Syk activation in dendritic cells is essential for airway hyperresponsiveness and inflammation

We evaluated the role of Syk, using an inhibitor, on allergen-induced airway hyperresponsiveness (AHR) and airway inflammation in a system shown to be B cell- and mast cell-independent. Sensitization of BALB/c mice with ovalbumin (OVA) and alum after three consecutive OVA challenges resulted in AHR to inhaled methacholine and airway inflammation. The Syk inhibitor R406 (30 mg/kg, administered orally, twice daily) prevented the development of AHR, increases in eosinophils and lymphocytes and IL-13 levels in bronchoalveolar lavage (BAL) fluid, and goblet cell metaplasia when administered after sensitization and before challenge with OVA. Levels of IL-4, IL-5, and IFN-gamma in BAL fluid and allergen-specific antibody levels in serum were not affected by treatment. Because many of these responses may be influenced by dendritic cell function, we investigated the effect of R406 on bone marrow-derived dendritic cell (BMDC) function. Co-culture of BMDC with immune complexes of OVA and IgG anti-OVA together with OVA-sensitized spleen mononuclear cells resulted in increases in IL-13 production. IL-13 production was inhibited if the BMDCs were pretreated with the Syk inhibitor. Intratracheal transfer of immune complex-pulsed BMDCs (but not nonpulsed BMDCs) to naive mice before airway allergen challenge induced the development of AHR and increases in BAL eosinophils and lymphocytes. All of these responses were inhibited if the transferred BMDCs were pretreated with R406. These results demonstrate that Syk inhibition prevents allergen-induced AHR and airway inflammation after systemic sensitization and challenge, at least in part through alteration of DC function.     

Respiratory syncytial virus infection prolongs methacholine-induced airway hyperresponsiveness in ovalbumin-sensitized mice

Severe respiratory syncytial virus (RSV)-induced disease is associated with childhood asthma and atopy. We combined models of allergen sensitization and RSV infection to begin exploring the immunologic interactions between allergic and virus-induced airway inflammation and its impact on airway hypersensitivity. Airway resistance was measured after methacholine challenge in tracheally intubated mice by whole body plethysmography. Lung inflammation was assessed by bronchoalveolar lavage (BAL) and histopathology. RSV infection alone did not cause significant airway hyperresponsiveness (AHR) to methacholine. Ovalbumin (OVA)-induced AHR lasted only a few days past the discontinuance of OVA aerosol in mice that were ovalbumin sensitized and mock infected. In contrast, OVA-sensitized mice infected with RSV during the OVA aerosol treatments (OVA/RSV) had AHR for more than 2 weeks after infection. However, 2 weeks after either RSV or mock infection, OVA/RSV mice had significantly more lymphocytes found during BAL than OVA mice, whereas the OVA and OVA/RSV groups had the same number of eosinophils. Histopathologic analysis confirmed an increased inflammation in the lungs of OVA/RSV mice compared with OVA mice. In addition, OVA/RSV mice had a more widespread distribution of mucus in their airways with increased amounts of intraluminal mucus pools compared with the other groups. Thus, prolonged AHR in RSV-infected mice during ovalbumin-sensitization correlates with increased numbers of lymphocytes in BAL fluid, increased lung inflammation, and mucus deposition in the airways, but not with airway eosinophilia. A further understanding of the immunologic consequences of combined allergic and virus-induced airway inflammation will impact the management of diseases associated with airway hyperreactivity. J. Med. Virol. 57:186–192, 1999. © 1999 Wiley-Liss, Inc.     

