Effect of the S-nitrosoglutathione reductase inhibitor N6022 on bronchial hyperreactivity in asthma.

RATIONALE: Patients with asthma demonstrate depletion of the endogenous bronchodilator GSNO and upregulation of GSNOR. OBJECTIVES: An exploratory proof of concept clinical study of N6022 in mild asthma to determine the potential bronchoprotective effects of GSNOR inhibition. Mechanistic studies aimed to provide translational evidence of effect. METHODS: Fourteen mild asthma patients were treated with intravenous N6022 (5 mg) or placebo and observed for 7 days, with repeated assessments of the provocative dose of methacholine causing a 20% fall in FEV1 (methacholine PC20 FEV1), followed by a washout period and crossover treatment and observation. In vitro studies in isolated eosinophils investigated the effect of GSNO and N6022 on apoptosis. MEASUREMENTS AND MAIN RESULTS: This was a negative trial as it failed to reach its primary endpoint, which was change from baseline in methacholine PC20 FEV1 at 24 h. However, our exploratory analysis demonstrated significantly more two dose-doubling increases in PC20 FEV1 for N6022 compared with placebo (21% vs 6%, P < 0.05) over the 7-day observation period. Furthermore, a significant treatment effect was observed in the change in PC20 FEV1 from baseline averaged over the 7-day observation period (mean change: +0.82 mg/ml [N6022] from 1.34 mg/ml [baseline] vs -0.18 mg/ml [placebo] from 1.16 mg/ml [baseline], P = 0.023). N6022 was well tolerated in mild asthmatics. In vitro studies demonstrated enhanced eosinophilic apoptosis with N6022. CONCLUSIONS: In this early phase exploratory proof of concept trial in asthma, N6022 did not significantly alter methacholine PC20 FEV1 at 24 h, but did have a treatment effect at 7 days compared to baseline. Further investigation of the efficacy of S-nitrosoglutathione reductase inhibition in a patient population with eosinophilic asthma is warranted.

Nonallergic airway hyperresponsiveness and allergen-specific IgE levels are the main determinants of the early and late asthmatic response to allergen.

BACKGROUND: Conflicting results have been reported in studies of predictive factors for airway responsiveness to allergens during bronchial challenges. OBJECTIVE: The aim of this study was to assess determinants of airway responsiveness to 3 different allergens during standardized bronchial challenges. METHODS: Data were collected from asthmatic patients who participated in allergen challenge trials between 2000 and 2006 (cat, n = 37; house dust mite [HDM], n = 35; grass pollen, n = 27). PD20 (provocative dose causing a 20% fall in forced expiratory volume in the first second) methacholine, PD20 allergen, allergen skin test endpoint, allergen-specific immunoglobulin (Ig) E levels, and late asthmatic response were analyzed for each allergen group. RESULTS: During the early asthmatic response, a significant relationship was found between PD20 allergen and PD20 methacholine (P < .01 for cat, HDM, and grass pollen), as well as between PD20 allergen and allergen-specific IgE levels (P < .05 for cat and HDM). No relationship was observed between PD20 allergen and allergen skin test endpoint (P > .05). Late asthmatic response was significantly more frequent after HDM challenge than after cat or grass pollen challenges (57.1% vs16.2% and 33.3%, P < .01). Dual responders during HDM challenges had significantly higher allergen-specific IgE levels (P < .05) and higher nonallergic airway responsiveness (P < .05). CONCLUSION: Nonallergic airway hyperresponsiveness and allergen-specific IgE levels were the main determinants of early and late asthmatic responses. HDM challenges were the most interesting model with regard to the occurrence of late asthmatic response. In contrast to previous publications and to the official statement on standardized challenge testing with sensitizing stimuli, skin sensitivity appears to be a poor predictor of the early asthmatic response.

Sodium metabisulfite as a contact allergen--an example of a rare chemical mechanism for protein modification.

