Induced sputum: validity of fluid-phase IL-5 measurement

Identification of Two Eosinophil Subsets in Induced Sputum from Patients with Allergic Asthma According to CD15 and CD66b Expression

Two subsets of eosinophils have been described: resident eosinophils with homeostatic functions (rEOS) in healthy subjects and in patients with nonallergic eosinophilic asthma, and inflammatory eosinophils (iEOS) in blood and lung samples from patients with allergic asthma. We explored if it would be possible to identify different subsets of eosinophils using flow cytometry and the gating strategy applied to induced sputum. We conducted an observational cross-sectional single-center study of 62 patients with persistent allergic asthma. Inflammatory cells from induced sputum samples were counted by light microscopy and flow cytometry, and cytokine levels in the supernatant were determined. Two subsets of eosinophils were defined that we call E1 (CD66b-high and CD15-high) and E2 (CD66b-low and CD15-low). Of the 62 patients, 24 were eosinophilic, 18 mixed, 10 paucigranulocytic, and 10 neutrophilic. E1 predominated over E2 in the eosinophilic and mixed patients (20.86% vs. 6.27% and 14.42% vs. 4.31%, respectively), while E1 and E2 were similar for neutrophilic and paucigranulocytic patients. E1 correlated with IL-5, fractional exhaled nitric oxide, and blood eosinophils. While eosinophil subsets have been identified for asthma in blood, we have shown that they can also be identified in induced sputum.

Improved detection of biomarkers in cervico-vaginal mucus (CVM) from postpartum cattle

Background

In the postpartum cow, early diagnosis of uterine disease is currently problematic due to the lack of reliable, non-invasive diagnostic methods. Cervico-vaginal mucus (CVM) is an easy to collect potentially informative source of biomarkers for the diagnosis and prognosis of uterine disease in cows. Here, we report an improved method for processing CVM from postpartum dairy cows for the measurement of immune biomarkers. CVM samples were collected from the vagina using gloved hand during the first two weeks postpartum and processed with buffer alone or buffer containing different concentrations of the reducing agents recommended in standard protocols: Dithiothriotol (DTT) or N-Acetyl-L-Cysteine (NAC). Total protein was measured using the bicinchoninic acid (BCA) assay; interleukin 6 (IL-6), IL-8 and α1-acid glycoprotein (AGP) were measured by ELISA.

Results

We found that use of reducing agents to liquefy CVM affects protein yield and the accuracy of biomarker detection. Our improved protocol results in lower protein yields but improved detection of cytokines and chemokines. Using our modified method to measure AGP in CVM we found raised levels of AGP at seven days postpartum in CVM from cows that went on to develop endometritis.

Conclusion

We conclude that processing CVM without reducing agents improves detection of biomarkers that reflect uterine health in cattle. We propose that measurement of AGP in CVM during the first week postpartum may identify cows at risk of developing clinical endometritis.

Can biomarkers help us hit targets in difficult-to-treat asthma?

Biomarkers may be a key foundation for the precision medicine of the future. In this article, we review current knowledge regarding biomarkers in difficult-to-treat asthma and their ability to guide the use of both conventional asthma therapies and novel (targeted) therapies. Biomarkers (as measured by tests including prednisolone and cortisol assays and the fractional exhaled nitric oxide (NO) suppression test) show promise in the assessment and management of non-adherence to inhaled and oral corticosteroids. Multiple markers of type 2 inflammation have been developed, including eosinophils in sputum and blood, exhaled NO, serum IgE and periostin. Although these show potential in guiding the selection of novel interventions for refractory type 2 inflammation in asthma, and in determining if the desired response is being achieved, it is becoming clear that different biomarkers reflect distinct components of the complex type 2 inflammatory pathways. Less progress has been made in identifying biomarkers for use in difficult-to-treat asthma that is not associated with type 2 inflammation. The future is likely to see further biomarker discovery, direct measurements of individual cytokines rather than surrogates of their activity and the increasing use of biomarkers in combination. If the promise of biomarkers is to be fulfilled, they will need to provide useful information that aids clinical decision-making, rather than being 'just another test' for clinicians to order.

Reliability of a rapid hematology stain for sputum cytology

Objective:

To determine the reliability of a rapid hematology stain for the cytological analysis of induced sputum samples.