IL-10-treated dendritic cells decrease airway hyperresponsiveness and airway inflammation in mice

BACKGROUND: IL-10 affects dendritic cell (DC) function, but the effects on airway hyperresponsiveness (AHR) and inflammation are not defined. OBJECTIVE: We sought to determine the importance of IL-10 in regulating DC function in allergen-induced AHR and airway inflammation. METHODS: DCs were generated from bone marrow in the presence or absence of IL-10. In vivo IL-10-treated DCs from IL-10(+/+) and IL-10(-/-) donors pulsed with ovalbumin (OVA) were transferred to naive or sensitized mice before challenge. In recipient mice AHR, cytokine levels, cell composition of bronchoalveolar lavage (BAL) fluid, and lung histology were monitored. RESULTS: In vitro, IL-10-treated DCs expressed lower levels of CD11c, CD80, and CD86; expressed lower levels of IL-12; and suppressed T(H)2 cytokine production. In vivo, after transfer of OVA-pulsed IL-10-treated DCs, naive mice did not have AHR, airway eosinophilia, T(H)2 cytokine increase in BAL fluid, or goblet cell metaplasia when challenged, and in sensitized and challenged mice IL-10-treated DCs suppressed these responses. Levels of IL-10 in BAL fluid and numbers of lung CD4(+)IL-10(+) T cells were increased in mice that received OVA-pulsed IL-10-treated DCs. Transfer of IL-10-treated DCs from IL-10-deficient mice were ineffective in suppressing the responses in sensitized and challenged mice. CONCLUSIONS: These data demonstrate that IL-10-treated DCs are potent suppressors of the development of AHR, inflammation, and T(H)2 cytokine production; these regulatory functions are at least in part through the induction of endogenous (DC) production of IL-10. CLINICAL IMPLICATIONS: Modification of DC function by IL-10 can attenuate lung allergic responses, including the development of AHR.     

CD1d restricted natural killer T cells are not required for allergic skin inflammation

BACKGROUND: Invariant T-cell receptor-positive natural killer (iNKT) cells have been shown to be essential for the development of allergen-induced airway hyperreactivity (AHR). OBJECTIVE: We examined the role of iNKT cells in allergic skin inflammation using a murine model of atopic dermatitis (AD) elicited by epicutaneous sensitization with ovalbumin (OVA). METHODS: Wild-type (WT) and natural killer T-cell-deficient CD1d-/- mice were epicutaneously sensitized with OVA or normal saline and challenged with aerosolized OVA. iNKT cells in skin and bronchoalveolar lavage fluid were analyzed by fluorescence-activated cell sorting, and cytokine mRNA levels were measured by quantitative RT-PCR. AHR to methacholine was measured after OVA inhalation. RESULTS: Skin infiltration by eosinophils and CD4+ cells and expression of mRNA encoding IL-4 and IL-13 in OVA-sensitized skin were similar in WT and CD1d-/- mice. No significant increase in iNKT cells was detectable in epicutaneously sensitized skin. In contrast, iNKT cells were found in the bronchoalveolar lavage fluid from OVA-challenged epicutaneously sensitized WT mice, but not CD1d-/- mice. Epicutaneously sensitized CD1d-/- mice had an impaired expression of IL-4, IL-5, and IL-13 mRNA in the lung and failed to develop AHR in response to airway challenge with OVA. CONCLUSION: These results demonstrate that iNKT cells are not required for allergic skin inflammation in a murine model of AD, in contrast with airway inflammation, in which iNKT cells are essential. CLINICAL IMPLICATIONS: Understanding the potential role of iNKT cells in AD will allow us to have a more specific target for therapeutic use.     

Divergent effects of biolistic gene transfer in a mouse model of allergic airway inflammation