BACKGROUND: Skin-sensitizing chemicals that cause allergic contact dermatitis do so by reacting with self-proteins such that the modified structure becomes antigenic. The reaction chemistry involved is well characterized, but there are exceptions, such as the occasional allergen sodium metabisulfite. OBJECTIVES: To identify the potential in cutaneo reaction chemistry of sodium metabisulfite. METHODS: The established protein reaction chemistry associated with aqueous sulfite chemistry was explored in the context of the protein modification stage in allergic contact dermatitis. RESULTS: A probable mechanism for the in cutaneo modification of proteins by sodium metabisulfite involves the sulfite di-anion, acting as a nucleophile towards electrophilic centres in proteins, which is a rare mechanism, as most known skin-sensitizing chemicals behave as electrophiles. CONCLUSIONS: Sodium metabisulfite is an unusual but not infrequent contact allergen whose chemistry suggests a previously unrecognized protein modification mechanism involving nucleophilic attack by sulfite di-anions on target electrophilic centres in skin proteins. The chemical properties required for sensitization by nucleophilic attack on skin proteins are quite restrictive, so the domain of nucleophilic sensitizers is expected to be small. Thiourea derivatives are among the sensitizers likely to act by this mechanism.

Bronchial hyperresponsiveness to methacholine and adenosine 5'-monophosphate, and the presence and degree of atopy in young children with asthma.

BACKGROUND: Bronchial hyperresponsiveness (BHR) is a characteristic feature of asthma, and is usually measured by bronchial challenges using direct or indirect stimuli. The relationship between atopy and BHR remains to be clarified, particularly in a population selected for asthma. Furthermore, data for young children are limited, although asthma frequently occurs in early childhood. OBJECTIVE: The aim of this study was to investigate methacholine (direct stimulus) and adenosine 5'-monophosphate (AMP) (indirect stimulus) responsiveness according to the presence and degree of atopy in young children with asthma. METHODS: A retrospective analysis of data from 122 preschool children (median age [range]: 5.3 years [4.0-6.8]) presenting with the diagnosis of asthma was performed. These children were characterized by skin-prick tests (SPTs) and bronchial challenges with methacholine and AMP, using a modified auscultation method. The end-point concentration, resulting in audible wheezing and/or oxygen desaturation, was determined for each challenge. Atopy was defined by at least one positive reaction to SPTs, and its degree was assessed using serum total IgE levels, number of positive SPTs, and atopic scores (sum of graded weal size). RESULTS: Atopic patients (n=97) had a significantly lower AMP end-point concentration than non-atopic patients (n=25), whereas the methacholine end-point concentration was not different between the two groups. Among the atopic patients, there was no association between the methacholine end-point concentration and any of the atopy parameters. By contrast, a significant association was found between the AMP end-point concentration and the degree of atopy reflected in serum total IgE and atopic scores (χ² test for trend, P=0.001, 0.003, respectively). CONCLUSION AND CLINICAL RELEVANCE: Young children with atopic asthma had a significantly greater AMP responsiveness than those with non-atopic asthma, whereas methacholine responsiveness was not significantly different between the two groups. The degree of atopy appeared to be an important factor in AMP responsiveness, but not in methacholine responsiveness, and thus might be a marker of airway inflammation in asthma.

Human bronchial epithelial cells express an active and inducible biosynthetic pathway for leukotrienes B4 and C4.

BACKGROUND: Human bronchial epithelial cells synthesize cyclooxygenase and 15-lipoxygenase products, but the 5-lipoxygenase (5-LO) pathway that generates the leukotriene (LT) family of bronchoconstrictor and pro-inflammatory mediators is thought to be restricted to leucocytes. OBJECTIVE: We hypothesized that human bronchial epithelial cells (HBECs) express a complete and active 5-LO pathway for the synthesis of LTB4 and LTC4, either constitutively or after stimulation. METHODS: Flow cytometry, RT-PCR, Western blotting, enzyme immunoassays and reverse-phase high-performance liquid chromatography were used to investigate constitutive and stimulated expression of 5-LO pathway enzymes and the synthesis of LTs B4 and C4 in primary HBECs and in the 16-HBE 14o- cell line. RESULTS: Constitutive mRNA and protein expression for 5-LO, 5-LO-activating protein (FLAP), LTA4 hydrolase and LTC4 synthase were demonstrated in primary HBECs and in the 16-HBE 14o- cell line. In 16-HBE 14o- cells, treatment with calcium ionophore A23187, bradykinin or LPS up-regulated the expression of these enzymes. The up-regulation of 5-LO was blocked by the anti-inflammatory glucocorticoid dexamethasone. Human bronchial epithelial cells were shown to generate bioactive LTs, with primary HBECs generating 11-fold more LTC4 and five-fold more LTB4 than 16-HBE 14o- cells. LT production was enhanced by ionophore treatment and blocked by the FLAP inhibitor MK-886. CONCLUSIONS: Expression of an active and inducible 5-LO pathway in HBEC suggests that damaged or inflamed bronchial epithelium may synthesize LTs that contribute directly to bronchoconstriction and leucocytosis in airway inflammation.

