Selective differences in the expression of the homing receptors of helper lymphocyte subsets

Effector functions are acquired by mature CD4 T lymphocytes in an exquisitely antigen-specific and antigen-dependent fashion. T cell receptor recognition of the processed antigen presented on the major histocompatibility complex molecule by antigen-presenting cells dictates the specificity of the T cell clones that will be expanded. A complex array of further coreceptor and lymphokine-mediated interactions determines whether activation or inhibition will follow and which effector phenotype will be acquired by the lymphocytes. On the basis of a first antigen encounter, CD4 T cells are functionally defined as naive or memory/effector cells. In memory/effector T cells, the pattern of cytokine production permits further classification as Th1 or Th2 cells. Th1 cells mainly produce IFN-gamma, whereas Th2 cells mainly produce IL-4. The functional properties of these cell subsets derive from the biological activities of these (and the related) lymphokines they produce. An established body of data supports the view that the migration of T lymphocytes is distinctively different in naive and memory/effector T cells. Both CD4 and CD8 memory/effector T cells selectively migrate into nonlymphoid organs, such as the skin, the gut, and the lung through the peripheral extravascular route, whereas naive T cells migrate through the high endothelial venules and enter lymphoid tissues, such as lymph nodes, Peyers' patches, and tonsils. Furthermore, the acquisition of a Th1 or Th2 profile further implies the coordinated expression of a relatively selective array of receptors capable of rerouting them differentially. These events have a dramatic effect on the outcome of an immune response and determine whether it will be protective or not. New therapeutic strategies can be envisaged that interfere with the key molecular processes taking place during these coordinated differentiation events.

Airway eosinophilic inflammation and bronchial hyperresponsiveness after allergen inhalation challenge in asthma

Allergen exposure in atopic asthmatic patients is associated with recruitment and activation of eosinophils in the airways. Once activated, eosinophils release toxic products, including the eosinophil cationic protein (ECP), able to damage bronchial structures and to increase bronchial hyperresponsiveness. With this background, the present study was designed to evaluate whether ECP levels in bronchoalveolar lavage (BAL) fluid could reflect, better than BAL eosinophil counts, the cellular activation that follows allergen exposure in atopic asthmatics. Twenty-two atopic patients attended the laboratory on two separate days. On the 1st day, they underwent methacholine (MCh) inhalation challenge to detect the degree of nonspecific bronchial hyperresponsiveness. On the 2nd day, they underwent fiberoptic bronchoscopy and BAL, at baseline or 4-6 h after allergen inhalation challenge. In this latter patient group, MCh challenge was repeated 3-5 h after allergen challenge, 1 h before fiberoptic bronchoscopy. The analysis of the mean baseline FEV1 values and the degree of bronchial reactivity to MCh (MCh Pd20) on the 1st study day did not demonstrate differences between the two patient groups (p > 0.1, each comparison). In addition, in the allergen-challenged group, MCh Pd20 was decreased significantly after allergen challenge (151.4 micrograms/ml and 67.6 micrograms/ml, respectively, before and after challenge; p < 0.05). Evaluation of the different BAL cell types demonstrated that the proportions of eosinophils and epithelial cells were increased significantly in the allergen-challenged group compared with the group evaluated at baseline (p < 0.01 and p < 0.05, respectively). Moreover, ECP levels, corrected by the correspondent albumin levels (ECP/Alb), were higher in the allergen-challenged group compared with the group evaluated at baseline (p < 0.05). In addition, although a positive correlation was demonstrated between BAL eosinophil percentages and ECP/Alb values (r = 0.72, p < 0.05) in the group evaluated at baseline, no links were found between these parameters in the allergen-challenged group (p > 0.1). However, in this latter group, a weak positive correlation was demonstrated between eosinophil percentages and delta Mch, i.e., the increased non-specific bronchial reactivity, which is observed after allergen challenge (r = 0.55; p < 0.05). Thus, in stable asthmatic patients an ongoing activation of eosinophils parallels their migration, but this eosinophilic inflammation is not strictly related to bronchial reactivity to Mch. By contrast, after allergen inhalation challenge, eosinophil recruitment and activation seem to follow different temporal kinetics, and eosinophilic inflammation may be partially associated with the degree of airway hyperresponsiveness.

