Antigen Provocation Research Articles

DIFFERENCE IN BRONCHOPROTECTIVE EFFECTS OF BRONCHODILATORS ON POSTALLERGIC PROPRANOLOL-INDUCED BRONCHOCONSTRICTION

Administration of propranolol provokes bronchoconstriction only in asthmatic patients. It is unknown whether bronchodilator therapy can prevent the propranolol-induced bronchoconstriction (PIB). We previously reported an animal model of PIB in which bronchoconstriction is caused by propranolol when inhaled 20 minutes after an antigen provocation in passively sensitized guinea pigs. Our goal was to evaluate the bronchoprotective effects of bronchodilators on the PIB in our animal model. Propranolol was inhaled 20 minutes after an antigen challenge in passively sensitized, anesthetized, and artifically ventilated guinea pigs. Atropine (5mg/kg) and equipotent doses of salbutamol (0.6ug/kg) and aminophylline (25mg/kg), which were determined by the dose-response curves for inhibition of histamine induced bronchoconstriction, were intravenously administered 5 minutes before the propranolol inhalation. Treatment of the animals with 25 mg/kg of aminophylline, but not with 0.6ug/kg of salbutamol or 5mg/kg of atropine, significantly prevented the PIB. These results show that our animal model is an experimental model of PIB which is resistant to beta2 -agonists or anticholinergics and suggest that amino-phylline may be useful to prevent and treat PIB resistant to beta2 -agonists.

IL-5-Producing T Cells that Induce Airway Eosinophilia and Hyperresponsiveness Are Suppressed by Dexamethasone and Cyclosporin A in Mice

We have recently demonstrated that airway eosinophilic inflammation can be transferred to unprimed mice by infusion of IL-5-producing T cell clones. In this study, we investigated the effects of dexamethasone and cyclosporin A on the airway eosinophilic inflammation in mice transferred with T cell clones. An ovalbumin-reactive T cell clone, KW29, produced IL-5 as well as IL-2 and IL-4 upon stimulation with relevant antigen. Dexamethasone and cyclosporin A dose-dependently suppressed the production of these cytokines in vitro. The number of eosinophils recovered in the bronchoalveolar lavage fluid and the airway responsiveness to acetylcholine were increased in KW29-transferred mice after antigen provocation. Both responses were dose-dependently suppressed by the administration of dexamethasone or cyclosporin A in vivo. We concluded that airway eosinophilic inflammation can be controlled by agents capable of downregulating IL-5 production in T cells.

Correlation between antigen-specific IL-2 response test and provocation test for egg allergy in atopic dermatitis.

The antigen-specific interleukin-2 response (AIR) test using lymphocytes is effective in searching for the antigen which causes allergic diseases and understanding their disease activity. The correlation between the raw egg oral provocation test and egg white antigen-specific interleukin-2 (IL-2) response test was investigated in 123 children with infantile atopic dermatitis and 13 children with bronchial asthma. Among the 83 who showed positive reactions to provocation, 75 also reacted positively to the AIR test (sensitivity, 90.4%), while among the 53 children who showed negative responses to antigen provocation, 45 produced negative responses to the AIR test (specificity, 84.9%). The specificity of egg white IgE RAST score and skin-prick test are 88.7 and 81.3% which are comparable to that of the AIR test. However, their sensitivity was low (38.6 and 66.7%). In the patterns of symptom developed in the provocation AIR displayed late and delayed type allergic responses in addition to the immediate type which RAST reflected. The RAST-negative group composed of 98 patients included 51 (52.0%) who exhibited positive reactions to the provocation test. Among these 44 responded positively to the AIR test (86.3%). The AIR test is effective for screening egg white antigen as part of the tests for antigens responsible for allergic diseases and as a test to ascertain the relevant antigens, and that the conditions that could not be diagnosed by RAST can be detected by the AIR test.

Evidence that cyclosporin A and dexamethasone inhibit allergic airway eosinophilic inflammation via suppression of interleukin-5 synthesis by T cells.

