Sputum induction: review of literature and proposal for a protocol

Since the 1980s, sputum induction by inhalation of hypertonic saline has been successfully used for diagnosing Pneumocystis carinii pneumonia in patients infected with HIV. In recent years, sputum induction and its subsequent processing has been refined as a noninvasive research tool providing important information about inflammatory events in the lower airways, and it has been used for studying various illnesses. In asthma, one application is to use sputum inflammatory indices to increase our understanding of complex relationships between inflammatory cells, mediators, and cytokine mechanisms. In chronic obstructive pulmonary disease, sputum assessment could be used as a screening test before deciding on long-term corticosteroid treatment. In tuberculosis, sputum induction is a valuable diagnostic tool for HIV-seropositive patients who do not produce sputum. Sputum induction appears to be a relatively safe, noninvasive means of obtaining airway secretions from subjects with cystic fibrosis, especially from those who do not normally produce sputum. Moreover, sputum induction can also be used in chronic cough and lung cancer. Generally, induction is performed through ultrasonic nebulizers, using hypertonic saline. It is recommended that sputum be processed as soon as possible, with complete homogenization by the use of dithiothreitol. We have also shown in this article an example of a protocol for inducing and processing sputum employing a nebulizer produced in Brazil.

Study of cytokine gene expression in small cell samples: use in induced sputum

Sputum examination is being increasingly used as a non-invasive method for the study of airway inflammation. However, the technical applications of sputum are still limited because of the small number of cells recovered. In attempt to extend applications of sputum examinations, we developed and standardised, the reverse transcriptase-polymerase chain reaction (RT-PCR), a sensitive and specific technique of detection of mRNA, in induced sputum samples. Total RNA were extracted from samples containing as few as 50 to 80,000 cells, using a phenol-chloroform extraction method. RT-PCR was successfully tested on beta-actin, interferon-gamma (IFN-gamma), interleukin-4 (IL-4) and tumour necrosis factor-beta (TGF-beta) genes. This protocol provides a simple technique to extract total RNA from a few number of induced sputum cells. It permits the semi-quantitatively study of cytokine gene expression in airways with simple means.

Subepithelial basement membrane immunoreactivity for matrix metalloproteinase 9: association with asthma severity, neutrophilic inflammation, and wound repair

BACKGROUND

Asthma likely involves an active injury and repair process, including components such as neutrophils and matrix metalloproteinase 9 (MMP-9). Although MMP-9 is increased in lavage fluid and sputum in patients with asthma, controversy exists as to the role of tissue MMP-9.

OBJECTIVE

The purpose of this study was to determine whether increases in submucosal cellular MMP-9, matrix MMP-9 (subepithelial basement membrane [SBM]), or both would be associated with severe asthma, neutrophilic inflammation, and wound repair.

METHODS

Immunohistochemical staining and analyses of MMP-9, inflammatory cells, transforming growth factor beta, and collagen I were performed in endobronchial biopsy specimens, bronchoalveolar lavage fluid, or both from 38 patients with severe asthma and compared with results in 10 patients with mild asthma, 8 patients with moderate asthma, and 10 healthy control subjects.

RESULTS

A significantly greater proportion of patients with severe asthma demonstrated MMP-9 staining of the SBM than control subjects (P =.02). Bronchoalveolar lavage MMP-9 levels were also increased in patients with severe asthma (P =.0004). The numbers of submucosal neutrophils and macrophages, but not eosinophils, were significantly higher in asthmatic individuals with MMP-9 staining of the SBM (P =.004 and P =.01, respectively). However, the presence of SBM MMP-9 was associated with a high correlation between lavage and tissue eosinophils (r = 0.58, P =.009). Although the SBM thickness did not differ between groups, higher numbers of transforming growth factor beta-positive cells were seen in subjects with SBM MMP-9 staining. Pulmonary function was significantly lower in those asthmatic subjects with SBM staining.

CONCLUSIONS

These results suggest that localized tissue MMP-9 might play an important role in wound repair and cell trafficking.

Asthma remission: does it exist?

Subjects believed to have grown out of asthma often develop symptoms again later in life. Ongoing airway inflammation may determine the risk of relapse, although the mechanisms involved are still misunderstood. Additionally, patients with asthma during childhood may develop irreversible airflow obstruction ( airway remodeling) as a result of chronic airway inflammation. Recently, airway inflammation and remodeling could be demonstrated in bronchial biopsy specimens from young adults who considered themselves grown out of asthma. It is also shown that evidence of airway inflammation and remodeling can be obtained noninvasively, thereby providing the opportunity to monitor disease activity. If chronic airway inflammation and/or remodeling are consistent findings in asymptomatic subjects with a history of atopic asthma, the question arises whether natural history can be positively altered with prolonged antiinflammatory therapy. Benefits of long-term prognosis are, however, not yet shown. Since epidemiologic work has demonstrated that a certain percentage of subjects with apparently outgrown atopic asthma remains asymptomatic without needing therapy for the rest of their lives, it can be argued that "asthma remission does exist." The question is whether this percentage can be increased with prolonged antiinflammatory therapy and regular control.

The effect of dithiothreitol on VLA-4 detection in peripheral blood and induced sputum cells

BACKGROUND

Induced sputum has been shown to be a reliable technique for investigating airway inflammation non-invasively. Flow cytometry could provide useful information in this area. However, the viscosity of the sample entails the use of a mucolytic agent. Dithiothreitol (DDT) is the most frequently used agent although it could affect detection of different inflammatory markers.

METHODS

To measure the effect of DDT on the detection of certain adhesion molecules in eosinophils and lymphocytes, sputum was induced from seven non-smoking asthmatic and non-asthmatic subjects treated with 0.1 M DDT. The samples were analyzed by flow cytometry. Whole blood samples from the same subjects were also processed with DTT and analyzed by flow cytometry.

RESULTS

Very late activated antigen-4 (VLA-4) levels on eosinophils in intracellular and surface staining were much lower than expected. VLA-4 on lymphocytes was also altered but less so than on eosinophils. VLA-4 levels were also decreased on blood cells after DTT treatment. No abnormalities were found in the detection of CD29 on eosinophils and the beta7-chain in lymphocytes.

CONCLUSIONS

Flow cytometry could be used as a complementary method to induced sputum in the investigation of airway inflammation. However, DTT could interfere with the detection of some inflammatory markers, as is the case with VLA-4.