Dissociation between airway inflammation and airway hyperresponsiveness in allergic asthma

In asthma, the acute increment of airway responsiveness caused by exposure to allergen is associated with influx of eosinophils into the airways. The relationship between chronic airway hyperresponsiveness and airway inflammation is unclear, as they do not change consistently following long-term anti-inflammatory treatments. We studied 71 patients with chronic asthma and allergic sensitization to perennial allergens. Airway responsiveness was determined by inhalation of methacholine, and airway inflammation was quantified by induced sputum (n = 28) or bronchoalveolar lavage (n = 43) and bronchial biopsy (n = 20). The relationships between airway responsiveness and the numbers of different inflammatory cells were assessed by multiple regression analysis. No significant correlations were found between the degree of airway responsiveness and the numbers of inflammatory cells in sputum or bronchoalveolar lavage or bronchial biopsy. By contrast, baseline lung function was inversely related to the numbers of eosinophils and directly related to the numbers of macrophages. The eosinophil cationic protein contents of either sputum or bronchoalveolar lavage were significantly correlated with the percentages of eosinophils but not with airway responsiveness. We suggest that other factors (e.g., airway wall remodeling or autonomic dysfunction) may be responsible for most of the interindividual variability of airway responsiveness in asthma.

Recruitment of circulating allergen-specific T lymphocytes to the lung on allergen challenge in asthma

BACKGROUND

In allergic subjects with asthma, the migration of CD4+ T cells to the lungs in the hours after allergen exposure may contribute to allergic inflammation in the target organ.

OBJECTIVE

We studied allergen-specific T cells from the peripheral blood and lungs of allergic subjects with asthma at baseline and after allergen challenge.

METHODS

In each patient, blood samples were taken 10 minutes before and 24 hours after the inhalation of a major sensitizing allergen. In vitro proliferation of peripheral blood CD4+ T cells specific for the same allergen used in the in vivo challenge was assessed. In one patient two Dermatophagoides pteronyssinus-specific T-cell clones (TCCs) were derived from peripheral blood, and their T-cell receptors were sequenced to determine their clonotypic determinants on the beta chains. The T-cell receptor determinants of the allergen-specific TCCs were sought in blood and bronchoalveolar lavage samples taken from this patient.

RESULTS

We found that allergen inhalation is followed by a decrement in the specific proliferation of peripheral CD4+ T cells to the same allergen used for bronchial provocation. In one patient the clonotypic determinants of two allergen-specific TCCs diminished in the peripheral blood, whereas they were simultaneously expanded in the lower respiratory tract.

CONCLUSION

Our data suggest that allergen-specific T cells are recruited from the peripheral blood to the bronchial lumen after allergen challenge.

Depletion of circulating allergen-specific TH2 T lymphocytes after allergen exposure in asthma

BACKGROUND

In allergic asthma, CD4+ T lymphocytes are a fundamental component of local chronic inflammation. Their cytokine profile is oriented toward a TH2 phenotype, characterized by production of IL-4, IL-5, IL-10, and IL-13. Egress of T cells from blood to airways after allergen challenge has been described.

OBJECTIVE

We have studied a cohort of six patients with asthma who had multiple allergies to investigate how exposure to allergen affects the proliferation of peripheral CD4+ T lymphocytes with different allergen specificities and lymphokine profiles.

METHODS

For each patient, CD4+ T-cell lines were generated by in vitro stimulation with sensitizing and with nonsensitizing allergens, and IL-4 and interferon-gamma production by these lines was assessed. Proliferation of peripheral blood CD4+ T lymphocytes in response to the same allergens was measured before and 24 hours after inhalation challenge with a sensitizing allergen.

RESULTS

We found that each single sensitizing allergen can deplete peripheral blood of TH2-type CD4+ T lymphocytes specific for all sensitizing allergens, but not of TH1-type CD4+ T lymphocytes.

CONCLUSIONS

Our results suggest the existence of mechanisms capable of sorting disease-associated antigen specificities together with defined lymphokine patterns into T lymphocytes that can migrate to target organs, in allergic asthma.

