Repeated aerosol allergen exposure suppresses inflammation in B-cell-deficient mice with established allergic asthma

BACKGROUND: Repeated allergen administration is a well-established therapeutic strategy for desensitizing patients with allergic disease. Similarly, repeated inhalation of antigen by mice with established allergen-induced asthma suppresses allergic inflammation. The mechanisms underlying antigen-dependent suppression of allergic immune responses remain unknown. In previous studies, we found that repeated aerosol antigen challenges in sensitized mice reduced eosinophils while increasing plasma cells and antibody in the lungs. We sought to test whether plasma cells and antibody played a role in suppression of allergic disease. METHODS: We primed wild-type and B-cell-deficient (microMT) mice with 25 microg ovalbumin (OVA) precipitated in alum on days 0 and 5, nebulized weekly with 1% OVA, 1 h, twice daily, for up to 6 weeks, and assessed lung inflammation, mucus hypersecretion, and IgE/IgG1. RESULTS: Kinetic studies revealed that initial aerosol exposure induced high numbers of eosinophils, lymphocytes, and macrophages within lung infiltrates and increased mucus production in wild-type mice. After 3-4 weeks of antigen exposure, eosinophils diminished while lymphocytes, plasma cells, and macrophages and mucus hypersecretion increased. However, by 6 weeks, lung inflammation and mucus hypersecretion were dramatically reduced. In contrast, repeated aerosol challenges maintained OVA-specific IgG1 and IgE production. Repeated aerosol antigen challenges in microMT mice resulted in reduced lung inflammation and mucus hypersecretion and the development of smooth muscle hypertrophy of the pulmonary microvasculature. CONCLUSIONS: B cells and antibody do not appear to play a role in antigen-dependent suppression of allergic responses in mice.     

Capsaicin and histamine antagonist-sensitive mechanisms in the immediate allergic reaction of pig airways

The airway vascular and bronchial responses were studied in pigs sensitized with Ascaris suum. Ascaris, histamine (H) and capsaicin aerosol all induced a clear-cut increase in blood flow in the nasal, laryngeal and bronchial circulation with a decrease in vascular resistance of 20-40%. When delivered to the lung both ascaris and histamine, but not capsaicin, caused pulmonary airflow obstruction with increase in resistance and a fall in dynamic compliance of 40-70%. After pretreatment of pigs with a combination of the H1- and H2-receptor antagonists terfenadine and cimetidine, the vascular and bronchial responses were strongly reduced to both histamine (by greater than 77%) and ascaris (by greater than 58%), but not to capsaicin aerosol. The bronchoconstriction to histamine was found to be mediated by H1-receptors only, while both H1- and H2-antagonists were necessary to block the vasodilatory response, with H2-receptors being more important in the bronchial circulation and H1-receptors being more important in the laryngeal and nasal circulation. Furthermore, when pigs were pretreated with capsaicin systemically 2 days before the experiment, the vasodilation was decreased upon capsaicin (by 80%), ascaris (by greater than 40%) and histamine (by greater than 50%) aerosol challenge. When histamine was administered intravenously the desensitizing effect of capsaicin pretreatment was much less pronounced. The effect of capsaicin desensitization on the pulmonary obstruction upon ascaris and histamine challenge was limited to a 60% reduction of the fall in dynamic compliance and a delayed peak in resistance upon ascaris challenge. We conclude that histamine is one of the main vasodilatory mediators released upon allergen challenge at three different levels of the pig airways. A considerable part of the histamine effect is indirect and probably due to activation of capsaicin-sensitive sensory nerves.     

Effects of beta adrenergic blockade on histamine and prostaglandin-F2 alpha responsiveness in the dog

To examine whether either the degree of existing beta adrenergic tone or the magnitude of beta adrenergic response during bronchoconstriction might account for the differences that exist between dogs in their pulmonary responsiveness to aerosol challenge with bronchoconstrictor agents, dose-response curves were performed in a group of dogs to either histamine or prostaglandin-F2 alpha, both before beta blockade with propranolol. Beta blocked had no significant effect on control values of dynamic compliance (Cdyn) or resistance of the lung (RL) or on pulmonary responsiveness to prostaglandin f2 alpha. Although propranolol did not have a significant effect on aerosol responsiveness to histamine for the group of dogs taken together, those dogs initially least responsive to aerosol histamine did become more responsive after beta blockade. This effect of beta blockade was statistically significant only for Cdyn and not for RL, suggesting enhancement of peripheral airway effects. We conclude that a beta adrenergic mechanism may contribute to the range of responsiveness found among dogs in their pulmonary responsiveness to histamine but that other as yet undefined factors must also contribute to the differences that exist among dogs in their pulmonary responsiveness to bronchoconstrictor agents.     

