serum immunoglobulin E (IgE), chemokine ligands 13 and 17 by approximately 25% (P < 0.01). Lebrikizumab was well tolerated. CONCLUSION AND CLINICAL RELEVANCE: Lebrikizumab reduced the LAR in subjects with mild asthma. Clinical trial number NCT00781443.

The relationship between eosinophilia and airway remodelling in mild asthma.

BACKGROUND: Eosinophilia is a marker of corticosteroid responsiveness and risk of exacerbation in asthma; although it has been linked to submucosal matrix deposition, its relationship with other features of airway remodelling is less clear. OBJECTIVE: The aim of this study was to investigate the relationship between airway eosinophilia and airway remodelling. METHODS: Bronchial biopsies from subjects (n = 20 in each group) with mild steroid-naïve asthma, with either low (0-0.45 mm(-2)) ) or high submucosal eosinophil (23.43-46.28 mm(-2) ) counts and healthy controls were assessed for in vivo epithelial damage (using epidermal growth factor receptor staining), mucin expression, airway smooth muscle (ASM) hypertrophy and inflammatory cells within ASM. RESULTS: The proportion of in vivo damaged epithelium was significantly greater (P = 0.02) in the high-eosinophil (27.37%) than the low-eosinophil (4.14%) group. Mucin expression and goblet cell numbers were similar in the two eosinophil groups; however, MUC-2 expression was increased (P = 0.002) in the high-eosinophil group compared with controls. The proportion of submucosa occupied by ASM was higher in both asthma groups (P = 0.021 and P = 0.046) compared with controls. In the ASM, eosinophil and T-lymphocyte numbers were higher (P < 0.05) in the high-eosinophil group than both the low-eosinophil group and the controls, whereas the numbers of mast cells were increased in the high-eosinophil group (P = 0.01) compared with controls. CONCLUSION: Submucosal eosinophilia is a marker (and possibly a cause) of epithelial damage and is related to infiltration of ASM with eosinophils and T lymphocytes, but is unrelated to mucus metaplasia or smooth muscle hypertrophy.

Anti-IL-5 attenuates activation and surface density of ß(2) -integrins on circulating eosinophils after segmental antigen challenge.

BACKGROUND: IL-5 activates α(M) ß(2) integrin on blood eosinophils in vitro. Eosinophils in bronchoalveolar lavage (BAL) following segmental antigen challenge have activated ß(2) -integrins. OBJECTIVE: To identify roles for IL-5 in regulating human eosinophil integrins in vivo. METHODS: Blood and BAL eosinophils were analysed by flow cytometry in ten subjects with allergic asthma who underwent a segmental antigen challenge protocol before and after anti-IL-5 administration. RESULTS: Blood eosinophil reactivity with monoclonal antibody (mAb) KIM-127, which recognizes partially activated ß(2) -integrins, was decreased after anti-IL-5. Before anti-IL-5, surface densities of blood eosinophil ß(2) , α(M) and α(L) integrin subunits increased modestly post challenge. After anti-IL-5, such increases did not occur. Before or after anti-IL-5, surface densities of ß(2) , α(M) , α(L) and α(D) and reactivity with KIM-127 and mAb CBRM1/5, which recognizes high-activity α(M) ß(2) , were similarly high on BAL eosinophils 48 h post-challenge. Density and activation state of ß(1) -integrins on blood and BAL eosinophils were not impacted by anti-IL-5, even though anti-IL-5 ablated a modest post-challenge increase on blood or BAL eosinophils of P-selectin glycoprotein ligand-1 (PSGL-1), a receptor for P-selectin that causes activation of ß(1) -integrins. Forward scatter of blood eosinophils post-challenge was less heterogeneous and on the average decreased after anti-IL-5; however, anti-IL-5 had no effect on the decreased forward scatter of eosinophils in post-challenge BAL compared with eosinophils in blood. Blood eosinophil KIM-127 reactivity at the time of challenge correlated with the percentage of eosinophils in BAL post-challenge. CONCLUSION AND CLINICAL RELEVANCE: IL-5 supports a heterogeneous population of circulating eosinophils with partially activated ß(2) -integrins and is responsible for up-regulation of ß(2) -integrins and PSGL-1 on circulating eosinophils following segmental antigen challenge but has minimal effects on properties of eosinophils in BAL. Dampening of ß(2) -integrin function of eosinophils in transit to inflamed airway may contribute to the decrease in lung inflammation caused by anti-IL-5.

Segmental allergen challenge enhances chitinase activity and levels of CCL18 in mild atopic asthma.

