Phenotypic analysis of alveolar macrophages and lymphocytes following allergen inhalation by atopic subjects with mild asthma

BACKGROUND: The airway inflammation associated with allergic asthma is initiated through a complex interaction of antigen-presenting cells (APC) and T lymphocytes resulting in the release of a cascade of cytokines regulating the progress of the allergic inflammatory response. In the present study the state of alveolar macrophage (AM) and T cell activation was investigated following induction of allergic airway inflammation in individuals with atopic asthma. METHODS: Eleven individuals with mild, atopic asthma received cumulated allergen inhalations. Before and one day after challenge, bronchoalveolar lavage (BAL) was performed, and peripheral blood samples obtained. Ten healthy individuals served as controls. The expression of cell surface markers by BAL fluid AMs and T cells, and by blood T cells, was investigated by flow cytometry. RESULTS: All patients developed early asthmatic reactions (EAR) with increased numbers of eosinophils and mast cells in BAL fluid following allergen challenge. After allergen challenge, patients had relatively fewer pulmonary CD4+ T cells expressing CD69 and HLA class II and also relatively fewer pulmonary CD8+ T cells expressing HLA class II, compared to before challenge. An increased quantitative expression of CD14 and CD86 was seen within the AM population following allergen challenge. CONCLUSION: The results indicate a recruitment of non-activated, immature macrophages and CD4+ T cells to the airways as well as an altered phenotype pattern within the AM population following induction of allergic airway inflammation by allergen inhalation challenge in asthma.     

Bronchoalveolar lavage fluid from asthmatic subjects is mitogenic for human airway smooth muscle

Airway smooth muscle proliferation may contribute to the airway wall remodeling seen in asthma. In this study we tested for the presence of airway smooth muscle mitogenic activity in bronchoalveolar lavage (BAL) fluid obtained from 12 atopic asthmatics before and serially after segmental allergen challenge, and from four normal subjects who did not undergo allergen challenge. Mitogenic effect was assessed by coincubating BAL fluid with human airway smooth muscle cells, and measuring its effect on (3)[H]thymidine incorporation and cell number. Induction of ERK phosphorylation and cyclin D(1) protein abundance were also assessed. Compared with serum-free medium alone, BAL fluid obtained from normal subjects increased thymidine incorporation, cell number, ERK phosphorylation, and cyclin D(1) abundance. BAL fluid from asthmatic subjects prior to allergen challenge induced even greater increases in all measures, except for cell number, which was similar to that observed with normal subjects' BAL fluid. Incubation with lavage fluid obtained 48 h after segmental allergen challenge in atopic asthmatics caused yet further increases in thymidine incorporation, cell number, and cyclin D(1) protein abundance. Molecular sieving of prechallenge BAL fluid from three asthmatic subjects demonstrated that mitogenic activity was present exclusively in the > 10 kD fraction. These results provide the first direct demonstration that fluid lining the airways of asthmatics contains excess mitogenic activity for human airway smooth muscle, and that this activity increases further after allergen challenge.     

Local allergen challenge and bronchoalveolar lavage of allergic asthmatic lungs. Description of the model and local airway inflammation

The local mechanisms that result in the cellular inflammation and bronchial airway hyperreactivity that characterize allergic bronchial asthma are poorly defined. In order to study these processes, we developed a method for local allergen challenge using a fiberoptic bronchoscope and direct observation and bronchoalveolar lavage (BAL) to assess the airway responses to allergen. In these studies, 11 allergic asthmatics (all of whom had previously demonstrated a late-phase asthmatic response to aeroallergen challenge) and 6 healthy, asymptomatic subjects volunteered to undergo bronchoalveolar lavage after local airway challenge via a bronchoscope wedged into subsegmental airways. These studies revealed that asthmatic airways respond to allergen with an immediate pallor followed by reactive hyperemia, edema, and bronchial narrowing. This site and a control site were relavaged at 48 or 96 h after the immediate response. Neutrophils and eosinophils increased significantly at 48 h after challenge, as did helper T-lymphocytes. Characteristically, at 96 h, neutrophil counts returned to normal values, whereas eosinophiles and helper T-cells remained elevated. Peroxidase-staining cells were also elevated at 48 h after local allergen challenge. Electron microscopy revealed degranulation of mast cells and eosinophils, both immediately and later (48 and 96 h) after local allergen challenge. Macrophages were highly activated and had phagocytized, partially intact granules from both eosinophils and mast cells. There was a significant correlation (p less than 0.001) between the concentration of allergen required to produce a visible airway response and a positive end-point skin titration in the asthmatic subjects.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of lipopolysaccharide exposure on airway function and allergic responses in developing mice

