Comparison of incremental and bolus dose inhaled allergen challenge in asthmatic patients

BACKGROUND: Attenuation of airway responses to inhaled allergen is increasingly used to evaluate anti-asthma drugs. Many studies use different allergen challenge methods and the presence of the late asthmatic response can be identified by a screening challenge with inhalation of incremental doses of allergen. Once defined, subsequent challenges are often administered as a constant dose based on the dose from the screening challenge. Previously, constant dose challenges have been employed but never validated. OBJECTIVE: A comparative study of two methods of delivering inhaled allergen by evaluating the responses of an incremental dose allergen challenge and the same cumulative dose administered as a bolus over a single inhalation. METHODS: Thirty-five male patients with mild allergic asthma underwent incremental dose challenge followed 3-6 weeks later by a bolus dose challenge. Bronchoconstrictor responses were expressed as the maximum percentage fall in FEV1 from baseline during the early (0-2 h) and late (4-10 h) asthmatic responses and area under the percentage change in FEV1-time curve (AUC). RESULTS: There were no significant differences between the challenges. The mean +/- SEM fall in FEV1 following incremental and bolus dose challenge was 33.1 +/- 1.8% and 29.9 +/- 2.2% during the early response, and 36.9 +/- 2.4% and 34.0 +/- 3.1% during the late response, respectively. The mean +/- SEM AUC following incremental and bolus dose challenge was 35 +/- 3 and 33 +/- 3 Delta%FEV1/h for the AUC0-2 h, 147 +/- 12 and 139 +/- 16 Delta%FEV1/h for the AUC4-10 h, and 204 +/- 14 and 190 +/- 19 Delta%FEV1/h for the AUC0-10 h, respectively. CONCLUSION: Bolus dose allergen challenge is a safe method to administer inhaled allergen in clinical trials with a valid response when compared with incremental dose allergen challenge.     

Effect of ciclesonide on allergen challenge in subjects with bronchial asthma

BACKGROUND: The aim of this clinical trial was to investigate whether repeated inhalation of the new inhaled steroid ciclesonide reduces the early-phase (EAR) and late-phase (LAR) reactions after allergen challenge in patients with mild allergic asthma. Also, this study provides further data on safety and tolerance of ciclesonide. METHODS: The study was designed as a double-blind placebo-controlled randomized crossover trial. Following a baseline period, patients were randomized to either of two treatment sequences (ciclesonide/placebo, placebo/ciclesonide) each of which lasted for one week and were separated by 3-5 weeks from the alternate treatment sequence. Patients received 800 micro g ciclesonide twice daily by means of a Cyclohaler. At the end of each treatment patients were subjected to an allergen challenge. RESULTS: Thirteen asthmatic patients (mean FEV1 of 91% predicted) who experienced an EAR and LAR after allergen challenge participated in the study. The time-average FEV1 decreases 0-2 h (2-12 h) after allergen challenge as measure of the EAR (LAR) were significantly reduced (P < 0.05, one-sided) from 0.426 L to 0.233 L (EAR) and from 0.443 L to 0.213 L (LAR), respectively. Thus, the study results suggest that ciclesonide significantly lowered the extent of EAR and LAR compared to placebo. Ciclesonide was well tolerated and no drug-related adverse events were reported. Cortisol excretion in 24-h urine showed no significant difference between ciclesonide and placebo. CONCLUSIONS: The study supports the efficacy and safety of ciclesonide.     

Increases in eotaxin‐positive cells in induced sputum from atopic asthmatic subjects after inhalational allergen challenge

