Leukocyte activation in allergen-induced late-phase asthmatic reactions

Some patients with allergen-induced asthma have both an early and late reaction to allergen (dual asthmatic reactions). To investigate the role of leukocyte activation in dual asthmatic reactions, we measured neutrophil chemotactic activity, percentages of neutrophil and monocyte complement rosettes, and one-second forced expiratory volume (FEV1) in 11 patients with allergen-induced dual asthmatic reactions after a challenge with allergen. To control for the effects of bronchoconstriction, the same studies were done after a challenge with methacholine. In all subjects there was a biphasic increase in neutrophil chemotactic activity and the percentages of neutrophil and monocyte complement rosettes, accompanied by a reduction in the FEV1. After methacholine, there were no significant changes in neutrophil chemotactic activity or percentages of complement rosettes, despite bronchoconstriction. Six patients with single-phase allergen-induced asthma had similar responses, but they were monophasic. We conclude that allergen-induced early and late asthmatic reactions are accompanied by activation of leukocytes and that these alterations probably reflect the release of mediators from mast cells rather than an effect of bronchoconstriction.     

Ketotifen does not inhibit asthmatic reactions induced by toluene di-isocyanate in sensitized subjects

In order to determine whether treatment with ketotifen inhibits asthmatic reactions induced by toluene di-isocyanate (TDI), we studied six sensitized subjects with previously demonstrated dual or late asthmatic reaction after inhalation challenge with TDI. Ketotifen (1 mg b.i.d., orally) or placebo was administered for 7 days to the examined subjects, according to a double-blind, cross-over, placebo-controlled study design. When the subjects were treated with either ketotifen or placebo, FEV1 markedly decreased after exposure to TDI. These results suggest that the anti-asthmatic agent ketotifen is not effective in TDI-induced asthma and suggest that it should not be used in the prophylaxis of asthmatic reactions induced by TDI in sensitized subjects.     

Neutrophil activation following TDI bronchial challenges to the airway secretion from subjects with TDI-induced asthma

BACKGROUND: The immunopathological mechanism for occupational asthma induced by toluene diisocyanate (TDI) remains to be further clarified. There have been few reports suggesting involvement of neutrophils in inducing bronchoconstriction after TDI inhalation. OBJECTIVES: To further understand the role of neutrophils in the pathogenesis of TDI-induced asthma. MATERIALS AND METHODS: Eight TDI-induced asthmatic subjects were classified as group I, and five exposed workers who had complained of work-related symptoms and worked in the same workplace, but showed negative bronchial challenges were enrolled as controls (group II). Serum neutrophil chemotactic activity during TDI bronchial challenge test was measured by the Boyden chamber method. Induced sputum was collected before and after the TDI bronchial challenge test. The myeloperoxidase (MPO) and interleukin (IL) -8 levels in the sputum were measured using RIA and ELISA. RESULT: Serum neutrophil chemotactic activity significantly increased at 10 min (P = 0.01), then decreased at 60 min (P = 0.02) and remained unchanged for up to 420 min (P = 0.07) in group I subjects, while no significant changes were found in group II subjects (P > 0.05). MPO and IL-8 were abundantly present in the sputum of all the TDI-induced asthmatic subjects and they increased significantly at 420 min after the bronchial challenges (P = 0.02, P = 0.03, respectively), while no significant changes were noted in group II subjects (P > 0.05). CONCLUSION: These findings support the view that activated neutrophils may contribute to bronchoconstriction induced by TDI which may be associated with IL-8 release.     

Dexamethasone isonicotinate inhibits dual and late asthmatic reactions but not the increase of airway responsiveness induced by toluene diisocyanate in sensitized subjects

To determine whether treatment with aerosolized dexamethasone isonicotinate inhibits asthmatic reactions and the associated increase in airway responsiveness induced by toluene diisocyanate (TDI), we studied six sensitized subjects with previously demonstrated dual or late asthmatic reaction after inhalation challenge with TDI. Dexamethasone isonicotinate (four puffs bid for seven days, ie, 0.5 mg bid for seven days; last four puffs 30 minutes before TDI) was administered for seven days before the inhalation challenge with TDI (0.010 to 0.015 ppm for 10 to 30 minutes) to each subject, according to a single-blind study design. When the subjects received no treatment, FEV1 markedly decreased and airway responsiveness increased after exposure to TDI. By contrast, when the subjects were treated with dexamethasone-isonicotinate, FEV1 decreased significantly less, but airway responsiveness still significantly increased after exposure to TDI. These results suggest that aerosolized dexamethasone isonicotinate may be used in the prophylaxis of TDI-induced late asthmatic reactions.     