Airway hyperreactivity in exacerbation of chronic asthma is independent of eosinophilic inflammation.

We have developed an animal model to investigate the mechanisms underlying an acute exacerbation of chronic asthma. Sensitized BALB/c mice were exposed to aerosolized ovalbumin, either as chronic low-level challenge (mass concentration approximately 3 mg/m(3)) for 4 wk, a single moderate-level challenge (approximately 30 mg/m(3)), or chronic low-level followed by single moderate-level challenge (the acute exacerbation group). Compared with animals receiving chronic challenge alone, mice in the acute exacerbation group exhibited a more marked inflammatory response, with involvement of intrapulmonary airways and lung parenchyma, and increased numbers of lymphocytes and eosinophils in bronchoalveolar lavage fluid. They also developed airway hyperreactivity (AHR) to methacholine, demonstrable as increased transpulmonary resistance and decreased compliance. This pattern of AHR was absent in chronically challenged animals, but was also present in animals given single moderate-level challenge. However, compared with animals receiving a single moderate-level challenge, inflammation and AHR were induced more rapidly in the acute exacerbation group. Eosinophil-deficient GATA1 Deltadbl mice exhibited undiminished AHR in the acute exacerbation model. We conclude that in mice with pre-existing airway lesions resembling mild chronic asthma, exposure to a moderately high concentration of inhaled antigen induces features of an acute exacerbation. The inflammatory response involves distal airways and is associated with a distinct pattern of AHR, which develops independent of the enhanced eosinophilic inflammation.

Bronchial plasma exudation after adenosine monophosphate or methacholine challenge.

Nonspecific hyperresponsiveness to adenosine monophosphate is better related to airway inflammation than methacholine. Adenosine induces mast cells and other cells to release inflammatory mediators that produce bronchoconstriction and perhaps other inflammatory effects, such as plasma exudation, which have not been well studied. We compared the plasma exudation effect, as measured in induced sputum, between adenosine and methacholine challenge in healthy and asthmatic subjects. In a cross-over design, 42 subjects were randomly challenged with adenosine or methacholine. After recovery, induced sputum was collected on 2 separate days, 48 to 72 hours apart. In the control group, an additional challenge with saline was performed. Differential cell counts and albumin and alpha2-macroglobulin levels were determined. The sputum volume obtained was sufficient to measure proteins in only 34 subjects: 10 healthy individuals and 24 mild asthmatics. There was a significant difference between adenosine and methacholine in sputum albumin (mean differences: 68[73.4] microg/L in controls, p = 0.039 and 48.0[162.9] microg/L in asthmatics) and cell counts, but only a tendency in alpha2-macroglobulin. PC20 adenosine was better related to eosinophil counts than methacholine (r = -0.44, p = 0.014). Albumin or alpha2-macroglubulin levels were not significantly correlated with baseline FEV1, PC20, or eosinophil counts. Adenosine, but not methacholine challenge, produces a mild airway plasma exudation that does not seem to be relevant to bronchoconstriction. However, this could be relevant, to some supernatant measurements after adenosine challenge.

The pattern of methacholine responsiveness in mice is dependent on antigen challenge dose.