Exposure to endotoxin has been associated with an exacerbation of asthmatic responses in humans and animal models. However, recent evidence suggests that microbial exposure in early life may protect from the development of asthma and atopy. In this study, we sought to evaluate the effects of lipopolysaccaride (LPS) on airway function in developing mice. In addition, we evaluated the influence of LPS on subsequent allergen sensitization and challenge. Under light anesthesia, 2-3-week-old Balb/c mice received a single intranasal instillation of LPS or sterile physiologic saline. Measurements of airway function were obtained in unrestrained animals, using whole-body plethysmography. Airway responsiveness was expressed in terms of % enhanced pause (Penh) increase from baseline to aerosolized methacholine (Mch). In additional studies, we assessed the functional and cellular responses to ovalbumin sensitization and challenge following prior exposure to LPS.We found that exposure to LPS induced transient airway hyperresponsiveness to Mch. These functional changes were associated with the recruitment of neutrophils and lymphocytes into the bronchoalveolar lavage (BAL) fluid. Airway responsiveness after allergen sensitization and challenge was decreased by prior exposure to LPS. The analysis of BAL cells and cytokines (interferon-gamma and interleukin-4) did not reveal alterations in the overall Th1/Th2 balance.Our findings suggest that LPS leads to airway hyperresponsiveness in developing mice, and may protect against the development of allergen-driven airway dysfunction.     

Response of upper and lower airway inflammation to bronchial challenge with house dust mite in Chinese asthmatics: a pilot study

BackgroundAllergen nasal challenge can induce increase of eosinophils in sputum, but report about eosinophilic inflammation in upper airway after allergen bronchial challenge in Chinese asthmatics was rare. The article aims to evaluate response of upper and lower airways to house dust mite (HDM) allergen bronchial challenge.MethodsHDM allergen bronchial challenge was carried out in asthmatic patients with allergic rhinitis (AR). Bronchial methacholine challenge and blood test were performed before and at 24 hours after allergen challenge. Nasal lavage and induced sputum for differential cells count and fractional exhaled nitric oxide (FeNO) measurement were performed before, 7 and 24 hours after allergen challenge.ResultsEighteen asthmatic patients with AR underwent HDM allergen bronchial challenge with no serious adverse events reported. Fifteen patients showed dual asthmatic response (DAR), while 2 patients showed early (EAR) and 1 late asthmatic response (LAR) only. At 24 hours after allergen bronchial challenge testing, average PC₂₀FEV₁ to methacholine significantly decreased (1.58 to 0.81 mg/mL, P=0.03), while both FeNO and the percentage of eosinophils in blood and sputum were significantly increased [52.0 (54.0) to 69.0 (56.0) ppb, P=0.01; 4.82% to 6.91%, P<0.001; 20.70% to 27.86%, P=0.03, respectively], but with no significant differences found in the percentage of eosinophils in nasal lavage (39.36% to 38.58%, P=0.89). However, at 7 hours after allergen challenge, the eosinophils in sputum were significant increased to 40.45% (P<0.001), but there was an increase (39.36% to 48.07%) with no statistical difference (P=0.167) found in nasal lavage.ConclusionsHDM allergen bronchial challenge induced different response of airway inflammation in upper and lower airways.     