Enhanced serum neutrophil chemotactic activity was noted in both early and late asthmatic responses during lysine-aspirin bronchoprovocation test in ASA-sensitive asthmatic patients

To investigate the pathogenic mechanism of late asthmatic response in comparison to early asthmatic response, changes of serum neutrophil chemotactic activity (NCA) using the Boyden chamber method and histamine level using the automated fluorometric analyzer were observed in 13 aspirin (ASA)-sensitive asthma subjects (group I: 7 early responders and group II: 6 dual responders) during lysine aspirin bronchoprovocation test (L-ASA BPT). Sera were collected before, and 30 min and 240 min after L-ASA BPT. Serum NCA increased significantly after 30 min (p=0.02) and decreased significantly at 240 min (p=0.02) in group I, while serum NCA of group II increased significantly at 30 min (p=0.04), tending to increase further up to 240 min with no statistical significance. NCA at 240 min in group II subjects was significantly higher than baseline NCA (p=0.02). The serum NCAs collected before and 240 min were significantly higher in group II than in group I (p<0.05, respectively). There were no significant changes in serum histamine levels during L-ASA BPT in both groups. NCA derived from mast cell may contribute to the development of early asthmatic response induced by L-ASA inhalation. There may be a possible involvement of NCA derived from mononuclear cells during late asthmatic response.     

Neutrophil chemotactic factor of anaphylaxis (NCF-A) release in aspirin-induced asthma

Neutrophil chemotactic activity (NCA) following oral challenge with aspirin (ASA) was determined in ASA-intolerant asthmatic subjects, and in ASA-tolerant asthmatic and normal subjects. There was a statistically significant fall in FEV₁ and a rise in NCA (P <0.01) following challenge in the ASA-sensitive subjects compared with that of the ASA-tolerant subjects and normal controls. No significant difference was observed between the latter two groups. The chemotactic factor identified in this study had a molecular weight greater than 150 000 which is consistent with NCF-A (neutrophil chemotactic factor of anaphylaxis). The ASA-induced fall in FEV₁ and rise in NCA was further studied in three of the ASA-intolerant asthmatic subjects, with and without pretreatment with inhaled sodium cromoglycate. In these subjects, the drug inhibited both the oral ASA-induced bronchoconstriction and the increase in neutrophil chemotactic activity. These results suggest that ASA-induced asthma involves mediator release from mast cells, as shown by the increase in NCA following ASA challenge and the protective effect of sodium cromoglycate which is considered to inhibit mast-cell degranulation.     

Combined asthma and alveolitis due to diphenylmethane diisocyanate (MDI) with demonstration of no crossed respiratory reactivity to toluene diisocyanate (TDI)

Two workers, who developed asthmatic symptoms, were studied with inhalation provocation tests using diphenylmethane diisocyanate (MDI) and toluene diisocyanate (TDI). The subjects showed specific asthmatic reactions to MDI challenge (more than 20% fall in FEV1), and one also had an alveolar response. Alveolitis was suggested by fever, basal crackles, increased neutrophil counts in venous blood and in bronchoalveolar lavage. The asthmatic reaction to MDI challenge was associated with an increase in airway responsiveness to methacholine in both subjects. We conclude that MDI is a cause of asthma and/or hypersensitivity pneumonitis in workers exposed to diphenylmethane diisocyanate.     

Neutrophil chemotactic activity in milk-induced asthma

Four subjects with clinical histories of milk-induced asthma were studied (three allergic to cow's milk; one to soya milk). In each instance, skin prick tests, RAST (IgE and IgG₄), the basophil histamine release, and serum precipitins, using appropriate milk extracts, were negative. After the ingestion of milk all the subjects developed a reproducible and dose-dependent increase in airflow limitation. Three patients (two allergic to cow's milk; one to soya milk) gave a characteristic immediate-type reaction, which was maximal at 30 min after challenge. The fourth individual developed an isolated late-phase response, with maximal airways obstruction 3 hr after ingesting milk. In the three subjects who gave an early reaction, wheezing was accompanied by an elevation in circulating neutrophil chemotactic activity (NCA). This was not observed in the individual with the isolated late reaction. By Sephacryl S-400 gel-filtration chromatography it was shown that NCA of the early reactions eluted with proteins having an estimated molecular weight of 600,000 daltons. The immediate asthmatic response in peak expiratory flow rate and the elevation in NCA were inhibited by the prior oral administration of either disodium cromoglycate (DSCG) or oral beclomethasone dipropionate (BDP). In contrast, DSCG had no effect on airways obstruction in the subject with the isolated late asthmatic response, although inhibition was achieved by BDP.     