Effects of combined receptor antagonists of leukotriene D4 (LTD4) and platelet-activating factor (PAF) on rhesus airway responses to LTD4, PAF and antigen

Rhesus monkeys with IgE-mediated asthmatic-type responses to Ascaris suum antigen were pretreated with a combination of 2 receptor antagonists to leukotriene D4 (LTD4) and platelet-activating factor (PAF). This combination of anti-LTD4 and anti-PAF was shown to inhibit airway responses to either LTD4 or PAF in separate experiments in these Ascaris airway-reactive animals. When the same combination of LTD4 and PAF receptor antagonists was used to pretreat the same animal prior to aerosol challenge with Ascaris antigen we could not demonstrate inhibition of the antigen-induced airway response. Thus, combined receptor blockade for LTD4 and PAF did not alter IgE-mediated acute airway responses to antigen in this species. We review the current status of rhesus asthma and LTD4 and PAF receptor antagonist activity in this model.     

Allergic asthma induced in rhesus monkeys by house dust mite (Dermatophagoides farinae)

To establish whether allergic asthma could be induced experimentally in a nonhuman primate using a common human allergen, three female rhesus monkeys (Macaca mulatta) were sensitized with house dust mite (Dermatophagoides farinae) allergen (HDMA) by subcutaneous injection, followed by four intranasal sensitizations, and exposure to allergen aerosol 3 hours per day, 3 days per week for up to 13 weeks. Before aerosol challenge, all three monkeys skin-tested positive for HDMA. During aerosol challenge with HDMA, sensitized monkeys exhibited cough and rapid shallow breathing and increased airway resistance, which was reversed by albuterol aerosol treatment. Compared to nonsensitized monkeys, there was a fourfold reduction in the dose of histamine aerosol necessary to produce a 150% increase in airway resistance in sensitized monkeys. After aerosol challenge, serum levels of histamine were elevated in sensitized monkeys. Sensitized monkeys exhibited increased levels of HDMA-specific IgE in serum, numbers of eosinophils and exfoliated cells within lavage, and elevated CD25 expression on circulating CD4(+) lymphocytes. Intrapulmonary bronchi of sensitized monkeys had focal mucus cell hyperplasia, interstitial infiltrates of eosinophils, and thickening of the basement membrane zone. We conclude that a model of allergic asthma can be induced in rhesus monkeys using a protocol consisting of subcutaneous injection, intranasal instillation, and aerosol challenge with HDMA.     

The modification by ketotifen of respiratory responses to histamine and antigen in guinea-pigs

Aerosolized solutions of histamine or ovalbumin were administered to control or ovalbumin-sensitized guinea-pigs. The time to onset of respiratory distress (preconvulsion time) during challenge with these agents was measured using a force-displacement transducer on the animal's back. The preconvulsion time for each guinea-pig was compared with and without ketotifen pretreatment. Ketotifen administered both by aerosol and intraperitoneal injection (i.p.) significantly protected (p<0.001) each guinea-pig from the effects of aerosol challenge with histamine. Ovalbumin-sensitized animals were also protected from the effects of antigen aerosol challenge by ketotifen pretreatment. Sodium cromoglycate (DSCG), administered as an aerosol, did not protect sensitized animals from ovalbumin challenge. The Konzett-Rössler technique was used to measure the response to the intravenous injection (i.v.) of histamine in anaesthetized artificially ventilated guinea-pigs. Ketotifen was three times more potent than mepyramine in inhibiting the histamine-induced increase in air overflow volume.     