Early changes in T lymphocytes recovered by bronchoalveolar lavage after local allergen challenge of asthmatic airways.

To assess the role of T lymphocytes in the initiation of the allergic asthmatic response we have investigated T-cells subsets and their activation markers in bronchoalveolar lavage (BAL) fluid recovered 10 min after local challenge of the bronchial mucosa with allergen or saline. Endobronchial challenge was performed in 13 mildly atopic asthmatic patients (FEV1% predicted range, 78.2 to 116.5) and 10 normal volunteers. In all of the asthmatics but in none of the normal subjects allergen but not saline exposure resulted in visible bronchoconstriction. Analysis of BAL by flow cytometry showed no differences in the overall number of T cells (CD3+) and their CD4+ and CD8+ subsets per milliliter of BAL between the groups of normal subjects and asthmatics. However, within 10 min of allergen challenge, in the asthmatics but not in the normal subjects, there occurred a significant loss of CD3+ cells (p less than 0.01) comprising mostly CD4+ (p less than 0.05) but also CD8+ cells, with a consequent decrease in the CD4:CD8 ratio. At this early time point no differences in the extent of expression of the T-cell activation markers, IL-2 receptor, and HLA-DR were found. These results provide evidence to support a role of T lymphocytes early in the allergen-induced inflammatory response in asthma.     

Allergen-induced airway reactions in atopic asthmatics correlate with allergen-specific IL-5 response by BAL cells

Abstract Allergen-specific cytokine responses in the airways are thought to play a critical role in the pathogenesis of atopic asthma. This study examined whether there is a quantitative difference in bronchoalveolar lavage (BAL) cell allergen-induced IL-5 production between atopic subjects with and without asthma which may relate to a difference in airway response induced by allergen exposure. Twelve atopic asthmatics (AA), nine atopic non-asthmatics (AN) and 10 normal controls (N) underwent inhalation challenge with house dust mite allergen (HDM) extract. AA differed from AN in having late airway reactions (LAR) after HDM inhalation ( P < 0.01), which correlated with an increased percentage of BAL eosinophils and increased BAL cell IL-5 production after in vivo or in vitro HDM challenge for the AA group ( P < 0.01). IL-5 production by PBMC from both atopic groups was elevated with HDM stimulation in vitro , but AA again had a higher level under baseline conditions than AN ( P < 0.02). Furthermore, there was a greater effect of BAL fluid from AA on ECP release by eosinophils compared to that for AN ( P < 0.01). These findings suggest that increased IL-5 production in atopic asthmatic airways contributes to the increased physiological response to allergen inhalation, by modulating local eosinophil recruitment and activation.     

Effects of an eosinophil chemotaxis inhibitor,TAK-661, on antigen-induced asthmatic responses in allergic sheep

Eosinophils have been shown to play a role in allergen-induced airway responses. The aim in this study was to examine the effects of TAK-661, a newly developed product as a specific inhibitory agent of eosinophil chemotaxis, on antigen-induced asthmatic responses in allergic sheep model. Seven Ascaris-sensitive, "dual-respondent" allergic sheep were provocated by an Ascaris suum antigen or phosphate-buffered saline 2 hrs after intra-stomach administration of TAK-661 or a placebo. Pulmonary resistances were measured throughout the experiment, and airway responsiveness to methacholine, bronchoalveolar lavage (BAL), and histological examination were performed 8 hrs after the antigen challenge. Antigen provocation induced dual-phase bronchoconstriction, eosinophilia in BAL and eosinophil infiltration into the airway wall, and an increase in airway responsiveness in placebo-treated sheep. The administration of TAK-661 significantly reduced the bronchoconstriction during the late phase, along with the inhibition of eosinophilia in BAL and the eosinophil infiltration into the airway wall. TAK-661 had a tendency to reduce early-phase bronchoconstriction and airway hyperresponsiveness, but there were no significant differences. These findings suggest that the eosinophil accumulation into the airway induced by antigen provocation may contribute to the development of late-phase bronchoconstriction, however, the development of airway hyperresponsiveness during late asthmatic response may not always be due to only eosinophilic inflammation in the airway.     