Allergen challenge of passively sensitized human bronchi alters M2 and beta2 receptor function

We investigated whether antigen challenge may alter M2 and beta2 receptor function in isolated passively sensitized human bronchi. Bronchial rings (2-4 mm internal diameter) were obtained from 12 patients. Passive sensitization was induced by serum containing high IgE levels to Dermatophagoides pteronyssinus and Dermatophagoides farinae. Rings from six patients were used to study M2 receptor function by incubating with cumulatively increasing concentrations (10(-8) M to 10(-4) M) of pilocarpine and applying electric field stimulation (EFS) at 24 Hz. The rings from the other six patients were used to study beta2 receptor function by precontracting with carbachol 10(-6) M and adding cumulatively salbutamol (10(-9) M to 10(-4) M). Additional rings from these patients were used to determine whether dysfunction occurred distal to cAMP production by precontracting with carbachol 10(-6) M and adding cumulatively theophylline (10(-9) M to 10(-4) M). The attenuation of EFS-induced force by pilocarpine and the relaxation of carbachol-precontracted rings by salbutamol were less in challenged than in control and sensitized rings. No difference between challenged, sensitized, and control rings was observed with theophylline. We conclude that allergen challenge in passively sensitized isolated human bronchial rings may result in M2 and beta2 receptor dysfunction without involving mechanisms distal to cAMP formation. It appears that products from inflammatory cells recruited from blood are not necessary for this receptor dysfunction.

Expression of cytokine mRNA in bronchoalveolar lavage cells from atopic asthmatics before late antigen-induced reaction

Recently, much attention has been given to the possible role of lymphocytes and their soluble products in causing and maintaining allergic inflammation. The aim of this study was to assess the production of mRNAs for interleukins (IL) in bronchoalveolar lavage (BAL) cells obtained from allergic asthmatics after challenge with the relevant allergen in the period between early and late reactions. We evaluated BAL fluid cells obtained from six asthmatic subjects and four nonatopic controls. Challenge was performed with the relevant allergen. BAL fluid cells were obtained by fiberoptic bronchoscopy and bronchoalveolar lavage. To detect mRNA encoding each cytokine in BAL cells we used a reverse transcriptase polymerase chain reaction method. We evaluated IL-1 alpha, -2, -4, -5, -6, -13, and granulocyte-macrophage colony-stimulating factor (GM-CSF), and interferon-gamma (IFN-gamma). mRNAs for IL-1 alpha, -2, -4, -5, and IFN-gamma were detected in all of the atopic subjects; mRNAs for IL-6 and GM-CSF were found in five asthmatics; and mRNA for IL-13 was found in one patient only. In contrast, no mRNAs for IL-2, -4, -5, -6, -13, and GM-CSF were detected in the nonatopic healthy controls; mRNA for IL-1 alpha was found in one out of four normal subjects; and mRNA for IFN-gamma was evidenced in two of four subjects. The cellular environment in BAL fluids from allergic asthmatics before the clinical appearance of the late airway reaction shows an unrestricted expression of mRNA for cytokines. The local cytokine milieu could have an important role in the modulation of bronchial inflammation and in the appearance of allergic symptoms.

Bronchial and bronchoalveolar inflammation in single early and dual responders after allergen inhalation challenge

To characterize the cellular inflammation at the bronchial and bronchoalveolar levels, we evaluated 43 patients with asthma who were sensitized to house dust mites. On 2 consecutive days patients underwent methacholine challenge and allergen bronchial challenge. In addition, 6, 24, or 72 h after allergen challenge, fiberoptic bronchoscopy with bronchial lavage (BL) and bronchoalveolar lavage (BAL) was performed. Patients belonging to the 6-h, 24-h, or 72-h group were divided further into two subgroups: those with isolated early response to allergen (LAR-), and those with dual response to allergen (LAR+). The percentage of eosinophils and of epithelial cells in BAL fluid was significantly higher in LAR+ than in LAR- patients in the 6-h group (p < 0.05, each comparison), but not 24 or 72 h after (p > 0.05, each comparison). Similarly, the proportion of BL eosinophils was also higher in LAR+ than in LAR- patients, both in the 6-h and in the 24-h group (p < 0.05, each comparison). In addition, increased proportions of BL neutrophils were present in the LAR+ patients belonging to the 24-h group (p < 0.05). Comparing "proximal" = BL vs "distal" = BAL data, we found a significantly higher proportion of epithelial cells in BL compared with BAL, in both LAR- and LAR+ subjects, either 6, or 24, or 72 h after challenge (p < 0.01, each comparison) and increased percentages of BL neutrophils and eosinophils in LAR+ patients (p < 0.05, each comparison), but not in LAR- patients, in the 24-h group. The percentages of BL or BAL macrophages and lymphocytes did not differ significantly among the different patient groups. These data indicate that the development of LAR after allergen inhalation challenge is associated with an early recruitment of eosinophils and with epithelial desquamation in the airways. In addition, after allergen challenge epithelial desquamation is more pronounced in the proximal than in the distal airways, independently of the type of bronchial response.