Particle-mediated epidermal delivery (PMED) of allergen genes efficiently prevents systemic sensitization and suppresses specific immunoglobulin E synthesis. We investigated in a mouse model of allergic airway disease the effect of PMED on the elicitation of local inflammatory reactions in the lung. BALB/c mice were biolistically transfected with plasmids encoding beta-galactosidase (betaGal) as model allergen under control of the DC-targeting fascin promoter and the ubiquitously active cytomegalovirus promoter, respectively. Mice were challenged intranasally with betaGal-protein with or without intermediate sensitization with betaGal adsorbed to aluminiumhydroxide. Subsequently, local cytokine production and recruitment of IFN-gamma-producing CD8(+) effector T cells into the airways were determined, and inflammatory parameters such as cellular infiltration in the bronchoalveolar lavage (BAL) and airway hyperresponsiveness (AHR) were measured. PMED of betaGal-encoding plasmids before sensitization significantly reduced frequencies of eosinophils in the BAL and shifted the local T helper (Th) cell response from a distinct Th2 response toward a Th1-biased response. However, AHR triggered by allergen challenge via the airways was not alleviated in vaccinated mice. Most important, we show that PMED using betaGal-encoding DNA without subsequent sensitization recruited Tc1 cells into the lung and caused a Th1-prone local immune response after subsequent intranasal provocation, accompanied by neutrophilic infiltration into the airways and elicitation of AHR. We conclude that robust Th1/Tc1 immune responses, although highly effective in the counter-regulation of local Th2-mediated pathology, might as well trigger local inflammatory reactions in the lung and provoke the induction of AHR in the mouse model of allergic airway disease.     

4-1BB stimulation inhibits allergen-specific immunoglobulin E production and airway hyper-reactivity but partially suppresses bronchial eosinophilic inflammation in a mouse asthma model

BACKGROUND: 4-1 BB, a member of the tumour necrosis factor receptor superfamily, functions as a co-stimulatory molecule. Recently, stimulation of the 4-1 BB pathway was shown to suppress antigen-specific CD4(+) T cell and subsequent T cell-dependent humoral immune responses. OBJECTIVE: We examined the effect of agonistic anti-4-1 BB monoclonal antibody (mAb) treatment on allergic asthma, in which allergen-specific type 2 helper T cells (Th2) have been shown to play an important role. METHODS: BALB/c mice were systemically sensitized with intraperitoneal injections of ovalbumin (OVA) and alum on days 0 and 14, and then challenged with inhaled OVA on days 28, 29 and 30. In test groups, the agonistic anti-4-1 BB mAb was administered at the time of initial systemic sensitization with OVA. On day 31, mice were challenged with inhaled methacholine, and enhanced pause was measured as an index of airway hyper-responsiveness (AHR). Levels of OVA-specific IgE in serum, and levels of various cytokines in bronchoalveolar lavage (BAL) fluids were measured. The severity of airway inflammation was determined by differential cell counts in BAL fluids and histopathologic lung analysis. To evaluate local immunity, we cultured lymphocytes from draining perihilar lymph nodes and evaluated the proliferative response to OVA and the levels of IL-5 in the culture supernatant. In addition, the functional mechanism of 4-1 BB stimulation was evaluated in splenocytes obtained at day 7 after systemic OVA sensitization. RESULTS: We found that treatment with the anti-4-1 BB mAb significantly decreased AHR and the production of allergen-specific IgE. Bronchial inflammation, however, had only partially improved and the levels of IL-4 and IL-5 in BAL fluids showed only a small degree of reduction compared with the control Ig-treated mice. Thoracic lymphocytes from anti-4-1 BB-treated mice showed significant suppression of OVA-induced proliferation and IL-5 production. In anti-4-1 BB-treated mice, splenocytes exhibited poor proliferation and marked apoptosis 7 days after systemic OVA challenge. CONCLUSION: These results suggest that stimulation of the 4-1 BB pathway effectively suppresses some features of allergic asthma, including allergen-specific IgE production and AHR, through deletion of allergen-specific Th2 cells. However, we found that bronchial allergic inflammation was not strictly mediated by suppression of the Th2 immune response in this murine model of asthma. Despite these somewhat contradictory effects, intervention in the 4-1 BB pathway might provide a potential novel immunotherapeutic approach for treatment of allergic asthma.     