Effect of age on allergen-induced structural airway changes in brown Norway rats

It remains to be fully established whether allergen-induced airway inflammation and remodeling are influenced by age. The aim of the present study was to compare allergen-induced airway changes in young and adult rats. Brown Norway rats were sensitized at 4 weeks of age (young) or 13 weeks of age (adult) and exposed to aerosolized ovalbumin (OA) or phosphate-buffered saline for 2 weeks. In both age groups OA exposure induced an increase in OA-specific Immunoglobulin E and in the number of peribronchial eosinophils. OA-challenged animals also developed an increase in total airway wall area, enhanced fibronectin deposition, and goblet cell hyperplasia. Both inflammatory and structural alterations were more pronounced in the airways of young compared with adult OA-exposed rats. The number of peribronchial eosinophils was increased in young animals (685.4 +/- 75.0 versus 389.9 +/- 37.8/mm2 in adult rats; p < 0.001). A higher degree of goblet cell hyperplasia was observed in young rats (65.37 +/- 4.68 versus 34.74 +/- 3.68/mm basement membrane in adult rats; p < 0.001) and area of fibronectin deposition in the airway wall was higher in young compared with adult animals (5.08 +/- 0.46 versus 3.62 +/- 0.29 microm2/microm basement membrane; p < 0.005). In conclusion, in young rats airways are more susceptible to allergen-induced inflammatory and structural airway changes.

Sputum processing: a new method to improve cytospin quality

BACKGROUND

Sputum examination is being increasingly used as a non-invasive method for studying airway inflammation. However, the application of sputum still presents some methodological problems and the results of sputum analysis may be substantially flawed by salivary contamination, cell and mucus debris. In addition, much work is needed to deepen the possibility of extensive application of cell and molecular biology techniques to sputum analysis.

OBJECTIVE

In an attempt to improve the technique of sputum processing, we investigated the effect of: (i) 20 and 11 microm filtration in addition to 40 microm on salivary contamination; (ii) Percoll density gradient centrifugation on sputum slides quality; (iii) a culture medium (Minimum Essential Medium containing HEPES 22 mm, pH 7.4: MEM) as washing and suspension solution compared to PBS on cell viability.

METHODS

Induced sputum samples were obtained in 37 asthmatics. 21 samples were processed as selected sputum and 16 samples as entire expectorates. After dithiotreitol (DTT) homogenization, each specimen was aliquoted in two parts of equal volume. One portion was processed with the usual method, the other using a modified method: cell pellet was suspended in sterile MEM, filtered through 40, 20 and 11 microm net filters and separated from the residual debris by Percoll gradient centrifugation.

RESULTS

As compared to the current sputum processing this method resulted in: (i) no selective bronchial cellular loss; (ii) a significant decrease of salivary contamination, particularly in entire expectorates in which squamous cells were reduced from 47 (36) to 15.5% (20) as median values and interquartile range; (iii) a higher proportion of good quality cytospins; (iv) maintenance of cell viability over the time (88% vs. 81% in MEM and PBS, respectively) 1 h after sample collection.

CONCLUSION

In the present study we demonstrated that the proposed method is feasible and makes it possible to overcome most of the technical limits met with the commonly used method, pointing to a potential extension of induced sputum application for more sophisticated techniques.

Eosinophilic airway inflammation as an underlying mechanism of undiagnosed prolonged cough in primary healthcare patients

Prolonged cough is a common problem in patients seen in general practice. Using a simple method of sputum induction and processing of sputum samples, we determined whether eosinophilic airway inflammation could be a cause of undiagnosed prolonged cough. Eighty-two patients who had had cough for more than 1 month were enrolled into the study, in six primary healthcare centres. Patients with known pulmonary disease, including asthma or chronic obstructive pulmonary disease (COPD), or who were known to have another cause of cough, or to have recently suffered from a respiratory infection, were excluded. Fifty-three healthy individuals served as controls. Sputum was induced by inhalation of 3% saline. Inflammatory cells in smears were studied semi-quantitatively. Concentrations of eosinophil cationic protein (ECP), eosinophil peroxidase (EPO), myeloperoxidase (MPO) and human neutrophilic lipocalin (HNL) were determined. Sputum induction proved safe and adequate samples were obtained from 91%. Sputum eosinophilia (eosinophils accounting for more than 5% of all cells in smears) was present in 14 patients with prolonged cough (19%) but in no healthy individual (P=0.001). Five of the 14 individuals (36%) who exhibited sputum eosinophilia appeared to have asthma, while nine of the 14 (64%) did not. Concentrations of ECP and EPO were higher in patients with prolonged cough than in healthy individuals (P=0.02 for ECP; 0.005 for EPO). We conclude that eosinophilic airway inflammation is a fairly common cause of prolonged cough, even in patients not suffering from asthma or COPD, or in whom no other cause of cough is known to be present. Induced sputum samples obtained in health centres can be studied in a central laboratory. Detection of eosinophilic airway inflammation could aid the decision regarding treatment.

Induced sputum derives from the central airways: confirmation using a radiolabeled aerosol bolus delivery technique

Indirect evidence suggests that induced sputum derives from the surfaces of the bronchial airways. To confirm this experimentally, we employed a radiolabeled aerosol bolus delivery technique that preferentially deposits aerosol in the central airways in humans. We hypothesized that there would be significantly more radioactivity recovered in an induced sputum sample, and greater airways clearance of radiolabeled particles, immediately after a central versus peripheral airways deposition. Ten healthy volunteers underwent radiolabeled aerosol deposition ((99m)Tc sulfur colloid particles) to the central and peripheral airways on separate occasions followed immediately by induced sputum or no sputum (control), while seated in front of a gamma camera. Radioactivity was measured in the selected sputum sample, processed cell pellet, and supernatant fraction. Significantly more radioactivity was present in all portions of the sputum sample after central versus peripheral airways deposition (i.e., selected sample: 15,607 counts +/- 2,985 versus 943 counts +/- 298, p = 0.001). Clearance from the whole lung was significantly greater 40 min after central versus peripheral airways deposition (48 +/- 3% versus 5 +/- 1%, p = 0.0001). Compared with control, induced sputum greatly enhanced clearance after central deposition (48 +/- 3% versus 11 +/- 6%, p = 0.0001), but not after peripheral deposition (5 +/- 1% versus 3 +/- 0.8%). These results provide direct evidence that induced sputum derives from the central airways with little or no contribution from the peripheral airways.