Immunohistochemical characterization of the cellular infiltrate in airway mucosa of toluene diisocyanate (TDI)-induced asthma: comparison with allergic asthma.

Toluene diisocyanate (TDI) is the most prevalent agent in occupational asthma (OA) in Korea. The immuno-pathologic mechanism for TDI-induced bronchoconstriction remains to be clarified. We studied the immunohistochemical finding of inflammatory cells in bronchial mucosa in subjects with TDI-induced asthma. Fiberoptic bronchial biopsy specimens were obtained from nine subjects with TDI-induced asthma. Six allergic asthma sensitive to house dust mite were enrolled as controls. Bronchial biopsy specimens were examined by immunohistology with a panel of monoclonal antibodies to mast cell tryptase (AA1), secretary form of eosinophil cationic protein (EG2), pan T-lymphocyte (CD3) and neutrophil elastase (NE). There was a significant increase in the number of AA1+, EG2+ and NE+ cells in TDI-induced asthma compared to those of allergic asthma (p=0.02, p=0.04, p=0.03, respectively). No significant differences were observed in the number of CD3+ cells (p=0.27). These findings support the view that neutrophil recruitment together with eosinophil and mast cell, may contribute to the bronchoconstriction induced by TDI.     

Expression of interleukin (IL)-4 and IL-5 proteins in asthma induced by toluene diisocyanate (TDI)

Background TDI-induced asthma exhibits clinical, functional and morphological similarities with allergen-induced asthma, suggesting that an immunological mechanism is involved in the sensitization to TDL In vitro studies using the technique of cloning lymphocytes demonstrated that a great proportion of T-cell clones derived from bronchial mucosa of subjects with TDI-induced asthma produced IL-5 and interferon-gamma, but not IL-4, upon in vitro stimulation. Objectives To investigate in vivo the role of IL-4 and IL-5 on the inflammatory response of the bronchial mucosa to TDI in sensitized subjects, we performed a quantitative analysis of bronchial biopsies. Methods We obtained bronchial biopsies from six subjects with TDI asthrha 48 h after an asthmatic reaction induced by TDI challenge (challenged group), in six subjects with TDI asthma 1–4 weeks after the last exposure to TDI (chronic group), and in six non-asthmatic controls. The number of eosinophils, mast cells, T-lymphocytes, and IL-4 and IL-5 protein positive cells was determined by immunohistochemistry in the area 100 μn beneath the epithelial basement membrane. Results The characteristic increase of submucosal eosinophils, but not of mast cells and T-lymphocytes, was observed in the subjects with TDI-induced asthma when compared with controls. No differences were detected between the two groups of asthmatics. In the subjects with TDI-induced asthma, cell immunoreactivity for IL-5 was increased when compared with normal controls. There was no difference in the expression of IL-5 protein between challenged and chronic asthmatics. In contrast, the expression of IL-4 protein was increased only in the asthmatic subjects tested after recent exposure to TDI. Conclusions We demonstrated that TDI asthma 48 h after specific bronchial challenge was associated with increased numbers of cells expressing IL-4 and IL-5, whereas chronic TDI asthma was associated with increased expression of IL-5, but not of IL-4. The results suggest that subjects who developed TDI asthma exhibit increased production of IL-5 even in the absence of a recent trigger by the exogenous sensitizer and that production of TH₂-like cytokines in TDI-induced asthma may not always be co-ordinately regulated in vivo.     