Increased interleukin-13 mRNA expression in bronchoalveolar lavage cells of atopic patients with mild asthma after repeated low-dose allergen provocations

Immune and inflammatory responses mediated by cytokines are essential in the pathophysiology of asthma. The aim of this study was to analyse the cytokine mRNA profiles in bronchoalveolar lavage (BAL) cells of patients with mild atopic asthma, before and after induction of a subclinical allergic airway inflammation. For this purpose, eight patients with mild atopic asthma received low-dose allergen inhalations equivalent to 10% of a provocational dose causing a 20% fall in forced expiratory flow in 1 sec (PD20) for 7 weekdays. BAL was performed before and after low-dose provocations in patients, and without provocation in five healthy controls. Alveolar macrophages (AM) were enriched by negative selection, using magnetic beads, to enable separate studies of the BAL cells. Using a semiquantitative RT-PCR technique, the mRNA expression of macrophage-derived cytokines interleukin (IL)-1, IL-6, IL-8, IL-10, IL-12, IL-13, interferon (IFN)-gamma, tumour necrosis factor (TNF)-alpha and transforming growth factor (TGF)-beta was analysed. After low-dose provocations, we observed a significant increase in the expression of IL-13 mRNA (P = 0.01) in BAL cells enriched for AM of the asthmatic patients. The increased IL-13 mRNA positively correlated with the proportion of BAL fluid eosinophils (r = 0.7, P = 0.05). Moreover, a tendency was found towards an increased IL-1 and a reduced IL-6, IL-8, IFN-gamma and TNF-alpha expression by the BAL cells. Comparing asthmatic patients before low-dose provocations and healthy controls, a significantly higher expression of IL-6 (P<0.003), IL-10 (P<0.005) and TGF-beta (P<0.003) and a significantly lower expression of IL-8 (P<0.005) and TNF-alpha (P<0.01) was detected in the patients. In summary, repeated low-dose allergen provocations of asthmatic patients results in a modified BAL cell cytokine mRNA profile with increased production of IL-13, that may be of importance for the development of a Th2-like immune response. A possible source of the increased IL-13 mRNA is AM, which may have a more active function in the allergic inflammation than previously thought.     

Platelet dynamics following allergen challenge in allergic asthmatics

BACKGROUND: There is evidence that platelet activation occurs in allergic inflammation and asthma, but little is known about the role platelets play in airway inflammation associated with asthma. Objectives: In the present study, we have investigated the kinetics of platelet activation following allergen provocation of allergic asthmatics to determine the dynamics of platelet activation relative to changes in lung function and changes in airway inflammation. METHODS: Changes in platelet count and haematocrit from baseline were measured during the early asthmatic response (EAR), late asthmatic response (LAR; or at corresponding time points) and at 24 h were compared between allergen- and saline-challenged groups. A subgroup of allergen-challenged asthmatics, a group of 7 challenged asthmatics and 7 controls were bronchoscoped, and BAL fluid was collected and analysed for levels of histamine and eosinophil cationic protein. RESULTS: There was a fall in circulating platelet count, but not haematocrit after allergen challenge when compared with saline during the LAR or at 24 h. At 24 h FEV(1) had returned to within 20% of baseline in all subjects, although the thrombocytopaenia and airway inflammation persisted. CONCLUSIONS: Our results suggest that persistent thrombocytopaenia accompanies allergen exposure and persists beyond changes in airway obstruction at a time when airway inflammation is present. Our results provide further evidence that platelets may be involved in allergic disease.     