BAL neutrophilia in asthmatic patients. A by-product of eosinophil recruitment?

Although neutrophil number may be increased in the airways of patients with asthma, its pathogenetic role in this disorder remains unclear. We evaluated BAL of 8 normal control subjects, 30 +/- 2 years of age, and 24 patients with mild asthma: 17 patients with allergic asthma, 24 +/- 1 years of age, and 7 patients with nonallergic asthma, 30 +/- 1 years of age. The BAL of asthmatic patients showed increased numbers of neutrophils (p < 0.01), eosinophils (p < 0.01), and ciliated epithelial cells (p < 0.05) and increased concentrations of myeloperoxidase (MPO) (p < 0.01) compared with control subjects. Positive correlations were observed between the number of BAL neutrophils and eosinophils (Rs = 0.780, p < 0.0001) and between BAL neutrophil numbers and BAL MPO levels (Rs = 0.40, p < 0.05). No correlations were found between the following: (1) BAL eosinophils or neutrophils and BAL epithelial cells (p > 0.05, each comparison); (2) BAL neutrophils or eosinophils and log Pd15 methacholine (MCh) (p > 0.05, each comparison); or (3) BAL epithelial cells or log Pd15 MCh and BAL MPO (p > 0.05, each comparison). Dividing the patient population into two groups, allergic asthmatics and nonallergic asthmatics, similar BAL neutrophil, eosinophil, and epithelial cell numbers and similar MPO levels were found (p > 0.05, each comparison). In addition, the correlations between BAL neutrophils and eosinophils showed similar significance in the two patient subgroups (p > 0.05, each comparison). These results suggest that, both in allergic and nonallergic asthma, airway recruitment and activation of neutrophils occur as does parallel eosinophil migration. However, airway neutrophils do not seem to contribute significantly to epithelial cell injury or to airway hyperresponsiveness in the steady state.

Postjunctional effect of pinacidil on contractility of isolated bovine trachealis

Potassium channel openers hyperpolarize the smooth muscle cell membrane and relax airway smooth muscle. In this study, pre- and postjunctional effects of pinacidil ((+/-) N-cyano-N'-(4-pyridil)-N"-(1,2,2-trimethylpropyl)-guanidine monohydrated), an adenosine triphosphate (ATP)-sensitive K(+)-channel opener, were determined in isolated bovine trachealis. The effects of pinacidil on the frequency-response to electrical field stimulation (EFS), 0.1-32 Hz, and on the concentration response to acetylcholine (ACh), 10(9)-10(-4) M, were compared in muscle strips from six animals. In addition, the effect of pinacidil on the inhibitory nonadrenergic noncholinergic (iNANC) system was evaluated in histamine-contracted muscle strips from another eight animals. Pinacidil (10(-6) or 10(-5) M) shifted both the EFS frequency-response and the ACh concentration-response curves significantly (p < 0.01) to the right. Glibenclamide (10(-7)-10(-5) M) antagonized these responses in a concentration-dependent manner. The inhibitory effects of pinacidil on contractions of the same magnitude induced by EFS or exogenous ACh were not significantly different (p = 0.11), suggesting that pinacidil had only a postjunctional effect. Pinacidil had no effect on iNANC-mediated muscle relaxation. We conclude that pinacidil attenuates the contraction of isolated bovine tracheal smooth muscle by postjunctional mechanisms.