The effect of a bradykinin B2 receptor antagonist, NPC-567, on allergen-induced airway responses in a porcine model

OBJECTIVE AND DESIGN: In order to assess the effect of selective blocking of the bradykinin (BK) B2 receptor in allergic airway reactions, the BK B2 receptor antagonist NPC-567 was administered to sensitized pigs before allergen challenge. MATERIAL: Fourteen specific pathogen-free pigs sensitized to Ascaris suum were used. TREATMENT: NPC-567 (2.5 mg, in 1 ml saline) was delivered as an aerosol twice to six pigs. METHODS: Ascaris antigen (in 2 ml saline) was given as an aerosol to all pigs and airway mechanics were monitored for 8 h. NPC-567 (2.5 mg) was given at t = -30 min (in 1ml saline) and mixed with the antigen at t = 0 to six pigs. RESULTS: Allergen challenge caused an acute reaction with a rapid, significant increase in airways resistance from 4.1 +/- 0.5 cm H2O/l/s to a maximum of 16.2 +/- 3.0 cm H2O/l/s in the control pigs. In the NPC-567-treated pigs, the resistance only increased from 2.9 +/- 0.3 cm H2O/l/s to 6.5 +/- 0.9 cm H2O/l/s (p<0.005 compared to controls). There was also a higher reduction in dynamic lung compliance in the controls than in the treated animals upon allergen challenge. The histamine concentration in urine in the control pigs was markedly elevated after allergen challenge peaking at 15-30 min. This release was inhibited in the NPC-567-treated pigs. CONCLUSIONS: The BK B2 receptor antagonist NPC-567 seems to be effective in inhibiting the acute response to allergen in the pig airways, possibly due to inhibition of mast cell activation via indirect mechanisms. The late obstructive response was reduced as well, probably as a consequence of the reduced mediator release in the acute reaction.     

Vascular permeability and airway narrowing during late asthmatic response in dogs treated with Metopirone.

Recently, we have developed an animal model of late asthmatic response (LAR) by treating naturally sensitized dogs to Ascaris suum antigen with the cortisol-synthesizing inhibitor, Metopirone. By using this animal model, we examined the contribution of edema in the airway wall to the development of LAR. To study whether airway microvascular leakage is increased in association with LAR, we performed antigen challenge in dogs treated with Metopirone. We measured the amount of extravasated Evans blue (EB) dye from the esophagus, trachea, and large and small bronchi 8 hours after the antigen challenge in dogs demonstrating immediate asthmatic response alone (IAR) and in dogs demonstrating both IAR and LAR. Airway responses to A. suum antigen were assessed by changes in respiratory resistance measured with the force oscillation technique at 3 Hz. EB dye extravasation did not increase significantly from that of control in any tissues in IAR (P greater than 0.10), but in LAR, it increased significantly from that of control (p less than 0.01) and IAR (p less than 0.05) in large and small bronchi. Histologic assessment of vascular permeability revealed that Monastral blue-labeled leaking vessels were only in sections from LAR, and leaking vessels were limited to small vessels (10 to 25 microns) in the trachea, large (diameter, greater than 5 mm) and small bronchi (2 to 4 mm in diameter), and bronchiole. The permeability index defined as the ratio of area of small vessels labeled with Monastral blue to that of the total small vessels in the walls was highest in the small bronchi. LAR significantly increased submucosal thickness of the small bronchi (p less than 0.05) compared with that in IAR. Both EB dye extravasation and permeability index in large and small bronchi also significantly increased during IAR within 3 minutes after the antigen challenge (p less than 0.05), but IAR did not alter the submucosal thickness of the small bronchi. These results imply that the increase in vascular permeability and submucosal thickness, especially in small bronchi, may be an important factor in the pathogenesis of LAR.     

Hypersensitivity to histamine and systemic anaphylaxis in mice with pharmacologic beta adrenergic blockade: protection by nucleotides.