Methods:

This was a cross-sectional study comparing the standard technique (May-Grünwald-Giemsa stain) with a rapid hematology stain (Diff-Quik). Of the 50 subjects included in the study, 21 had asthma, 19 had COPD, and 10 were healthy (controls). From the induced sputum samples collected, we prepared four slides: two were stained with May-Grünwald-Giemsa, and two were stained with Diff-Quik. The slides were read independently by two trained researchers blinded to the identification of the slides. The reliability for cell counting using the two techniques was evaluated by determining the intraclass correlation coefficients (ICCs) for intraobserver and interobserver agreement. Agreement in the identification of neutrophilic and eosinophilic sputum between the observers and between the stains was evaluated with kappa statistics.

Results:

In our comparison of the two staining techniques, the ICCs indicated almost perfect interobserver agreement for neutrophil, eosinophil, and macrophage counts (ICC: 0.98-1.00), as well as substantial agreement for lymphocyte counts (ICC: 0.76-0.83). Intraobserver agreement was almost perfect for neutrophil, eosinophil, and macrophage counts (ICC: 0.96-0.99), whereas it was moderate to substantial for lymphocyte counts (ICC = 0.65 and 0.75 for the two observers, respectively). Interobserver agreement for the identification of eosinophilic and neutrophilic sputum using the two techniques ranged from substantial to almost perfect (kappa range: 0.91-1.00).

Conclusions:

The use of Diff-Quik can be considered a reliable alternative for the processing of sputum samples.

Effects of oral prednisone on sputum eosinophils and cytokines in patients with severe refractory asthma

BACKGROUND

Severe asthma occurs in a heterogeneous group of patients in whom symptoms and airway inflammation persist despite maximal antiasthma treatment.

OBJECTIVE

To verify whether a short-term course of oral steroids would modify sputum inflammatory cytokine and sputum eosinophil concentrations and whether this effect is related to the presence of sputum eosinophilia.

METHODS

In 59 patients with severe refractory asthma, we measured pulmonary function and inflammatory markers in hypertonic saline-induced sputum before and after 2 weeks of treatment with 0.5 mg/kg of oral prednisone (n = 39) or placebo (n = 20) daily. Selected sputum portions were assayed for total and differential cell counts and supernatant interleukin (IL) 5 and IL-8 concentrations.

RESULTS

At baseline, no statistical differences were found among placebo- and prednisone-treated patients in terms of sputum inflammatory cell percentages and IL-5 and IL-8 concentrations. After treatment, forced expiratory volume in 1 second significantly increased and sputum eosinophil percentages and IL-5 and IL-8 concentrations significantly decreased in the prednisone group, whereas no changes were observed in the placebo group. The positive effect of prednisone treatment was observed only in patients with baseline sputum eosinophilia, whereas in noneosinophilic patients with severe asthma prednisone induced only a significant decrease of sputum IL-8.

CONCLUSIONS

Additional high-dose oral corticosteroids improve pulmonary function and reduce not only sputum eosinophil but also sputum proinflammatory cytokine concentrations in patients with severe refractory asthma.

Sputum IL-5 concentration is associated with a sputum eosinophilia and attenuated by corticosteroid therapy in COPD

BACKGROUND

Airway inflammation in chronic obstructive pulmonary disease (COPD) is predominately neutrophilic, but some subjects demonstrate eosinophilic airway inflammation. Whether these inflammatory phenotypes have differential cytokine and chemokine expression is unknown.

OBJECTIVES

To assess the sputum concentrations of cytokines and chemokines and their response to oral corticosteroid therapy in COPD subjects with or without a sputum eosinophilia.

METHODS

Cytokine and chemokine concentrations were measured using the meso-scale device platform. To assess validity, recovery of exogenous spikes was examined. The concentrations of the validated mediators were measured in COPD sputum from subjects with or without a sputum eosinophilia. In a subgroup with a sputum eosinophilia, the response to oral prednisolone 10 mg for 1 month was examined.

RESULTS

The recovery in sputum of exogenous spiked mediators was >80% in 11/26 cytokines and chemokines. In supernatants from eosinophilic (n = 39) versus non-eosinophilic (n = 59) sputa, the geometric mean (95% CI) concentration was increased for IL-5 [9.0 (4.5-18) pg/ml vs. 3.6 (2.7-6.3) pg/ml, p = 0.03]. IL-5 alone was correlated with sputum eosinophil counts (r = 0.33, p = 0.001), and was attenuated following treatment with prednisolone [n = 9; mean difference 2.3 pg/ml (0.2-4.3), p = 0.032].

