Bronchoalveolar neutrophilia during late asthmatic reactions induced by toluene diisocyanate

Eosinophils in the 1990s: new perspectives on their role in health and disease

Eosinophils are characterized by their unique crystalloid granules that contain four basic proteins--MBP, ECP, EDN and EPO. The cell has many common features with neutrophils but, unlike that cell type, eosinophils utilize VLA-4/VCAM-1 as an adherence pathway and have a number of other receptors not shared by neutrophils. These include recognition units for IgE (distinct from CD23), and receptors for IL-5, IL-3 and RANTES. Following stimulation with a variety of agents, eosinophils preferentially elaborate LTC4 as the major 5-lipoxygenase product of arachidonic acid and produce substantial amounts of PAF. Of particular interest is the ability of eosinophils to synthesize a number of cytokines. Thus eosinophils have marked pro-inflammatory potential. There is now convincing evidence that eosinophilia is T-cell dependent. The Th2-type cell, which selectively secretes IL-5 and IL-4, seems particularly involved. IL-5, IL-3 and GM-CSF are required for eosinophil maturation, and cause activation and prolonged survival of the mature cell. IL-5 is unique in that it promotes terminal differentiation of the committed eosinophil precursor and in vivo in mice appears to be sufficient on its own for eosinophil growth from uncommited stem cells. IL-4 selectively upregulates VCAM-1 expression on endothelial cells thus augmenting VLA-4-dependent eosinophil adhesion. The role of eosinophils in disease is complex but in general their numbers are increased in helminthic parasitic disease and atopic allergy and asthma. Eosinophil products can produce many of the pathological features of asthma, and helminthic larvae coated with immunoglobulin or complement are particularly susceptible to eosinophil-mediated cytotoxicity. Eosinopenia is often related to acute inflammation or stress.

The effects of toluene diisocyanate and of capsaicin on human bronchial smooth muscle in vitro

Toluene diisocyanate contracts guinea-pig bronchial smooth muscle through a mechanism involving capsaicin-sensitive sensory nerves. In the present study, we investigated the effects of toluene diisocyanate, capsaicin and tachykinins on isolated human bronchi. In 44 rings, toluene diisocyanate (0.3 mM) produced a relaxation which averaged 16.9 +/- 1.1%, in ten rings it produced a shortening that was 15.1 +/- 3.3% and in ten preparations it gave no response. A second administration of toluene diisocyanate (0.3 mM) always produced a relaxation (n = 13, 18.1 +/- 3.9%). Capsaicin (0.03 mM) produced shortening in 15 (35 +/- 6.6%) and relaxation in 11 preparations (41 +/- 6.8%), whereas a second administration caused shortening in nine (25.1 +/- 6.1%) and relaxation in 16 rings (36.4 +/- 4.9%). When toluene diisocyanate was given after two consecutive capsaicin administrations, we observed shortening in two rings (10.0 +/- 3.6%), relaxation in ten rings (15.9 +/- 3.6%), and no response in four preparations. To test the role of NK1 and NK2 receptors in these conflicting responses, we performed concentration-response curves to different tachykinins. Substance P, neurokinin A and neurokinin A-(4-10), a specific NK2 receptor agonist, gave a concentration-dependent shortening, with neurokinin A being the most effective and neurokinin A-(4-10) the least. The specific NK1 receptor agonist, [Sar9, Met(O2)11]substance P, produced both shortening and relaxation. We conclude that toluene diisocyanate and capsaicin may produce both shortening and relaxation in isolated human bronchi through NK1 receptors.

Bronchial biopsy evidence for leukocyte infiltration and upregulation of leukocyte-endothelial cell adhesion molecules 6 hours after local allergen challenge of sensitized asthmatic airways

We have examined the mucosal changes occurring in bronchial biopsies from six atopic asthmatics 5-6 h after local endobronchial allergen challenge and compared them with biopsies from saline-challenged segments from the same subjects at the same time point. All the subjects developed localized bronchoconstriction in the allergen-challenged segment and had a decrease in forced expiratory volume in 1 s (FEV1) (P < 0.01) and a decrease in their methacholine provocative concentration of agonist required to reduce FEV1 from baseline by 20% (P < 0.05) 24 h postchallenge. At 6 h we observed an increase in neutrophils (P = 0.03), eosinophils (P = 0.025), mast cells (P = 0.03), and CD3+ lymphocytes (P = 0.025), but not in CD4+ or CD8+ lymphocyte counts. We also detected an increase in endothelial intercellular adhesion molecule type 1 (P < 0.05) and E-selectin (P < 0.005), but not vascular cell adhesion molecule type 1 expression with a correlative increase in submucosal and epithelial LFA+ leucocytes (P < 0.01). Thus, in sensitized asthmatics, local endobronchial allergen instillation leads to an increased inflammatory cell infiltrate of the airway mucosa that involves upregulation of specific adhesion molecules expressed on the microvasculature.

Nasal neutrophilia and eosinophilia induced by challenge with platelet activating factor

BACKGROUND

It has been demonstrated that in vitro platelet activating factor-acether (1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphorylcholine; PAF) has the capacity to attract eosinophils and neutrophils. We investigated whether the same applies when human nasal airways are stimulated with PAF.

METHODS

Symptom scores and cytologic changes in nasal lavage fluids were evaluated in 10 atopic and 10 nonatopic subjects after nasal challenge with PAF, its precursor and metabolite, 1-O-hexadecyl-sn-glycero-3-phosphorylcholine (lyso-PAF), or saline solution.

RESULTS

Nasal obstruction was reported by all the atopic subjects and seven of the 10 nonatopic subjects after nasal challenge with PAF; other symptoms such as rhinorrhea, itching, and sneezing were generally mild. PAF induced neutrophilia, which appeared after 30 minutes in atopic subjects and after 1 hour in nonatopic subjects, and peaked at 3 hours in both. Less neutrophilia was found 3 hours after stimulation with lyso-PAF in both groups of subjects. PAF also induced eosinophilia, which appeared after 30 minutes in atopic subjects and only after 3 hours in nonatopic subjects. An increase in eosinophil counts was observed 3 hours after lyso-PAF stimulation in atopic but not in nonatopic subjects.

CONCLUSION

PAF can attract neutrophils and eosinophils into human nasal airways; however, the recruitment of inflammatory cells is more rapid in atopic than in nonatopic subjects, suggesting a different degree of responsiveness to PAF challenge in the two groups of subjects.