Mediators of Hypersensitivity and "Fog"-Induced Asthma

Seven asthmatic and five normal subjects inhaled increasing amounts of nebulized water ("fog"). Neutrophil chemotactic activity (NCA), histamine and FEV1 measurements were undertaken before and at time intervals after challenge. In asthmatics, the mean maximal reduction in FEV1 (+/- 1 SD) was 46.6% +/- 11.5; whereas, in normal subjects, the reductions were less than 20% of pre-challenge values after the inhalation of 33 ml of water. There were no significant differences in the pre-challenge values for NCA between the asthmatics and the normal controls. When the highest values for NCA during the 30 min after challenge in the asthmatics were compared with controls there was a significant increase (P less than 0.02). The percentage change in NCA was also significantly greater in the asthmatics compared with the controls at 10 min after challenge (P less than 0.05). Fog-induced NCA was shown to be associated with proteins with approximate molecular weight of 600,000 daltons (as assessed by gel filtration chromatography on Sephacryl-S400). There was an increase in plasma histamine in the asthmatics after challenge but this was not significantly greater than the controls. These findings support the view that mediators might be involved in fog-induced asthma, possibly as a result of mast cell degranulation by "osmotic shock".     

Exercise-induced asthma and the generation of neutrophil chemotactic activity

Heat-stable neutrophil chemotactic activity (HS NCA) has been demonstrated in serum of subjects with asthma after exercise and after allergen inhalation challenge. Heat-labile neutrophil chemotactic activity (HL NCA) has been investigated only after allergen inhalation challenge. In this study, we have measured HS NCA and HL NCA after exercise of 22 adult patients with asthma, 13 of whom had exercise-induced asthma (EIA). In the 13 patients, the effect of pharmacologic pretreatment on the generation of HS NCA and EIA was evaluated in a double-blind study with inhalation of either disodium cromoglycate, terbutaline, or budesonide 15 minutes before exercise. Additionally, the effect of 4 weeks of treatment with budesonide aerosol was evaluated in an open study. A significant increase (p less than 0.01) in HS NCA was found in the patients with EIA with peak activities 15 minutes after exercise. In patients without EIA, the activity of HS NCA was variable. No HL NCA was detectable after exercise. EIA was inhibited by disodium chromoglycate, terbutaline, and 4 weeks of treatment with budesonide. The generation of HS NCA was more or less inhibited by all three drugs with 4 weeks of treatment with budesonide as the most potent regimen. No late-phase asthmatic reactions to exercise were found. It is concluded that only HS NCA is generated after exercise of subjects with asthma and that this production is controlled by antiasthmatic drugs. However, the generation of HS NCA occurs irrespective of EIA.     

Generation and partial characterization of eosinophil chemotactic activity and neutrophil chemotactic activity during early and late-phase asthmatic response

Asthma has been recognized to consist of hyperresponsive airways and cellular inflammation. Allergen bronchoprovocation (BPC) may define the early (EAR) and late-phase asthmatic response (LAR). The LAR has now been associated with increased nonspecific airway hyperresponsiveness and cellular inflammation consisting of neutrophils and eosinophils. We used BPC to demonstrate EAR and LAR in 12 subjects with seasonal allergic asthma. One normal subject and one subject with asthma who had been treated with allergy immunotherapy were challenged but did not respond. Plasma was sampled at frequent intervals during these aeroallergen challenges and assayed for eosinophil chemotactic activity (ECA) and neutrophil chemotactic activity (NCA). Of the 12 subjects with asthma who were challenged, nine had dual responses (both EAR and LAR), and three subjects demonstrated only an LAR. Those subjects who had dual airway responses had biphasic rises in both ECA (early = 267 +/- 28%; late = 286 +/- 28%) and NCA (early = 279 +/- 24%; late = 215 +/- 15%) in their plasma, whereas those subjects who demonstrated only an LAR had only a late rise in ECA (218 +/- 61%) and NCA (188 +/- 31%). The two individuals who did not respond to aeroallergen challenge demonstrated no change in their plasma chemotactic activity toward either eosinophils or neutrophils. Those individuals with the most severe LAR (greater than or equal to 1,000 mm2) had combined ECA plus NCA peak values of greater than 500%.(ABSTRACT TRUNCATED AT 250 WORDS)     

Sputum eosinophilia after asthmatic responses induced by isocyanates in sensitized subjects