CONCLUSION

We have validated the use of the meso-scale device platform for cytokine and chemokine measurements in the sputum supernatants in COPD. Sputum IL-5 was associated with a sputum eosinophilia and was attenuated following oral corticosteroid therapy. Whether this cytokine is important in the pathogenesis of COPD in a subgroup of patients warrants further investigation.

Optimized dialysis and protease inhibition of sputum dithiothreitol supernatants

RATIONALE

Dithiothreitol (DTT) is commonly used to liquefy induced sputum samples before assessment of cytology, but causes reduction of disulfide bonds and denaturation of proteins.

OBJECTIVES

To process sputum supernatants containing DTT to enable quantification of cytokines and chemokines.

METHODS

A standard solution of 22 pooled chemokines and cytokines was incubated with DTT at the concentrations used during sputum liquefaction and then dialyzed under 20 different denaturant and redox conditions.

MEASUREMENTS AND MAIN RESULTS

After incubation of the standard solution with DTT there was loss of detectable protein mediators on immunoassay, but optimized dialysis permitted recovery of chemokines to 96 +/- 4% and cytokines to 91 +/- 6%. Optimized dialysis of DTT supernatants from subjects with asthma covering a range of severities (n = 35) was performed in the presence of a cocktail of protease inhibitors and demonstrated significantly elevated levels of the chemokine CXCL10 (IFN-gamma-inducible protein-10), CXCL8 (IL-8), and CCL3 (macrophage inflammatory protein-1alpha); with lower but significantly elevated levels of CCL2 (monocyte chemotactic protein-1), CCL11 (eotaxin), and CCL5 (regulated on activation, normal T-cell expressed and secreted) in severe asthma. In sputum from subjects with severe asthma there were also significantly elevated levels of IL-4, IL-5, IL-13, tumor necrosis factor-alpha, IL-6, granulocyte-macrophage colony-stimulating factor, and IL-12(p40).

CONCLUSIONS

The technique of optimized dialysis and protease inhibition of sputum DTT supernatants aids the detection of chemokines and cytokines. The detection of elevated levels of particular sputum chemokines and cytokines in individual patients may provide a rationale for specific therapies.

Profiles of proinflammatory cytokines in sputum from different groups of severe asthmatic patients

BACKGROUND

Severe asthma represents a heterogeneous group of patients whose characteristics of airway inflammation are poorly known.

OBJECTIVE

To evaluate the sputum cytokine profiles of different phenotypes of severe asthma.

METHODS

Severe asthmatic patients (n = 45) were divided into 3 groups: frequent exacerbations, persistent bronchoconstriction, and both features. Two other groups (9 patients with untreated mild asthma and 10 control subjects) were also studied. Selected sputum portions were assayed for differential cell count, supernatant interleukin 5 (IL-5), granulocyte-macrophage colony-stimulating factor, IL-8, and eosinophil cationic protein.

RESULTS

There were no statistically significant differences among the 3 severe asthma groups in terms of sputum inflammatory cell percentages, IL-8 levels, and eosinophil cationic protein levels, although IL-8 levels tended to be higher in patients with persistent bronchoconstriction. Sputum concentrations of granulocyte-macrophage colony-stimulating factor and IL-5 were significantly higher in patients with frequent exacerbations compared with the other 2 groups. Levels of IL-5 and IL-8 were higher in severe asthmatic patients compared with mild asthmatic patients and controls, whereas sputum eosinophil percentages were intermediate between those of mild asthmatic patients and controls.

CONCLUSIONS

Proeosinophilic cytokine levels are increased in severe asthmatic patients with frequent exacerbations but not in severe asthmatic patients with persistent bronchoconstriction, suggesting that different cytokine profiles could be associated with different phenotypes of severe asthma.