Antiasthmatic activity and selective inhibition of type 2 helper T cell response by aqueous extract of semen armeniacae amarum

Semen armeniacae amarum (SAA) has long been used to control asthma in Korean traditional medicine. However, its antiasthmatic action still remains poorly understood. In the current study, effective mechanism of SAA was investigated in a mouse model of allergic asthma induced by repeated sensitization and intranasal challenge with OVA. Airway hyperreactivity (AHR) measured by β-methacoline-induced airflow obstruction and airway recruitment of leukocytes including eosinophils were significantly reduced by oral treatment of SAA water extract. Level of interleukin (IL)-4, but not Interferon gamma (IFN-γ), in the bronchoalveolar lavage fluid (BALF) also appeared considerably lower in SAA-treated mice than in controls. Collectively, these data show that SAA suppresses type 2 helper T cell (Th2), but not type 1 helper T cell (Th1), response. This hypothesis was supported further by the data of ex vivo cytokine production of peribronchial lymph node cells. Thus, oral administration of SAA attenuates asthmatic manifestations including AHR and airway inflammation, which possibly result from selective inhibition of Th2 response to allergen. Our data strongly suggest that SAA may be effectively applied to control other Th2-related diseases as well as allergic asthma.     

Antiasthmatic Activity and Selective Inhibition of Type 2 Helper T cell Response by Aqueous Extract of Semen Armeniacae Amarum

Semen armeniacae amarum (SAA) has long been used to control asthma in Korean traditional medicine. However, its antiasthmatic action still remains poorly understood. In the current study, effective mechanism of SAA was investigated in a mouse model of allergic asthma induced by repeated sensitization and intranasal challenge with OVA. Airway hyperreactivity (AHR) measured by β-methacoline-induced airflow obstruction and airway recruitment of leukocytes including eosinophils were significantly reduced by oral treatment of SAA water extract. Level of interleukin (IL)-4, but not Interferon gamma (IFN-γ), in the bronchoalveolar lavage fluid (BALF) also appeared considerably lower in SAA-treated mice than in controls. Collectively, these data show that SAA suppresses type 2 helper T cell (Th2), but not type 1 helper T cell (Th1), response. This hypothesis was supported further by the data of ex vivo cytokine production of peribronchial lymph node cells. Thus, oral administration of SAA attenuates asthmatic manifestations including AHR and airway inflammation, which possibly result from selective inhibition of Th2 response to allergen. Our data strongly suggest that SAA may be effectively applied to control other Th2-related diseases as well as allergic asthma.     

L-Selectin is required for the development of airway hyperresponsiveness but not airway inflammation in a murine model of asthma

BACKGROUND: Airway inflammation and airway hyperresponsiveness (AHR) are fundamental features of asthma. Migration of inflammatory cells from the circulation into the lungs is dependent on adhesion molecule interactions. The cell surface adhesion molecule L-selectin has been demonstrated to mediate leukocyte rolling on inflamed and noninflamed pulmonary endothelium. However, its role in the development of airway inflammation and AHR in asthma has not been examined. OBJECTIVE: We sought to characterize the role of L-selectin in the recruitment of inflammatory cells to the airway-lung and the development of AHR in a murine model of asthma. METHODS: An ovalbumin (OVA)-induced allergic airway disease model of asthma was applied to L-selectin-deficient (LKO) mice and C57BL/6 wild-type (WT) control mice. The development of airway inflammation was assessed by examining leukocyte influx into bronchoalveolar lavage (BAL) fluid and the lung. Total and differential BAL leukocyte counts were determined, and the immunophenotype of BAL lymphocytes was assessed by means of flow cytometry. The development of AHR was assessed by means of whole-body plethysmography. RESULTS: Airway-lung inflammation was equivalent in LKO and WT mice sensitized-challenged with OVA, as measured by total and differential BAL cell counts and histologic analysis of lung tissue. Numbers of eosinophils, neutrophils, lymphocytes, and monocytes in BAL fluid were equivalent in LKO and WT mice. However, phenotypic analysis of BAL lymphocytes demonstrated significantly reduced CD3(+) populations and increased B220(+) populations in LKO compared with WT mice (P <.05). Remarkably, despite a fulminant inflammatory response in the airway-lung in LKO mice sensitized-challenged with OVA, AHR was completely abrogated. CONCLUSION: L-selectin plays a crucial role in the development of AHR but not allergic inflammation in an animal model of asthma. L-selectin represents a potential target for novel asthma therapies specifically aimed at controlling AHR.     