Increased expression of the chemoattractant cytokines eotaxin, monocyte chemotactic protein-4, and interleukin-16 in induced sputum in asthmatic patients

BACKGROUND

Induced sputum from asthmatic patients has been recently used to assess inflammatory cells. We have previously reported an increased expression of Th-2-type cytokines in induced sputum of asthmatic patients. C-C chemokines, particularly eotaxin and monocyte chemotactic protein (MCP)-4, are associated with eosinophilic infiltration. Interleukin (IL)-16 is associated with chemotactic activity for CD4+ cells. Chemokine expression in BAL and bronchial biopsy specimens has been demonstrated in asthmatic airways, but not in induced sputum.

METHODS

We examined whether eotaxin, MCP-4, and IL-16 expression could be detected in induced sputum of asthmatic patients (n = 10), and whether the expression was increased compared to normal control subjects (n = 9). Eotaxin, MCP-4, and IL-16 immunoreactivity were determined by immunocytochemistry. In addition, inflammatory cells were investigated using markers for T cells (CD3), eosinophils (major basic protein [MBP]), macrophages (CD68), neutrophils (elastase), and epithelial cells (cytokeratin).

RESULTS

Our results showed that there was a significant difference in the percentages of MBP-positive and epithelial cells between asthmatic patients and normal control subjects (p < 0.05). However, there was no difference between these two groups in the percentage of CD3-, elastase-, and CD68-positive cells. Immunoreactivity for eotaxin, MCP-4, and IL-16 was expressed in the induced sputum of all asthmatic patients, and expression of these chemotactic cytokines was significantly greater than in control subjects (p < 0.001, p < 0.005, and p < 0.001, respectively).

CONCLUSIONS

This study showed that induced sputum could be used to detect chemokines in patients with bronchial asthma, and that the upregulation of chemotactic cytokines in the airways can be seen using noninvasive techniques.

Granulocyte markers in induced sputum in patients with respiratory disorders and healthy persons obtained by two sputum-processing methods

Induced sputum is increasingly used to detect and monitor airway inflammation in respiratory diseases. However, the processing of sputum has been rather laborious for clinical practice. The aim of this study was to improve the practicality of induced-sputum studies by simplifying sample processing. Eosinophil cationic protein (ECP), eosinophil peroxidase (EPO), neutrophil lipocalin (HNL) and myeloperoxidase (MPO) were used as biochemical markers of airway inflammation and the results of the study method were compared with a previously validated (reference) method. Induced sputum was obtained from 42 healthy controls, 10 subjects with acute respiratory infection, eight patients with chronic obstructive pulmonary disease (COPD) and 17 asthmatics. The sputum sample was divided into two parts and treated either: (i) by the reference method (released markers), where sputum was homogenized with dithiotreitol and centrifuged to yield cell-free supernatant and a cell pellet, or (ii) by the study method (total markers), where the cells were lysed after homogenization so that cell-associated markers were released and solubilized. For comparison, the four biochemical markers were measured in sputum supernatant and in sputum lysate. The differential cell count was performed from the cell pellet in the reference method. Repeatability was assessed in a group of 16 subjects. The effect of reagents and the recovery of assays were also evaluated. Released and total markers correlated well (ECP r(s)=0.80, P<0.0001; EPO r(s)=0.49, P<0.0001; HNL r(s)=0.87, P<0.0001; MPO r(s)=0.71, P<0.0001). Incubation with dithiotreitol and lysis reagent had no negative influence on marker assays. The within-subject variability of total ECP, MPO and HNL in both methods was small in two measurements taken I week apart. The study method, measuring total inflammatory markers, gave comparable results to the reference method, measuring released markers. In the study method the sputum processing was simplified, which may improve its applicability.

Sputum phagocytes from healthy individuals are functional and activated: a flow cytometric comparison with cells in bronchoalveolar lavage and peripheral blood

Cells in the bronchial airways of healthy individuals are continuously exposed to inhaled particulates in the size range 2-5 microm, which preferentially deposit in the bronchial rather than the alveolar lung. Induced sputum obtains cells primarily from the surfaces of bronchial airways. Using flow cytometry, we investigated whether sputum phagocytes demonstrate phenotypes indicative of increased functional activation and inflammation compared to phagocytes from the alveolar airways and peripheral blood (PB) in healthy subjects (N = 17). Sputum macrophages demonstrated increased levels of CD11b, increased oxidative burst, and greater phagocytosis than autologous alveolar macrophages. Expression of CD11b, CD64, and HLA-DR in sputum monocytes was upregulated compared to that in PB monocytes. Sputum neutrophils showed increased expression of CD11b, CD64, CD14, and HLA-DR and were more phagocytic than PB neutrophils. In conclusion sputum/bronchial phagocytes from healthy individuals express an inflammatory phenotype and are functionally more active than phagocytes from the alveolar airways and peripheral blood.

Induced sputum: diagnostic value in interstitial lung disease

Induced sputum by inhalation of hypertonic saline solution is a noninvasive technique used to collect cellular and soluble material from lung airways. During the past decade, this method has been widely used to assess airway inflammation in asthma and chronic obstructive pulmonary disease, since it produces reliable results and compares favorably to other invasive techniques, such as biopsy and bronchoalveolar lavage (BAL). Induced sputum has been recently used to study interstitial lung disease (ILD), more specifically pneumoconiosis, sarcoidosis, and nongranulomatous ILD. Moreover, results from induced sputum supplied information comparable to BAL findings for occupational lung disease and were able to distinguish sarcoidosis patients from healthy subjects and from patients with nongranulomatous ILD. Although induced sputum had previously provided promising results in assessing patients with ILD, its diagnostic role has not yet been well defined. Further studies of the evaluation by induced sputum of grading of severity, follow-up of disease, and effects of treatment are needed. Additionally, to date no specific studies have been undertaken to evaluate the safety and functional effects of sputum induction on patients with ILD. In conclusion, we think that induced sputum can be used as a complementary tool to BAL both in research and in clinical monitoring of patients with ILD.

House dust mite-specific IgE antibodies in induced sputum are associated with sputum eosinophilia in mite-sensitive asthmatics

BACKGROUND

Although allergen-specific IgE antibodies have been considered to play an important role in the pathogenesis of atopic asthma, the role of IgE antibodies in the development of airway inflammation is not well defined.

OBJECTIVE

To evaluate the association between allergen-specific IgE antibodies and inflammation of the asthmatic airway.

METHODS

We measured house dust mite (HDM; Dermatophagoides farinae)-specific IgE antibodies in both serum and induced sputum from 16 HDM-sensitive asthmatic patients, and evaluated their association with sputum eosinophilia and eosinophil cationic protein (ECP) levels in induced sputum.