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 MDI, six exhibited a late asthmatic reaction to TDI (n = 5) or MDI (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.(ABSTRACT TRUNCATED AT 250 WORDS)

Leukotrienes as a target in asthma therapy

Asthma is a chronic inflammatory condition characterised by bronchial hyper-responsiveness and reversible airways obstruction. Research has demonstrated that these effects are mediated by a wide range of compounds. In the last decade leukotrienes have been identified as products of arachidonic acid metabolism. Their effects mimic the pathological changes seen in asthma both in vitro and in vivo. Further research has demonstrated increased production of leukotrienes both during episodes of asthma and in patients with stable asthma. The demonstration that leukotrienes have proinflammatory biological properties relevant to the pathogenesis of asthma has stimulated the development of many potential therapeutic compounds to block these actions. Early studies in laboratory-induced asthma in human volunteers have shown the efficacy of some of these compounds. They have been shown to attenuate the bronchoconstriction caused by allergen challenge, exercise, aspirin and exposure to cold air. Most encouraging of all have been recent placebo-controlled studies in clinical asthma where significant improvements in terms of spirometry, symptoms and beta 2-agonist use have been demonstrated. Leukotriene receptor antagonists and synthesis inhibitors are the first mediator antagonists to have been shown to be effective in treating clinical asthma and as such represent one of the most interesting new classes of antiasthma drugs in development at present.

Circadian variation of bronchial caliber and antigen-induced late asthmatic response

To study whether circadian variation of bronchial caliber participates in causing late asthmatic response (LAR), house-dust inhalation was made at 10 AM and 6 PM on separate days in 6 house-dust-sensitive asthmatic children aged 8 to 13 years. Bronchial obstruction was assessed through measurements of FEV1 at 4-h intervals from 24 h before to 24 h after the inhalation. The LAR, which is a 15 percent or greater decrease in FEV1 from the value at the same hour of the previous day, occurred 4 h or later after the inhalation in all challenges. The mean (+/- SD) time to the occurrence of the lowest FEV1 (maximum LAR) following the morning inhalation was 14.7 +/- 2.1 h versus 10.0 +/- 2.2 h following the evening inhalation (p < 0.05). Regardless of the hour of inhalation, FEV1 after the inhalation was lowest or near-lowest at 2 AM in all. Therefore, the maximum LAR was indistinguishable from the trough of further amplified circadian variation in FEV1 following the inhalation. These findings suggest that the downward arm of circadian variation may partially participate in causing the LAR.

Effect of nedocromil sodium on specific mediator- and antigen-induced airway responses in allergic sheep

This study evaluated the airway effects of nedocromil sodium in the sheep model of allergic bronchoconstriction. Nedocromil sodium provided statistically significant protection against both reflex- and mediator-induced bronchoconstriction in allergic sheep as assessed by bronchial responses to inhaled bradykinin and platelet-activating factor, respectively. When administered before antigen challenge, nedocromil sodium blocked both the immediate and late asthmatic response and prevented the subsequent increase in airway hyperresponsiveness. The protective effect of nedocromil sodium against the antigen-induced late response was associated with a significant decrease in the number of airway eosinophils measured by bronchoalveolar lavage. Although nedocromil sodium has no direct bronchodilatory activity, it prevented antigen-induced contractions in sheep tracheal smooth muscle in vitro. These results suggest that nedocromil sodium is active in the sheep model of allergic bronchoconstriction and may be useful in the treatment of reversible obstructive airway disease in human beings.

Mechanism of airway inflammation in asthma

Airway inflammation has emerged as an important contributor to mechanisms of asthma. Furthermore, the presence of airway inflammation is present even in the absence of severe symptoms. To study the mechanisms by which bronchial inflammation can occur in asthma, a number of models have been developed including the airway response to antigen in allergic subjects. The pattern that has emerged from such studies indicates prompt pulmonary mast-cell activation and the apparent initiation of an inflammatory response. This inflammatory response develops over hours and is important in the later and more persistent development of bronchial obstruction. The eosinophil is an important cell in this process as are proinflammatory cytokines generated from activated lung mononuclear cells. The consequence of this multiple cell, multiple proinflammatory product interaction is the establishment of a self-perpetuating, redundant process by which asthma severity increases.

Plasma exudation and solute absorption across the airway mucosa

The airway mucosa responds to inflammatory provocations with bulk exudation of plasma into the airway tissue (vascular exudation) and lumen (mucosal exudation). The intensity and time course of the exudative response can be relevantly examined by sampling and analysing airway surface liquids, because the luminal entry of plasma proteins/tracers promptly and quantitatively reflects the exudative response of the airways. The process of mucosal exudation of plasma is a prominent feature of airway inflammation and has been demonstrated in rhinitis, asthma, and bronchitis. Inflammatory mediators and allergen produce mucosal exudation of plasma into the airway lumen (outward permeability) whereas the solute absorption across the mucosa (inward permeability) is unaffected. Hence, in contrast to current views, we have demonstrated that in airway inflammation the solute absorption across the airway mucosa is not increased. The findings suggest the plasma exudation response also as a first line respiratory mucosal defence, allowing potent plasma protein systems to appear on an airway mucosa functionally intact as a barrier toward undue luminal material. Our data on plasma exudation and solute absorption across the mucosa of upper and lower airways further suggest the human nasal airways as a model relevant also for the tracheobronchial airways.

Cells and mediators in bronchoalveolar lavage of asthmatic patients: the example of eosinophilic inflammation

Bronchoalveolar lavage (BAL) greatly improved our understanding of asthma allowing to demonstrate the key role of inflammation in the pathogenesis of the disease. BAL is a safe procedure, even in severe patients when properly performed. BAL samples large and small airways and alveoli. Cells and mediators may be measured in BALF but they only represent an indirect estimation of the bronchial inflammation. Before performing BAL, the clinical status of the patients should be ascertained and drugs taken may have to be withdrawn. BALF markers should follow some requirements: (1) markers should be released by cells that are pertinent to airways inflammation (and reparation) in asthma, and, if possible they should be specific of a single cell type, (2) the enumeration of cells or titration of the marker or of its metabolites should be specific and sensitive, (3) if possible the titration should not be modified by the sampling procedure, (4) pilot studies should have demonstrated that the cell is increased or the secretory product is released during challenge in asthmatic subjects, (5) studies in a large number of patients should have demonstrated that the levels of the marker are increased in chronic asthmatics, that these levels are correlated with the severity of the disease and are decreased during effective anti-inflammatory treatment, and (6) if possible the cell or marker should be specific to asthma (but at present there is no such cell or marker). Eosinophils and granule secretory products follow most of these requirements. BAL represents an important research tool to assess the effects of therapeutic interventions.