BACKGROUND: Eosinophils are believed to be critical proinflammatory cells in airway mucosal damage in asthma. Eotaxin is a C-C chemokine with selective activity for eosinophils and basophils. Previous studies have shown increased expression of eotaxin in the airways of asthmatics at baseline. We aimed to investigate eotaxin expression during the late-phase reaction to allergen inhalation in atopic asthmatics. METHODS: Sputum induction was performed before and 24 h after inhalational allergen challenge in atopic asthmatics, and eotaxin protein was detected immunocytochemically. RESULTS: Thirteen patients with a mean decrease in forced expiratory volume in 1 s of 28% (+/-1.5) during the early asthmatic reaction, and 39% (+/-4.7) during the late asthmatic reaction produced sufficient sputum for study. The percentage of eosinophils in sputum was increased 24 h after allergen challenge (P<0.004), and eosinophil percentages in sputum after challenge correlated with the magnitude of the late-phase reaction (r=0.56, P=0.05). The percentage of eotaxin-positive cells increased from 12.6% (range 2-43.8) to 24.3% (8.1-47.1, P<0.005). Allergen-induced increases in eotaxin-positive cells correlated with increases in eosinophils (r=0.63, P<0.01). CONCLUSIONS: These findings suggest that eotaxin may contribute to allergen-induced recruitment of eosinophils to the airway in asthmatic subjects.     

Influence of bronchial allergen challenge on histamine release by human basophils

BACKGROUND: Basophils can be primed by cytokines such as interleukin (IL) -3, IL-5 or granulocyte macrophage-colony stimulating factor (GM-CSF). It has been described that the concentrations of these cytokines are enhanced at sites of allergic inflammation as well as systemic in allergic asthma. OBJECTIVE: To investigate the priming status of basophils as detected by thapsigargin-induced histamine release during bronchial allergen challenge. METHODS: Ten subjects allergic to house dust mite were challenged via an aerosol delivery system. Spontaneous leucocyte histamine release as well as histamine release induced by various stimuli was measured in vitro at several time points. In addition, lung function parameters, serum IL-5 and blood eosinophil counts were evaluated. RESULTS: We found no effect of bronchial allergen challenge upon spontaneous leucocyte histamine release, nor upon histamine release induced by anti-immunoglobulin (Ig) E, house dust mite extract, C5a, fMLP, IL-3, PMA+ thapsigargin or IL-3+ thapsigargin. However, the priming status of basophils as measured by thapsigargin-induced histamine release was enhanced at 24 h after bronchial allergen challenge. Analysis of the individual data showed a heterogeneous initial response (30 min, 6 h) followed by a predominant increase at 24 h after allergen challenge. This increase in the thapsigargin-induced histamine release correlated with the increase in serum IL-5 levels at 24 h after allergen challenge. CONCLUSION: The priming status of human basophils as measured by thapsigargin-induced histamine release is enhanced 24 h after allergen challenge.     

Changes in serum haptoglobin level after allergen challenge test in asthmatic children

Bronchial asthma is characterized by airway inflammation, which underlies the phenomenon of bronchial hyperresponsiveness. Previous studies have shown that this correlates with the serum concentration of haptoglobin. The occurrence of the late asthmatic response (LAR) after an allergen challenge test is associated with airway inflammation. The objectives of this study were to examine serum levels of haptoglobin during the 24 h after allergen challenge and to compare changes between the subjects with and without LAR. We studied two groups of children with perennial asthma who developed the early asthmatic response (EAR) only (group 1: n = 14), and EAR but also LAR (group II: n = 14) after an allergen (Dermatophagoides pteronyssinus) challenge test. Serum concentrations of haptoglobin were measured at baseline, at EAR, and at 2 h (recovery), 8 h (LAR), and 24 h after the challenge. Baseline levels were similar in the two groups (group I: 128±57 mg/dl: group II: 129±50 mg/dl). In group I, there was no significant change in the level at any time point; in contrast, the subjects in group II showed a relative fall (92±40 mg/dl) at 8 h, and an increase (161±79 mg/dl) at 24 h after the challenge. Our results indicate that the serum concentration of haptoglobin decreases at the time of LAR and is subsequently replenished during the ensuing time. Although further studies are needed, we think that haptoglobin may be inflused into the airways during the inflammatory process associated with LAR, and that this may be followed by "overshooting" production.     