RESULTS

Levels of HDM-specific IgE antibodies in induced sputum were significantly higher in asthmatic patients than in controls (P < .01). In asthmatic patients, levels of HDM-specific IgE antibodies were significantly higher in induced sputum samples with eosinophilia (sputum eosinophil count > or = 5% of 200 counted non-squamous cells) than in those without eosinophilia (P < .05). There were no significant differences in serum levels of HDM-specific IgE antibodies between asthmatic patients with sputum eosinophilia and asthmatic patients without sputum eosinophilia. In asthmatic patients, sputum ECP levels were significantly correlated with levels of HDM-specific IgE antibodies (r = 0.60, P = .01) in induced sputum but not with those in serum.

CONCLUSION

We conclude that allergen-specific IgE antibodies in induced sputum from atopic asthmatics are associated with sputum eosinophilia. This result suggests that IgE-dependent mechanisms are involved in eosinophilic inflammation of the airway in atopic asthmatics.

Induced sputum and bronchoalveolar lavage as tools for evaluating the effects of inhaled corticosteroids in patients with asthma

Changes in airway inflammation can be studied with bronchoalveolar lavage, but the widespread use of this procedure is limited by its invasiveness. The aim of this study was to evaluate the usefulness of induced sputum as a non-invasive alternative to bronchoalveolar lavage for studying changes in airway inflammation in patients with asthma. Thirty patients were treated for 12 weeks with an inhaled corticosteroid (fluticasone propionate (FP), 250 microg twice daily) or a short-acting beta-agonist (salbutamol (Sb), 400 microg twice daily) in a double-blind, double-dummy, randomized parallel group study. Sputum induction with hypertonic saline solution was performed twice before treatment and after 4, 8, 10, and 11 weeks of treatment. Bronchoalveolar lavage fluid divided into two pools (first 60 mL portion as bronchoalveolar lavage/bronchial wash (BAL/BW) and subsequent 80 mL as bronchoalveoalar lavage (BAL)) was obtained before and after 12 weeks of treatment. Changes in cell differentials and plasma-protein leakage (alpha2-macroglobulin, albumin, and their ratio (relative coefficient of excretion, RCE)) were analyzed in induced sputum and were compared with changes in BAL/BW and BAL. During treatment with FP, the PC20histamine (interpolated concentration of histamine that caused a fall in FEV1 of 20% of the baseline value) increased (P < .0001), and the percentage of eosinophils (P = .004), levels of (alpha2-macroglobulin (P = .09) and RCE (P = .007) decreased in sputum. These changes were different from those in the Sb group (PC20histamine P< .0001, eosinophils P= .004, alpha2-macroglobulin P= .003, RCE P = .01), in which alpha2-macroglobulin showed a significant increase (P = .015). Changes in the percentage of eosinophils and in the levels of alpha2-macroglobulin in sputum were associated with changes in the PC20histamine (Rs = -0.59, P = .007 and Rs = -0.47, P = .03, respectively). These correlations did not reach significance in BAL/BW and BAL fluid. The statistical power to detect changes in induced sputum was higher for the percentage of eosinophils and similar for plasma protein leakage as compared with analysis of BAL/BW and BAL fluid. We conclude that the analysis of induced sputum is a useful, non-invasive alternative to bronchoalveolar lavage for assessing the effects of antiinflammatory drugs in asthma.

Noninvasive measurement of airway inflammation using exhaled nitric oxide and induced sputum. Current status and future use

The recent use of IS and the analysis of exhaled mediators such as NO are important steps forward in our ability to noninvasively assess airway inflammation without the need to resort to bronchoscopy. Exhaled NO and IS are complementary techniques that provide different information (Table 1). Induced sputum can provide knowledge regarding the cells and mediators participating in the inflammatory response, but is time consuming and expensive. Exhaled NO measurement is performed simply and quickly, and is a nonspecific marker of an inflammatory process. The initial capital costs of equipment for NO analysis are high, however. Once the problems of standardized collection and oropharyngeal contamination have been dealt with, BC may also prove to be an additional tool for the assessment of airway inflammation. It is likely that the next 10 years will see the establishment of these noninvasive tools for the clinical assessment of airway inflammation and oxidative stress, and change the entire way we manage asthma.

Airway inflammation in asthma and perennial allergic rhinitis. Relationship with nonspecific bronchial responsiveness and maximal airway narrowing

BACKGROUND

Eosinophilic airway inflammation is the hallmark of asthma, but it has also been reported in other conditions such as allergic rhinitis. We have tested whether the analysis of cells and chemicals in sputum can distinguish between patients with mild allergic asthma, those with allergic rhinitis, and healthy controls. The relationship between inflammation markers in sputum and nonspecific bronchial hyperresponsiveness to methacholine (BHR) (PD20 and maximal response plateau [MRP] values) was also evaluated.

METHODS

We selected 31 mild asthmatics and 15 rhinitis patients sensitized to house-dust mite. As a control group, we studied 10 healthy subjects. Every subject underwent the methacholine bronchial provocation test (M-BPT) and sputum induction. Blood eosinophils and serum ECP levels were measured. Sputum cell differentials were assessed, and eosinophil cationic protein (ECP), tryptase, albumin, and interleukin (IL)-5 levels were measured in the entire sputum supernatant.

RESULTS

Blood eosinophils and serum ECP levels were higher in asthma patients and rhinitis than in healthy controls, but no difference between asthma patients and rhinitis patients was found. Asthmatics had higher eosinophil counts and higher ECP and tryptase levels in sputum than rhinitis patients or control subjects. Sputum albumin levels were higher in asthmatics than in controls. Rhinitis patients exhibited higher sputum eosinophils than healthy controls. An association between sputum eosinophil numbers and MPR values (r= -0.57) was detected, and a trend toward correlation between sputum ECP levels and PD20 values (r= -0.47) was found in the rhinitis group, but not in asthmatics. No correlation between blood eosinophilic inflammation and lung functional indices was found.

CONCLUSIONS

Induced sputum is an accurate method to study bronchial inflammation, allowing one to distinguish between rhinitis patients and mildly asthmatic patients. The fact that no relationship was detected between sputum inflammation and BHR suggests that other factors, such as airway remodeling, may be at least partly responsible for BHR in asthma.