BACKGROUND: Allergic airway inflammation contributes to the airway remodelling that has been linked to increased obstruction and morbidity in asthma. However, the mechanisms by which allergens contribute to airway remodelling in humans are not fully established. CCL18, chitotriosidase (CHIT1) and YKL-40 are readily detectable in the lungs and contribute to remodelling in other fibrotic diseases, but their involvement in allergic asthma is unclear. OBJECTIVE: We hypothesized that CCL18, YKL-40 and CHIT1 bioactivity are enhanced in allergic asthma subjects after segmental allergen challenge and are related to increased pro-fibrotic and Th2-associated mediators in the lungs. METHODS: Levels of CCL18 and YKL-40 protein and chitotriosidase (CHIT1) bioactivity in bronchoalveolar lavage (BAL) fluid, as well as CCL18, YKL-40 and CHIT1 mRNA levels in BAL cells were evaluated in patients with asthma at baseline and 48 h after segmental allergen challenge. We also examined the correlation between CCL18 and YKL-40 levels and CHIT1 activity with the levels of other pro-fibrotic factors and chemokines previously shown to be up-regulated after allergen challenge. RESULTS: Chitotriosidase activity and YKL-40 and CCL18 levels were elevated after segmental allergen challenge and these levels correlated with those of other pro-fibrotic factors, T cell chemokines, and inflammatory cells after allergen challenge. CCL18 and YKL-40 mRNA levels also increased in BAL cells after allergen challenge. CONCLUSIONS AND CLINICAL RELEVANCE: Our results suggest that CCL18 and YKL-40 levels and CHIT1 activity are enhanced in allergic airway inflammation and thus may contribute to airway remodelling in asthma.

Human eosinophils release IL-1ß and increase expression of IL-17A in activated CD4+ T lymphocytes.

BACKGROUND: Differentiation and activation of CD4(+) T cells is controlled by various cytokines produced by innate immune cells. We have shown that eosinophils (EOS) have the potential to influence Th1 and Th2 cytokine generation by CD4(+) cells, but their influence on IL-17A (IL-17) has not been established. OBJECTIVE: The purpose of this study is to determine the effect of EOS on IL-17 production by lymphocytes. METHODS: Pre-activated CD4(+) T cells were cultured in the presence of either autologous EOS or EOS culture supernatants. Expression of IL-17 was determined by real-time quantitative PCR (qPCR) after 5 h and protein level was measured after 48 h. To determine the effect of allergen-induced airway EOS on IL-17, subjects with mild allergic asthma underwent bronchoscopic segmental bronchoprovocation with allergen (SBP-Ag) after a treatment with an anti-IL-5 neutralizing antibody (mepolizumab) to reduce airway eosinophilia. IL-17 mRNA was measured in bronchoalveolar lavage (BAL) cells by qPCR. RESULTS: In vitro, EOS significantly increased IL-17 production by CD4(+) T cells. Addition of exogenous IL-1ß increased expression of IL-17 mRNA by CD4(+) T cells. EOS expressed and released IL-1ß. Furthermore, levels of IL-1ß in EOS supernatants highly correlated with their ability to increase IL-17 expression by CD4(+) T cells, and neutralizing antibody to IL-1ß reduced expression of IL-17 mRNA. In vivo, reduction of EOS in the airway using mepolizumab was associated with diminished IL-17 expression after SBP-Ag. CONCLUSIONS AND CLINICAL RELEVANCE: Our data demonstrate that EOS can promote IL-17 production through the release of IL-1ß. Enhanced IL-17 cytokine production is another mechanism by which EOS may participate in pathogenesis of allergic airway inflammation in asthma.

Predicting worsening asthma control following the common cold.

The asthmatic response to the common cold is highly variable, and early characteristics that predict worsening of asthma control following a cold have not been identified. In this prospective multicentric cohort study of 413 adult subjects with asthma, the mini-Asthma Control Questionnaire (mini-ACQ) was used to quantify changes in asthma control and the Wisconsin Upper Respiratory Symptom Survey-21 (WURSS-21) to measure cold severity. Univariate and multivariable models were used to examine demographic, physiological, serological and cold-related characteristics for their relationship to changes in asthma control following a cold. Clinically significant worsening of asthma control was observed following a cold (mean+/-SD increase in mini-ACQ score of 0.69+/-0.93). Univariate analysis demonstrated that season, centre location, cold duration and cold severity measurements were all associated with a change in asthma control. Multivariable analysis of the covariates available within the first 2 days of cold onset revealed that the day 2 and cumulative sum of day 1 and 2 WURSS-21 scores were significant predictors of the subsequent changes in asthma control. In asthmatic subjects, cold severity within the first 2 days can be used to predict subsequent changes in asthma control. This information may help clinicians prevent deterioration in asthma control following a cold.