1. We have recently demonstrated that airway eosinophilic inflammation can be transferred to unprimed mice by infusing interleukin (IL)-5-producing T cell clones. Using that murine model, we performed this study to delineate the mechanism of cyclosporin A and dexamethasone to inhibit allergic airway eosinophilic inflammation. 2. The ovalbumin-reactive murine T cell clones, FJ17, produced IL-2, IL-4 and IL-5 upon stimulation with relevant antigen. In FJ17-transferred mice, messenger RNA (mRNA) of IL-2 and IL-5 expressed in the lungs, the number of eosinophils in bronchoalveolar lavage fluid (BALF) was increased and the bronchial responsiveness to acetylcholine was enhanced after antigen provocation. 3. Cyclosporin A (10, 100 ng ml(-1)) and dexamethasone (10, 100 ng ml(-1) suppressed the production of IL-5 as well as IL-2 and IL-4 by FJ17 in vitro. 4. Subcutaneously administered cyclosporin A (30 mg kg(-1)) and dexamethasone (10 mg kg(-1)) inhibited antigen-induced mRNA expression of IL-2 and IL-5, increase of BALF eosinophils and bronchial hyperresponsiveness of FJ17-transferred mice in vivo. The number of BALF eosinophils was correlated with the bronchial responsiveness to acetylcholine (r=0.672). 5. The results clearly indicated that the suppression of IL-5 synthesis by T cells is involved in the effects of cyclosporin A and dexamethasone to inhibit allergic airway eosinophilic inflammation.

PAF- and histamine-receptor antagonists lessen allergen-induced hearing impairment in guinea pigs

We have demonstrated degranulation of mast cells in the endolymphatic sac as well as an increase in audiological threshold shift in the experimental animal models following antigen provocation. Mast cells, however, release such chemical mediators as histamine, platelet activating factor (PAF), and leukotriene due to an antigen-antibody reaction on the cell surface. The aim of this study was to clarify the major chemical mediators resposible for hearing impairment in the animal models following antigen provocation. Guinea pigs were actively sensitized with DNP-Ascaris and provoked with an injection of DNP-BSA. A significant audiological threshold shift was observed at 1, 10, 24, and 72 h following challenge with allergen. The peak shift was at 10 h; all changes were reversed after 7 days. This threshold shift was abolished by prior injection of either a histamine- or PAF-receptor antagonist to allergen, but not of a leukotriene-receptor antagonist. Results suggest that histamine and PAF are involved in the hearing impairment induced by allergen exposure in the guinea pig.

1,5-Disubstituted indazol-3-ols with anti-inflammatory activity.

A series of new indazol-3-ol derivatives was synthesized. Some of these compounds exhibit interesting anti-inflammatory activities in various models of inflammation. 5-Methoxy-1-[quinoline-2-yl-methoxy)-benzyl]-1H-indazol-3-ol (27) strongly inhibits the oxidation of arachidonic acid to 5-hydroperoxyeicosatetraenoic acid catalyzed by 5-lipoxygenase (IC50 = 44 nM). 27 also inhibits the contraction of sensitized guinea pig tracheal segments (IC50 = 2.9 microM). In guinea pigs treated with 27 (1 mg/kg i.p.) 2 h before antigen provocation, there was a marked inhibition (47%) of the antigen-induced airway eosinophilia. After topical application of 1 microgram/ear 27 inhibits the arachidonic acid induced mouse ear edema (41%).

ヨード強化卵抽出画分のヒト肺切片からのヒスタミン，ＬＴ‐Ｃ４放出に及ぼす効果とヒト白血球由来アラキドン酸代謝酵素に及ぼす影響

The authors investigated anti-allergic and anti-inflammatory mechanisms in iodine enriched eggs. Both total and neutral lipid fractionation in iodine enriched eggs suppressed the histamine release in response to an antigen challenge of passively immunized lung mast cells in a dose dependent manner. LT-C4 production in antigen challenged atopic leukocytes was also suppressed by both total and neutral lipid fractionation. The suppressive mechanisms of iodine enriched eggs were investigated using leukocyte lysate as enzyme preparations of 5-lipoxygenase system. Neutral lipid fractionation did not inhibit LT-B4 production, ie., 5-lipoxygenase activity, but did inhibit LT C4 production, i.e., LT-C4 synthase activity. Polar lipid fractionation inhibited neither LTB4 production nor LT-C4. These results suggested that neutral lipid fractionation of iodine enriched eggs modulated histamine release in lung mast cells and LT-C4 production in leukocytes with antigen provocation. Furthermore, it was possible for neutral lipid fractionation to inhibit LT C4 synthase activity in leukocytes.