Early and late phase asthmatic response in lower airways of cat-allergic asthmatic patients--a comparison between experimental and environmental allergen challenge

BACKGROUND: Standardized experimental allergen challenges are usually adopted to investigate the effect of allergen exposure on the lower airways. Environmental (natural) allergen challenges are used less often, mainly because of difficulties in standardizing the method, safety reasons and costs. The aim of this study was to investigate the relationship between an experimental and an environmental bronchial challenge. For this reason a natural challenge model was developed. METHODS: Sixty-two patients with a history of cat allergen-induced symptoms involving the lower airways, positive skin prick test, positive in vitro specific IgE to cat allergen and bronchial hyper-responsiveness were included. All 62 patients underwent an experimental challenge in the laboratory followed by an environmental allergen challenge. RESULTS: All 62 patients developed an early asthmatic response [>or=20% fall in forced expiratory volume in 1 s (FEV1)] in the experimental challenge and 60% (37/62) during the environmental challenge. A late asthmatic response (>or=15% fall in FEV1 within 3-24 h) was seen in 56% (35/62) of the patients after the experimental challenge. Following the environmental challenge 47% (29/62) of the patients developed a late response. Thirty-four per cent (21/62) of the patients developed a late response in both challenge models and 31% (19/62) did not develop a late response in any model. Thus, there was consistency in 65% (40/62) of the patients in both challenge models. CONCLUSION: We found consistency in the pattern of response to inhaled allergen between the two challenge models and we believe that experimental bronchial challenge is likely to reflect the development of relevant inflammation in the lower airways after low-dose allergen exposure in the environment.     

Predictors of early- and late-phase reactions to bronchial allergen challenge

The influence of inhaled steroids and predictive factors on the response to bronchial allergen challenge (BCA) was evaluated in. 80 asthmatics allergic to Dermatophagoides pteronyssinus (Der p). All underwent BCA with Der p and measurement of early (EAR) and late asthmatic reaction (LAR). The cumulative dose of allergen producing 20% fall in FEV₁, in the EAR (PD₂₀) was calculated. Bronchial histamine provocation, conjunctival provocation test (CPT), and skin prick test with Der p extract were performed. Specific IgE to Der p in serum (RAST), blood eosinophil (EOS) count, serum eosinophil cationic protein, and eosinophil protein X were measured. Thirty patients (38%) were treated with inhaled steroids. All patients had at least a 20% fall in FEV₁ in EAR. Some 42% of nonsteroid- and 33% of steroid-treated patients had LAR with fall in peak flow of at least 20%. For patients not treated with steroid, 35% of variation in PD₂₀ was explained by RAST and histamine reactivity, and 53% of variation of observed PD₂₀ could be predicted. The baseline FEV₁, EOS, and EAR explained 28% of variation in LAR, and 28% of variation in observed LAR could be predicted. For patients treated with steroids, 38% of variation in PD₂₀ was explained by EOS and histamine reactivity, and only 18% of variation of observed PD₂₀ could be predicted. For patients treated with steroids, it was impossible to predict LAR. We conclude that to achieve a quantitative estimation of allergen-specific EAR and LAR, BCA cannot be replaced by the tests used in this study. Treatment with inhaled steroids modifies the response to BCA, making quantitative prediction of EAR less accurate and prediction of the magnitude of LAR impossible.     

Eosinophils in bronchial mucosa of asthmatics after allergen challenge: effect of anti-IgE treatment

Background: Anti‐IgE, omalizumab, inhibits the allergen response in patients with asthma. This has not been directly related to changes in inflammatory conditions. We hypothesized that anti‐IgE exerts its effects by reducing airway inflammation. To that end, the effect of anti‐IgE on allergen‐induced inflammation in bronchial biopsies in 25 patients with asthma was investigated in a randomized, double‐blind, placebo‐controlled study. Methods: Allergen challenge followed by a bronchoscopy at 24 h was performed at baseline and after 12 weeks of treatment with anti‐IgE or placebo. Provocative concentration that causes a 20% fall in forced expiratory volume in 1 s (PC₂₀) methacholine and induced sputum was performed at baseline, 8 and 12 weeks of treatment. Changes in the early and late responses to allergen, PC₂₀, inflammatory cells in biopsies and sputum were assessed. Results: Both the early and late asthmatic responses were suppressed to 15.3% and 4.7% following anti‐IgE treatment as compared with placebo (P < 0.002). This was paralleled by a decrease in eosinophil counts in sputum (4–0.5%) and postallergen biopsies (15–2 cells/0.1 mm²) (P < 0.03). Furthermore, biopsy IgE+ cells were significantly reduced between both the groups, whereas high‐affinity IgE receptor and CD4+ cells were decreased within the anti‐IgE group. There were no significant differences for PC₂₀ methacholine. Conclusion: The response to inhaled allergen in asthma is diminished by anti‐IgE, which in bronchial mucosa is paralleled by a reduction in eosinophils and a decline in IgE‐bearing cells postallergen without changing PC₂₀ methacholine. This suggests that the benefits of anti‐IgE in asthma may be explained by a decrease in eosinophilic inflammation and IgE‐bearing cells.     