Allergic Airway Inflammation in Mice Deficient for the Antigen-Processing Protease Cathepsin E

Background: Allergic asthma is a Th2-type chronic inflammatory disease of the lung. It is characterized by infiltration of eosinophils, neutrophils, mast cells and T lymphocytes into the airways. Th2 cytokines like interleukin (IL)-4, IL-5 and chemokines like eotaxin are increased in the asthmatic response. The processing and presentation of exogenous antigens is important in the sensitization to an allergen. Cathepsin E (Ctse) is an intracellular aspartic endoprotease which is expressed in immune cells like dendritic cells (DCs). It was found to play an essential role in the processing and presentation of ovalbumin (OVA). The aim of the present study was to investigate the inhibition of Ctse in two different experimental models of allergic airway inflammation. Methods: Ctse wild-type (Ctse(+/+)) and Ctse-deficient (Ctse(-/-)) bone marrow-derived DCs (BMDCs) were pulsed with OVA/OVA peptide and cocultured with OVA transgenic T II (OT II) cells whose proliferation was subsequently analyzed. Two different in vivo asthma models with Ctse(+/+) and Ctse(-/-) mice were performed: an acute OVA-induced and a subchronic Phleum pratense-induced airway inflammation. Results: Proliferation of OT II cells was decreased when cocultured with BMDCs of Ctse(-/-) mice as compared to cells cocultured with BMDCs of Ctse(+/+) mice. In vivo, Ctse deficiency led to reduced lymphocyte influx after allergen sensitization and challenge in both investigated airway inflammation models, compared to their control groups. Conclusion: Ctse deficiency leads to a reduced antigen presentation in vitro. This is followed by a distinct effect on lymphocyte influx in states of allergic airway inflammation in vivo.     

Effect of anti-mIL-9 antibody on the development of pulmonary inflammation and airway hyperresponsiveness in allergic mice.

Interleukin (IL)-9 is a T-cell-derived cytokine with pleiotropic activities on T helper 2 cells, B cells, and mast cells. IL-9 may therefore play an important role in the development of allergic pulmonary inflammatory diseases. In this study, an antimouse IL-9 (anti-mIL-9) antibody (Ab) was evaluated against pulmonary eosinophilia, histopathologic changes in lung tissues, serum immunoglobulin (Ig) E levels, and airway hyperresponsiveness (AHR) to methacholine in mice sensitized and challenged with ovalbumin (OVA). Additionally, steady-state levels of IL-4, IL-5, IL-13, and interferon-gamma messenger RNA (mRNA) in the lungs were measured. The anti-mIL-9 Ab (200 microg/mouse, intraperitoneally) was given as either four doses during the sensitization period or as a single dose before OVA challenge. Sensitized mice challenged with OVA displayed marked pulmonary eosinophilia, epithelial damage, and goblet cell hyperplasia. OVA challenge also increased mRNA levels of IL-4, IL-5, and IL-13 in the lungs. AHR was also increased twofold in sensitized, challenged mice. Treatment of sensitized, challenged mice with four doses of anti-mIL-9 Ab significantly reduced pulmonary eosinophilia, serum IgE levels, goblet cell hyperplasia, airway epithelial damage, and AHR, but had no effect on IL-4, IL-5, and IL-13 mRNA levels in the lungs. A single dose of the antibody was ineffective on all measures. These results indicate that an antibody to mIL-9 inhibits the development of allergic pulmonary inflammation and AHR in mice.     