Immunohistological study of infiltrating cells in nasal mucosa and nasal lavage fluid of perennial allergic rhinitis

It is well known that EG2-positive cells, CD68-positive cells and other inflammatory cells significantly increase after antigen provocation in the nasal mucosa of an allergic patient. However, there are few reports of the immunohistological study if the infiltrating cells in nasal lavage fluid are not seen. In this study, the infiltrating cells in nasal mucosa as well as in nasal lavage fluid were immunohistologically examined by means of monoclonal antibodies 30 minutes after the antigen provocation. Seven patients with perennial allergic rhinitis were challenged by an antigen disk placed on one side of the inferior turbinates and each nasal cavity was irrigated separately 30 minutes after the antigen provocation. About seven days later, these patients were operated on and the nasal mucosa was removed 30 minutes after the antigen provocation. No marked change in CD4- and CD8 positive cells in the nasal mucosa and lavage fluid was found after provocation. On cytospin glass slides, there was a slight increase in the number of CD68 (P = 0.1), EG2 (P = 0.09), and neutrophil elastase positive (P = 0.2) cells. A significant increase in EG2-positive cells was also seen in the superficial layer of the lamina propria (P < 0.05) but not in the deep layer. CD22 positive cells were not seen on the cytospin glass slide, whereas many positive cells were observed in the deep layer of the lamina propria. These results indicate that EG2-positive cells participate strongly in the early phase of the allergic response after provocation in spite of the absence of significant changes in CD4- and CD8 positive cells. Immunohistological evaluation of nasal lavage is thought to be beneficial concerning the movement of each kind of cells. Each kind of cell is thought to fulfill the main physiological role in the epithelial layer or the lamina propria in early allergic inflammation.

Late airway obstruction and neutrophil infiltration in sensitized mice after antigen provocation were suppressed by selective and non-selective phosphodiesterase inhibitors

Suppression of antigen-induced late airway obstruction associated with neutrophilic inflammation by selective and non-selective phosphodiesterase (PDE) inhibitors was investigated in mice. Respiratory resistance (Rrs) increased in sensitized BDF1 mice 4-6 h after antigen provocation, whereas no obvious immediate reaction was observed. This reaction was associated with marked airway neutrophilia without significant infiltration of eosinophils. A selective PDE IV inhibitor, T-440 (10-30 mg/kg), and a non-selective PDE inhibitor, theophylline (10 mg/kg), significantly inhibited airway obstruction and neutrophilia when administered orally. An anti-allergic drug, ketotifen (1 mg/kg), caused slight inhibition of airway obstruction, whereas it did not affect airway neutrophilia. These results suggest that neutrophilic inflammation plays a role in the airway obstructive reaction and that PDE has a regulatory role in obstructive airway disease associated with airway inflammation.

Dysfunctional muscarinic M 2 autoreceptors in vagally induced bronchoconstriction of conscious guinea pigs after the early allergic reaction

We studied the function of autoinhibitory muscarinic M 2 receptors on vagal nerve endings in the airways of conscious, unrestrained, ovalbumin-sensitized guinea pigs after the early and late allergic reaction. For this purpose, the effects of the selective muscarinic M 2 receptor antagonist gallamine were examined on unilateral vagus nerve stimulation-induced bronchoconstriction, which was determined as an increase in basal respiration amplitude, measured as changes in pleural pressure. Under control conditions, i.e., before antigen challenge, a significant increase in the pleural pressure was found after inhalation of 0.1 mM and, even more pronounced, 1.0 mM gallamine, at medium stimulation frequencies (2–16 Hz), leading to a leftward shift of the frequency-response curve. After inhalation of 10 mM of gallamine, a complete reversal of the left-shift was observed and the frequency-response curve was depressed. However, 6 h after challenge with ovalbumin (i.e., after the early allergic reaction) no increase in nerve stimulation-induced bronchoconstriction by gallamine was found; a decrease in this bronchoconstriction was again observed with the highest concentration. At this moment, bronchial responsiveness to histamine was enhanced 4.5-fold compared to control, i.e., prior to antigen provocation. Both after the late allergic response (24 h after challenge; 1.6-fold histamine hyperresponsiveness) and 4 days after allergen challenge (normal histamine responsiveness) the gallamine-induced potentiation of the bronchoconstriction was restored, similar to the responses under control conditions. The results clearly demonstrate that prejunctional muscarinic M 2 receptors control bronchoconstriction in conscious, unrestrained guinea pigs in vivo. Furthermore, these autoinhibitory receptors appear to be completely dysfunctional after the early allergic phase, but their function is largely restored after the late phase. The results indicate that dysfunction of autoinhibitory muscarinic M 2 receptors might contribute to the strongly enhanced responsiveness to histamine after the early allergic response.