Frequency and intensity of late asthmatic reactions after bronchial allergen challenge in asthma and rhinitis

The occurrence of late asthmatic reactions after bronchial allergen challenge was studied in 50 house dust mite allergic patients subdivided in three groups: one group had asthma without nasal symptoms, another group had rhinitis without pulmonary symptoms and a third group had a combination of both asthma and rhinitis. Late asthmatic reactions were present in 80% of asthmatic patients and in 18.7% of rhinitis patients. The degree of non-specific bronchial reactivity to histamine (provocative dose 15 or PD15 histamine) and the degree of immediate reactivity to allergen (PD15 house dust mite) did not differ significantly between patients with and without late asthmatic reactions. These findings suggest that an important difference between asthma and rhinitis is the lack of late asthmatic reactions in rhinitis patients, whereas the degree of immediate bronchial reactivity to the allergen is similar in asthma and rhinitis.     

Similar levels of nitric oxide in exhaled air in non-asthmatic rhinitis and asthma after bronchial allergen challenge

BACKGROUND: Nitric oxide in exhaled air (eNO) is elevated in allergic asthma compared with healthy subjects and has been proposed as a marker of bronchial inflammation. However, eNO is elevated to a lesser extent in allergic non-asthmatic rhinitis as well. Considering the distinctive clinical appearances of both allergic diseases, differences in eNO are expected to persist after allergen exposure. The aim of the study was to compare allergen-induced changes in eNO in house dust mite sensitized patients with asthma and patients with perennial rhinitis without asthma symptoms. METHODS: Bronchial allergen challenge was performed in 52 patients sensitized to house dust mite (Dermatophagoides pteronyssinus), of whom 26 had non-asthmatic rhinitis and 26 had asthma. Levels of eNO were measured before and 1 h, 1 day and 1 week after challenge. RESULTS: At baseline eNO was significantly lower in non-asthmatic rhinitis compared with asthma (geometric mean eNO (SEM): 121 (1.1) in non-asthmatic rhinitis vs 197 (1.1) nl/min in asthma, P < 0.006). However, the increase in eNO after bronchial allergen challenge in non-asthmatic rhinitis, in particular in those patients with a dual asthmatic response, significantly exceeded the increase in asthma resulting in similar levels of eNO after challenge (geometric mean eNO (SEM) at 24 h postchallenge 204 (1.1) in non-asthmatic rhinitis vs 244 (1.1)nl/min in asthma, P = 0.3). CONCLUSION: The difference in eNO between non-asthmatic rhinitis and asthma at baseline is abolished after allergen exposure due to a significantly greater increase in eNO in non-asthmatic rhinitis.     

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

BACKGROUND: Seasonal allergic rhinitis (SAR) is a risk factor for asthma in affected individuals. Nasal allergic inflammation enhances bone-marrow eosinophil production, mainly via IL-5, and rhinitis patients have increased airway inflammation during the pollen season. OBJECTIVE: To assess the impact of nasal allergy on sputum inflammatory markers. METHODS: In an open-labelled, randomized, placebo-controlled cross-over study with 16 non-asthmatic SAR patients (median age 25 years, 56% males), the effect of a single nasal allergen challenge performed out of season on induced sputum inflammatory parameters was evaluated. SAR patients were identified by history, skin-prick test and specific IgE. All patients had normal lung function/bronchial hyper-responsiveness out of season and a negative asthma/wheezing history. Sputum cells and supernatant levels of ECP, sICAM, IL-5 and IL-10, and plasma levels of IL-5 and ECP, were measured before and 24 h after nasal allergen challenge. After a washout period of at least 4 weeks, the procedure was repeated with placebo challenge (diluent). RESULTS: Nasal allergen challenge led to an increase in sputum ECP (pre = 60 +/- 12, post = 212 +/- 63 micro g/L, P = 0.02 vs. placebo), and sICAM (4.8 +/- 2.7 to 6.5 +/- 2.9 ng/mL, P = 0.02 vs. placebo), whereas IL-10 decreased after provocation (44 +/- 11 to 29 +/- 6 pg/mL, P = 0.06 vs. placebo). Sputum IL-5 was undetectable in all patients. The absolute number of blood and sputum eosinophils did not change significantly after allergen or placebo challenge (P > 0.07, both comparisons). Plasma levels of IL-5 increased after allergen challenge (8.7 +/- 2.9 to 14.5 +/- 3.9 pg/mL, P = 0.001), and the increase in plasma IL-5 was positively correlated with the rise in sputum ECP in a subgroup of 'responders' (n = 12, r = 0.71, P = 0.01). CONCLUSIONS: A single nasal allergen challenge in SAR patients increased markers of allergic inflammation in the lower respiratory tract, possibly via pronounced activation of inflammatory cells through circulating immediate-type reaction cytokines like IL-5. These findings may provide additional explanatory data for the high susceptibility of SAR patients to incident asthma.     