BACKGROUND: Considerable variation exists in the protocols used to induce hyperresponsiveness in murine models of allergic sensitisation. We examined the effect of varying the number of antigen exposures at challenge on the development of methacholine responsiveness in systemically sensitised mice. METHODS: BALB/c mice were sensitised with ovalbumin (OVA), challenged with 1, 3 or 6 OVA aerosols. Lung function was measured using low frequency forced oscillations and partitioned into components representing the airways (Raw) and lung parenchyma (tissue damping (G) and tissue elastance (H)). Responsiveness to inhaled methacholine (MCh), inflammatory cell profile and circulating IgE were assessed 24 and 48 hours after challenge. The threshold dose of MCh required to elicit a detectable response (sensitivity) and response to 30 mg x mL(-1) (maximal response) were determined for each compartment. RESULTS: Sensitivity; All three OVA protocols resulted in an increased sensitivity to MCh in Raw but not in G or H. These responses where present at 24 and 48 hrs, except 1 OVA aerosol in which changes had resolved by 48 hrs. Maximal response; 1 OVA aerosol increased maximal responses in Raw, G and H at 24 hrs, which was gone by 48 hrs. Three OVA aerosols increased responses in H at 48 hrs only. Six OVA challenges caused increases in Raw, G and H at both 24 and 48 hrs. Eosinophils increased with increasing antigen challenges. IgE was elevated by OVA sensitisation but not boosted by OVA aerosol challenge. CONCLUSIONS: The pattern of eosinophilia, IgE and MCh responsiveness in mice was determined by antigen dose at challenge. In this study, increased sensitivity to MCh was confined to the airways whereas increases in maximal responses occurred in both the airway and parenchymal compartments. The presence of eosinophilia and IgE did not always coincide with increased responsiveness to inhaled MCh. These findings require further systematic study to determine whether different mechanisms underlie airway and parenchymal hyperresponsiveness post antigen challenge.

Bronchial hyperreactivity and spirometric impairment in patients with seasonal allergic rhinitis.

UNLABELLED: We previously demonstrated in a group of patients with perennial allergic rhinitis alone, impairment of spirometric parameters and high percentage of bronchial hyperreactivity (BHR). Thus, the present study aimed at evaluating a group of subjects suffering from seasonal allergic rhinitis alone to investigate the presence of spirometric impairment and BHR both during and outside the pollen season. METHODS: One-hundred rhinitics sensitized to pollen allergens only were evaluated during and outside the pollen season. Spirometry and methacholine bronchial challenge were performed. RESULTS: Four rhinitics showed impaired values of FEV1 without referred symptoms of asthma during the pollen season. FEF 25-75 values were impaired in 17 rhinitics during the pollen season and in 11 rhinitics outside the pollen season (P<0.05). Fifty-four patients showed positive methacholine bronchial challenge both during and outside the pollen season. PD20/FEV1 methacholine was lower during the pollen season than outside (P<0.05). In BHR positive patients, reduced values of FVC (P<0.05), FEV1 (P<0.05), and FEF 25-75 (P<0.01) were significantly demonstrated in comparison with BHR negative rhinitics. There was a relationship between BHR degree and FEF 25-75 values only during the pollen season (P<0.001). CONCLUSIONS: This study evidences that an impairment of spirometric parameters may be observed also in patients with seasonal allergic rhinitis alone during the pollen season. A high percentage of these patients had BHR. A close relationship between upper and lower airways is confirmed also in the model of pollen allergy. Thus, a careful evaluation of lower airways should be performed also in those patients with seasonal allergic rhinitis alone.

Recall helper T cell response: T helper 1 cell-resistant allergic susceptibility without biasing uncommitted CD4 T cells.

Effector and memory T lymphocytes differ significantly, and there is no experimental evidence that memory cells are sufficient to render an otherwise normal individual susceptible to localized allergic inflammation. Furthermore, nothing is known about the kinetics of memory responses after inhalation of antigen or interplay between an allergen-specific memory helper T (Th) cell Th2 population and uncommitted or competing Th1 cells. To study these processes, T cell receptor-transgenic CD4(+) effector cells were generated in vitro, transferred into naive recipients, and allowed to resume a quiescent state. Inhalation of protein antigen reactivated these Ag-specific Th2 donor cells, leading to allergic pulmonary inflammation and airway hyperreactivity. Susceptibility was correlated with the size of the input Th2 population, but Th1 cells neither enhanced nor reduced inflammation in this model. Importantly, the reactivation of these antigen-experienced cells by inhaled antigen did not skew the cytokine balance of recipient-derived T cells recruited to the lung nor did it inhibit the development of donor-derived Th1 cells from uncommitted antigen-experienced cells that form a normal part of immune responses. These data indicate that a quiescent memory Th2-cell population can create susceptibility to allergic pulmonary inflammation in a manner refractory to inhibition by Th1 cells or endogenous inhibitory mechanisms.