Interaction between nitric oxide and prostaglandin synthesis in the acute phase of allergic conjunctivitis

Both nitric oxide and prostaglandins induce vasodilatation which is an important feature of local inflammation. The purpose of the study described here was to investigate a possible interaction between these two types of mediators in an experimental model of allergic conjunctivitis. A conjunctival allergic reaction was induced with antigen in sensitized guinea pigs. Conjunctival vascular permeability changes were evaluated with the prophylactic use of an inhibitor of nitric oxide synthase (L-NAME) and a cycloxygenase inhibitor (indomethacin). To study a possible interaction between nitric oxide and prostaglandin synthesis in the acute phase of allergic conjunctivitis, the levels of nitrite and PGE 2 were determined in lavage fluid. The prophylactic use of L-NAME on the formation of conjunctival edema in response to topical PGD 2 administration was studied by measurement of albumin levels in lavage fluid. Both nitric oxide and PGE 2 are synthesized in response to antigen provocation and after histamine administration. Nitric oxide and PGE 2 are produced simultaneously in the conjunctiva and they showed identical synthesis profiles in response to antigen provocation. Pretreatment with L-NAME inhibited the synthesis of PGE 2 whereas exogenous administration of nitric oxide increased the level of PGE 2 in lavage fluid. Prophylactic treatment with L-NAME significantly inhibited the PGD 2 induced albumin extravasation. Nitric oxide seems to play an important role in the acute phase of allergic conjunctivitis it may stimulate PGE 2 production and acts as a secondary mediator in PGD 2 and histamine induced conjunctival edema.

Origin of late phase histamine release

The early response to antigen precedes the onset of a chronic inflammatory response that includes the late reaction, defined as the recurrence of symptoms and mediator release hours later. We hypothesized that during the late-phase nasal response to antigen provocation, released histamine originates from basophils, on the basis of the pattern of mediator release. ~ We subsequently showed the presence of basophils in the late reaction 2 but could not exclude mast cells as a source of histamine release. With the development of assays to measure tryptase, a sensitive and specific marker of mast cell degranulation, and 9c~,1113 PGF2, the major metabolite of prostaglandin (PG) D2, it became possible to exclude the mast cell as the source of histamine release. METHODS Study design Twe]ve volunteers who were free of symptoms but had a history of ragweed- or grass-induced allergic rhinitis, a positive intradermal skin test result, and a positive early response to nasal challenge were selected. The Internal Review Board of the Johns Hopkins Medical Institutions gave approval for the study, and each patient gave informed consent. Nasal challenges During the laboratory visit, the subjects underwent a nasal challenge with a relevant antigen extract5 The recovered fluid from the lavage was processed immediately for prostanoids, and the remainder was stored on ice until the completion of the experiment. After centrifuging, the supernatants obtained were processed for the

The role of interleukin-5 (IL-5) in allergic airway hyperresponsiveness in mice.