Plasma protein profiles in early asthmatic responses to inhalation allergen challenge

Although mediators, such as lipids, cytokines, and chemokines, are related to the appearance of an IPR, there has been no reliable indicator to predict conditions for the appearance of an IPR.
In this study, we adopted a proteomic approach to investigate the pathogenesis at the level of the plasma proteins and to develop plasma markers to predict the appearance of an IPR following an inhalation challenge with Dermatophagoides pteronyssinus (D.p.). Sixteen mild asthmatics were recruited. Plasma was obtained before challenge and when a decline in forced expiratory volume in 1 s (FEV₁) values greater than 20% from the phosphate-buffered saline value was achieved during D.p. allergen challenge (positive responders), or at 60 min after the highest concentration of D.p. allergen was inhaled (negative responders). After comparing normalized volumes of the spots in the two groups, differentially expressed spots were identified using intra-gel digestion and mass spectrometric analysis. Before D.p. antigen challenge, four spots of gamma fibrinogen and its isoforms were significantly decreased and two spots of complement C3 fragments were significantly increased in the positive responders compared to the negative responders. After D.p. antigen challenge, complement C3 fragment was persistently higher, while gamma fibrinogen was lower in the positive responders than in the negative responders. A validation study using Western blotting showed that gamma fibrinogen expression in the IPR-positive asthmatics was significantly decreased compared to the average of the IPR-negative asthmatic control group. These results indicate that alterations in the complement cascade and fibrinogen may predispose patients to the appearance of an immediate response to D.p. allergen challenge and may provide plasma markers to predict the appearance of an IPR.     

Bronchial allergen challenge in subjects with low levels of allergic sensitization to indoor allergens

BACKGROUND: Low skin reactivity to common inhalant allergens is frequently found in asymptomatic individuals as well as in patients with respiratory complaints. However, most studies on bronchial allergen challenge concern patients with high levels of allergic sensitization. The present study was directed to bronchial reactions after allergen challenge in subjects with low skin reactivity to Dermatophagoides pteronyssinus or cat dander. METHODS: Titrated intracutaneous skin tests, skin prick tests, specific IgE assays, histamine release on washed leukocytes, and bronchial histamine and allergen-challenge tests were performed in 20 subjects with an intracutaneous skin test threshold for cat dander (Felis domesticus) or D. pteronyssinus above 0.1 BU/ml (mean wheal diameter in skin prick test with 10000 BU/ml: 4.4mm). Ten of the 20 patients had specific IgE below the detection limit in at least one of the three IgE assays which were done. Fifteen patients had a specific IgE level below 2 kU/I in all three tests. As a positive control group, the same parameters were studied in seven moderately sensitized patients with an intracutaneous skin test threshold below 0.1 BU/ml (mean wheal diameter with 10000 BU/ml: 7.2mm). RESULTS: The 20 subjects with low levels of allergic sensitization had an early decrease in FEV1 of 8.6% (P<0.01) and a mean late decrease of 6.3% (P<0.05). There was a trend for decrease in PC20 histamine 24h after allergen challenge (-0.4 doubling doses, P=0.09). CONCLUSIONS: In this group of subjects with low levels of allergic sensitization, a statistically significant early and late decrease in FEV1 was found. However, the decrease in lung function was small and unnoticed by most patients. The increase in nonspecific bronchial hyperresponsiveness after bronchial allergen challenge did not reach statistical significance in the study group. The results indicate that allergen exposure in patients with low levels of allergic sensitization may lead to airways changes in the absence of acute symptoms.     