Comparison of early and late asthmatic responses between patients with allergic rhinitis and mild asthma

Allergic rhinitic subjects without symptoms of asthma show airway hyperresponsiveness, but to a lesser degree than asthmatics. As airway responsiveness is a determinant of the bronchial response to allergen, rhinitic subjects should also respond to allergen challenge, but to a lesser extent than asthmatics. However, studies have so far failed to show quantitative differences in allergen responses between patients with rhinitis and patients with asthma. We studied 123 allergic subjects classified, on the basis of a scored symptom questionnaire, as follows: pure rhinitics without any symptom of asthma (Group 1, n = 39), true asthmatics with or without rhinitis (Group 2, n = 41), and subjects with borderline symptoms of asthma (Group 3, n = 43). All subjects underwent both methacholine and allergen inhalation challenges, with pollen challenges performed out of season. When the three groups were pooled, the asthma symptom score was directly correlated with the sensitivities both to methacholine and allergen, whilst both the sensitivity to allergen and the severity of late-phase response were correlated with the sensitivity to methacholine. The percentage of subjects with a positive early-phase asthmatic response to allergen was similar in Groups 1 and 2. Group 2 had higher sensitivities both to methacholine and to allergen than Group 1. A late-phase asthmatic response occurred more frequently in Group 2 than in Group 1, and this difference was due to a higher occurrence of late-phase response in subjects allergic to house dust mite in Group 2. This study confirms that the bronchial response to allergen can be predicted, in rhinitic as well as in asthmatic allergic subjects, on the basis of airway responsiveness to methacholine. We conclude that the presence or the absence of asthma symptoms in allergic subjects may be related to a quantitatively different airway responsiveness to allergen.

Cutaneous antihistaminic action of cetirizine and dose-related EEG concomitants of sedation in man

The cutaneous antihistaminic action (prick test; 1:100, 1:200 and 1:1000) and neuropsychological and electroencephalographic (EEG) concomitants of sedation following the histamine H1 receptor antagonist cetirizine (10- and 20-mg acute oral doses) and chlorpheniramine, 4 mg, were investigated in a cross-over, placebo-controlled study in healthy male volunteers (age 23-29 years). With an average Cmax of cetirizine of 697.0 ng/ml (10 mg) and 1000.2 ng/ml (20 mg), the diameter of histamine-induced skin weals was reduced by 24.0-74.9% depending on histamine concentration and with no dose dependence for cetirizine. Placebo and chlorpheniramine were ineffective. Behavioral or neuropsychological signs of sedation were never observed. An increase of the 6.5-14.5 Hz EEG power, with anterior scalp preponderance, was observed after chlorpheniramine or cetirizine 20 mg. This effect of cetirizine was accounted for by a substantial increase of power in the 6.5-8.0 Hz frequency subsegment and is regarded, for these experimental conditions, as an established early EEG indication of mild sedation (vigilance 'state A'). No EEG effects were observed after placebo or cetirizine at the 10 mg dose. The existence of some histaminergic (H1) specificity of the mechanisms modulating vigilance and of a threshold dose of cetirizine for sedative action is suggested.

Airway eosinophilic inflammation, epithelial damage, and bronchial hyperresponsiveness in patients with mild-moderate, stable asthma

Allergic asthma is characterized by chronic recruitment of eosinophils in the airways. Once activated, eosinophils release toxic products, including eosinophil cationic protein (ECP), able to damage airway epithelial cells. To test the hypothesis that also in mild-moderate stable asthma, a significant eosinophil activation could occur, we studied 25 asthmatic patients (34 +/- 19 years old), of whom 18 were allergic (27 +/- 12 years) and seven nonallergic (42 +/- 10 years), with FEV1 values > or = 70% of predicted, and eight normal volunteers (controls, 33 +/- 11 years). All subjects underwent methacholine (MCh) challenge on the first visit, and bronchoalveolar lavage (BAL) on the second visit (approximately 3-4 days later). BAL cells were counted and albumin (Alb) (as index of protein dilution in BAL fluid) and ECP levels (as index of eosinophil activation) in BAL fluid were measured. As compared to controls, a significant increase in BAL eosinophil and in BAL epithelial cell numbers was observed in asthmatic patients (P > 0.05, each comparison), with no differences between the two asthmatic patient subgroups. Detectable ECP levels (> 2 micrograms/1) were found in BAL of 18 asthmatic patients (14 allergic and four nonallergic asthmatic patients), while Alb levels were measurable in 25 BAL fluids and found to be similar in controls and asthmatic patients, and in the two asthmatic patient subgroups (P > 0.05, each comparison). In BAL of asthmatic patients, positive correlations were found between eosinophil numbers and 1) ECP/Alb levels (r = 0.50, P = 0.020); 2) epithelial cell numbers (r = 0.50, P = 0.014). In asthmatic patients, a significant negative correlation was found between bronchial reactivity to MCh (log Pd15) and ECP/Alb levels in BAL fluid (r = -0.6, P = 0.005), whereas no correlation was found between log Pd15 MCh and BAL eosinophil or epithelial cell number (P > 0.1, each correlation). These data suggest that bronchial eosinophil recruitment and activation may occur also in mild-moderate stable asthma and that bronchial epithelium damage and airway responsiveness may be partially associated with the eosinophilic inflammatory reaction.