Nordic consensus report on asthma management. Nordic Asthma Consensus Group

The work with the Nordic consensus report on asthma management started some years ago. The Nordic countries have common socioeconomic conditions. We acknowledge the international as well as other European guidelines providing valuable recommendations. Nevertheless, we felt the need to combine the common Nordic experiences in order to have a local statement of asthma and asthma care, based upon Nordic clinical science and tradition. The work has been rewarding and we acknowledge many valuable contributions from paediatricians, allergologists and lung physicians in all Nordic countries. The response has so far been positive and we feel that the present material reflects the main opinion of Nordic physicians taking care of asthma patients of all ages. However, the asthma and allergy research field is rapidly developing. Thus, this document should merely be regarded as a time-limited contribution to the continuing scientific discussion of this fascinating field.

A long-term study of the antiinflammatory effect of low-dose budesonide plus formoterol versus high-dose budesonide in asthma

Adding inhaled long-acting beta(2)-agonists to a low dose of inhaled corticosteroids (ICS), results in better clinical asthma control than increasing the dose of ICS. However, this approach may mask underlying airway inflammation. In a double-blind parallel-group study, we evaluated the effect of adding formoterol to a low dose of budesonide, compared with a higher dose of budesonide, on the composition of induced sputum. After a 4-wk run-in period of treatment with budesonide (800 microg, twice daily), 60 patients with moderate asthma were randomly assigned to a 1-yr treatment with 400 microg of budesonide plus placebo, twice daily (BUD800), or 100 microg of budesonide plus 12 microg of formoterol, twice daily (BUD200+F). All drugs were administered via Turbuhaler. Budesonide (800 microg, twice daily) during run-in significantly reduced median sputum eosinophils from 4.5 to 0.68%. No significant changes in the proportion of eosinophils, EG2(+) cells, other inflammatory cells, or ECP levels in sputum were observed over the ensuing 1-yr treatment with BUD200+F or BUD800. Clinical asthma control was not significantly different between both groups. In conclusion, no significant differences in sputum markers of airway inflammation were observed during a 1-yr treatment with a low dose of inhaled budesonide plus formoterol compared with a higher dose of budesonide.

Prostaglandin H synthase 2 expression in airway cells from patients with asthma and chronic obstructive pulmonary disease

Products of the prostaglandin H synthase (PGHS) metabolic pathway are thought to play a role in the pathogenesis of asthma. We determined the level of expression of the constitutive (PGHS-1) and inducible (PGHS-2) isoforms of the enzyme in induced sputum and bronchial biopsies of patients with asthma, patients with chronic obstructive pulmonary disease (COPD), and unaffected control subjects by immunocyto- and immunohistochemistry. Immunoreactivity for PGHS-2 was significantly greater in the induced sputum of patients with asthma and patients with COPD compared with unaffected control subjects. The level of PGHS-2 was greater in asthma than in COPD. Immunoreactivity for PGHS-1 increased in cells in the induced sputum of patients with asthma and patients with COPD compared with that of unaffected control subjects. Immunostained cells included macrophages, eosinophils, and neutrophils. Greater PGHS-2 immunoreactivity was seen in the submucosal inflammatory infiltrate and in the airway epithelium of patients with asthma compared with unaffected control subjects. In summary, we demonstrate an induction of PGHS-2 in asthma, suggesting increased formation of prostanoids, which may contribute to the inflammatory process.

The relationship between airways inflammation and asthma severity

In order to investigate the relationship between airways inflammation and disease severity, and improve the understanding of persistent asthma, 74 asthmatics, with disease severity ranging from intermittent, to mild to moderate and severe persistent (classified according to the Global Initiative for Asthma [GINA] guidelines), and 22 nonatopic control subjects were studied using the method of induced sputum. Sputum was analyzed for total and differential cell counts concentrations of albumin, and levels of eosinophil cationic protein (ECP), myeloperoxidase (MPO), and tryptase, inflammatory mediators reflecting eosinophil, neutrophil, and mast cell activation. Asthma severity (assessed by FEV(1), peak expiratory flow [PEF] variability, and daily symptom scores) and methacholine airways responsiveness were related to sputum eosinophilia and ECP. In addition, sputum neutrophilia and MPO levels correlated, albeit weakly, with PEF variability and symptom scores, respectively. Tryptase concentrations were raised in mild to moderate asthmatics. Albumin concentrations were significantly raised across the spectrum of asthma severity and correlated with those of tryptase and ECP. Despite treatment with either high doses of inhaled corticosteroids or oral corticosteroids, prominent eosinophilic inflammation with raised ECP was noted. This study points to persistent, disease severity-related airways inflammation in asthma, involving eosinophils, mast cells, and neutrophils, which is evident despite treatment with corticosteroids.

Eosinophilic tracheobronchitis and airway cough hypersensitivity in chronic non-productive cough

BACKGROUND

We have shown that some patients presenting with chronic bronchodilator-resistant non-productive cough have global atopic tendency and airway cough hypersensitivity without non-specific bronchial hyperresponsiveness, abbreviated as atopic cough. The cough is successfully treated with histamine H1-antagonists and/or glucocorticoids.

OBJECTIVE

This prospective study was conducted to elucidate the histological feature of atopic cough.

METHODS

Tracheal and bronchial mucosa obtained by transbronchoscopic biopsy and bronchoalveolar lavage (BAL) cell component were studied with special emphasis on eosinophils in eight non-smokers diagnosed with atopic cough, all of whom had increased sensitivity of cough response to inhaled capsaicin, normal lung function and bronchial responsiveness to methacholine and normal chest roentgenogram. Their cough completely resolved on histamine H1-antagonists and/or glucocorticoids. Transbronchoscopic tracheal and bronchial biopsy and BAL were also performed in healthy non-smokers as a control.

RESULTS

A small number of eosinophils was detected in subepithelium of trachea in six of seven patients and in subepithelium of bronchi in seven of eight cough patients. The numbers of eosinophils in subepithelium of trachea and bronchi were significantly increased in the patients compared with control subjects. There was no BAL eosinophilia in any patients.

CONCLUSION

It is concluded that eosinophilic tracheobronchitis and cough hypersensitivity are pathological and physiological characteristics of atopic cough.

The increased number of very late activation antigen-4-positive cells correlates with eosinophils and severity of disease in the induced sputum of asthmatic patients

BACKGROUND

Lymphocyte function associate-1 (LFA-1), macrophage antigen-1 (Mac-1), and very late activation antigen-4 (VLA-4) are involved in the infiltration of leukocytes into the tissues. Experimental models of allergic inflammation suggest that VLA-4 could determine the selective recruitment of eosinophils into the inflamed airways.

OBJECTIVE

Our purpose was to evaluate the involvement of integrins in eosinophil recruitment in asthma.