Nedocromil sodium. An updated review of its pharmacological properties and therapeutic efficacy in asthma

Nedocromil sodium, the disodium salt of a pyranoquinoline dicarboxylic acid, has anti-inflammatory properties in vitro, in animal models of asthma, and in humans, as evidenced by inhibition of inflammatory cell activation and mediator release, early and late allergen-induced bronchoconstriction and airway hyperresponsiveness. Recent therapeutic trials confirm the safety and efficacy of inhaled nedocromil sodium as adjunctive therapy in adult patients whose asthma is not adequately controlled by beta-agonists alone. Nedocromil sodium has also been shown to improve symptoms when added to existing treatment with methylxanthines and corticosteroids. Some studies show nedocromil sodium to be successful replacement therapy for methylxanthines, in addition to enabling a modest reduction in inhaled corticosteroids in some patients. Thus, nedocromil sodium may be suitable in patients with asthma as an adjunct to existing therapy, as an alternative to regularly administered oral and inhaled beta-agonists and oral methyl-xanthines, and potentially, to low dose inhaled corticosteroids as maintenance therapy in patients with mild to moderate asthma being considered for corticosteroid therapy.

Inhaled methacholine does not influence the cellular composition of bronchoalveolar lavage fluid

A methacholine or a histamine test is often used to quantitate bronchial responsiveness, in studies investigating the influence of various inhaled stimuli on the responsiveness and composition of bronchoalveolar lavage (BAL) fluid. Histamine has been shown to evoke an inflammatory cell response in BAL fluid. In order to test the influence of the methacholine test on the cellular composition of BAL fluid, we investigated 14 healthy, nonsmoking volunteers with a methacholine test 24 h before performing a BAL. The results showed no significant changes in the cellular composition of BAL fluid, as compared with control BAL in the same persons.

Immunoglobulin E-mediated increase in vascular permeability correlates with eosinophilic inflammation

An increase in bronchovascular permeability is thought to play an important role in the pathogenesis of allergic asthma. We sought to determine whether the increase in permeability observed 24 h after segmental antigen challenge in ragweed-allergic human volunteers was associated with the infiltration and degranulation of a specific cell type. A 20,000-fold range of antigen concentrations was used to alter the number and type of inflammatory cells recruited to the lung by challenge. Although large numbers of inflammatory cells were recruited to lung air spaces over a large range of antigen concentrations, significant numbers of eosinophils (731.3 +/- 232.9 x 10(3)/ml) were recruited only when the concentration of antigen used for segmental challenge was > or = 100-fold higher than the concentration needed to produce an 8 to 10 mm wheal 20 min after intradermal skin testing. In addition, large increases in bronchoalveolar lavage (BAL) albumin concentration (636.3 +/- 170.5 micrograms/ml) were observed only in this same group of subjects. The correlation coefficient between the logarithms of the BAL eosinophil concentration and albumin concentration was +0.82 (p < 0.001), and between eosinophil-derived neurotoxin and albumin it was +0.88 (p < 0.001). In a stepwise, multiple regression analysis, eosinophils accounted for 67% of the variance in BAL albumin concentration, whereas no other cell type was a significant predictor of albumin flux into BAL fluid. We conclude that eosinophil recruitment and degranulation are associated with large increases in bronchovascular permeability after segmental antigen challenge in humans.

Occupational asthma and extrinsic alveolitis due to isocyanates: current status and perspectives

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Airway mucosal inflammation even in patients with newly diagnosed asthma

We have studied bronchial biopsies from 14 patients with newly diagnosed asthma (four men and 10 women), who had had asthma symptoms, on average, 7.4 months (range, 2 to 12 months) and from four control subjects. The patients had not received corticosteroids, disodium cromoglycate, or theophylline before the study. The bronchial biopsies were taken, using a rigid-tube bronchoscope under local anaesthesia, from two different airway levels: (1) inside the right upper lobe bronchus, and (2) at the opening of the right middle lobe. The specimens were prepared for both light and electron microscopy. The use of Slot grids 1 x 2 mm enabled a large area of the thin sections to be photographed and analyzed by applying a graphic Autocad program. There was an increase in the numbers of mast cells (p < 0.001), eosinophils (p < 0.05), lymphocytes (p < 0.05), and macrophages (p < 0.05) in the epithelium of patients with newly diagnosed asthma as compared with those in control subjects. In the lamina propria, these asthmatic patients had more eosinophils (p < 0.001), lymphocytes (p < 0.001), macrophages (p < 0.001), and plasma cells (p < 0.001) than did the control subjects. We conclude that, in asthma, an airway inflammatory process is present even at a clinically early stage of the disease. In the asthmatic airways, there are signs of a general inflammatory response caused by more than one cell type.

Isocyanate induced lung disease

A review of the pathogenesis of isocyanate induced lung disease is given with an emphasis on immunologic mechanisms of disease.

Increases in activated T lymphocytes, eosinophils, and cytokine mRNA expression for interleukin-5 and granulocyte/macrophage colony-stimulating factor in bronchial biopsies after allergen inhalation challenge in atopic asthmatics

Immunohistology and in situ hybridization were used to evaluate the presence, activation status, and cytokine mRNA profile of cells in the bronchial mucosa during human allergen-induced asthma. Fifteen atopic asthmatic subjects underwent inhalation challenge with allergen and with allergen diluent, performed in random order separated by an interval of at least 3 wk. Bronchial biopsies were obtained 24 h after challenge. Immunostaining revealed increases in the numbers of secreting eosinophils (EG2+; P < 0.05) and in interleukin-2 receptor (IL-2R)-positive cells (CD25+; P < 0.01) after allergen compared with diluent challenge. No differences were observed in the numbers of total leukocytes (CD45+), T lymphocytes (CD3+, CD4+, and CD8+), elastase-positive neutrophils, macrophages (CD68+), or mast cell subtypes (MCT+ or MCTC+). In situ hybridization revealed significant increases in the numbers of cells expressing mRNA for IL-5 (P < 0.02) and granulocyte/macrophage colony-stimulating factor (P < 0.01) after allergen compared with diluent challenge. A significant inverse relationship was observed between the number of cells expressing mRNA for IL-4 and for interferon-gamma (r = -0.75, P < 0.02). The results support the view that cytokines possibly from activated T lymphocytes may contribute to local eosinophil accumulation during allergen-induced asthma.