To assess the nature and the time–course of the cellular component of airway inflammation induced by isocyanates, we examined nine subjects with occupational asthma induced by toluene– or methylene diphenyl–diisocyanate (TDI, MDI) and four control subjects never exposed to isocyanates. Sputum was induced by inhalation of ultrasonically nebulized hypertonic saline (3–4% NaCl) before and 8, 24, 48 h after inhalation challenge with TDI or MDI. Expectorated samples were incubated with dithiothreitol, washed and cytocentrifuged. Differential cell counts were obtained on slides stained with May–Grünwald–Giemsa. Metachromatic cells (mast cells and basophils) were counted on slides stained with toluidine blue at pH 0.1. One occupational asthmatic exhibited a dual reaction to TDI, two exhibited a single early asthmatic reaction to M DI, six exhibited a late asthmatic reaction to TDI (n= 5) or M DI (n= 1), whereas no reactions were observed in control subjects after TDI challenge. In sensitized subjects eosinophils increased from a median value (interquartile range) of 5 (15)% before challenge to 29 (29)% (P= 0.014) and to 30 (31)% (P= 0.031) 8 and 24 h after TDI/MDI challenges, respectively. Sputum eosinophilia was observed both in early and late reactors and declined to near to baseline values 48 hr after challenge. Percentages of eosinophils in control subjects did not exceed 7% during the study. There was a significant correlation between the increase in eosinophil counts and the magnitude of the bronchoconstriction expressed as the area of FEV₁ response to isocyanate challenge (rank correlation coefficient = 0–71, P= 0.014). No significant changes in sputum neutrophils, macrophages, lymphocytes and mast cells were detected. The results indicate that isocyanate–induced asthmatic responses are associated with influx of eosinophils in airway secretion lasting up to 24 h.     

Activation of neutrophils and monocytes after allergen- and histamine-induced bronchoconstriction

To determine whether neutrophils and monocytes are activated after allergen-induced asthma, changes in the expression of complement (C3b) receptors were measured by use of the rosette technique. There was a time-dependent increase in the percentages of neutrophil and monocyte rosettes in 13 asthmatic patients for up to 60 min after allergen-inhalation challenge. This was preceded by elevations in the concentrations of serum neutrophil chemotactic activity and reductions in the FEV1. These changes were not observed in seven asthmatic patients who had histamine-induced bronchoconstriction. The present findings support the view that inflammatory cells are activated after allergen-induced asthma and that this may be the result of the release of mast cell-associated mediators rather than the consequence of bronchoconstriction per se.     

Significant changes of bronchial responsiveness to methacholine after early asthmatic reaction to toluene diisocyanate (TDI) in a TDI-sensitive asthmatic worker

Current asthma is often diagnostically excluded by the presence of normal bronchial responsiveness. We report on a TDI-induced occupational asthma patient with normal bronchial responsiveness. He had suffered from shortness of breath during and after TDI exposure for several months. His initial methacholine bronchial challenge test showed a negative response. The bronchoprovacation test with TDI showed an isolated immediate bronchoconstriction. The following methacholine bronchial challenge tests revealed that the bronchial hyperresponsiveness developed seven hours after the TDI challenge (methacholine PC20:5.1 mg/ml), progressed up until 24 hours, and returned to normal on the seventh day. This case provides evidence that the response of the airway to TDI may not always be accompanied by bronchial hyperresponsiveness to methacholine. Screening programs utilizing methacholine challenges may not always identify TDI-sensitized asthmatic workers.     

Immunologic studies in allergen-induced late-phase asthmatic reactions

We have measured plasma histamine, serum neutrophil chemotactic activity (NCA) and complement (C3 and C4) over a 24-hour period in patients experiencing either early- and late-phase (dual) or single early asthmatic reactions to inhaled allergens. There was a significant biphasic elevation in plasma histamine, which paralleled the fall in forced expiratory volume in 1 sec in 10 patients with dual responses, whereas in seven subjects with single early reactions, only a single early increase in histamine concentrations was observed. In general, in the individual subjects, the changes in plasma histamine paralleled both the elevations in serum NCA and the decreases in forced expiratory volume in 1 sec. By gel filtration on Sephacryl S-400, anion exchange chromatography on DEAE Sephacel, and chromatofocusing with Polybuffer Exchanger 94, the major NCA of both the early and the late reactions was associated with proteins having an estimated molecular size of 600,000 daltons, an elution from DEAE Sephacel at 0.15M to 0.30M of NaCl (pH 8.1), and a pI of approximately 6.5. There were no appreciable changes in serum C3 and C4 up to 24 hr after challenge in subjects with late-hase responses. The patterns of asthmatic response were not related to either the total or allergen-specific serum IgE or IgG₄ concentrations. These results support the view that mediators of hypersensitivity participate in late-phase as well as early asthmatic reactions.     