METHODS

We evaluated by immunocytochemistry the expression of VLA-4, LFA-1, and Mac-1 and their relationship with inflammatory cells and severity of disease in the induced sputum of 20 mild to moderate atopic asthmatic subjects and in 8 healthy subjects.

RESULTS

The number of VLA-4+ cells is increased in asthmatic patients and VLA-4 is mainly localized on eosinophils. Furthermore, VLA-4+ cells are significantly related to eosinophils. In contrast, LFA-1 and Mac-1 cellular expressions do not differ between asthmatic and control subjects and are not related to any specific cell type. Eosinophils and VLA-4+ cells are significantly higher in moderately compared with mildly asthmatic patients (P <.01, P <.05) and with healthy control subjects (P <.0005, P <.001). Eosinophils and VLA-4+ cells are also higher in mildly asthmatic patients compared with control subjects (P <.001, P <.005).

CONCLUSION

This is the first report demonstrating, by a noninvasive method in humans, that VLA-4+ cells are increased and correlate with the eosinophils in the induced sputum of atopic patients with mild to moderate asthma and that VLA-4 expression is related to the severity of disease.

Ozone-induced inflammation assessed in sputum and bronchial lavage fluid from asthmatics: a new noninvasive tool in epidemiologic studies on air pollution and asthma

We investigated correlations between ozone-induced increases in inflammatory markers in induced sputum and in bronchial lavage fluid. Sixteen volunteers with intermittent asthma participated in a placebo-controlled parallel study with two exposures. Six days before and 16 h after the first exposure to ozone (0.4 ppm during 2 h) sputum was induced with hypertonic saline. This resulted in a significant increase in the sputum levels of eosinophil cationic protein (ECP; 1.8-fold; p = .03), neutrophil elastase (5.0-fold; p = .005) and the total cell number (1.6-fold; p = .02). After 4 weeks, a second exposure was randomized for air or ozone. Six days before and 16 h after the second exposure a bronchial lavage was performed. ECP values in sputum and in bronchial lavage fluid obtained after ozone correlated significantly (Rs = .79; p = .04), as did interleukin-8 (IL-8) values (Rs = .86; p = .01), and the percentage eosinophils (Rs = .89; p = .007). Moreover, the ozone-induced changes in percentage eosinophils observed in sputum and lavage fluid were highly correlated (Rs = .93; p = .003). In conclusion, changes in eosinophils, IL-8, and ECP markers induced by ozone and measured in sputum reflect the inflammatory responses in the lower airways of asthmatics, and may provide a noninvasive tool in epidemiologic studies on air pollution and asthma.

Flow cytometry in the exploration of the physiopathology of occupational lung disease

Flow cytometry is a simple analytical technique used for the investigation of cells taken from various sources. Cells are identified by both their physical characteristics and the presence or absence of specific molecules on the cell surface. These molecules may be either phenotypic, or induced by a specific stimulus. Flow cytometry has been used to identify the nature and extent of the immune response in several occupational respiratory conditions including occupational asthma, irritant induced respiratory problems, and asbestos related lung disease. Also, it may be of value in monitoring workplace exposure to some hazardous materials. Although of limited diagnostic value at present, the technique has provided an insight into the modulation of immune cells, and their function, in people exposed to hazardous materials in the workplace. In this review, the principals of flow cytometry will be explored and the use of flow cytometry to investigate occupational respiratory disease will be discussed.

How do we monitor asthma control?

The present consensus on asthma management includes avoidance of triggers, education, regular follow-up, and an action plan that relies on symptoms and lung function measurements for the monitoring of disease severity. Inclusion of objective measurements for monitoring seems to be important because patients and physicians may not always recognize asthma symptoms or their severity. However, the additional value of monitoring peak flow and symptoms in guiding asthma therapy has not been well established. Furthermore, it can be questioned whether a treatment strategy which is solely based on optimizing symptoms and lung function leads to optimal control of asthma in each individual patient, since airway hyperresponsiveness (AHR) and airways inflammation may persist. The chronicity of such abnormalities may lead to airways remodelling, thereby worsening the long-term outcome of asthma. It has been shown that AHR provides prognostic information on asthma control, because it can serve as a valuable noninvasive surrogate marker of airways inflammation when added to the guides of asthma therapy. A limited increase in dose of inhaled steroids, instead of applying an increased dose indiscriminately, can be successfully tailored to the needs of the individual patient based on the degree of AHR. Such a strategy leads to both a better clinical outcome and a better histologic outcome. The present worldwide effort is to find alternative markers of airways inflammation in asthma that can be easily implemented in routine practice. In the near future, longitudinal studies will determine which parameter is potentially most useful in guiding asthma management.

Early treatment of asthma

The early treatment of asthma was not greatly studied before the 1990s. Subjects included in intervention trials have usually had persistent asthma with a long duration of symptoms. Only a few studies have been done on early intervention. It has also become obvious that eosinophilic airway inflammation is common and does not always significantly affect lung function. If patients do not fulfill the functional criteria for asthma, they may not receive specific diagnosis and effective treatment. I have suggested the term "asthma-like inflammation" to describe the disorder of such patients. Bronchial obstruction and increased bronchial responsiveness are outcomes of the inflammatory process, and it may be argued that detection of eosinophilic inflammation is always late at the time asthma is diagnosed. The diagnosis of asthma is often severely delayed, a fact which influences the prognosis and efficacy of therapeutic interventions. The benefits of early treatment of symptomatic asthma have been shown, and several international guidelines recommend anti-inflammatory medication, preferably with inhaled steroids as first-line treatment to gain control of the disease as fast as possible. Very few studies, however, have addressed the long-term influence of various therapeutic approaches. Usually, the beneficial effects gradually disappear when treatment is withdrawn. There is no convincing evidence that any of the current pharmacologic therapies can change the natural course of asthma. Nevertheless, inhaled steroids seem to have a disease-modifying effect if started early enough, and there is a consensus that steroids abolish symptoms, improve lung function, and decrease the need for hospitalization and probably the mortality rate. In future, various combinations of immunologic and pharmacologic treatments may offer more permanent results in asthma therapy.