Bronchial and cutaneous responses in atopic dermatitis patients after allergen inhalation challenge

Background Atopic dermatitis (AD) is often associated with allergic asthma (AA). Inhalation of allergens influences the activity of AA but the effect on the skin in AD is unclear. Objectives We evaluated the degree of bronchial hyperresponsiveness to methacholine in eight AD patients with AA (AD⁺) and eight AD patients without AA (AD^–) and studied bronchial and cutaneous responses after allergen inhalation challenge. Methods All patients were treated in hospital for their eczema with tar ointment (pix liquida) and orally administered antihistamines (mean hospital stay 37 days). After clearing of the skin lesions allergen inhalation challenge was performed. Cutaneous responses were studied by measuring the‘Costa’ score before and 24 h after allergen inhalation challenge. Results The median value of the provocative concentration of methacholine causing a 20% fall (PC₂₀ Mch) in forced expiratory volume in 1 second (FEV₁) was significantly higher in the AD^– group compared to the AD⁺ group with median values of 10.70 and 0.60mg/mL, respectively. These values did not change significantly in both groups during hospital stay. After challenge all AD⁺ patients showed early and late asthmatic responses whereas only four AD^– patients showed early asthmatic responses (mean values of the maximal fall in FEV_l during the EAR 37%/16% and in PEF during the LAR 27%/4% for AD⁺ and AD^–patients, respectively). The‘Costa’ score increased in both groups (mean score before 19.1/ 24.4 and after challenge 26.8/26.9 for AD⁺ and AD⁺ patients, respectively). The increase in the AD^– group was significantly higher compared with the AD^– group (P= 0.016). Conclusion We conclude that allergen inhalation challenge causes a flare up of the skin lesions in atopic dermatitis patients. This was more prominent in atopic dermatitis patients who already suffered from an IgE-mediated allergic inflammation in the lung.     

Predictors of response to bronchial allergen challenge in 5- to 6-year-old atopic children

BACKGROUND: The relationship between atopy and bronchial allergy in young children is not completely understood. OBJECTIVE: To examine the association between response to bronchial allergen challenge, immune markers of atopy and other clinical characteristics in 5- to 6-year-old children. METHODS: Children with positive skin test (SPT) to aeroallergen, together with a proportion of SPT negative children (as controls), were recruited from a birth cohort of 198 children at high risk of developing atopic disease and underwent allergen challenge. RESULTS: Thirty-seven children (26 atopic and 11 SPT negative), median age 74.5 months, were challenged: 31 with house dust mite and six with grass allergen. Only atopic children responded to challenge: n = 12/26 (46%). Wheal size [odds ratio (OR) 2.5 (1.2-5.3), P = 0.01], allergen-specific immunoglobulin E (IgE) [OR 3.4 (1.23-9.61), P = 0.02], total IgE [OR 8.6 (1.1-68.7), P = 0.04], current wheeze [OR 12 (1.7-81.7), P = 0.006] and persistent eczema [OR 11.0 (1.7-68.3), P = 0.006] emerged as the strongest independent predictors of response to allergen challenge. Prediction of response to allergen challenge was significantly improved when immune markers of atopy, and in particular wheal size, were combined with clinical characteristics. CONCLUSION: The relationship between atopy and bronchial allergy is quantitative at this age. There may be potential to create more powerful indicators of the presence of respiratory allergy in young children when immunological markers of atopy are considered quantitatively and when combined with clinical history of coexistent allergic disease.     