Cytokine profiles of stimulated blood lymphocytes in asthmatic and healthy adolescents across the school year.

T cell cytokines play an important role in mediating airway inflammation in asthma. The predominance of a Th2 cytokine profile, particularly interleukin (IL)-4 and IL-5, is associated with the pathogenesis and course of asthma. The aim of this study was to test the hypothesis that a stressful life event alters the pattern of cytokine release in asthmatic individuals. Thirteen healthy controls and 21 asthmatic adolescents gave blood samples three times over a semester: midsemester, during the week of final examinations, and 2-3 weeks after examinations. Interferon-gamma (IFN-gamma), IL-2, IL-4, and IL-5 were measured from supernatants of cells stimulated with PHA/PMA for 24 h. Cells from asthmatic subjects released significantly more IL-5 during the examination and postexamination periods, whereas cells from healthy controls released significantly more IL-2 during the midsemester and examination periods, thereby indicating a bias for a Th2-like pattern in asthmatics and a Th1-like pattern in healthy controls. IL-4 and IL-5 production showed a marked decrease during and after examinations in healthy controls, whereas this decline was absent in asthmatics. The ratios of IFN-gamma:IL-4 and IFN-gamma:IL-5 also revealed significant changes in the profile of cytokine release across the semester. These results indicate differential cytokine responses in asthmatics that may become pronounced during periods of cellular activation.

Endobronchial irradiation for malignant airway obstruction.

An afterloading endobronchial irradiation (EBRT) technique using Iridium-192 (Ir-192), was piloted for malignant airway obstruction. Under bronchoscopic guidance, a catheter is threaded distal to the lesion. Orthogonal radiographs and computerized tomographic (CT) scans are obtained for dosimetry. Forty implants in 38 patients have been performed. Thirty-two patients had lung cancer; 23 had received prior irradiation and eight had prior chemotherapy. Eight patients underwent pre-endobronchial irradiation laser excision. Median implant duration was 50.5 hr; median dose at 1 and 2 cm from source center was 50 and 20 Gy, respectively. The procedure was well tolerated with four long-term complications (10.5%). Twelve of 38 patients are currently alive with a median survival of 5+ months and a range of 1 to 21+ months. Changes in performance status (PS), symptom resolution, radiographic demonstration of re-aeration of atelectatic lung, changes in pulmonary function (PFT), and post-endobronchial irradiation bronchoscopy were used to assess response. Seventy percent of the patients' remaining life was rendered symptom-free or improved. A 70% radiographic response was noted. Fourteen patients underwent post-endobronchial irradiation bronchoscopy with 12 complete responses. Endobronchial irradiation, therefore, appears to be a safe, effective technique to palliate malignant airway obstruction.

Pneumocephalus associated with nasal continuous positive airway pressure in a patient with sleep apnea syndrome.

We report a new potentially dangerous complication of nasal continuous positive airway pressure applied for the treatment of obstructive sleep apnea syndrome. A middle-aged woman had cerebrospinal fluid leak after using nasal CPAP, with generalized seizures and pneumocephalus. She did fine with conservative therapy for the CSF leak and discontinuation of nasal CPAP.

Designing bronchial biopsy studies.

Bronchial biopsy provides valuable information about the inflammatory processes in lung tissue, but optimal results are only achieved if the design of intervention studies is sufficiently rigorous. The parallel-group design has merit, but the cross-over design is statistically superior, providing the wash-out period is effective. Heterogeneity of contributing pathologies in asthma patients results in large inter-patient variability which must be controlled for, for example by using strict inclusion criteria, which should ideally relate to the specific inflammatory marker being studied. The inclusion of a placebo group helps to quantify sample variability. The study must have sufficient statistical power to detect inter-group differences for each variable; appropriate adjustments should be made when multiple tests are used. Studies with larger patient numbers are best performed using a multi-centre design, with one centre analysing all tissue samples to reduce variability. Study duration depends on the type of investigation, but should ideally be short. Longer studies are necessary to evaluate chronic changes such as tissue remodelling. Changes in clinical status and cellular events may follow different time courses after intervention. Biopsy measurements are less reproducible than physiological tests, and diurnal variation in the number and function of inflammatory cells can further complicate measurement. The timing of clinical trial assessments needs to allow for these idiosyncrasies. Finally, a balance must be maintained between the risk, albeit small, and the benefit of performing bronchial biopsies.

Circadian variation in allergen and nonspecific bronchial responsiveness in asthma.