In order to investigate the role of IL-5 in allergic airway inflammation and hyperresponsiveness, the effects of rat anti-IL-5 monoclonal antibody (NC-17), recombinant soluble murine IL-5 receptor, and some immunosuppressors were studied in mice model. Three inhalations of an antigen by actively sensitized animals resulted in an increase in airway reactivity to acetylcholine. Twenty-four hours after the final inhalation, the number of leukocytes (mononuclear cells and eosinophils) and the amount of IL-4 and IL-5 in bronchoalveolar lavage fluid (BALF) increased significantly. NC-17 and soluble IL-5 receptor inhibited the antigen-induced increase of eosinophils with little effect on bronchial hyperreactivity. Cyclosporin A, FK-506, and cyclophosphamide clearly inhibited the antigen-induced increase of IL-5 and eosinophils in BALF. Airway hyperreactivity is inhibited by cyclosporine A and FK-506 but not by cyclophosphamide. Furthermore, to investigate the role of mast cells in the onset of allergic airway hyperreactivity, we have examined the effect of repeated antigen provocation in WBB6F1-W/Wv mice (W/Wv), mast-cell-deficient mice. Whereas significant elevation of IL-5 level and the number of eosinophils on BALF was observed, airway reactivity to acetylcholine was not changed at all. These results indicate that IL-5 may play an important role for the antigen-induced eosinophilia in BALF but not in airway hyperresponsiveness in mice.

Effect of the 21-aminosteroid U-74006F on antigen-induced bronchoconstriction and bronchoalveolar eosinophilia in allergic sheep.

U-74006F, a non-glucocorticoid 21-aminosteroid, has been developed as an inhibitor of iron-dependent lipid peroxidation. This class of compounds has been shown to prevent antigen-induced eosinophil accumulation in the lungs. In this study, Ascaris-sensitive, "dual-respondent" sheep (showing both immediate (IAR) and late (LAR) asthmatic response) (n = 6) were used to assess the effect of U-74006F on antigen-induced bronchoconstriction and airway inflammation and reactivity 8 h after antigen challenge. Antigen provocation induced dual-phase bronchoconstriction, bronchoalveolar eosinophilia and airway hyperreactivity (AHR) to methacholine. Throughout the experiment, intravenous administration of the drug significantly reduced the IAR and inhibited the LAR along with the inhibition of eosinophil influx, but did not inhibit the increase in airway reactivity observed 8 h after antigen challenge. Post-antigen challenge treatment with U-74006 from 3 h after antigen challenge also significantly reduced the LAR and bronchoalveolar eosinophilia, although the degree of inhibitory effect was milder. The development of the LAR appeared to be dependent on eosinophil recruitment into the lungs. These findings suggest that lipid peroxidation is involved in antigen-induced bronchoconstriction and eosinophil recruitment into the lungs, and that the inhibitor U-74006F may be an effective drug for the treatment of bronchoconstriction and airway inflammation characterized by eosinophil infiltration in asthmatics.

Unilateral nasal allergen challenge leads to bilateral release of prostaglandin D2

Multiple mediators including prostaglandin D2 and leukotriene B4 have been shown to increase in nasal secretions during the early response to nasal challenge with antigen. Our objective was to investigate the time course of prostanoid and leukotriene B4 release into nasal secretions on both the ipsilateral and contralateral side after a unilateral nasal allergen challenge. We performed a controlled, randomized trial. Six volunteers were challenged unilaterally with antigen or diluent in a randomized order and discs were used to collect nasal secretions from both nostrils at 2 min intervals for 20 min after the challenge. Prostanoids and leukotriene B4 (LTB4) in recovered nasal secretions were measured by combined capillary gas chromatography-negative ion chemical ionization mass spectrometry (GC/MS). Nasal allergen challenge resulted in a significant and immediate increase in symptoms and sneezing. PGD2 was significantly elevated above diluent values (0.6 +/- 0.6 pg) 30 s after removal of the allergen disc (P < 0.05), reached its peak (423.2 +/- 182.4 pg) at 2 min and then slowly decreased. PGD2 also increased on the contralateral side after unilateral allergen challenge, reaching peak values about six times lower than on the ipsilateral side (70.8 +/- 21.7 pg at 6 min). Levels of 9a, 11b-PGF2 after antigen provocation became significantly higher than after diluent (0 +/- 0 pg) on the ipsilateral side at 2 min (17.2 +/- 5.9 pg), and reached peak levels at 4 min (25.1 +/- 8.0 pg). LTB4 also increased significantly on the side of challenge. For the other prostanoids measured (PGF2, PGF2 alpha, TxB2, 6kPGF1 alpha), no significant changes in either ipsilateral or contralateral secretions were observed after allergen challenge. Our study described the kinetics of PGD2 and LTB4 release as well as the contralateral release of PGD2.