The effects of exogenous nucleotides on the histamine hypersensitivity of pharmacologically beta-blocked mice were investigated. Female HLA-SW (ICR) mice, 27-29 gm, were injected intraperitoneally with 20 to 100 mug of propranolol 45 min before intraperitoneal challenge with 1 mg histamine. These animals had a mortality which averaged approximately 80%. At various time intervals before histamine, doses of from 0.5 to 12 mumoles of nucleotides were administered intravenously. Noncyclic nucleotides, adenosine, adenosine 5'-monophosphate (AMP), and guanosine 5'-monophosphate (GMP) showed clear, dose-response protection against histamine death of propranolol-treated mice when they were given 45 to 90 min before histamine. Cyclic AMP showed significant protection only when it was given at a dose of 8 mumoles 45 to 90 min before histamine, and lower or higher doses gave equivocal or no protection. Cyclic GMP WAS Not protective at any dose tested. Propranolol treatment also produced enhanced sensitivity to passive systemic anaphylaxis. Mice were passively sensitized by intraperitoneal injection of mouse anti-egg albumin antibody 6 hr before intravenous challenge with 0.5 mg egg albumin. The mortality from anaphylaxis in the group treated with 20 mug propranolol 45 min before antigen challenge increased to 83%, while that of the group not given propranolol was only 10%. Nucleotides were given intravenously 45 min before antigen challenge. The nucleotides that protected mice from death due to histamine challenge also protected them from death due to systemic anaphylaxis. These protective nucleotides were the same nucleotides that had been reported previously to be protective against Bordetella pertussis-induced hypersensitivity to histamine and anaphylaxis.     

The tryptase inhibitor APC-366 reduces the acute airway response to allergen in pigs sensitized to Ascaris suum

BACKGROUND: Tryptase is a mast cell serine protease that is released during mast cell degranulation. It has been implicated as an important enzyme in the pathophysiology of asthma, but its role in this disease is not fully elucidated. OBJECTIVE: In this study, we investigated the effects of a tryptase inhibitor, APC-366, on the acute allergic airway reaction in specific pathogen-free pigs sensitized to the antigen Ascaris suum. METHODS: APC-366 (5 mg in 1 mL of water, each dose) was given as an aerosol to seven pigs two times (t); at t = - 60 min and t = - 15 min Control pigs received water. Ascaris antigen (in 2 mL saline) was nebulized to the airways over approximately 5 min at t = 0. All aerosols were generated with an ultrasonic nebulizer. RESULTS: The allergen challenge caused an acute reaction with a significant increase in airway resistance (R(aw)) in the control pigs from 3.3 +/- 0.6 cmH20/l/s to 10.2 +/- 2.3 cmH20/l/s, while in the APC-366-treated pigs, the R(aw) increased from 2.6 +/- 0.4 cmH20/l/s to 4.5 +/- 0.7 cmH20/l/s (P < 0.05 compared to controls). The dynamic lung compliance (C(dyn)) decreased significantly in the control pigs, but not in the APC-366-treated animals. The histamine concentration in urine in the control pigs was elevated immediately after allergen challenge, while this release was markedly reduced in the APC-366-treated pigs. CONCLUSION: The tryptase inhibitor APC-366 reduces the acute airway response to allergen significantly. There is also a reduced elevation in urine histamine concentration after challenge in the treated pigs, compared to controls. These results indicate that inhibition of mast cell tryptase might be a useful anti-allergic treatment in asthma.     

Cysteinyl leukotrienes in porcine acute allergic airway reactions: bronchial and vascular effects

OBJECTIVE AND DESIGN: The role of cysteinyl leukotrienes (cysLTs) in the acute allergic airway reaction in the pig was investigated, with focus on the effects on the bronchial circulation, and compared with histamine-induced effects. MATERIAL: 31 barrier-bred pigs were used, of which 24 pigs were actively-sensitised to Ascaris suum. METHODS: Leukotriene D(4) (LTD(4)) and histamine were injected intravenously (i.v.) and given as an aerosol to non-sensitised pigs. Seventeen animals, sensitised to Ascaris suum, were challenged with Ascaris antigen aerosol. The effect of MK-571, a CysLT(1)-receptor antagonist, on LTD(4)- and allergen-induced responses were investigated. RESULTS: LTD(4) (2 nmol/kg) i.v. injection increased the airways resistance (R(aw)) by 46 +/- 20% and reduced bronchial vascular conductance (BVC) by 38 +/- 2%. Both these effects were blocked by MK-571 (0.1 mg/kg i.v.). Histamine injections (i.v.) in equimolar doses caused similar dose-dependent increases in R(aw), (22 +/- 7%) but induced vasodilatation and an increase in BVC (22 +/- 8%). Aerosolised LTD(4) (4 nmol/kg) caused a decrease in BVC but did not affect R(aw). In sensitised pigs, challenge with Ascaris aerosol led to an acute increase in Raw (198 +/- 57%) and increase in BVC (62 +/- 35%). MK-571 (0.5 mg/kg i.v.) pre-treatment did not significantly affect these responses (n = 9). CONCLUSIONS: LTD(4) causes constriction of the pig bronchi and of the bronchial circulation via activation of the CysLT(1) receptor and may counteract histamine-induced vasodilatory effects. However, in the allergen-induced acute airway response in the pig, cysLTs do not seem to be important bronchoconstrictive mediators.     