In a majority of patients, exacerbations of asthma occur more frequently during the night than day. Many hypotheses have been proposed to explain such variation in asthma. The airways of asthmatic persons are characterized by an abnormal degree of inflammation and bronchial hyperresponsiveness to both nonspecific and specific challenges. Studies of both children and adults with asthma document marked circadian rhythmicity in the response of airways to bronchial challenges with histamine, methacholine, acetylcholine, saline, and house dust mite. Taken together, the findings of these investigations indicate that the hyperreactivity of airways to these agents is more profound and prolonged following evening and overnight tests compared to tests conducted in the midday and afternoon. The temporal pattern in bronchial response to the hyperventilation of cold dry air is different. The hyperresponsiveness of airways to this challenge is greatest in the afternoon. The amplitude of the circadian rhythm in airway hyperreactivity seems to be correlated to the amplitude of the circadian rhythm of pulmonary function; the greater the day-night difference in bronchial reactivity is, the greater is the day-night difference in flow rates.

Rhinovirus-induced modulation of gene expression in bronchial epithelial cells from subjects with asthma.

Rhinovirus (RV) infections trigger asthma exacerbations. Genome-wide expression analysis of RV1A-infected primary bronchial epithelial cells from normal and asthmatic donors was performed to determine whether asthma is associated with a unique pattern of RV-induced gene expression. Virus replication rates were similar in cells from normal and asthmatic donors. Overall, RV downregulated 975 and upregulated 69 genes. Comparisons of transcriptional profiles generated from microarrays and confirmed by quantitative reverse transcription PCR and cluster analysis showed some up- and downregulated genes in asthma cells involved in immune responses (IL1B, IL1F9, IL24, and IFI44) and airway remodeling (LOXL2, MMP10, FN1). Notably, most of the asthma-related differences in RV-infected cells were also present in the cells before infection. These findings suggest that differences in RV-induced gene expression profiles of cells from normal and mild asthmatic subjects could affect the acute inflammatory response to RV, and subsequent airway repair and remodeling.

Human airway and peripheral blood eosinophils enhance Th1 and Th2 cytokine secretion.

BACKGROUND: The effector function of eosinophils involves their release of toxic granule proteins, reactive oxygen species, cytokines, and lipid mediators. Murine studies have demonstrated that eosinophils can also enhance T cell function. Whether human eosinophils, in particular, airway eosinophils, have similar immunoregulatory activity has not been fully investigated. The aim of this study was to determine whether human blood and airway eosinophils can contribute to Th1 and Th2 cytokine generation from CD4+ T cells stimulated with superantigen. METHODS: Eosinophils were obtained from blood or bronchoalveolar lavage fluid 48 h after segmental allergen bronchoprovocation. Purified eosinophils were co-cultured with autologous CD4+ blood T cells in the presence of staphylococcal enterotoxin B (SEB). Cytokine levels in the supernatant fluid were determined by enzyme-linked immunosorbent assay (ELISA). Eosinophil expression of major histocompatibility complex (MHC) class II and co-stimulatory molecules was assessed by flow cytometry before culture, 24 h after granulocyte-macrophage colony-stimulating factor (GM-CSF) stimulation, and 24 h after co-culture with CD4+ T cells and SEB. RESULTS: Interleukin (IL)-5, IL-13, and interferon (IFN)-gamma generation increased when CD4+ T cells were co-cultured with either blood or airway eosinophils in the presence of SEB. The ability of eosinophils to enhance cytokine generation was independent of their source (blood vs airway), activation by GM-CSF, or detectable expression of human leukocyte antigen (HLA)-DR, CD80, or CD86. CONCLUSION: Our data demonstrate that SEB-induced generation of Th1 and Th2 cytokines is increased in the presence of human blood and airway eosinophils. Thus, eosinophils can have an immunoregulatory function in pathogen-associated allergic diseases such as atopic dermatitis, chronic sinusitis, and asthma exacerbations.

Cytokines in bronchoalveolar lavage fluid of patients with nocturnal asthma.