Induced sputum methodology: Validity and reproducibility of total glutathione measurement in supernatant of healthy and asthmatic individuals

Glutathione (GSH), a major antioxidant, has repeatedly been linked to the pathogenesis of pulmonary disease. The measurement of GSH in induced sputum (IS) offers a noninvasive tool for the study and monitoring of oxidative stress in airway diseases. In this study we assessed the validity and reproducibility of GSH quantification in IS from healthy subjects and individuals with mild asthma. We spectrophotometrically quantified total GSH in the IS of 31 healthy nonsmoking volunteers and 12 individuals with mild asthma. IS was processed with varying concentrations of dithiothreitol (DTT) in an effort to evaluate the effect of DTT on GSH measurements. We performed spiking experiments with defined concentrations of GSH and quantified the percentage of recovery and also analyzed the effect of induction time on GSH levels through sequential sampling of sputum portions (15, 30, and 45 minutes' induction). Finally we tested the reproducibility of GSH measurements at 2 separate time points (0 and 72 hours) and expressed it as an intraclass correlation coefficient (R(i)) with a coefficient of reliability (CR). Processing with DTT increased GSH values in IS (P <.05 for each DTT concentration > 0.001%). Recovery of GSH after spiking was complete, with a mean recovery of 102% +/- 4.8%. Increasing duration of induction led to an increase in sputum GSH (15 minutes, 10.2 +/- 2.3 micromol/L; 30 minutes, 18.4 +/- 3.5 micromol/L; 45 minutes, 26.1 +/- 4 micromol/L; P <.05 for all comparisons). Reproducibility of sputum GSH both in healthy subjects and asthmatic individuals was good (R(i) =.78, P <.001; and R(i) =.51, P =.003, respectively). With the use of standardized protocols for duration of induction and sample processing, sputum GSH measurement in healthy subjects and asthmatic individuals is valid and reproducible.

Measurement of eotaxin (CCL11) in induced sputum supernatants: validation and detection in asthma

BACKGROUND

Induced sputum is widely used in asthma research; however, for many mediators, the detection methods have not been validated.

OBJECTIVE

We sought to optimize the method of detection of eotaxin, an important chemokine acting through the CCR3 receptor on eosinophils, basophils, and T(H)2 cells.

METHODS

Induced sputum from normal and asthmatic subjects was processed with dithioerythritol (DTE) or PBS; recovery of eotaxin was assessed by means of ELISA before and after spiking with recombinant eotaxin. Furthermore, the effects of removing DTE by means of ultrafiltration or the addition of protease inhibitors and high-speed centrifugation on endogenous levels and spiking recovery of eotaxin were assessed.

RESULTS

Endogenous eotaxin was undetectable in DTE-processed samples, with a mean of only 30% (SD, 13%) spike recovery. DTE had no effect on the immunoassay capture antibody but dramatically reduced the detection of recombinant eotaxin. Removal of DTE from sputum before immunoassay did not improve detection, although it restored the recovery of a subsequent eotaxin spike. In contrast, PBS-processed sputum resulted in an eotaxin spike recovery of 101% (SD, 20%). Addition of protease inhibitors or high-speed centrifugation had no effect on eotaxin detection. By using this optimized protocol, eotaxin levels in PBS-processed sputum samples were found to be significantly increased in asthmatic sputum (P<.05).

CONCLUSION

Measurement of eotaxin by means of immunoassay is adversely affected by DTE, possibly through irreversible denaturation of epitopes, which makes eotaxin undetectable by using the immunoassay antibody. Sputum samples should be processed into PBS for assessment of eotaxin, which is present at increased levels in asthmatic sputum.

A single nasal allergen challenge increases induced sputum inflammatory markers in non-asthmatic subjects with seasonal allergic rhinitis: correlation with plasma interleukin-5

BACKGROUND

Seasonal allergic rhinitis (SAR) is a risk factor for asthma in affected individuals. Nasal allergic inflammation enhances bone-marrow eosinophil production, mainly via IL-5, and rhinitis patients have increased airway inflammation during the pollen season.

OBJECTIVE

To assess the impact of nasal allergy on sputum inflammatory markers.

METHODS

In an open-labelled, randomized, placebo-controlled cross-over study with 16 non-asthmatic SAR patients (median age 25 years, 56% males), the effect of a single nasal allergen challenge performed out of season on induced sputum inflammatory parameters was evaluated. SAR patients were identified by history, skin-prick test and specific IgE. All patients had normal lung function/bronchial hyper-responsiveness out of season and a negative asthma/wheezing history. Sputum cells and supernatant levels of ECP, sICAM, IL-5 and IL-10, and plasma levels of IL-5 and ECP, were measured before and 24 h after nasal allergen challenge. After a washout period of at least 4 weeks, the procedure was repeated with placebo challenge (diluent).