Eotaxin expression after segmental allergen challenge in subjects with atopic asthma

Expression of pulmonary eotaxin protein and mRNA was determined in six subjects with atopic asthma and five nonatopic normal subjects. Levels of eotaxin expression and eosinophil mobilization were compared before and after segmental allergen challenge in subjects with atopic asthma. In the absence of allergen challenge, we found significantly higher levels of eotaxin in the bronchoalveolar lavage (BAL) fluid of subjects with asthma than in that of normal subjects (25 +/- 3 versus 15 +/- 2 pg/ml, p < 0.05). BAL eotaxin levels increased after segmental allergen challenge in all six subjects with atopic asthma tested, with a mean increase from 22 +/- 4 to 53 +/- 10 pg/ml (p = 0.013). Segmental allergen challenge was associated with a significant increase in the percentage of BAL macrophages and eosinophils that were immunopositive for eotaxin. Eotaxin mRNA was detectable by northern analysis in BAL cells exclusively from allergen-challenged segments. Allergen- induced increases in eotaxin levels were strongly associated with increases in BAL eosinophil recovery (r(2) = 0.88, p = 0.0036). Segmental allergen challenge also increased eotaxin expression in airway epithelial and endothelial cells obtained by endobronchial biopsy. These findings demonstrate, for the first time, that the airways of subjects with allergic asthma respond to allergen by increasing eotaxin expression. The tissue loci of eotaxin expression, the levels of eotaxin recovered in BAL fluid, and the association of eotaxin levels with eosinophil mobilization suggest either that eotaxin plays a mechanistic role in allergen-induced airway eosinophilia or that it serves as a biomarker for the causal mechanisms.     

Roflumilast, a phosphodiesterase 4 inhibitor, reduces airway hyperresponsiveness after allergen challenge

BACKGROUND: Roflumilast, an oral, once-daily phosphodiesterase 4 inhibitor, is currently in clinical development for the treatment of asthma. OBJECTIVES: This pilot study examined the effect of roflumilast on allergen-induced airway hyperresponsiveness (AHR) to histamine challenge and asthmatic response to allergen challenge. METHODS: In a randomized, double-blind, 2-period, crossover trial, 13 patients with mild allergic asthma [mean forced expiratory volume in 1 s (FEV(1)) % predicted = 86%] received a single dose of oral roflumilast 1,000 microg or placebo. Patients were administered roflumilast 60 min before allergen challenge, and asthmatic responses were assessed via change in FEV(1) 相似文献   

CD69 surface expression on human lung eosinophils after segmental allergen provocation.

CD69 expression on eosinophils is observed in asthma and has been proposed as a marker of eosinophil activation. The role of allergens in the in vivo regulation of CD69 expression on eosinophils, however, remains incompletely understood. It was therefore investigated whether CD69 expression on eosinophils can be induced by allergen provocation in vivo. Ten allergic asthmatics were studied by segmental allergen provocation. Two segments of the right and left lung were challenged with allergen or saline. CD69 expression was determined by flow cytometry and concentrations of interleukins were analysed by enzyme-linked immunosorbent assay in bronchoalveolar lavage (BAL) fluid. Expression of CD69 on BAL eosinophils in the segments lavaged 10 min following saline instillation (28.3+/-8.8 specific mean fluorescence (SMF)) was not significantly different to segments lavaged 10 min after allergen (80.2+/-21.8 SMF) and segments lavaged 18 h after saline challenge (87.2+/-23.3 SMF). However, CD69 expression on eosinophils increased significantly 18 h after allergen challenge (128.6+/-21.9 SMF, p<0.03) which was accompanied by elevated granulocyte-macrophage colony-stimulating factor (GM-CSF) concentrations (114.9+/-42.9 pg x mL(-1), p<0.05). CD69 expression on eosinophils and GM-CSF concentrations correlated 18 h following allergen provocation (r = 0.7, p<0.025). These results suggest that in allergic asthma there is an allergen dependent, endobronchial upregulation of eosinophil activation as assessed by CD69 expression on eosinophils.     