Airway inflammation in asthma and chronic obstructive pulmonary disease with special emphasis on the antigen-presenting dendritic cell: influence of treatment with fluticasone propionate

Asthma is a chronic inflammatory disorder of the airways characterized by variable airflow limitation and airway hyperresponsiveness. The type of inflammatory response in asthma is compatible with a major contribution of professional antigen-presenting cells. The airways in chronic obstructive pulmonary disease (COPD) are also markedly inflamed; however, the predominant types of inflammatory cells and the main anatomical site of the lesion appear to differ from those in asthma. COPD is characterized by reduced maximum expiratory flow and slow forced emptying of the lungs. Steroids are the most prominent medication used in the treatment of asthma and COPD; however, the beneficial effect of steroid treatment in COPD is subject of debate. We investigated the efficacy of fluticasone propionate (FP) treatment in atopic asthmatics and in COPD patients with bronchial hyperreactivity who smoke. The effect of the treatment on bronchial hyperreactivity and indices of the methacholine dose-response curve were analysed, as well as indices of inflammation of the airway mucosa with special emphasis on the antigen presenting dendritic cell. Treatment of allergic asthmatic patients resulted in improvement of lung function (FEV1), a decrease in bronchial hyperresponsiveness and a decrease of maximal airway narrowing. During the FP-treatment of COPD patients, FEV1 remained stable, while FEV1 deteriorated significantly in the placebo group. Therefore, steroid treatment may have a beneficial effect in COPD patients with bronchial hyperresponsiveness (BHR). Since immunohistochemical analysis of bronchial biopsy specimens from asthma and COPD patients show disease-specific aspects of inflammation, the anti-inflammatory effect of FP is obtained through modulation of different cell populations in asthma and COPD.

Interleukin-5 production by human airway epithelial cells

Interleukin (IL)-5 is a pleiotropic cytokine that exhibits biologic activity on cells of diverse hemopoieitic lineages. IL-5 enhances mediator release from human basophils and plays a pivotal role in the chemoattraction, proliferation, differentiation, survival, and activation of eosinophils. Th2- and Tc2-like T cells, mast cells, basophils, and eosinophils are the known cellular sources of this cytokine. Using a sensitive and novel reverse transcription-polymerase chain reaction enzyme-linked immunosorbent assay system, we found that IL-5 messenger RNA (mRNA) was constitutively expressed in bronchial biopsies obtained from healthy individuals, and that the levels of IL-5 mRNA expression decreased 1. 5 h after exposure to 0.12 ppm ozone for 2 h. Because the oxidative effects of ozone are confined to the epithelial cell surface and it is known that ozone induces epithelial damage and shedding, we hypothesized that epithelial cells might be a source of IL-5 mRNA. We demonstrate here that both transformed human bronchial epithelial cell lines (A549 and 16HBE14o-) and primary human bronchial and nasal epithelial cells grown in culture constitutively express IL-5 mRNA, which is upregulated on stimulation with tumor necrosis factor (TNF)-alpha. Culture supernatants derived from A549 cells exposed to TNF-alpha and interferon-gamma demonstrated detectable levels of IL-5 protein, and immunostaining of bronchial biopsies obtained from healthy human airways revealed the presence of IL-5 protein localized to the bronchial epithelium. To our knowledge, this is the first report demonstrating IL-5 production by human airway epithelial cells. This observation provides further evidence for the role of airway epithelium in regulating airway immune responses, in particular enhancing chemotaxis, activation, and survival of eosinophils, which could play an important role in the pathogenesis of bronchial asthma.

Analysis of induced sputum to examine the effects of inhaled corticosteroid on airway inflammation in children with asthma

BACKGROUND

Analysis of induced sputum can be performed safely in children with asthma and is useful for both cellular and biochemical markers of inflammation. Glucocorticosteroid inhalation has become the first line therapy for chronic asthma by suppressing airway inflammation, which produces the decrease of bronchial hyperreactivity and reduces the number of eosinophil in bronchial submucosa.

OBJECTIVE

To determine the characteristics of the inflammatory cells and their markers in sputum and to examine the pharmacokinetic effects of glucocorticoid within 3 hours after inhalation therapy on FEV1 and sputum inflammatory indices in children with clinically defined chronic asthma.

METHODS

Thirty subjects with asthma included 14 current symptomatic asthmatics and 14 normal controls inhaled 4.5% hypertonic saline for 10 minutes by nebulizer. The expectorated sputum were collected from all asthmatics before and 3 hours after corticosteroid inhalation for children with asthma and were reduced by dithiotreitol. Total cell counts and differentials were determined. ECP was measured by CAP system. Interleukin-5, GM-CSF and albumin were measured by double sandwich ELISA.

RESULTS

The mean eosinophil percentage and ECP in induced sputum of asthmatics were significantly higher than that of controls. The induced sputum samples obtained after glucocorticoid inhalation showed a significant reduction in mean eosinophil percentage, but FEV1, IL-5, GM-CSF, albumin, and ECP values were not significantly decreased.

CONCLUSION

The present results in induced sputum may be interpreted to reflect direct steroid action on airways and lack of effect on bone marrow effectors at 3 hours after glucocorticoid inhalation.

Role of bronchoscopy in asthma research

Over the past 15 years, much has been learned about the presence of airway inflammation in asthma through the use of investigative bronchoscopy. It has become quite clear that inflammation is present even in mild asthma. In addition to the eosinophils, T-lymphocytes and a variety of cytokines have been identified to play a prominent role in asthmatic inflammation. The concept of delayed asthmatic response after allergen exposure and its relationship to cellular inflammation and airway hyper-reactivity has become more clearly established. Our understanding of asthmatic airway inflammation, however, is incomplete. As interesting as the database has been so far, investigative FB has not defined a unique profile for patients with asthma. Specifically, lavage or endobronchial biopsy has not identified parameters that help in the diagnosis, assessment of disease severity, prognosis, or likelihood to respond to specific therapies. Also, the exact relationship between parameters in lavage compared with mucosal biopsy and how these are related to airway hyper-reactivity and the clinical syndrome of asthma remains poorly understood. In this regard, it must be confessed that currently FB with lavage and biopsy in asthmatics needs to be considered as a research tool for specimen retrieval to help characterize and express inflammation. Although these techniques have contributed immensely to our understanding of asthma pathogenesis, presently these techniques do not have any practical role or clinical usefulness.