RESULTS

Nasal allergen challenge led to an increase in sputum ECP (pre = 60 +/- 12, post = 212 +/- 63 micro g/L, P = 0.02 vs. placebo), and sICAM (4.8 +/- 2.7 to 6.5 +/- 2.9 ng/mL, P = 0.02 vs. placebo), whereas IL-10 decreased after provocation (44 +/- 11 to 29 +/- 6 pg/mL, P = 0.06 vs. placebo). Sputum IL-5 was undetectable in all patients. The absolute number of blood and sputum eosinophils did not change significantly after allergen or placebo challenge (P > 0.07, both comparisons). Plasma levels of IL-5 increased after allergen challenge (8.7 +/- 2.9 to 14.5 +/- 3.9 pg/mL, P = 0.001), and the increase in plasma IL-5 was positively correlated with the rise in sputum ECP in a subgroup of 'responders' (n = 12, r = 0.71, P = 0.01).

CONCLUSIONS

A single nasal allergen challenge in SAR patients increased markers of allergic inflammation in the lower respiratory tract, possibly via pronounced activation of inflammatory cells through circulating immediate-type reaction cytokines like IL-5. These findings may provide additional explanatory data for the high susceptibility of SAR patients to incident asthma.

Neutrophil chemotactic activity of sputum from patients with COPD: role of interleukin 8 and leukotriene B4

STUDY OBJECTIVES

Neutrophilic inflammation is a major feature of COPD. Several factors in bronchial secretions have been identified as chemoattractants for neutrophils. The present study was designed to assess the contribution of interleukin (IL)-8 and leukotriene B(4) (LTB(4)) to neutrophil chemotaxis evoked by sputum obtained from patients with established COPD.

DESIGN

Sputum supernatant of 20 patients with COPD was used as chemoattractant in a 96-well chemotaxis chamber, with subsequent quantification of migrated cells by a luminescence assay. The contribution of IL-8 and LTB(4) to chemotaxis was determined by addition of a neutralizing antibody and a selective receptor antagonist, respectively.

MEASUREMENTS AND RESULTS

COPD sputum caused neutrophil chemotaxis in a concentration-dependent manner, with a maximum response evoked with a 10-fold dilution of the original sample. Pretreatment of sputum or neutrophils with either an anti-IL-8 antibody or the LTB(4) antagonist, SB 201146, led to a concentration-dependent inhibition of sputum-induced neutrophil chemotaxis, with a maximum suppression (mean +/- SEM) of 29.2 +/- 4.9% (p < 0.001) from baseline by 100 ng/mL of anti-IL-8 antibody, and 45.6 +/- 7% (p < 0.02) by 10 micro mol/L of SB 201146. The combination of the anti-IL-8 antibody and SB 201146 inhibited neutrophil chemotaxis, but this was not significantly greater than the effect of SB 201146 or anti-IL-8 alone.

CONCLUSIONS

These data confirm the importance of IL-8 and LTB(4) as chemoattractants for neutrophils in bronchial secretions from patients with COPD, and suggest that specific inhibitors may have therapeutic potential in COPD.

Long-term repeatability of induced sputum cells and inflammatory markers in stable, moderately severe COPD

STUDY OBJECTIVES

Neutrophilic inflammation is a major feature of COPD. Induced sputum is increasingly used to monitor inflammatory airway diseases. Although short-term repeatability of selected sputum markers has been extensively studied in several populations, data on the long-term repeatability of induced sputum markers in stable COPD are scant.

DESIGN

Sputum supernatant of 12 patients with stable COPD was analyzed on three separate occasions with 4-weekly intervals. Sputum cells and inflammatory markers interleukin (IL)-8 and soluble intercellular adhesion molecule (sICAM)-1 were measured in supernatant using enzyme-linked immunosorbent assay. Repeatability of sputum markers was expressed by intraclass correlation coefficients (Ri).

MEASUREMENTS AND RESULTS

Sputum induction was safe in all patients. None of the sputum parameters analyzed changed significantly throughout the study. The repeatability for cell differential counts in stable COPD was as follows: total cells, Ri = 0.07; neutrophils, Ri = 0.66; macrophages, Ri = 0.47; eosinophils, Ri = 0.49; and lymphocytes, Ri = 0.58. The repeatability of soluble markers was as follows: IL-8, Ri = 0.50; and sICAM, Ri = 0.58. Sputum neutrophils were negatively correlated with lung function on each separate occasion, whereas soluble markers were not correlated with sputum cells (p > 0.16, all correlations) or lung function (p > 0.24, all correlations).