Peripheral blood leukocyte count and respiratory symptoms

The relationship of peripheral blood leukocyte count to respiratory symptoms was explored in data from the Second Annual National Health and Nutrition Survey (NHANES II). The study sample consisted of 9237 white and nonwhite US adults between the ages of 30 and 74 years. Three respiratory symptom outcomes were utilized: physician-diagnosed chronic cough and chronic bronchitis and self-reported frequent wheeze apart from colds or flu in the past 12 months. Peripheral blood leukocyte counts were performed using a Coulter counter, model FN. Logistic regression analysis was performed for each of the three respiratory symptom outcomes controlling for age, race, gender, and cigarette-years of smoke exposure. The peripheral blood leukocyte count was a significant predictor for each symptom. For a standard deviation increase in the log leukocyte count, the relative odds of wheezing was 1.93 (95% confidence level [CI], 1.47 to 2.52); for chronic cough, 2.29 (95% CI, 1.74 to 3.00); and for bronchitis, 2.44 (95% CI, 1.77 to 3.35). Analyses restricted to never smokers gave similar results. These data suggest that peripheral blood leukocyte count correlates with respiratory symptoms and are consistent with the hypothesis that the leukocyte count is a serum marker of inflammation.

Effects of long-term glucocorticoid therapy on bronchoalveolar cells in adult patients with bronchial asthma

The effects of long-term glucocorticoid therapy on airway inflammation were examined in 84 asthma patients. The proportion of lymphocytes in bronchoalveolar lavage (BAL) fluid was significantly decreased in patients with steroid-dependent intractable asthma (SDIA) compared to results in non-SDIA patients, while BAL neutrophils were significantly increased in SDIA patients compared to results in non-SDIA patients. Regarding age, in patients under the age of 69 (except those between 30 and 39), BAL lymphocyte number was significantly decreased in SDIA compared with non-SDIA subjects, and in patients between 50 and 69, BAL neutrophils were significantly increased in SDIA compared with non-SDIA subjects. The number of BAL lymphocytes was significantly lower in patients with serum cortisol levels of less than 5.0 micrograms/dl than in those with levels of more than 5.1 micrograms/dl. BAL lymphocyte number was also significantly lower in patients who had received glucocorticoid therapy for more than 6 years than in those who had received such therapy for 2 years. These results show that long-term glucocorticoid therapy decreases the number of lymphocytes and increases neutrophil numbers in the airways.

Identification of epithelial cells in bronchoalveolar lavage

1. Damage to the bronchial epithelium occurs after the inhalation of toxic substances and allergens, and through virus infections and it may lead to increased desquamation of epithelial cells in bronchoalveolar lavage (BAL). 2. In this study we compared two methods of staining the epithelial cells of BAL, the conventional cytochemical May Grunwald-Giemsa stain (MGG) and an immunocytochemical technique using a monoclonal antibody anti-human cytokeratin (CK) detected with APAAP immuno-alkaline phosphatase. BAL was obtained from 13 subjects and the epithelial cells were cytocentrifuged either immediately after collection (fraction A) or after washing (fraction B). 3. Higher percentages of epithelial cells were identified in fraction A with CK (20.0 +/- 5.1%) than in fraction A with MGG (11.2 +/- 2.3%), which recognized only ciliated epithelial cells. In fact a proportion of CK-positive cells (34%) in fraction A were not ciliated. Underestimation of epithelial cells by MGG compared to CK was more pronounced in fraction B (8.0 +/- 2.9% and 22.9 +/- 3.0%, respectively) as there was a relative loss of ciliated CK+ cells after washings. 4. These results suggest that immunocytochemical staining with an anti-cytokeratin monoclonal antibody is more sensitive than using the MGG stain in detecting epithelial cells in BAL.

Effects of glucocorticoids on humoral and cellular immunity and on airway inflammation in patients with steroid-dependent intractable asthma

The effects of glucocorticoids on the proportion of lymphocytes in bronchoalveolar lavage (BAL) fluid in relation to humoral and cellular immunity were studied in 56 patients with steroid-dependent intractable asthma. To analyze the mechanism responsible for reduced numbers of BAL lymphocytes, we divided the subjects into 4 groups according to their BAL lymphocyte proportions: 0-4.9%, 5.0-9.9%, 10.0-14.9%, and 15.0-20.0%. Serum IgG levels and the peripheral lymphocyte count were significantly reduced in patients with a low proportion of BAL lymphocytes (less than 9.9%) than in those with more than 10% BAL lymphocytes. Delayed cutaneous reactivity to purified protein derivative was suppressed in patients with a low proportion of BAL lymphocytes (less than 4.9%). The mean proportion of BAL neutrophils tended to increase as the proportion of BAL lymphocytes decreased. These results show that the reduction in BAL lymphocytes produced by glucocorticoids is associated with suppressed humoral and cellular immunity, and that under such conditions the proportion of BAL neutrophils increases.

Occupational asthma--a model to study the natural history and pathogenic mechanisms in asthma

Occupational agents can give rise to asthma either through producing specific IgE antibodies or through some as yet unidentified immunological mechanism. Study of pathogenic mechanisms of occupational asthma can generate very useful information on the pathogenesis of nonoccupational asthma. Occupational asthma also provides an ideal model to study the natural history of asthma. As the agent responsible for asthma is known, it is possible to design a study to investigate predisposing host factors and level of exposure and their interaction in determining the onset, the severity, and the outcome of the disease.