The repertoire of T-lymphocytes recovered by bronchoalveolar lavage from healthy nonsmokers

We reasoned that persistent exposure to a limited set of airborne antigens could drive the preferential expansion of single T-cell clones in the lower respiratory tract of normal individuals. To explore this issue, the normal human alpha/beta T-cell receptor repertoire was studied in lung lymphocytes obtained by bronchoalveolar lavage (BAL) from the humen of the lower respiratory tract. BAL T-cells obtained from five healthy volunteers were first analysed using polymerase chain reaction to amplify all known V alpha and V beta genes of the T-cell receptor. T-cells from peripheral blood were used as an internal control. Heteroduplex analysis of the amplified products was then performed, to assess the clonal composition of the repertoire of lung- versus blood-derived T-lymphocytes within each amplified variable gene family. In all subjects, the T-cell repertoire in the lung was largely as heterogeneous as peripheral blood in terms of clonal composition. This indicated lack of preferential expansion of single T-cell clones. A few T-cell clones were simultaneously expanded in blood and lung in all individuals within a limited number of V beta (mean 2.4; range 2-4) and V alpha (mean 1.6; range 1-3) genes. We also found that lung T-lymphocytes expressed all of the V gene families of the T-cell receptor that were expressed by peripheral blood T-cells. Our results indicate that T-cell clones in the lower respiratory tract of normal individuals are distributed according to a largely polyclonal pattern, which corresponds to that found in peripheral blood.

Oligoclonality of lung T lymphocytes following exposure to allergen in asthma

We were interested in studying the lung allergen-specific T cell repertoire in different conditions of allergen exposure in subjects with atopic asthma. Twenty-one allergic individuals were studied: 17 subjects suffering mainly from asthma and 4 from rhinitis. They all performed spirometry and methacholine challenge. All patients were subjected to bronchoalveolar lavage (BAL), either at base line (no challenge) or after allergen or histamine challenge, and the TCR repertoire of their lung T cells was studied with heteroduplex analysis. Expansion of single T cell clones was observed in one (of seven) asthmatic subject that reported a recent exposure to allergen and had high bronchial hypersensitivity to methacholine, and in seven/seven asthmatic subjects who underwent BAL after they suffered an early asthmatic reaction to experimental allergen inhalation. Remarkably, ex vivo expanded clones included allergen-specific T cells. In two of the seven subjects who underwent BAL after allergen challenge, two different lung segments were lavaged. A strikingly symmetrical distribution of the expanded clones was found in these samples. Control subjects and six of seven asthmatic patients studied at base line showed polyclonality of lung T cells. In conclusion, T lymphocytes are clonally expanded in the lower respiratory tract only in asthmatic subjects exposed to allergen. These results suggest that in allergic asthma, the inhalation of sensitizing allergens can recruit to the lung T lymphocytes that include allergen-specific T cell clones.