CONCLUSIONS

Clinically stable, moderate COPD is associated with equally stable sputum inflammatory markers. Repeatability of induced-sputum markers of neutrophilic inflammation in stable COPD is satisfactory, even over extended periods of time. These data support the usefulness of serial monitoring of induced-sputum inflammatory markers in COPD.

Bronchial hyperresponsiveness and airway inflammation in adolescents with asymptomatic childhood asthma

BACKGROUND

About 70% of childhood asthmatics become free of asthma-related symptoms during adolescence. Little is known about bronchial hyperresponsiveness (BHR) and airway inflammation in young adults with "outgrown" childhood asthma.

METHODS

We studied 61 nonsmoking medical students (18 intermittent mild asthmatics, 23 students with outgrown childhood asthma but free of asthma-related symptoms for 10 years (asymptomatic asthmatics) and 20 healthy students). BHR and lung function were measured, and induced sputum samples analyzed for eosinophil count, eosinophilic cationic protein (ECP), granulocyte-macrophage colony stimulating factor (GM-CSF), and tumor necrosis factor-alpha (TNF-alpha).

RESULTS

BHR was still present in most asymptomatic asthmatics, but it was milder compared with healthy students. Only three subjects with previous asthma had no BHR and no signs of airway inflammation. Percentages of eosinophil, and ECP, TNF-alpha and GM-CSF concentrations in induced sputum of mild asthmatics and asymptomatic asthma groups were higher than in the healthy group. In asymptomatic asthmatics group, the duration of asthma, sputum eosinophil percentage, and the level of TNF-alpha in sputum correlated significantly with BHR.

CONCLUSIONS

Only a few subjects with longstanding asymptomatic asthma could be considered as cured; most asymptomatic asthmatics continued to exhibit BHR and signs of airway inflammation. The outcome of childhood asthma and BHR was associated with the degree of airway inflammation and the duration of childhood asthma.

Circadian variation of sputum inflammatory cells in mild asthma

BACKGROUND

Asthma, like many conditions, demonstrates a circadian rhythm with a worsening of lung function in the early morning hours compared with in the late afternoon.

OBJECTIVE

Because eosinophilic airway inflammation is a proposed mechanism for worsening asthma, we characterized circadian variation in airway eosinophils and determined its relationship to variability in airway function.

METHODS

Pulmonary function testing, sputum induction, and phlebotomy were performed at 7 am and 4 pm in 11 allergic subjects with mild asthma. Sputum was analyzed for cell viability, differential, and eosinophil-derived neurotoxin levels. IL-5 levels in serum were measured by means of ELISA.

RESULTS

Subjects had a significant decrease in FEV(1) (median [interquartile range] = 80% [70%-86%] vs 85% [82%-94%], P =.009) and a greater beta-agonist reversibility (median [interquartile range] = 13% [7%-32%] vs 8% [5%-14%], P =.024) in the early morning compared with in the late afternoon. Sputum analysis showed an increase in early morning total sputum leukocytes (median [interquartile range] = 4.3 x 10(6) [2.3 x 10(6) to 6.1 x 10(6)] vs 2.6 x 10(6) [1.7 x 10(6) to 3.6 x 10(6)], P =.044) and eosinophils (median [interquartile range] = 7.0 x 10(4) [2.7 x 10(4) to 18.7 x 10(4)] vs 3.6 x 10(4) [1.0 x 10(4) to 8.2 x 10(4)], P =.024). Furthermore, sputum eosinophils correlated with beta-agonist reversibility (R (s) = 0.665, P =.019). Finally, levels of IL-5 in serum and eosinophil-derived neurotoxin in sputum were significantly increased at 7 am.

CONCLUSION

These data suggest that circadian variability in pulmonary function in asthma could be related to changes in airway eosinophil recruitment and activation.