Bronchial hyperreactivity after inhalation of trimellitic anhydride dust in guinea pigs after intradermal sensitization to the free hapten

We have developed in the guinea pig, an animal model of bronchial hyperreactivity provoked by inhalation of trimellitic anhydride (TMA) dust, a known cause of occupational asthma in humans, after intradermal sensitization to the free hapten. Male Dunkin-Hartley guinea pigs (n = 6) were injected intradermally with 0.1 ml of 30% TMA in corn oil. Control animals (n = 7) were injected with 0.1 ml corn oil alone. On Days 21 to 28 after sensitization, guinea pigs were challenged (nose only) to 12 mg/m3 of inhalable TMA dust for 30 min. Bronchial reactivity was measured in sensitized animals and in control animals at 8 h after exposure to the dust. We also measured bronchial reactivity in sensitized exposed guinea pigs at 2 h (n = 5) and at 24 h (n = 5). Pulmonary inflation pressure (PIP) was used to assess bronchopulmonary response. Blood samples were taken for assessment of IgG-1 antibodies to TMA conjugated to guinea-pig albumin. The concentration of acetylcholine required to induce a 100% increase in PIP was used to assess bronchial reactivity. The lungs were eviscerated for histologic examination. All guinea pigs injected intradermally with TMA had high titers of specific IgG-1 antibodies to TMA conjugated to guinea-pig albumin. There was a significant increase in bronchial reactivity in sensitized guinea pigs 8 h after exposure to the TMA dust compared with that in the control animals. There was also a significant eosinophilic inflammatory influx in the subepithelium of the sensitized groups.(ABSTRACT TRUNCATED AT 250 WORDS)

The products of the reaction between toluene diisocyanate and water contract isolated guinea pig bronchi

We have investigated the ability of the products of the reaction between toluene diisocyanate (TDI) and water to contract bronchial smooth muscle. The experiments were performed in isolated guinea pig bronchi. TDI, both 2,4- and 2,6-toluenediamine (TDA) and mixtures of 2,4- and 2,6-TDA (ratio 80:20 and 20:80) caused concentration-dependent contraction in the isolated bronchi. The mixture of disubstituted urea and biuret also contracted the bronchi, but not in a concentration-dependent fashion. Our results provide evidence that all products of the reaction between toluene diisocyanate and water have the ability to contract isolated bronchial smooth muscle in guinea pigs. Whatever the role of toluenediamine in the adverse respiratory effects induced by exposure to isocyanates, our findings reveal the necessity of in vivo studies on the metabolism of inhaled toluene diisocyanate in humans to improve our understanding of the mechanism of action of isocyanates.

Comparison between bronchial and alveolar samples of bronchoalveolar lavage fluid in asthma

BACKGROUND

Cell content of BALF may vary according to the segment of the lung washed. It was proposed to separate BALF into several aliquots, the first sample being more related to bronchi. The present study compared bronchial and alveolar samples by fractionating aliquots of BALF in normal and asthmatic subjects.

METHODS

One hundred asthmatic subjects (mean +/- SEM: 37 +/- 1.5 yr in age) were compared with 31 normal subjects (mean +/- SEM: 32 +/- 2.2 yr in age). None of the subjects was a smoker and none was taking drugs that might interfere with the results. The severity of asthma was defined by the clinical score of Aas examining the chronic severity of asthma and ranging from 1 to 5 (range: 1 to 4; mean +/- SEM: 2.2 +/- 0.1) and FEV1 (range: 45 to 130 percent; mean +/- SEM: 82 +/- 1.8 percent of predicted values). Bronchoscopy was done in a standardized manner. A first aliquot of 50 ml of saline each were instilled and the BALF recovered was pooled (alveolar sample). After centrifugation, total and differential cell counts (May Grünwald-Giemsa) were carried out on bronchial and alveolar samples.

RESULTS

The alveolar sample contained significantly more cells per milliliter of BALF than the bronchial sample in normal (p less than 0.0077, Wilcoxon test) and in asthmatic subjects (p = 0.0001, Wilcoxon test). Both in normal and asthmatic subjects, bronchial samples contained significantly more neutrophils and epithelial cells and fewer macrophages and lymphocytes than alveolar samples. In asthmatic subjects, the bronchial sample contained a significantly greater percentage of eosinophils than the alveolar sample. Eosinophils were significantly increased in asthmatic subjects for both the bronchial and alveolar samples. Bronchial and alveolar eosinophilia both were correlated with the Aas score (r = 0.25, p = 0.024 and r = 0.38, p = 0.0006, respectively, by Spearman Rank test).

CONCLUSIONS

This study shows in a large number of subjects that the cell content of bronchial and more distal segments of the lung is not comparable, indicating that studies should not give pooled data in asthmatic subjects. Moreover, it confirms the presence of BALF eosinophilia in asthmatic subjects.

Inflammatory response to acute inhalation of endotoxin in asthmatic patients

Inhalation of 20 micrograms endotoxins (from the membrane of Gram-negative bacteria) has been reported to induce a bronchial obstructive response in asthmatic subjects. The aim of the present study was to evaluate in asthmatic patients the possibility of an inflammatory response to inhaled endotoxins. Eight patients with mild asthma were submitted to bronchial challenge tests, in a single-blind trial, on Day 1 with control solution and on Day 7 with 20 micrograms endotoxin of Escherichia coli (026:B6). Local inflammatory response was indirectly evaluated by the degree of bronchial hyperresponsiveness (BHR) expressed as PD20 FEV1 histamine (the dose of histamine inducing a 20% decrease in FEV1) at 0, 6, 24, and 48 h and 7 days. Systemic inflammation was investigated by sequential blood determinations of total (and differential) white cells, complement anaphylatoxin C5a, interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-alpha), and C-reactive protein (CRP). A significant (p < 0.01) bronchial obstructive response was demonstrable 45 min after lipopolysaccharide (LPS) inhalation, lasting 5 h. Comparing the level of BHR after control inhalation, a significant (p < 0.05) increase in BHR was shown 6 h after LPS, partially normalized at 24 and 48 h. A short peak in TNF-alpha at 60 min (p < 0.05) and an increase in total white blood cells (p < 0.01) and neutrophil polymorphonuclear neutrophils at 360 min (p < 0.05) and of CRP at 24 and 48 h (p < 0.05 and p < 0.01) were significant. The other blood parameters did not change significantly.(ABSTRACT TRUNCATED AT 250 WORDS)

The 5-lipoxygenase inhibitor zileuton blocks antigen-induced late airway responses, inflammation and airway hyperresponsiveness in allergic sheep