Oligoclonality of lung T lymphocytes following exposure to allergen in asthma

We were interested in studying the lung allergen-specific T cell repertoire in different conditions of allergen exposure in subjects with atopic asthma. Twenty-one allergic individuals were studied: 17 subjects suffering mainly from asthma and 4 from rhinitis. They all performed spirometry and methacholine challenge. All patients were subjected to bronchoalveolar lavage (BAL), either at base line (no challenge) or after allergen or histamine challenge, and the TCR repertoire of their lung T cells was studied with heteroduplex analysis. Expansion of single T cell clones was observed in one (of seven) asthmatic subject that reported a recent exposure to allergen and had high bronchial hypersensitivity to methacholine, and in seven/seven asthmatic subjects who underwent BAL after they suffered an early asthmatic reaction to experimental allergen inhalation. Remarkably, ex vivo expanded clones included allergen-specific T cells. In two of the seven subjects who underwent BAL after allergen challenge, two different lung segments were lavaged. A strikingly symmetrical distribution of the expanded clones was found in these samples. Control subjects and six of seven asthmatic patients studied at base line showed polyclonality of lung T cells. In conclusion, T lymphocytes are clonally expanded in the lower respiratory tract only in asthmatic subjects exposed to allergen. These results suggest that in allergic asthma, the inhalation of sensitizing allergens can recruit to the lung T lymphocytes that include allergen-specific T cell clones.

Nedocromil sodium versus theophylline in the treatment of reversible obstructive airway disease

BACKGROUND

Previous clinical therapeutic research has shown that inhaled nedocromil sodium can replace maintenance oral sustained release theophylline in the management of asthma patients.

OBJECTIVE

To compare directly the efficacy and safety of nedocromil sodium and sustained release theophylline.

METHODS

Using a randomized, double-blind, double-dummy, parallel-group design, 105 patients with reversible obstructive airways disease (77 asthmatic patients) recruited from four referred-care clinics received, in addition to their existing therapy, 4 mg nedocromil sodium four times daily or sustained release theophylline (maximum daily dose 13 mg/kg) for 6 weeks. Patients with serum theophylline levels within the therapeutic range of 10 to 20 micrograms/mL were retained for efficacy analysis. All were included in a tolerability analysis. Day and nighttime symptoms, inhaled bronchodilator use, morning tightness, cough, and twice daily peak flows were recorded on diary cards. Disease severity, lung function and unusual events were evaluated bi-weekly, and opinion of treatment after 6 weeks.

RESULTS

Both treatments improved symptoms, inhaled bronchodilator use and lung function to the same extent. Both treatments were very to moderately effective in > 70% patients. The occurrence of gastrointestinal (P < .05) and central nervous system (P < .01) unusual events was significantly lower for nedocromil sodium compared with theophylline treated patients.

CONCLUSIONS

Nedocromil sodium and theophylline were equally effective in this group of patients but nedocromil sodium treatment was associated with significantly fewer side effects, and therefore may be the treatment of choice.

Bronchial provocation test with allergen: comparison between two different techniques

Allergen bronchial provocation tests (BPTs) are often used for assessment of treatment efficacy. Usually, the allergen dose provoking a 20% fall of forced expiratory volume in one second (FEV1) (PD20) is determined on a prestudy day, and this single dose is administered for comparisons on study days. The inhalation of allergen may cause both an isolated early asthmatic response (EAR) or, more frequently, an EAR followed by a late asthmatic response (LAR). Whether the method used to elicit EAR, i.e. the inhalation of cumulative doses up to PD20 or the inhalation of a single predetermined PD20, give comparable results has not been established. We have, therefore, compared the results obtained using the two methods. Twelve patients underwent a first BPT with the increasing doses method and a second BPT with a single dose method. EAR, LAR, and allergen-induced increase of methacholine (MCh) sensitivity were compared. Both methods gave similar EAR's and LAR's although EAR tended to be more severe with the increasing dose method than with the single dose method. The ratio of postallergen/preallergen MCh sensitivity was poorly reproducible.

Allergy and sports: exercise-induced asthma

In some asthmatic subjects exercise is followed by a bronchospastic response that generally lasts 30-60 minutes and regresses spontaneously. The initiating stimulus is thought to be the cooling and/or dehydration of airways caused by hyperpnea. The mechanisms leading from thermodynamic changes to airway narrowing are object of controversy. Two hypotheses have been proposed, one suggesting that an increase in the osmolarity of airway lining fluid following water loss causes mediator release, and the other suggesting that an excessive vasodilation during airway rewarming causes vascular engorgement, thus reducing airway caliber. Other controversial issues in exercise-induced asthma are the role of airway inflammation and the question whether a late-phase response may occur. That inflammatory cells and mediators play a role is suggested by increased numbers of eosinophil and epithelial cells in bronchoalveolar lavage and by the efficacy of cromolyn and leukotriene antagonists in preventing EIA. The existence of late-phase response to exercise is questionable because exercise does not cause an increase in airway responsiveness, which usually accompanies late-phase responses to allergens. Furthermore, data of bronchoalveolar lavage and bronchial biopsy suggest that the delayed broncho-constriction that may be observed after exercise reflects airway instability in subjects with more prominent eosinophilic inflammation of airways and is not specific to exercise.