Reduced nonspecific bronchial reactivity and decreased airway response to antigen challenge in atopic asthmatic patients treated with the inhaled leukotriene D4 antagonist, L-648,051

We studied the effect of the inhaled leukotriene D4 antagonist, L-648,051, on antigen-induced bronchoconstriction and nonspecific bronchial reactivity. Ten males with mild atopic asthma completed a double-blind, randomized, two-period, placebo-controlled cross-over study. For a 7-day period patients inhaled either placebo or 6 mg of L-648,051 four times daily. Bronchial reactivity to methacholine was measured at base line (day 1) and after 6 days, treatment (day 7). On day 8, after inhaling 6 mg of the antagonist (or placebo), the patients were challenged by inhaled antigen; they received an additional 6 mg of the antagonist (or placebo) 3 h later. Pulmonary function (forced expiratory volume in 1 s, FEV1) was measured serially through an 8-h post-antigen challenge. Nonspecific airway reactivity was again measured on day 9. Compared to placebo, L-648,051 treatment diminished the methacholine reactivity, on both day 7 (NS) and on day 9 (P < 0.05). In addition, the immediate and late bronchial responses to antigen challenge on day 8 were attenuated in the patients when treated with L-648,051. In the immediate phase (0-3 h postchallenge), the airway response was significantly reduced at all recordings between 20 min and 1 h postchallenge. In the late phase (3-8 h postchallenge), the pulmonary response was also reduced. However, the reduction was statistically significant only at the 5-h recording. The results suggest that sulfidopeptide leukotrienes are of importance for nonspecific airway reactivity, and that leukotriene D4 is a significant mediator in the immediate asthmatic reaction.     

Twenty-four-hour time course of eosinophil granule proteins ECP and EPX during bronchial allergen challenges in serum of asthmatic children

To study in vivo monitoring variables for bronchial allergen challenges, we investigated the time course of the eosinophil granule proteins, eosinophil cationic protein (ECP) and eosinophil protein × (EPX) after allergen provocation in serum. Thirty-two asthmatic children sensitive to house-dust mites and six healthy young adult controls were challenged by bronchial allergen provocations with Dermatophagoides pteronyssinus and D. farinae. Blood samples were taken at regular intervals up to 24 h. Base-line concentrations of ECP ( P <0.004), EPX ( P <0.002), and eosinophils ( P <0.001) were found to be increased in asthmatic children, as compared with healthy controls. ECP and EPX concentrations showed a uniform pattern with two characteristic features: 1) a rapid increase for both mediators up to 30 min after provocation over base-line values ( P <0.0001 and P <0.001), followed by a rapid decrease nearly to base-line values in the next 30 min; and 2) a steady increase for ECP and EPX up to 10 h ( P <0.02 and P <0.01), and even higher levels at 24 h, after challenge ( P <0.002 and P <0.003). We conclude that although eosinophils are activated in asthmatic children after bronchial allergen challenge, ECP and EPX concentrations are not suitable monitoring variables. Base-line eosinophils seem to predict the occurrence of a late-phase asthmatic reaction after allergen provocation.     

Rapid response of circulating myeloid dendritic cells to inhaled allergen in asthmatic subjects

BACKGROUND: Dendritic cells (DC) are thought to play a key role in the initiation and maintenance of T cell immunity to inhaled antigens. While the density of DC within the bronchial mucosa is increased in stable asthma, there is little information currently available concerning the effects of allergen inhalation on DC in subjects with asthma. OBJECTIVES: To enumerate changes in the numbers of circulating CD33(+) myeloid DC in asthmatics, before and after allergen challenge. METHODS: Blood DC numbers were enumerated by flow cytometry before and at 3, 6 and 24 h after inhaled allergen and diluent in 10 mild, allergic asthmatic subjects. RESULTS: Blood DC numbers rapidly fell from 3.42 +/- 0.30 x 10(7)/L at baseline, to 2.10 +/- 0.17 x 10(7)/L by 3 h post-challenge (P < 0.01), and remained significantly below baseline values at both 6 and 24 h following allergen challenge. No such changes in DC numbers were noted after diluent challenge. A similar, early fall in circulating lymphocytes was also noted post-allergen challenge, whereas changes in circulating eosinophil and neutrophil numbers occurred more slowly. CONCLUSIONS: A significant proportion of myeloid DC rapidly 'disappear' from the circulation following allergen inhalation, suggesting that margination of circulating myeloid DC, and their recruitment into the airway mucosa, is an important feature of the immune response to inhaled allergen.