Sputum CD34+IL-5Ralpha+ cells increase after allergen: evidence for in situ eosinophilopoiesis.

Eosinophil lineage-committed progenitors increase in the bone marrow of subjects with asthma developing allergen-induced airway hyperresponsiveness and eosinophilia. Also, higher numbers of circulating eosinophil/basophil cfu have been demonstrated 24 hours after allergen inhalation and in bronchial and nasal biopsies of allergic individuals. These cells may undergo in situ eosinophilopoiesis, suggesting that after allergen inhalation, progenitor cells traffic from the bone marrow to the airways, providing an ongoing source of effector cells. To examine this possibility, CD34(+) and CD34(+)IL-5Ralpha(+) cells were measured in induced sputum from allergic subjects with asthma at baseline and at 7 and 24 hours after allergen and diluent inhalation, using flow cytometry. Isolated early responders (n = 9) were contrasted to dual responders (n = 9), who develop allergen-induced sputum and blood eosinophilia and airway hyperresponsiveness, and to normal control subjects. At baseline, there were significantly fewer sputum eosinophils and CD34(+) cells in normal control subjects compared with subjects with asthma. Sputum CD34(+) cells increased at 7 hours after allergen inhalation in both groups of subjects with asthma, which was sustained at 24 hours in the dual responder group only, associated with sustained increases in sputum CD34(+)IL-5Ralpha(+) cells, eosinophils, and interleukin-5. These results indicate that eosinophil progenitors can migrate to the airways and may differentiate toward an eosinophilic phenotype.

Respiratory hypersensitivity to trimellitic anhydride in Brown Norway rats: analysis of dose-response following topical induction and time course following repeated inhalation challenge.

Trimellitic anhydride (TMA) is a low-molecular-weight chemical known to cause occupational asthma. The dose-response study was designed to determine whether respiratory responses during a single inhalation challenge with TMA (25-30 mg/m3 for 30 min, 3 weeks after the initial induction), the ensuing non-specific airway hyperresponsiveness (AH) to methacholine (MCh) aerosol, and infiltration of eosinophilic granulocytes into the lungs of sensitized Brown Norway (BN) rats are associated and dependent on the concentration of TMA used for topical induction. The initial topical exposure concentrations were 1, 5, and 25% TMA in acetone:olive oil (AOO) followed by a booster induction 1 week later. In the time course study BN rats received AOO alone or were sensitized to the minimal sensitizing topical concentration of TMA (5%) and were the subsequently challenged with TMA on Days 17, 24, 41, 47, 55, and 66, followed by a MCh challenge 1 day later. One additional group of rats was sensitized to 5% TMA but were repeatedly challenged with MCh without prior TMA challenge. In the dose-response study the rats sensitized topically to TMA (5 and 25% in AOO) displayed unequivocal changes in breathing patterns upon challenge with TMA, including an increased responsiveness to MCh aerosol. These findings were associated with a sustained pulmonary eosinophilic inflammation. All endpoints demonstrated consistently that 5% TMA in AOO constitutes the minimal sensitizing concentration. When rats were topically sensitized with this concentration and repeatedly challenged with TMA over a time period of 7 weeks, it became apparent that challenge exposures in BN rats may be false negative when performed at time periods less than 3 weeks after the initial induction. Despite the time-related increased responsiveness elicited by the repeated TMA challenge exposures, the MCh challenge revealed increased non-specific airway hyperreactivity exclusively on Day 17. After the sixth TMA-challenge, the respiratory response and lung weights of rats sensitized topically were essentially similar to those observed in the repetitively re-challenged control group (induction: vehicle only; repeated booster challenge exposures with TMA). Thus, it appears, that in this animal model the effective concentration for successful topical sensitization must be at least approximately 5%. The repeated low-dose re-challenge with TMA in topically sensitized rats resulted in similar or slightly aggravated time-related responses over a period of 7 weeks. An over-proportionally increased susceptibility of rats receiving a topical priming dose prior to repeated inhalation challenge exposures was not observed. In summary, this study shows that the analysis of functional changes in breathing patterns is suitable to identify respiratory allergy. Repeated short-term inhalation exposures to mildly irritant concentrations (but low doses) of chemical asthmagens may be of higher concern than topical exposures.