Quantitative analysis of peripheral allergen-specific B lymphocytes in asthma

We have recently shown that the number of peripheral allergen-specific T cells can, in part, predict, together with methacholine hyperresponsiveness, the bronchial response to inhaled allergen in asthmatic patients. This study was designed to explore the role of blood B cells committed to produce allergen-specific IgE in asthma. Twenty-three asthmatic patients sensitized to Dermatophagoides pteronyssinus and 11 control subjects were studied. Peripheral blood B cells, committed to produce allergen-specific IgE, were enumerated by limiting dilution microcultures of Epstein-Barr virus (EBV)-transformed B cells. An allergen inhalation challenge was performed in all asthmatic subjects. No difference was found in the frequency of B cells committed to produce allergen-specific IgE either between asthmatic patients and controls or between asthmatic patients with or without late-phase bronchial response to allergen. No correlation was found between the frequency of B cells committed to produce allergen-specific IgE and the bronchial response to the allergen inhalation challenge. We conclude that, in quantitative terms, peripheral allergen-specific B cells are not as relevant as T cells to the development of the asthmatic response in the model of provoked asthma.

Effect of multiple doses of nedocromil sodium given after allergen inhalation in asthma

AIM

Twelve subjects with asthma took part in a placebo-controlled crossover study designed to investigate whether nedocromil sodium given after the occurrence of the early-phase asthmatic reaction to allergen has an effect on the late-phase response and the associated increase in airway responsiveness.

METHODS

The treatments were administered four times at 4-hour intervals at a dose of 4 mg, with the first dose given 1 hour after the last allergen challenge. Changes in airway caliber were monitored for 15 hours after allergen exposure by measuring forced expiratory volume in 1 second hourly. Airway responsiveness to methacholine was determined 24 hours before and 24 hours after allergen challenge.

RESULTS

Nedocromil sodium failed to reduce significantly the maximum late fall in forced expiratory volume in 1 second as compared with placebo but delayed its occurrence by 1.5 hours (p = 0.05). Nonspecific airway responsiveness to methacholine was similarly increased after allergen challenge when patients received nedocromil sodium and placebo. No unusual events were reported during the study period by any patient. These results indicate that nedocromil sodium is not able to interrupt the ongoing cascade of inflammatory events leading to the late-phase reaction and the associated increase in airway responsiveness.

CONCLUSION

In allergic asthma, nedocromil can be used only as a preventive treatment.

Effects of aerosol methacholine and histamine on airways and lung parenchyma in healthy humans

To investigate whether histamine (His) and methacholine (MCh) have different effects on airways and lung parenchyma, 11 healthy subjects were given aerosol MCh until a response plateau was obtained and then two doses of His. At the plateau, forced expiratory volume in 1 s and forced expiratory flow at 40% of vital capacity from partial flow-volume curves were reduced by 19 +/- 3 (SE) and 80 +/- 4%, respectively. Aerosol His decreased forced expiratory volume in 1 s by an additional 12 +/- 1% but left partial forced expiratory flow unchanged. The bronchodilator effect of deep inhalation, as inferred from the ratio of forced expiratory flow from maximal to that from partial flow-volume curves, increased after MCh and plateaued but decreased after His. Quasi-static transpulmonary pressure-volume area determined in seven subjects was unchanged after MCh but was increased by 57 +/- 10% after His. We conclude that adding His after the response to MCh plateaued does not increase the maximal degree of bronchoconstriction but may increase parenchymal hysteresis, thus blunting the bronchodilator effect of deep inhalation. These results suggest that His and MCh have similar effects on airway smooth muscle but different effects on lung tissue properties.