Leukotrienes are thought to be involved in allergen-induced airway responses. To test this hypothesis we used a newly described 5-lipoxygenase inhibitor, zileuton, and examined its effect on antigen-induced early and late bronchial responses, airway inflammation and airway hyperresponsiveness in allergic sheep. Early and late responses were determined by measuring specific lung resistance (SRL) before and serially for 8 h after antigen challenge. Airway inflammation was assessed by bronchoalveolar lavage performed before, 8 h after and 24 h after antigen challenge. Airway responsiveness was measured before and 24 h after challenge by determining the dose of inhaled carbachol that caused a 400% increase in SRL (PD400%). The sheep (n = 8) were challenged with Ascaris suum antigen once after vehicle treatment (methylcellulose) and once after treatment with zileuton (10 mg/kg in methylcellulose, p.o.) given 2 h before antigen challenge. Trials were separated by at least 21 days. Zileuton had no effect on the early bronchoconstrictor response to antigen but the drug inhibited the late bronchial response by 55% (P less than 0.05). Unlike the control trial, there was no significant increase in bronchoalveolar lavage eosinophils at 8 h post challenge in the zileuton-treated sheep. Furthermore, zileuton treatment blocked (P less than 0.05) the airway hyperresponsiveness seen 24 h after challenge. Ex vivo formation of leukotriene B4 was inhibited over several hours after a single oral dose of zileuton, indicating that the compound was acting as a 5-lipoxygenase inhibitor in vivo. These results suggest that 5-lipoxygenase metabolites contribute to allergen-induced late responses, airway inflammation and airway hyperresponsiveness in this animal model of asthma.

Occupational asthma

Occupational asthma is recognized as the most common form of occupational lung disease. Over 200 causative substances have been described. Major cases of occupational asthma are discussed along with valuable diagnostic approaches. Early diagnosis and removal of the patient from workplace exposure to the causative substance can prevent progression to severe asthma.

Safety of bronchoalveolar lavage and bronchial biopsies in patients with asthma of variable severity

The safety of fiberoptic bronchoscopy, bronchoalveolar lavage (BAL), and bronchial biopsies has been questioned in asthma, and current recommendations indicate that bronchoscopies should only be performed in mild to moderate asthma. Moreover, in most studies patients receive premedication with nebulized bronchodilators that may enhance the safety of the procedures. The purpose of this study was to determine (1) whether the overall safety of fiberoptic bronchoscopy, BAL, and bronchial biopsies in mild to moderate asthma could be extended to patients with more severe asthma and (2) whether these procedures are safe without premedication with nebulized bronchodilators. A group of 50 patients with asthma of variable severity (FEV1 ranging from 37 to 107% of predicted values) and 25 healthy volunteers were studied. Bronchoscopy, BAL (250 ml), and four bronchial biopsies were performed in a standardized manner, without premedication with a nebulized bronchodilator, by the same investigator. Safety was assessed by clinical follow-up, continuous recording of arterial oxygen saturation during the procedure with a digital oximeter, and measuring FEV1, FEF25-75, and FVC just before and 5 min after bronchoscopy. Arterial oxygen saturation decreased in asthmatic patients from 97% (range 91 to 99%) (T1) to 92% (range 79 to 98%) (T8) (ANOVA, Fisher's PLSD) and in control subjects from 97% (range 94 to 99%) (T1) to 93% (range 88 to 98%) (T8) (ANOVA, Fisher's PLSD). The fall in arterial oxygen saturation was not significantly different between asthmatic and normal subjects, and there was no correlation between arterial oxygen desaturation and the severity of asthma.(ABSTRACT TRUNCATED AT 250 WORDS)

Inflammation and airway reactivity in asthma

The increased airway reactivity characteristic of asthma may be due to contraction of airway smooth muscle, mucus hypersecretion, edema and thickening of airway walls, and the presence of serum proteins and inflammatory cells and their products in the airways. Increased airway reactivity in asthma correlates with airway epithelial damage and is clearly related to airway inflammation, a process that most likely involves a complex interaction among mast cells, lymphocytes, eosinophils, and macrophages. Thus, although symptomatic treatment of airway narrowing is best accomplished with bronchial smooth muscle relaxants, treatment of the basic pathophysiologic defect should attempt to reduce airway inflammation. Bronchodilators (inhaled beta-agonists and, occasionally, theophylline), which do not decrease airway reactivity, are often used to treat the symptoms of patients with mild or episodic asthma; inhaled corticosteroids, which do decrease airway inflammation and reactivity, are used to treat patients with more severe symptoms. Methotrexate and cromolyn sodium may also be used, although their role in treating the underlying pathophysiology remains controversial. Identification of new agents that are as effective as corticosteroids but that do not produce their side effects would represent a major therapeutic advance for patients with asthma.

A research method to induce and examine a mild exacerbation of asthma by withdrawal of inhaled corticosteroid

This study evaluated a research method to examine an exacerbation of asthma induced by corticosteroid withdrawal. Ten non-smoking adult asthmatics who were stable on treatment with inhaled steroid underwent a graded reduction of the daily dose by 200 micrograms at weekly intervals until an exacerbation of symptoms occurred. A daily symptom, peak expiratory flow rate (PEF) and medication diary was kept. Weekly clinic visits were used to assess symptoms, spirometry, methacholine airway responsiveness (expressed as the provocative concentration to cause a fall in FEV1 of 20%, PC20), circulating eosinophils, basophils and their progenitors (Eo/B-CFU), and sputum inflammatory cells. The laboratory tests were performed blind to the clinical details. Each subject developed an exacerbation of symptoms, on average at 16 (7-26) days after the onset of steroid reduction. This was accompanied by a deterioration in each of the objective measures. There was a fall in FEV1 by 320 ml (s.e.m. 9.5) and in PC20 from 0.8 to 0.43 mg/ml. Circulating eosinophils rose from 114 (24) x 10(3)/ml to 227 (50) x 10(3)/ml and Eo/B-CFU rose from 31 (5.6) to 44 (11.3)/10(6) cells. Sputum developed in five subjects and contained 36 (5.2)% eosinophils and 1.98 (0.21)% metachromatic cells (mast cells or basophils). The symptom diary and weekly questionnaire were demonstrated to be valid and responsive to change. A deterioration indicated by the daily symptom score preceded changes in PEF. Treatment by an increase in steroid was followed by reversal of each of the changes.(ABSTRACT TRUNCATED AT 250 WORDS)