Effect of respiratory protective devices on development of antibody and occupational asthma to an acid anhydride.

STUDY OBJECTIVES: To determine whether the use of respiratory protective equipment would reduce the incidence of occupational asthma due to exposure to hexahydrophthalic anhydride (HHPA). DESIGN: Prospective cohort study. SETTING: A facility that makes an epoxy resin product requiring HHPA for its manufacture. PARTICIPANTS: Sixty-six individuals newly hired at a facility that makes an epoxy resin product requiring HHPA for its manufacture. INTERVENTION: Employees who wished to use respiratory protective equipment could choose from three types of masks: dust mask, half-face organic vapor respirator, or full-face organic vapor respirator. MEASUREMENTS: Workers were evaluated annually for development of positive antibody to HHPA and occupational, immunologic respiratory disease, including occupational asthma. RESULTS: With use of respiratory protective equipment, the rate of developing an occupational immunologic respiratory disease was reduced from approximately 10 to 2% per year. Occupational asthma developed in only three individuals, and they were all in the higher exposure category. Statistically, one respirator was not superior to the others. CONCLUSION: Respiratory protective equipment can reduce the incidence of occupational immunologic respiratory disease, including occupational asthma, in employees exposed to HHPA.

The failure of interleukin-10-deficient mice to develop airway hyperresponsiveness is overcome by respiratory syncytial virus infection in allergen-sensitized/challenged mice.

Interleukin-10-deficient mice develop a robust pulmonary inflammatory response but no airway hyperresponsiveness (AHR) to inhaled methacholine (MCh) following allergen sensitization and challenge. In the present study, we investigated the effect of respiratory syncytial virus (RSV) infection on AHR and pulmonary inflammation in allergic IL-10-/- mice. Unlike littermate control mice, RSV-infected or ovalbumin (OVA)-sensitized/challenged IL-10-/- mice failed to develop significant AHR. In contrast, sensitized/challenged IL-10-/- mice infected with RSV did develop AHR accompanied by increased eosinophil numbers, both in bronchoalveolar lavage (BAL) and pulmonary tissue, and mucin production in airway epithelium. The cytokine profile in OVA-sensitized/challenged IL-10-/- mice was skewed toward a Th1 response but after RSV infection, this response was more of a Th2 type, with increased IL-5 levels in the BAL. Studies with an RSV mutant that lacks the G and SH genes showed equal enhancement of the AHR response as the parental wild-type strain, indicating that G protein is not essential to this response. These data suggest that RSV infection can overcome the failure of development of AHR in allergic IL-10-/- mice.

Comparison of 3 different doses of budesonide and placebo on the early asthmatic response to inhaled allergen.

BACKGROUND: A simple laboratory method to evaluate relative potency of inhaled corticosteroids in asthma would be valuable. Single-dose studies with the allergen-induced late asthmatic response have failed to show a useful dose-response relationship. Treatment for several days with inhaled corticosteroids will also inhibit the allergen-induced early asthmatic response. METHODS: Twelve atopic asthmatic subjects were studied during a season when no medications were required except ipratropium bromide as needed. These subjects had positive allergen and methacholine inhalation tests and FEV1 greater than 70% of predicted value. A double-blind, randomized, cross-over study compared placebo and budesonide 100, 200, and 400 microg administered by means of Turbuhaler twice daily for 7 days with 6-day washout periods. Methacholine PC20 was measured before and after 6 days of treatment, and allergen PC15 was measured after 7 days of treatment. RESULTS: The allergen PC15 (n = 11) was significantly larger (P = .0001) for all doses of budesonide compared with placebo, but there was no significant difference between the 3 doses of budesonide, and no dose response was demonstrated. The methacholine PC20 was significantly larger after all budesonide treatments compared with placebo (P = .024), but there was no difference between the 3 doses. There was a progressive increase in the allergen PC15 chronologically (sequence effect) that was not explained by improvement in FEV1 or airway responsiveness; sequence effects were not seen for FEV1 or for pretreatment or posttreatment methacholine PC20. Statistical adjustment for sequence effect did not alter allergen PC15 statistics. CONCLUSION: A 7-day course of budesonide administered by means of Turbuhaler at 200, 400, or 800 microg per day provided marked and significant inhibition of the allergen-induced early asthmatic response compared with placebo. There was, however, no difference between the 3 doses. Therefore this method with these doses is not useful for providing assessment of relative potency.