Diphenhydramine blocks the leukotriene-C4 enhanced mucus secretion in canine tracheain vivo

Leukotrienes (C₄, D₄) have been shown to enhance mucus seeretion in both isolated human airway tissue and intact canine tracheain vivo. They also have been implicated as putative mediators in several airways diseases. In previous canine studies the mucus enhancing effect of leukotriene-C₄ was blocked by atropine, FLP 55,712, and hexamethonium but not by cutting the superior laryngeal and vagus nerves. We anesthetized mongrel dogs with chloralose (100 mg/kg) and urethane (500 mg/kg) and ventilated them on a pump. To visualize the secretions from submucosal glands, we exposed the mucosa of the upper trachea and coated its surface with powdered tantalum. Seeretions from the glands formed elevation in the tantalum layer (hillocks) with time: the number of tracheal hillocks (an index of mucus secretion) was measured at one or more of the four time points on six dogs after each treatment of the treatment sequence: no LTC₄, LTC₄, no LTC₄+ blocker, and LTC₄+ blocker. The potential blocker was diphenhydramine, an H₁ antagonist for histamine. LTC₄ was injected into the cranial thyroid artery which directly feeds the tracheal segment. We observed hillocks through a dissecting microscope, and the number of hillocks per 1.2 cm² were counted for a 1–4 min interval. In 6 dogs with 12 responses, LTC₄ (10 μg) gave a positive response that was significantly different from control (p<0.01–0.05) at 2–4 min. Diphenhydramine (n=6), 0.5 mg/kg, a dose which blocked a histamine challenge without blocking an acetylcholine challenge of secretion, gave a statistically significant (p<0.01–0.05) reduction in mucus secretion at 1–4 min. These results support the conclusion that leukotriene C₄ induces mucus secretion in dogs that is blocked by prior diphenhydramine administration. This would indicate histamine has a role, but as yet an unknown mechanism in the action of leukotriene-C₄ in enhancing mucus.     

In vivo effect of cimetidine on canine pulmonary responsiveness to aerosol histamine

A series of experiments were designed to discover whether pulmonary histamine H₂ receptors might be of physiologic importance in vivo in the dog. Dose-response curves were performed to aerosol histamine in 11 dogs both before and 1 hr after H₂ receptor blockade with cimetidine (1 mg/kg as a rapid intravenous infusion). Cimetidine had no significant effect on control values of dynamic compliance or resistance of the lung. In the 11 dogs tested H₂ receptor antagonism significantly potentiated (p < 0.05) the animals' pulmonary responsiveness to aerosol histamine. The potentiation of histamine constrictor effects produced by cimetidine were more marked on those dogs initially least responsive to aerosol histamine (p < 0.01). We have found evidence for the presence of inhibitory H₂ receptors in canine airways and for the distribution of these receptors among dogs, explaining in part the previously described differences among dogs in the pulmonary responsiveness to aerosol histamine.     

Airway response to leukotriene D4 in rhesus monkeys

We studied the effect of leukotriene D4(LTD4) given by aerosol challenge on asthmatic and normal monkeys. The response to LTD4 occurred within 2 min., was prolonged at higher concentrations, was reversed by epinephrine, and more closely resembled an antigen response than a histamine response. Since LTD4 concentrations of 30-100 micrograms/ml produced a response similar to 2-20 mg/ml of histamine, the LTD4 was 300-900 times as potent as histamine on a molar basis. Thus, LTD4, which appears to reproduce an antigen-induced response in rhesus monkeys, may be a mediator of allergic asthma in these animals.     