Airflow obstruction can have a circadian pattern with nocturnal worsening. Airway inflammation is a cardinal feature of asthma, and it has been shown to increase at night in association with the decline in pulmonary function. Although the mechanisms regulating enhanced airway inflammation in asthma at night have yet to be ascertained, we hypothesized that circadian variation in cytokine expression or production is an important factor in the development of nocturnal airflow limitation. To investigate this possibility, spirometry and bronchoscopy were performed; the bronchoalveolar lavage (BAL) fluid obtained at 4:00 A.M. and at 4:00 P.M. were measured for IL-1 beta in asthmatics with (n = 5) and without (n = 9) nocturnal asthma. In addition, the activity of IL-3, IL-5, and GM-CSF was measured using a biologic assay (eosinophil survival-enhancing activity). BAL fluid concentrations of IL-1 beta were significantly greater at 4:00 A.M. than at 4:00 P.M. (1.14 +/- 0.6 versus 0.7 +/- 0.6 pg/ml; p = 0.05) in asthmatics with nocturnal airflow obstruction. Moreover, IL-1 beta levels at 4:00 A.M. tended to be higher in subjects with nocturnal asthma than in those without nighttime airflow reduction (1.14 +/- 0.6 versus 0.3 +/- 0.4 pg/ml; p = 0.1). On the other hand, eosinophil survival-enhancing activity in BAL fluid, which is usually associated with IL-3, IL-5, or GM-CSF, was not detected in relationship to nocturnal asthma. Because IL-1 beta can activate air-space cells, particularly alveolar macrophages, we propose that an increased release of this cytokine is a significant contributor to nocturnal airway inflammation and obstruction in asthma.

Exercise-induced asthma is not associated with mast cell activation or airway inflammation.

Exercise-induced asthma (EIA) may affect up to 90% of patients with asthma. Hyperpnea associated with exercise leads to increased airway water and heat loss, which contributes to the development of EIA. Measurement of circulating mediators has suggested that mast cells may participate in the development of EIA via release of histamine and neutrophil chemotactic factor. To evaluate further the contribution of pulmonary mast cell-mediator release in the pathogenesis of EIA and to determine whether EIA is associated with enhancement of airway inflammation, we studied 11 subjects with mild stable asthma (FEV1, 93% +/- 3% predicted; mean +/- SEM) with significant EIA (after exercise fall in FEV1, 41% +/- 5%). Bronchoalveolar lavage (BAL) was performed immediately (less than 1 hour) after exercise challenge (EC) and repeated 24 hours later (exercise studies). On another occasion, paired BALs were done 24 hours apart (control studies). A minimum of 2 weeks separated the exercise and control pairs. No changes were observed in BAL cell counts, differentials, or reactive oxygen species metabolism after EC. Neither BAL histamine nor BAL tryptase levels increased, either shortly (less than 1 hour) or 24 hours after EC. We conclude that EC in subjects with asthma is not associated with cellular influx to airspace and that mechanisms other than histamine release by pulmonary mast cells may be responsible for EIA.

Antigen-induced airway inflammation in atopic subjects generates dysfunction of pulmonary surfactant.

If pulmonary surfactant develops a dysfunction, its ability to maintain patency of narrow conducting airways diminishes, which is likely to cause an increased airway resistance. We hypothesized that antigen challenge will cause inflammation in the conducting airways and that this will cause a surfactant dysfunction. Twenty atopic patients underwent bronchoalveolar lavage (BAL) 5 min and 48 h after challenge with antigen in one segment and with saline solution in another. BAL fluid (BALF) cell count, differential, and proteins were determined. Surfactant function was studied with a capillary surfactometer (CS), an instrument specifically designed to evaluate surfactant's ability to maintain patency. Eosinophils increased 80-fold 48 h after antigen challenge and total protein increased from 84 to 241 micrograms/ml (median values). BALF surfactant lost part of its ability to maintain openness of the capillary, from 68.8% to 14.0% (p < 0.05). Protein concentration negatively correlated with percent openness (r = -0.62, p = 0.005). We conclude that the antigen challenge resulted in an inflammatory reaction that caused pulmonary surfactant to lose some of its ability to maintain airway patency and speculate that surfactant dysfunction is probably an important factor contributing to increased airway obstruction in allergen-induced exacerbation of asthma.

Bronchoalveolar lavage in stable asthmatics does not cause pulmonary inflammation.

Bronchoalveolar lavage (BAL) has become an important tool for evaluating changes in airway cells and fluid in asthma, and it may give insights into mechanisms of bronchial inflammation. Many factors contribute to airway inflammation in asthma including, possibly, airway instrumentation. To establish whether BAL leads to diffuse airway inflammation in stable asthmatics, we performed paired BAL studies (24 h apart) in eight subjects with mild asthma whose prebronchoscopy spirometric results were similar on both days. Airflow limitation did not occur in any subject after bronchoscopy. We observed no significant changes in BAL volume return, cell differential, lymphocyte subsets, reactive oxygen species metabolism by air-space cells, or BAL total protein. There was a slight increase in second-day BAL total cell return. We conclude that bronchoscopy and BAL in stable asthmatics with mild disease is not associated with evidence of diffuse airway inflammation.