Eosinophilic inflammation assessed by induced sputum in corticosteroid-dependent asthma

Sputum induction can be used to study airway inflammation in asthmatics. However, it has not been used in patients with corticosteroid-dependent asthma requiring long-term oral corticosteroids. The aim of the study was to assess the number of eosinophils and the levels of eosinophil cationic protein (ECP) in sputum of 17 corticosteroid-dependent asthmatics by comparison with nine mild untreated asthmatics, 10 moderate asthmatics receiving inhaled steroids (ICS) and 11 healthy subjects. In the 17 corticosteroid-dependent asthmatics, we examined sputum eosinophil markers on two occasions and correlated with the control of asthma. Eosinophils were undetectable in controls and were detected in 63.8% of asthmatics. There were no significant differences between the three groups of asthmatics. ECP levels were significantly increased in ICS or corticosteroid-dependent asthmatics by comparison to controls and mild asthmatics. There was no significant difference between ICS and corticosteroid-dependent asthmatics. During follow-up, corticosteroid-dependent asthmatics with a controlled disease had no significant change in eosinophil numbers or ECP levels. On the other hand, corticosteroid-dependent asthmatics with recent exacerbations had a non-significant increase in eosinophil numbers and a significant increase in ECP levels. This study shows that ECP levels may be more accurate than eosinophil numbers in assessing exacerbations in corticosteroid-dependent asthmatics.

Suppressive activity of bronchial macrophages recovered by induced sputum

BACKGROUND

The immunomodulatory activity of macrophages was shown to be a crucial mechanism in the pathogenesis of asthma.

METHODS

Induced sputum (IS) and methacholine challenge (MC) were carried out in 21 atopic subjects. Suppressive activity (SA) of sputum macrophages (SMO) was investigated on autologous peripheral lymphocytes (APL) proliferation in 12 of these patients and compared to the MC.

RESULTS

In 10 of the 21 patients, the FEV1 was >80%; five of these had a nonreactive MC. Eosinophils and metachromatic cells correlated well (r=0.6442; P=0.0029), but not with the MC. The SA of SMO correlated (P=0.0152) with the MC: SMO enhanced APL proliferation in five patients with a positive MC, while SMO showed SA in five with a negative MC. Only two patients with suppressive SMO had a positive MC. Cytokine profiles from five patients showed that two patients with a negative MC had interleukin (IL)-1alpha and beta, IL-6, and transforming growth factor (TGF)-beta transcripts, while two patients with a positive MC transcripted IL-4 and IL-5. One patient with a borderline MC transcripted IL-5, but not IL-4.

CONCLUSIONS

These data support the theory that patients with reduced suppressive bronchial macrophages display clinical bronchial hyperreactivity.

The effect of montelukast (MK-0476), a cysteinyl leukotriene receptor antagonist, on allergen-induced airway responses and sputum cell counts in asthma

BACKGROUND

Cysteinyl leukotrienes are capable of inducing chemotaxis of eosinophils in vitro and within the airways of animals and humans in vivo.

OBJECTIVE

We hypothesized that montelukast (MK-0476), a potent cysLT1 receptor antagonist, would protect against allergen-induced early (EAR) and late (LAR) asthmatic responses by virtue of anti-inflammatory properties. Hence, we studied the effect of pretreatment with oral montelukast on allergen-induced airway responses. As an exploratory endpoint, changes in inflammatory cell differentials and eosinophil cationic protein (ECP) were evaluated in hypertonic saline-induced sputum.

METHODS

Twelve asthmatic men (20-34 years, FEV1 79-109% predicted, histamine PC20FEV1 <4 mg/mL) with dual responses to inhaled house dust mite extract participated in a two-period, double-blind, placebo-controlled, crossover study. Three oral doses of montelukast (10 mg) or matching placebo were administered 36 and 12 h before, and 12 h post-allergen. The airway response to allergen was measured by FEV1, and the EAR and LAR were expressed as the corresponding areas under the time-response curves (AUC0-3 h and AUC3-8h, respectively). During each study period, sputum was induced with 4.5% NaCl 24 h before and 24 h after a standardized allergen challenge. Processed whole sputum cytospins were stained with Giemsa, and cell counts expressed as percentage nonsquamous cells. ECP was measured by FEIA in sputum supernatants.

RESULTS

All subjects completed the study. The changes in baseline FEV1 were not significantly different between the two pretreatments (P = 0.183). Montelukast significantly inhibited the EAR and LAR, reducing the AUC0-3h by 75.4% (P<0.001) and the AUC3-8h by 56.9% (P = 0.003) as compared with placebo. Sputa of nine subjects could be included in the analysis (<80% squamous cells). Allergen challenge significantly increased sputum eosinophils after placebo (mean change +/- SD: 4.8 +/- 5.8%, P = 0.038), with a similar trend after montelukast (mean change +/- SD: 4.1 +/- 5.4%; P = 0.056). The allergen-induced changes in sputum eosinophils and ECP, however, were not significantly different between the two pretreatments (P = 0.652 and P = 0.506, respectively).

CONCLUSION

We conclude that oral montelukast protects against allergen-induced early and late airway responses in asthma. However, using the present dosing and sample size, this protection was not accompanied with changes in sputum eosinophil percentage or activity, which may require more prolonged pretreatment with cysLT1 receptor antagonists.

CD11b and L-selectin expression on eosinophils and neutrophils in blood and induced sputum of patients with asthma compared with normal subjects

BACKGROUND

Patients with asthma show altered surface expression of the adhesion molecules CD11b and L-selectin on airway granulocytes compared with blood granulocytes.

OBJECTIVE

To investigate whether this modulation is related to disease activity or due to transendothelial migration, we compared the CD11b and L-selectin expression on blood and induced sputum eosinophils and neutrophils between patients with asthma and normal subjects.

METHODS

Eleven normal subjects (21-43 years), nine patients (21-34 years) with mild atopic asthma and 10 patients (20-47 years) with moderate to severe atopic asthma on regular treatment with inhaled steroids underwent sputum induction by inhalation of nebulized hypertonic saline (4.5%). CD11b and L-selectin expression on granulocytes from blood and DTT-homogenized sputum were analysed by flow cytometry. Eosinophils could be discriminated from neutrophils by using depolarized light scatter. Disease activity was assessed by baseline FEV1 and airway responsiveness to histamine (PC20).

RESULTS

Sputum eosinophils showed higher expression of CD11b (P<0.001) and lower expression of L-selectin (P<0.001) compared with peripheral blood eosinophils. CD11b and L-selectin expression on eosinophils from blood or sputum did not differ between the three groups. Similar results were obtained for neutrophils. The PC20 in the patients with moderate-to-severe asthma was related to CD11b expression on blood (R=-0.92, P=0.001) and sputum eosinophils (R=0.75, P=0.02).

CONCLUSIONS

Flow cytometry of induced sputum granulocytes from asthmatic as well as normal subjects is feasible. We conclude that the modulated expression of CD11b and L-selectin on airway granulocytes is not specific for asthmatic airway inflammation, but is probably the result of tissue migration per sé. This implies that CD11b and L-selectin expression on granulocytes in induced sputum cannot be used as marker of disease activity.