Effect of an inhaled glucocorticosteroid (budesonide) on post-antigen induced increases in airway responsiveness

We examined the effects of an inhaled glucocorticosteroid, budesonide, on antigen-induced early and late bronchial responses and the development 24 h after challenge of increased airway responsiveness to carbachol in allergic sheep. Six allergic sheep were used for this study and, on occasions separated by at least three weeks, they were treated: with placebo (treatment 1); 16 h and 20 min prior to antigen challenge with budesonide (treatment 2); 16 h and 20 min prior to and 8 h after antigen challenge with budesonide (treatment 3); or 16 h and 1 h prior to and 8 h after antigen challenge with budesonide (treatment 4). Airway responsiveness to carbachol was determined prior to and 24 h after antigen challenge by measuring specific lung resistance (sRL) after administering increasing doses of carbachol aerosol (0.5, 1 and 2.5% w/v) and determining the concentration of carbachol needed to increase sRL 150% over baseline (PC150). Placebo treatment did not affect the early or late increases in sRL after airway challenge with Ascaris suum antigen; 24 h after challenge, airway responsiveness to carbachol increased (p less than 0.05); at this time, PC150 was (mean +/- SEM) 0.88 +/- 0.15% as compared to 1.56 +/- 0.26% before challenge. Both treatments 2 and 3 blunted the early response to antigen and blocked the late response, but treatment 2 did not modify the antigen-induced increase in airway responsiveness, whereas treatment 3 did. Treatment 4 blocked both antigen-induced responses and was effective in blunting the increased airway responsiveness. These results suggest that antigen-induced increases in airway responsiveness: occur 24 h after a challenge in allergic sheep with early and late responses; can be blunted by budesonide; and are not dependent on the late response.     

Parainfluenza virus type-3 infection attenuates the respiratory effects of antigen challenge in sensitized guinea pigs

Respiratory viral infections not only exacerbate asthma symptoms but may also be important in the pathogenesis of the disease. We therefore explored the effects of respiratory viral infection on the respiratory response of sensitized guinea pigs to antigen challenge. Lung tissue obtained from uninfected guinea pigs sensitized to ovalbumin aerosol released histamine upon incubation with the antigenin vitro. After antigen challengein vivo, sensitized animals had significantly greater numbers of eosinophils in their bronchoalveolar lavage fluid than did nonsensitized animals and exhibited airway hyperresponsiveness to methacholine aerosol. When ovalbumin sensitization was initiated 7 days after inoculation with parainfluenza virus type-3 (PI-3), antigen challenge elicited little histamine release from infected lung tissuein vitro. Likewise, subsequent to antigen challengein vivo, animals failed to exhibit airway hyperresponsiveness or an increased eosinophil population in bronchoalveolar lavage fluid. Similar effects were observed when sensitization was begun 19 days after PI-3 virus inoculation. The mechanism(s) responsible for the attenuated responses to antigen in PI-3 infected animals are unknown but may involve virus-induced effects on immune cells.     

The qualitative evaluation of airway responses to immunologic and pharmacologic stimuli in rhesus monkeys.

This report describes the current status of a colony of rhesus monkeys composed of a group of animals with consistent asthmatic responses to Ascaris antigen challenge, a variable group and a negative group. The cumulative experience with the consistent group of 5 animals totals 144 months of observation with 86 positive respiratory responses to 86 aerosol challenges. Further studies compare rhesus airway responses to Ascaris antigen, anti-IgE, histamine, prostaglandin (PG)F2alpha, carbocholine, and physostigmine. We report that two abnormalities of pulmonary function which occur as a result of aerosol challenge, an increase in breathing frequency (f) and pulmonary resistance (PR), differ in degree of abnormality and time of onset following challenge with different agonists. These results indicate that the f and PR changes in response to these agonists are controlled by different physiologic mechanisms in rhesus monkeys. We suggest that the f changes may occur as a result of reflex afferent vagal stimulation and PR changes as a result of direct effect on smooth muscle receptors. The effect of histamine and PGF2alpha on the airway of rhesus monkeys more closely simulates the airway response to immunologic stimuli than does the effect of cholinergic type agonists.     