Theophylline inhibits late asthmatic reactions induced by toluene diisocyanate in sensitised subjects

Toluene diisocyanate (TDI)-induced asthma is a frequent occupational airway disease. To determine whether a calibrated dosage of oral slow-release theophylline inhibits asthmatic reactions and the associated increase of airway responsiveness to methacholine induced by TDI, we examined six asthmatic subjects who developed a late or a dual asthmatic reaction after TDI inhalation challenge. We administered oral slow-release theophylline or placebo to each subject for 7 days according to a double-blind, randomized, cross-over study design. When the subjects received a placebo, TDI caused a late or a dual asthmatic reaction. When the subjects received theophylline. TDI caused significantly reduced late asthmatic reactions. Mean serum theophylline concentrations were within the therapeutic range. Theophylline neither modified the baseline airway responsiveness to methacholine, nor the increase of airway responsiveness to methacholine induced by TDI. These results suggest that slow-release theophylline may improve TDI-induced late asthmatic reactions, but it does not change the baseline airway responsiveness to methacholine and the increase of airway responsiveness to methacholine induced by TDI.

DNA damage in human white blood cells after inhalative exposure to methylenediphenyl diisocyanate (MDI)--case report

A workplace-related inhalative exposure test in a challenge chamber was performed on an industrial worker in a methylenediphenyl diisocyanate (MDI) atmosphere from 5 to 20 ppb and the isolated white blood cell DNA was analysed by electrophoresis, anion-exchange chromatography and melting behaviour. The results of electrophoresis indicate that inhaled MDI induces double-strand breaks of DNA. Some of the DNA fragments were estimated to be in the region of 100-500 bp. Anion-exchange chromatography confirmed this finding. Following denaturation and rapid renaturation the results demonstrated that some DNA fragments are cross-linked by MDI. Comparing the melting curves before and after inhalative exposure in the challenge test chamber, genomic DNA revealed differences in the shape of the melting curve (hyperchromic effect). The results suggest that occupational MDI exposure could be associated with white blood cell DNA damage.

Airway mucosal inflammation in occupational asthma induced by toluene diisocyanate

We examined the light and electron microscopic structure of lobar bronchial biopsies of nine subjects with occupational asthma induced by toluene diisocyanate (TDI) and of four control nonasthmatic subjects who had never been exposed to TDI. Inflammatory cell numbers were separately assessed in the intact epithelium, in the more superficial layer of the submucosa, and in the total submucosa. Asthmatic subjects had an increased number of inflammatory cells in the airway mucosa compared with control subjects. Eosinophils were significantly increased in all compartments, CD45-positive cells were significantly increased in the epithelium and in the more superficial layer of the submucosa, and mast cells were significantly increased only in epithelium. By electron microscopy eosinophils and mast cells appeared degranulated only in asthmatic patients. In the areas of epithelium that appeared intact by light microscopy, electron microscopy showed that, although the intercellular spaces between columnar cells were similar in asthmatic and control groups, the intercellular spaces between basal cells were significantly wider in patients with asthma. Patients with TDI-induced asthma also had a thicker subepithelial reticular layer, where immunohistochemistry showed the presence of collagen III. In conclusion, in patients with asthma induced by TDI, the airway mucosa shows pathologic features, such as inflammatory cell infiltrate and thickening of subepithelial collagen, similar to those described in atopic asthma.

Inflammatory mediators and cellular infiltration of the lungs in a guinea pig model of the late asthmatic reaction

Alterations in cell numbers, vascular permeability, and concentrations of various inflammatory mediators in the lung were measured in a guinea pig model of the late asthmatic reaction. Animals sensitized by inhalation of ovalbumin were challenged with an aerosol of ovalbumin or saline, and bronchoalveolar lavage fluid (BALF) and peripheral blood were collected after periods ranging from 5 min to 72 h. Increased vascular leakage within the lungs was indicated by elevated BALF/plasma albumin ratios at all time points, and was maximal 6 h after challenge. There were increased numbers of eosinophils in BALF by 6 h after challenge and they remained elevated at least until 72 h. A corresponding increase in the proportion of blood leukocytes represented by eosinophils was observed at 6 and 17 h, which suggests that these cells may be drawn to the lung following their release into the circulation, but by 72 h the proportion in blood had returned to normal. A transitory neutrophilia was evident in BALF and blood 6 h after allergen exposure, but there were no allergen-induced changes in BALF numbers of macrophages, lymphocytes, epithelial cells, or mast cells (as assessed by concentrations of cell-associated histamine). beta-Glucuronidase activity was significantly increased in BALF of guinea pigs at 2 h and 17 h following challenge. The degree to which eicosanoids can be recovered in BALF was investigated by instilling a range of tritiated compounds into the lungs of normal guinea pigs at the time of lavage. Ratio high-performance liquid chromatography revealed that there had been little metabolism of the eicosanoids recovered in BALF. However, there was evidence for a rapid removal of these mediators from the lung, a process which will militate against their accurate quantitation in BALF. Histamine, prostaglandin D2, and thromboxane B2 were detected in BALF but did not differ between treatment groups, and levels showed no simple relationship with the other inflammatory changes measured.

The effect of immunotherapy on eosinophil accumulation and production of eosinophil chemotactic activity in the lung of subjects with asthma during natural pollen exposure

Two groups of birch pollen--allergic patients with seasonal rhinoconjunctivitis and asthma were followed during two consecutive birch-pollen seasons, one group, N = 10, during a season with high pollen load, and one group, N = 15, during a season of low pollen load. Half the patients were treated with immunotherapy (IT) for 3 and 4 years, respectively. The other half of the patients served as control group (non-IT). Bronchoalveolar lavage (BAL) was performed once before each season and once during the pollen season. Eosinophil (EOS) numbers in BAL were increased (p less than 0.01) during the season with high pollen load but not in the season with a low pollen load, and this increment was absent in the IT-treated group. Also, the EOS cationic protein levels were raised in the non-IT-treated group during the season with a high pollen load. The levels of EOS and neutrophil chemotactic activity were raised in BAL in both seasons in the non-IT-treated group compared with the IT-treated group (p less than 0.02, p less than 0.003, p less than 0.04, and p less than 0.005 in high- and low-load pollen season, respectively). Serum and BAL eosinophil chemotactic activity (ECA) were positively correlated (p less than 0.001). We conclude that there is an influx of active EOSs into the lung of pollen-allergic patients with asthma during a pollen season, which may be abrogated by IT. Furthermore, the generation of ECA appears to be an extremely sensitive marker of antigenic exposure, and the potent inhibition of the generation of ECA by IT may provide a clue as to the mechanism of this treatment.