Effect of antigen provocation of IL-5 transgenic mice on eosinophil mobilization and bronchial hyperresponsiveness

We investigated whether allergen-induced eosinophil recruitment into mouse airways modifies the in vivo bronchopulmonary responses to standard agonists, and adaptation of a technique described for larger animals. Swiss, CBA, and IL-5 transgenic mice were immunized with ovalbumin and challenged intranasally after 14 days. Immunization alone was followed by increased eosinophil counts in bone marrow and blood, whereas antigenic challenge induced eosinophil infiltration in lungs and bronchoalveolar lavage fluid, which was suppressed by dexamethasone. Despite the high eosinophil counts, no bronchopulmonary hyperreactivity to methacholine or serotonin was detected 3 to 96 hours after antigenic provocation. Our results demonstrate that immunization augments the production of eosinophils by mice, which is further increased by antigenic challenge, but that eosinophil overproduction and lung infiltration, per se, are not sufficient to induce bronchopulmonary hyperreactivity, even in constitutively hypereosinophilic IL-5 transgenic mice.

Involvement of NK2 receptors rather than NK1 receptors in bronchial hyperresponsiveness induced by allergic reaction in guinea-pigs.

1. In this study, the role of neuropeptides in antigen-induced bronchoconstriction and bronchial responsiveness in guinea-pigs was evaluated by use of phosphoramidon, the inhibitor of neutral endopeptidases (NEP), the NK1 receptor antagonist, FK888, and the dual NK1/NK2 receptor antagonist, FK224. The role of endogenous tachykinins in bronchial hyperresponsiveness induced by inhaled capsaicin was also observed with FK888 and FK224. 2. Allergic bronchoconstriction and bronchial responsiveness was evoked by inhalation of ovalbumin (OA), and increasing doses of methacholine were inhaled at 5-min intervals for 30 min after OA challenge in passively sensitized and artificially ventilated guinea-pigs. Animals were treated with a 30 s inhalation of phosphoramidon (10(-3)M) or saline 10 min before the OA challenge. FK888 (1.0 or 10 mg kg-1) or FK224 (1.0 or 10 mg kg-1) was administered intravenously 5 min before the OA challenge. 3. Treatment with phosphoramidon did not alter the increase in the lateral pressure at the tracheal tube (Pao) caused by OA inhalation or the increase in bronchial response to methacholine following the allergic reaction. Pretreatment with FK224 did not inhibit the increase in Pao after antigen provocation but did significantly inhibit antigen-induced bronchial hyperresponsiveness in a dose-dependent manner, while FK888 did not affect either allergic bronchoconstriction or post-allergic bronchial hyperresponsiveness. 4. Histamine, 25, 50, 100 or 200 micrograms ml-1 was inhaled for 20 s at 5-min intervals in non-sensitized guinea-pigs which were pretreated with inhalation of subthreshold dose of capsaicin (10(-7) M). FK888 or FK224, each at a dose of 0.1 or 1.0 mg kg-1, or vehicle was given to guinea-pigs intravenously 3 min before inhalation of capsaicin. The capsaicin inhalation significantly potentiated bronchial responsiveness to histamine, compared with control. The capsaicin-induced bronchial hyperresponsiveness was completely blocked by FK224 in a dose-dependent manner but not by FK888. 5. These results suggest that NK2 receptors rather than NK1 receptors may play an important role in bronchial hyperresponsiveness induced by antigen challenge as well as capsaicin while tachykinins do not play a primary role in the acute bronchospasm elicited by antigen challenge in passively sensitized guinea-pigs.

Eosinophil recruitment into the respiratory epithelium following antigenic challenge in hyper-IgE mice is accompanied by interleukin 5-dependent bronchial hyperresponsiveness.