Larval exoantigens from ascarid nematodes are potent inducers of histamine release from human blood basophils

Histamine release (HR) from washed human blood cells after challenge with the excretory-secretory antigens (ES) of the parasitic nematodes Toxocara canis and Ascaris suum was studied, employing a recently developed microfibre-based assay combined with hyperosmolar release media for maximal sensitivity. Blood samples were obtained from 30 patients suspected of parasite infection and 11 healthy volunteers serving as controls. Specific antibodies of IgE, IgG1 and IgG4 subclasses were determined by ELISA. Virtually no HR could be provoked by ES in the 11 controls. In contrast, HR was seen in 16 patients after challenge with T. canis ES and in 11 patients with A. suum ES. In the majority of these, HR was detectable after challenge with ES protein concentrations of less than 1 ng/ml, and the maximal HR obtained with ES was greater than that seen with optimal concentrations of anti-IgE. The HR after ES antigen challenge correlated with the amount of specific IgE in patient plasma, and coincided with the presence of specific IgG1 and IgG4.     

Mucin is produced by clara cells in the proximal airways of antigen-challenged mice

Airway mucus hypersecretion is a prominent feature of many obstructive lung diseases. We thus determined the ontogeny and exocytic phenotype of mouse airway mucous cells. In naive mice, ciliated (approximately 40%) and nonciliated (approximately 60%) epithelial cells line the airways, and > 95% of the nonciliated cells are Clara cells that contain Clara cell secretory protein (CCSP). Mucous cells comprise < 5% of the nonciliated cells. After sensitization and a single aerosol antigen challenge, alcian blue-periodic acid Schiff's positive mucous cell numbers increase dramatically, appearing 6 h after challenge (21% of nonciliated/nonbasal cells), peaking from Days 1-7 (99%), and persisting at Day 28 (65%). Throughout the induction and resolution of mucous metaplasia, ciliated and Clara cell numbers identified immunohistochemically change only slightly. Intracellular mucin content peaks at Day 7, and mucin expression is limited specifically to a Clara cell subset in airway generations 2-4 that continue to express CCSP. Functionally, Clara cells are secretory cells that express the regulated exocytic marker Rab3D and, in antigen-challenged mice, rapidly secrete mucin in response to inhaled ATP in a dose-dependent manner. Thus, Clara cells show great plasticity in structure and secretory products, yet have molecular and functional continuity in their identity as specialized apical secretory cells.     

Immunologic release of histamine from dog lung: comparison of in vivo and in vitro responses in the same animal

The purpose of this study was to compare, for the first time, antigen-induced histamine release from the lung in the same natively allergic dogs both in vitro and in vivo. In six dogs, maximal antigen-induced histamine release from the lung correlated closely in vitro and in vivo (r = 0.94), although it varied widely between dogs (0% to 75.5% of total tissue histamine content); similarly, the antigen concentration to produce 50% of maximal histamine release varied sixfold between dogs (40 micrograms/ml to 250 micrograms/ml). In each of five other dogs, terbutaline sulfate administered intravenously caused a dose-dependent inhibition of antigen-induced histamine release from lung fragments in vitro: the maximal inhibition produced by 1 mg/kg was 60 +/- 4.5% (mean +/- SEM). In these same dogs, 10(-5)M terbutaline incubated with lung fragments in vitro caused inhibition of antigen-induced histamine release comparable to 1 mg/kg terbutaline in vivo. Increasing the dose of terbutaline in vitro produced maximal inhibition at 10(-4)M with no greater effect of the drug at 10(-3)M (71.4 +/- 3.8% inhibition). In both experimental situations propranolol caused a dose-dependent inhibition of beta-adrenergic modulation of Ascaris-induced release of histamine. This result supports the conclusion that terbutaline produced its effects by actions mediated by beta-adrenergic receptors on pulmonary mast cells. This experimental approach provides a suitable preparation in which to estimate the effective dose of agonists that modulate antigen-induced mast cell function in vivo.