Late asthmatic reactions and changes in histamine responsiveness provoked by occupational agents

The temporal and quantitative relationship between increases in airway responsiveness and late asthmatic reactions provoked by inhalation challenge with occupational agents was studied in nine individuals who underwent a total of thirteen active inhalation challenge tests with one of the following agents: toluene diisocyanate (TDI), maleic anhydride (MA), trimellitic anhydride (TMA), carmine, or colophony (pine wood resin). Airway responsiveness to inhaled histamine (histamine PC20) was measured before and at approximately 3 and 24 h after control and active challenge exposure, when, on all but four occasions, FEV1 was within 10% of pre-challenge values. Significant increases (p less than 0.02) in histamine responsiveness were present at 3 h following challenge exposures which subsequently provoked a definite late asthmatic reaction (FEV1 decrease greater than 15% 3-11 h post challenge). These increases in histamine responsiveness were significantly greater than those at 3 h following the challenges which provoked an isolated early (FEV1 decrease less than 6% 3-11 h post-challenge) or equivocal late asthmatic reaction (FEV1 decrease 6-15% 3-11 h post-challenge) (p less than 0.03). Although histamine responsiveness remained high at 24 h after challenges provoking late asthmatic reactions (p less than 0.05), this was less than the increase at 3 h and not significantly different from the PC20 at 24 h after challenges provoking either single early or equivocal late asthmatic reactions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Prednisone, indomethacin and airway responsiveness in toluene diisocyanate sensitized subjects

We investigated whether late asthmatic reactions and the associated increase in airway responsiveness induced by toluene diisocyanate (TDI) in sensitized subjects are inhibited by indomethacin and/or prednisone. Four sets of experiments were conducted in five subjects sensitized to TDI. To assess late asthmatic reactions to TDI, FEV1 was measured immediately before and after exposure to TDI and then hourly for 8 h. To assess change in airway responsiveness, the provocative dose (mg) of methacholine that caused a decrease in FEV1 of 20% (PD20FEV1) before treatment, and then before and after exposure to TDI was measured. In the first set of experiments, each subject was given no treatment and was studied before and 8 h after exposure to TDI; in the other two sets, each subject was studied before treatment, then during treatment with indomethacin (50 mg q.i.d. for 3 days, orally) or prednisone (50 mg once a day, for 3 days, orally), both before and 8 h after TDI exposure. In a fourth series of experiments, each subject was again given no treatment and studied before and 8 h after TDI. When the subjects were given no treatment or indomethacin, TDI caused late asthmatic reactions and increased airway responsiveness to inhaled methacholine. In contrast, when the subjects were given prednisone, TDI caused neither late asthmatic reactions nor increased airway responsiveness. Treatment with indomethacin and prednisone did not change baseline FEV1 and airway responsiveness. These results suggest that release of prostaglandins does not contribute to late asthmatic reactions and the associated increase in airway responsiveness induced by TDI. Inflammatory mediators inhibited by prednisone but not by indomethacin may be involved.     

Pathogenesis of late asthmatic reactions induced by exposure to isocyanates

The importance of airways inflammation for the development of bronchial hyperresponsiveness and for exacerbation of asthma was investigated in subjects with occupational asthma. We examined subjects sensitized to isocyanates, a small molecular weight compound that causes occupational asthma. Studies in asthmatic subjects sensitized to toluene diisocyanate (TDI) demonstrated that late, but not early, asthmatic reactions induced by TDI were associated with an acute increase in bronchial responsiveness, and with a marked infiltration of neutrophils and a slight infiltration of eosinophils into the airways, both prevented by steroids. As the late asthmatic reactions and the increase in responsiveness induced by TDI were prevented by steroids, but not by indomethacin, we speculated that cell membrane phospholipid metabolites, which are inhibited by steroids but not by indomethacin, may be involved in TDI induced hyperresponsiveness. The results of these studies suggest that bronchial hyperresponsiveness and exacerbation of asthma may be related to inflammation of the airways and that cell membrane phospholipid metabolites may be involved.