Use of segmental airway lavage to obtain relevant mediators from the lungs of asthmatic and control subjects

Studies have demonstrated that increased amounts of histamine in the airways of asthmatic patients are associated with increased airway reactivity. However, using routine bronchoalveolar lavage (BAL), histamine can be detected in only a portion of asthmatic subjects and a minority of control populations. To obtain relevant mediators from the airways in higher concentrations by avoiding the dilution inherent with a standard BAL, a technique was developed to lavage isolated airway segments of the human lung that employed a double-lumen bronchoscope and a balloon-tipped catheter. Lavage fluid obtained by this method yielded significantly higher concentrations of histamine than that obtained with routine BAL (asthmatic subjects, 2,403 +/- 633 pg/ml vs 188 +/- 42 pg/ml; rhinitis subjects, 533 +/- 187 pg/ml vs 113 +/- 53 pg/ml; normal subjects, 174 +/- 63 pg/ml vs 11 +/- 11 pg/ml). Similar findings were also noted for prostaglandin D2 (PGD2). Segmental airway lavage also resulted in higher lavage fluid concentrations of LTB, than routine BAL. Segmental airway lavage should help in studying the relationship of mast cell degranulation to airways reactivity in both asthmatic and other study populations.     

Safety of research bronchoscopy, biopsy and bronchoalveolar lavage in asthma.

Bronchoscopy with endobronchial biopsy (EBB) and/or bronchoalveolar lavage (BAL) has become an important research tool in asthma. A recent report has suggested audit and reporting of the safety of these procedures. A total of 159 asthmatic patients (84 males, 75 females), aged 18-52 (median 27) yrs, forced expiratory volume in one second 53-120 (median 88) % predicted, underwent 273 bronchoscopies in six clinical research studies. On 228 occasions, EBB and BAL were performed and, on 45 occasions, EBB was performed alone. On 48 occasions, bronchoscopy was performed 24 h post-allergen challenge. Adverse events occurred on 34 out of 273 occasions, none of which were following allergen challenge. Post-EBB and BAL, four patients developed pleuritic chest pain, shortness of breath and fever. A further two patients experienced pleuritic chest pain alone post-EBB/BAL. Bronchospasm or worsening of asthma symptoms occurred on 14 occasions, 13 post-EBB/BAL and on one occasion post-EBB alone. Fever/flu-like symptoms were reported on nine occasions following EBB and BAL. One subject had haemoptysis post-EBB/BAL, but required no intervention. In conclusion, bronchoscopy, endobronchial biopsy and bronchoalveolar lavage can be performed safely in asthmatic patients. Most of the complications were seen where bronchoalveolar lavage and endobronchial biopsy were both performed, suggesting that bronchoalveolar lavage accounts for most of the adverse events.     

Enhanced generation of helper T type 1 and 2 chemokines in allergen-induced asthma

Allergen-induced asthma is characterized by airway eosinophilia and recruitment of helper T (Th) Type 2 lymphocytes. We hypothesized that lymphocyte-associated chemokines contribute to allergen-induced airway inflammation. Sixteen subjects with asthma were phenotyped according to their response to inhaled antigen as single- or dual-phase responders, and then underwent bronchoscopy and segmental allergen bronchoprovocation. Bronchoalveolar lavage fluids were obtained before and 48 hours after segmental challenge with allergen to determine the cellular response and patterns of Th1 and Th2 chemokines and cytokines. Airway cells, cytokines, and lymphocyte-associated chemokines increased after segmental challenge. Th2 chemokines (thymus and activation-regulated chemokine, macrophage-derived chemokine) correlated with airway eosinophils and concentrations of interleukin-5 and -13. In contrast, airway lymphocytes correlated with both Th2 and Th1 (monokine-induced by IFN-gamma, IFN-gamma-inducible protein-10) chemokines. Notably, when subjects were analyzed according to the presence of a late-phase response, concentrations of both types of lymphocyte-associated chemokines were significantly greater in subjects with a dual-response phenotype. Our findings suggest that both Th2 and Th1 chemokines may be involved in allergen-induced airway inflammation. However, asthma subjects with a dual-responder phenotype have greater generation of chemokines that may lead to enhanced airway inflammation and obstruction after allergen exposure.     