School examinations enhance airway inflammation to antigen challenge

Psychological stress can lead to asthma exacerbations in some patients. It is our hypothesis that the stress effect can occur through an enhancement of allergic inflammatory response. To investigate this possibility, airway antigen challenge was evaluated in 20 college students with mild asthma during both a low-stress phase (midsemester or two weeks postfinal examination) and a stress phase (final examination week). Subjects completed questionnaires to assess psychological state and underwent inhaled antigen challenge. Sputum samples were collected before challenge, and six and 24 hours and seven days postchallenge. Leukocytes were counted and eosinophil-derived neurotoxin (EDN) was measured in sputum supernates. Sputum cells were cultured and stimulated ex vivo with phytohemagglutinin (10 microg/ml), and culture supernates were assayed for interleukin-5 (IL-5) and interferon-gamma by enzyme-linked immunosorbent assay. Sputum eosinophils and EDN levels significantly increased at six and 24 hours postchallenge and were enhanced during the stress phase (p < 0.01). IL-5 generation by sputum cells was also increased at 24 hours during stress and correlated with airway eosinophils (r(s) = 0.65, p < 0.05). Students' anxiety and depression scores were significantly higher during the examination period. Our findings suggest that stress associated with final examinations can act as a cofactor to increase eosinophilic airway inflammation to antigen challenge and thus may enhance asthma severity.

Measurement of airway inflammation in asthma

Chronic airway inflammation is considered responsible for symptoms and disorders of airway function associated with asthma. This process is the target of anti-inflammatory therapy, so a number of standardized, noninvasive techniques have been developed to assess it. More recent approaches include the measurement of exhaled gases and nonvolatile substances in breath condensate. Results from studies using a wide variety of inflammatory markers have shown group differences between patients with asthma and healthy control subjects, but evidence for the diagnostic use of these markers in individual patients is scarce. Similarly, despite many studies demonstrating some correlation between markers of airway inflammation and a measure of disease control, none has yet convincingly shown a place for the use of these markers in an individual with corticosteroid-treated asthma. However, application of these markers continues to further our understanding of the disease process and provides the potential for more appropriate, customized therapy.

Increased detection of interleukin-5 in sputum by addition of protease inhibitors

The measurement of interleukin (IL)-5 in sputum is problematic, with interfering factors affecting immunoassay. The authors investigated whether sputum proteases could be acting as interfering factors by studying the effect of protease inhibitors (PI) on sputum IL-5 measurement. Induced sputa from 20 subjects with asthma were divided into aliquots, processed with and without protease inhibitors (in low and high concentrations) and the levels of IL-5 (spiked and endogenous) measured by enzyme immunoassay were compared. The concentration of sputum IL-5 was significantly increased by PI, with median (interquartile range) levels processed with no, low and high PI concentrations being 0 (0), 41.8 (75.6) and 66.1 (124.4) pg x mL(-1), respectively. There was also a significant increase in percentage recovery of spiked IL-5. Although high concentrations of PI reduced cell viability, there was no effect on total or differential cell counts and low concentrations of PI had no effect on cell counts or viability. Levels of endogenous interleukin-5 in sputum of asthmatic subjects can be significantly increased by the addition of protease inhibitors, and samples which would be regarded as negative for interleukin-5 without protease inhibitors may instead have considerable amounts of interleukin-5 detected.

Characterization of airway inflammation after repeated exposures to occupational agents

BACKGROUND

Little is known about the comparative kinetics of eosinophil recruitment after exposure to low- and high-molecular-weight sensitizers in subjects with occupational asthma (OA).

OBJECTIVES

The aims of the study were to investigate the kinetics of changes in inflammatory mediators associated with eosinophil infiltration (IL-5 and eotaxin) and to examine the nature of the airway inflammation induced in response to different types of occupational agents.

METHODS

We investigated 15 subjects with OA caused by high- and low-molecular-weight agents. The subjects were exposed to increasing doses of the relevant occupational agent over 3 to 4 days until a 20% fall in FEV(1) occurred. Methacholine challenge and sputum induction were performed at the end of each day of exposure. Sputum samples were assessed for differential cell counts, including eosinophils, IL-5, and eotaxin messenger RNA.

RESULTS

There was an increase in sputum eosinophils, eotaxin, and IL-5 on the day preceding the occurrence of asthmatic reaction, although there was no change in functional parameters (FEV(1) and PC(20)). Increase in sputum eosinophils was more prominent in subjects exposed to low-molecular-weight agents than to high-molecular-weight agents.

CONCLUSION

Changes in eosinophils, IL-5, and eotaxin precede functional changes after exposure to occupational agents in subjects with OA. Eosinophil inflammation is a feature of exposure to both high- and low-molecular-weight agents. Induced sputum may be a useful tool in the early diagnosis of OA.