A murine model for antigen-induced bronchial hyperreactivity (BHR) and airway eosinophilia, two hallmarks of asthma, was developed using ovalbumin-immunized mice, which produce large amounts of IgE (named BP2, "Bons Producteurs 2," for High Line of Selection 2). A single intranasal ovalbumin challenge failed to modify the bronchial responses, despite the intense eosinophil recruitment into the bronchoalveolar lavage fluid and airways. When mice were challenged twice a day for 2 days or once a day for 10 days, BHR in response to i.v. 5-hydroxytryptamine or to inhaled methacholine was induced in BP2 mice but not in BALB/c mice. Histological examination showed that eosinophils reached the respiratory epithelium after multiple ovalbumin challenges in BP2 mice but remained in the bronchial submucosa in BALB/c mice. Total IgE titers in serum were augmented significantly with immunization in both strains, but much more so in BP2 mice. Interleukin 5 (IL-5) titers in serum and bronchoalveolar lavage fluid of BP2 mice were augmented by the antigenic provocation, and a specific anti-IL5 neutralizing antibody suppressed altogether airway eosinophilia and BHR, indicating a participation of IL-5 in its development. Our results indicate that the recruitment of eosinophils to the airways alone does not induce BHR in mice and that the selective effect on BP2 mice is related to their increased IgE titers associated with antigen-driven eosinophil migration to the epithelium, following formation and secretion of IL-5.

SVCAM-1 levels after segmental antigen challenge correlate with eosinophil influx, IL-4 and IL-5 production, and the late phase response.

Evidence from in vitro studies suggests a potential role for vascular cell adhesion molecule-1 (VCAM-1) in eosinophil trafficking. We hypothesized that induction of VCAM-1 occurs in the lung during IgE-mediated airway inflammation in humans. The technique of segmental antigen provocation followed by bronchoalveolar lavage (BAL) at 24 h was used to study 27 ragweed-allergic asthmatics (AA) and 18 atopic nonasthmatics (ANA). Total and differential cell counts were performed, and IL-4, IL-5, and soluble (VCAM) (sVCAM) levels in concentrated BAL fluid were measured by ELISA. A large increase in sVCAM levels after segmental challenge in both AA and ANA (1.79 +/- 0.31 to 139.39 +/- 68.58 ng/ml, p < 0.0005 and 2.85 +/- 0.80 to 98.25 +/- 77.35 ng/ml, p < 0.05, respectively) was observed. BAL IL-4 and IL-5 also increased after challenge (IL-4: 51.7 +/- 17.72 to 150.1 +/- 58.82 pg/ml, 0.05 < p < 0.10, n = 20 for AA, and 36.6 +/- 9.05 to 116.8 +/- 51.5 pg/ml, 0.05 < p < 0.10, n = 15 for ANA; IL-5: 0 to 2.67 +/- 1.62 ng/ml, p < 0.01, n = 16 for AA, and 0 to 2.87 +/- 2.16 ng/ml, 0.05 < p < 0.10, n = 10 for ANA). In both groups, the majority of the increase in sVCAM, IL-4, and IL-5 was accounted for by subjects who displayed a dual phase response after whole-lung antigen inhalation. This fact, plus the strong correlation observed between postchallenge sVCAM, IL-4, and IL-5 levels and eosinophil influx, suggests that VCAM, IL-4, and IL-5 play important roles in the recruitment of eosinophils to the lung of humans after antigen challenge.

Platelet‐activating factor: an inflammatory mediator in the acute phase of allergic conjunctivitis in a guinea‐pig model

The role of platelet-activating factor (PAF) as a mediator of increased conjunctival vascular permeability was investigated in a guinea-pig model of immediate hypersensitivity. Vascular permeability of the conjunctiva was determined by measuring the albumin content in lavage fluid (LF) after topical challenge with either PAF or ovalbumin. PAF produced a dose-dependent increase of the vascular permeability within minutes. Topical pretreatment with levocabastine, a potent histamine H1-antagonist demonstrated no effect towards the vascular permeability in response to PAF provocation. Pretreatment with eyedrops containing the specific PAF antagonist BN 52021 (1%) showed a significant inhibition of the vascular permeability (60.2%) and the clinical score (27.5%) after PAF challenge. In sensitized guinea-pigs, levocabastine showed a marked inhibition of both the vascular permeability (80.5%) and the clinical score (70%) after topical challenge with ovalbumin. BN 2021, although to a lesser extent, showed a similar effect towards the vascular permeability (26.8%) and the clinical score (28%) after antigen provocation. When BN 52021 and levocabastine were administered in combination, the vascular permeability was significantly decreased after antigen challenge in comparison with eyes pretreated with levocabastine alone. These results indicate that PAF plays a role in the acute phase of allergic conjunctivitis in the guinea-pig.