The significance of specific IgG4 antibodies to methyltetrahydrophthalic anhydride in occupationally exposed subjects.

BACKGROUND: A definitive role for allergen-specific IgG4 as either an anaphylactic or a blocking antibody, or both, remains controversial. OBJECTIVE: A population of 148 workers from two condenser plants (A and B) using epoxy resin with methyltetrahydrophthalic anhydride (MTHPA) was studied to evaluate the significance of MTHPA-specific IgG4 antibody. METHODS: The workers were evaluated through questionnaire and serological investigations. RESULTS: Ninety-seven (66%) of the currently exposed workers had positive MTHPA-specific IgE. IgE-sensitized workers in each plant had significantly more eye and nose complaints than unsensitized workers (P < 0.03). As the result of multiple logistic analysis, specific IgE antibodies was the most important predictor of work-related symptoms and its effect was greater than that of specific IgG4 (odds ratio 16.7 and 3.68, respectively). These indicate an IgE-mediated mechanism in most cases of work-related symptoms associated with MTHPA exposure. However, it cannot be denied that specific IgG4 is an anaphylactic antibody. Furthermore, IgE-sensitized workers in these plants displayed work-related symptoms despite the presence of specific IgG4. The frequency of positive specific IgG4 in continuously exposed workers was significantly (P < 0.02) higher in plant A than in plant B, reflecting the difference of the MTHPA levels between the two plants. In plant A, the frequency of positive specific IgG4 was significantly (P < 0.002) higher in continuously exposed workers than in intermittently exposed workers. Multiple regression analysis also confirmed that plant and exposure style contributed significantly (P < 0.01) to the determination of specific IgG4 levels. CONCLUSION: These results suggest that work-related eye and nasal symptoms are likely to be IgE-mediated, and that specific IgG4 may reflect the intensity of MTHPA exposure and may not act as a blocking antibody.

Histamine and tryptase in nasal lavage fluid following challenge with methacholine and allergen.

BACKGROUND: The level of histamine in nasal lavage fluid has been used as an index of mast cell/basophil activation in a number of studies. Obviously, such an index can only be valid if changes in the secretory activity of nasal glands do not affect the level of histamine in lavage fluid (i.e. hypersecretion, without a simultaneous activation of mast cells/basophils in the nasal mucosa, must not increase the level of histamine). OBJECTIVES: To asses the effect of nasal hypersecretion on histamine levels in lavage fluid. METHODS: Nasal challenges were performed with methacholine and allergen in grass pollen-allergic patients and non-allergic controls. Nasal lavage fluid was collected before and repeatedly for nine hours after nasal challenge, and the level of histamine was compared with that of a specific mast cell-derived enzyme, tryptase. In addition, the effect of methacholine on basophils was examined in vitro. RESULTS: Allergen challenge of allergic patients produced sneezing and a significant increase in histamine and tryptase levels, whereas challenge of non-allergic subjects produced no such response. Interestingly, challenge with methacholine also induced a significant increase in histamine levels. This increase was seen in both allergic and non-allergic subjects and it was not associated with any sneezing or increase in tryptase levels, indicating that mast cells were not activated. Furthermore, stimulation of basophils with methacholine did not induce any histamine release in vitro. CONCLUSIONS: Apparently, there exists a pool of histamine in the human nose that can be transferred to lavage fluid during glandular hypersecretion. The source of this histamine is yet to be identified. As the level of histamine seems to be affected by the secretory activity of nasal glands, we question the use of this single mediator as an index of mast cell/basophil activation in nasal lavage studies.