Time course of IL1 and IL6 synthesis and release in human bronchial epithelial cell cultures exposed to toluene diisocyanate

We have previously demonstrated that human bronchial epithelial cells release appreciable amounts of interleukin 1 (IL1) and interleukin 6 (IL6) when exposed to toluene diisocyanate (TDI) in vitro. TDI is an inflammatory and asthmogenic stimulus presumed to act at least in part through immunological mechanisms. The epithelial cell-derived IL1 and IL6 can promote T cell activation and proliferation in culture, and if this also happens in vivo they may contribute to the persistence of the inflammatory response of the bronchial mucosa observed in TDI-sensitive asthmatics. In this study, we confirmed the release of biologically active IL1 beta and IL6-like substances from bronchial epithelial cells exposed to isocyanates in vitro, and related the rate and the magnitude of the cytokine secretion with the pattern of IL1 beta and IL6 gene expression and the extent of epithelial cell injury. In the epithelial cell cultures exposed to TDI, there was a parallel, progressive increase in the expression of IL6 mRNA and in the secretion of IL6 protein between 48 hours and 6 days after exposure. By contrast, although increasing amounts of biologically active IL1 beta were detected in the supernatants of TDI-exposed epithelial cells throughout the 6-day period following exposure, augmented levels of IL1 beta mRNA were only evident 6 days after exposure, suggesting that TDI exposure might have initially affected the enzymatic cleavage of the intracellular IL1 beta precursor and the mechanisms which regulate the secretion of mature IL1 beta.

Toluene diisocyanate produces an increase in airway tone that outlasts the inflammatory exudation phase

Toluene diisocyanate (TDI) is a causative agent in occupational asthma. Through an oral catheter TDI, 0.03 microliters, dissolved in 0.02 ml olive oil, was superfused on the tracheobronchial mucosa of anaesthetized guinea-pigs. TDI induced plasma exudation into both airway tissue and lumen (peak effect: 5 hr; duration approximately 17 hr). Light microscopy examinations demonstrated that the epithelium was not disrupted by this process (and that microvessels are abundant just beneath the epithelium). At days 6 and 21 after exposure to TDI PAS-positive cells were increased, but no other histological alterations were found. Also, the occurrence of peptide-containing nerve fibres was not altered by TDI. After TDI-exposure the airway smooth muscle tone was elevated as examined in vitro at base-line and at concentration-response to carbachol. The largest increases in tone were recorded 21 days after exposure to TDI. The abnormally large tone was not associated with an increased thickness of the smooth muscle layer nor was it associated with reduced effects of either beta 2-agonist (terbutaline) or xanthine- (theophylline) relaxants. It is concluded that TDI-induced plasma exudation into guinea-pig airways occurs for 17 hr without disrupting the epithelial lining and without causing major changes in the airway peptidergic innervation. Both the airway tone, and the number of mucous cells, are increased for at least 3 weeks after exposure to TDI.

Bronchoscopy with bronchoalveolar lavage causes neutrophil recruitment to the lower respiratory tract

Bronchoscopy with bronchoalveolar lavage (BAL) is a technique now widely utilized for both clinical and investigational purposes. At times, it is useful to perform bronchoscopy with BAL in a serial fashion. However, previous work in animals indicates that bronchoscopy with BAL can cause lower respiratory tract inflammation. To determine if BAL also causes lower respiratory tract inflammation in humans, sequential bronchoscopy with BAL was performed in 30 human subjects. Inflammation was evaluated using a quantitative visual assessment of bronchitis and by BAL. BAL was performed by instilling and aspirating five 20-ml aliquots of saline in each of three areas of the lung. The fluid returned from the first aliquot from each site was pooled as the bronchial fraction, and that from the remaining four aliquots was pooled as the alveolar fraction. Each volunteer was restudied at 2, 7, 24 or 72 h. Findings at the second bronchoscopy with BAL included an elevation in visual signs of large airways inflammation, which was greatest at 24 h. Bronchial neutrophils increased significantly, with the greatest effect seen at 7 h (5.3 +/- 2.0 versus 59.5 +/- 11.0%, SEM). The effect was most pronounced in the area of the lung previously lavaged, but was also seen in lobes that had not received BAL at the first bronchoscopy. Alveolar neutrophils also increased, with the maximal effect also seen at 7 h. Visible bronchial inflammation, bronchial neutrophils, and alveolar neutrophils returned to the normal range by 72 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of leukocyte depletion in noncholinergic bronchoconstriction of guinea pigs

To test the role of leukocytes in the activation of afferent C-fibers in the lung, 33 guinea pigs, 18 control and 15 experimental or leukocyte depleted, were used. The leukocyte depletion was accomplished with an intraperitoneal injection of cyclophosphamide (100 mg/kg) 96 h prior to the study. On the day of the study, bronchial constriction was produced either by exsanguination (n = 17) or by capsaicin injection (16 micrograms/kg, i.v.) (n = 16) in anesthetized-paralyzed animals. Venous blood samples were collected for leukocyte counts. At 1-30 min following the above treatment, the maximal expiratory flow maneuver was performed and a decrease in the maximal expiratory flow at 50% baseline total lung capacity (Vmax50) was used as an index of bronchoconstriction. The leukocyte count decreased significantly following the pretreatment with cyclophosphamide [an average of 6217 +/- 612 (control) vs. 2242 +/- 334/mm3 (experimental)]. Exsanguination caused a gradual decrease in Vmax50 with time, indicating a temporal increase in bronchoconstriction. Capsaicin injection, on the other hand, caused an immediate (1 min) marked bronchoconstriction, which attenuated gradually with time. At a specific time point, leukocyte depletion did not produce any significant change in Vmax50 compared to the control group for both types of bronchoconstrictions. Based on these results, we conclude that leukocytes may play an insignificant role in the bronchoconstriction caused by the activation of afferent C-fibers in guinea pig lungs under our experimental conditions.