Immediate and late inflammatory responses to ragweed antigen challenge of the peripheral airways in allergic asthmatics. Cellular, mediator, and permeability changes

Asthma may represent the clinical manifestations of a unique form of chronic airway inflammation and is often associated with allergy. To better define the components of allergic inflammation in the lung, fluids obtained by bronchoalveolar lavage (BAL) were examined for cells, inflammatory mediators, and markers of airway permeability 5 min and 19 h following instillation of ragweed antigen directly into an airway segment of allergic asthmatic subjects. The 5-min response to antigen challenge (n = 10) was characterized by 17- to 208-fold increases in histamine, prostaglandin D2 (PGD2), and its metabolite, 9 alpha,11 beta-PGF2, thromboxane B2, and 6-keto-PGF1 alpha compared with a saline-challenged segment (0.004 less than p less than 0.017). The increases in most of these mediators were significantly correlated with each other (0.0001 less than p less than or equal to 0.01), and the magnitude of all significant mediator increases was directly correlated with skin test sensitivity to ragweed antigen (0.007 less than or equal to p less than or equal to 0.05). There was also a slight increase in kinins (p = 0.04). Changes in cells and airway permeability were not detected. In contrast, the 19-h response to antigen challenge (n = 9) was characterized by a 13-fold increase in total cells recovered by BAL. Eosinophils, basophils, and lymphocytes were significantly increased and comprised 38, 1, and 9% of total cells, respectively. A neutrophil influx was also observed but was not specific for antigen challenge since a similar change was observed in a sham, saline-challenged site.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of ozone exposure on airway responses to inhaled allergen in asthmatic subjects

BACKGROUND: Controlled human exposure studies have produced conflicting results regarding the effect of ozone on the early bronchoconstrictor response to inhaled allergen in specifically sensitized asthmatic subjects. Spirometric parameters do not necessarily reflect the airway inflammatory effects of inhaled ozone or allergen. OBJECTIVE: This study was designed to investigate whether exposure to ozone enhances the late airway inflammatory response, as well as the early bronchoconstrictor response, to inhaled house dust mite allergen in sensitized asthmatic subjects. DESIGN: Randomized, counter-balanced, cross-over study. SETTING: Human exposure laboratory. METHODS: Fourteen subjects were exposed to 0.2 ppm O(3) or filtered air, on separate days, for 1 h during exercise. After each exposure, the subjects were challenged with doubling doses of Dermatophagoides farinae (DF) allergen (provocative concentration of DF causing a 15% decrease in FEV(1) [PC(15)]). At 6 h after allergen challenge, bronchoscopy with BAL, proximal airway lavage (PAL), and endobronchial biopsy were performed. The second exposure/allergen challenge/bronchoscopy sequence was performed at least 4 weeks after the first sequence. RESULTS: No significant difference in cellular or biochemical markers of the late inflammatory response after allergen was found between the ozone and air exposures (although a trend toward increased neutrophils was noted after ozone exposure in the PAL fluid, p = 0.06). For the group as a whole, no significant difference in PC(15) was demonstrated after ozone exposure compared to air exposure. However, subjects with the greatest ozone-induced decrements in FEV(1) tended to have lower PC(15) values after ozone exposure. CONCLUSION: Exposure to a relatively low-level concentration of ozone does not enhance the late inflammatory or early bronchoconstrictor response to inhaled antigen in most allergic asthmatic subjects. Our results do suggest, however, that a subgroup of asthmatics may acquire increased sensitivity to aeroallergens after exposure to ozone.