Inhibition of early airway neutrophilia does not affect development of airway hyperresponsiveness

The effect of modifying early neutrophil-mediated inflammation on the development of airway hyperresponsiveness (AHR) was investigated using an interleukin (IL)-1 receptor antagonist (IL-1Ra), an anti-IL-18 antibody (anti-IL-18) or a p38 mitogen-activated protein kinase (MAPK) inhibitor (M39). Balb/c mice were sensitized to ovalbumin (OVA) and challenged with a single intranasal dose of OVA. Treatment with the IL-1Ra or anti-IL-18 was initiated 20 min before challenge, whereas M39 was administered 4 h before the challenge. Eight hours after challenge, sensitized mice showed significantly higher numbers of neutrophils in bronchoalveolar lavage (BAL) fluid; treatment with IL-1Ra, anti-IL-18, or M39 significantly decreased the influx of neutrophils. At 48 h, none of the treatments affected eosinophil inflammation in BAL fluid and lung tissue, goblet cell hyperplasia, or cytokine levels (IL-4, IL-5, IL-12, IL-13, interferon-gamma) in BAL fluid. Anti-IL-18 or IL-1Ra had no effect on the development of AHR, whereas M39-treated mice showed a decrease in methacholine responsiveness. These results demonstrate that early neutrophil influx following allergen challenge is mediated by IL-1, IL-18, and p38 MAPK. However, neutralization of IL-1 and IL-18 did not affect the later development of AHR and eosinophilic airway inflammation. The effects of inhibiting p38 MAPK in decreasing AHR indicate activities independent of its prevention of neutrophil accumulation.     

RANTES (CCL5) regulates airway responsiveness after repeated allergen challenge

RANTES (CC chemokine ligand 5) contributes to airway inflammation through accumulation of eosinophils, but the exact role of RANTES (CCL5) is not defined. C57BL/6 mice, sensitized by injection of ovalbumin (OVA) on Days 1 and 14, were challenged with OVA on Days 28, 29, and 30 (3 challenges, short-term-challenge model) or on Days 28, 29, 30, 36, 40, 44, and 48 (7 challenges, repeated-challenge model) and evaluated 48 h later. Anti-mouse RANTES was given intravenously, and recombinant mouse RANTES or PBS was given intratracheally. These reagents were given on Days 28, 29, and 30 in the short-term-challenge study and on Days 44 and 48 in the repeated-challenge study. After short-term challenge, there were no effects after administration of anti-RANTES or RANTES. In the repeated-challenge study, although control mice showed a decrease in airway hyperresponsiveness, administration of anti-RANTES sustained and enhanced airway hyperresponsiveness and increased goblet cell numbers. In contrast, administration of RANTES normalized airway function but reduced goblet cell numbers. IL-12 and IFN-gamma levels in BAL decreased in the anti-RANTES group and increased in the RANTES group. IFN-gamma-producing CD4 T cells in lung, and IFN-gamma production from lung T cells in response to OVA in the anti-RANTES group, were significantly decreased but were increased in the RANTES group. Anti-IFN-gamma, administered with RANTES, decreased the effects of RANTES on AHR after repeated challenge. These data indicate that RANTES plays a role in the regulation of airway function after repeated allergen challenge, in part through modulation of levels of IFN-gamma and IL-12.     

EGF receptor activation during allergic sensitization affects IL‐6‐induced T‐cell influx to airways in a rat model of asthma

EGF receptor (EGFR) is involved in cell differentiation and proliferation in airways and may trigger cytokine production by T cells. We hypothesized that EGFR inhibition at the time of allergic sensitization may affect subsequent immune reactions. Brown Norway rats were sensitized with OVA, received the EGFR tyrosine kinase inhibitor, AG1478 from days 0 to 7 and OVA challenge on day 14. OVA‐specific IgE in serum and cytokines and chemokines in BAL were measured 24 h after challenge. To evaluate effects on airway hyperresponsiveness (AHR), rats were sensitized, treated with AG1478, intranasally challenged, and then AHR was assessed. Furthermore chemotactic activity of BALF for CD4⁺ T cells was examined. The eosinophils, neutrophils and lymphocytes in BAL were increased by OVA and only the lymphocytes were reduced by AG1478. OVA significantly enhanced IL‐6 concentration in BAL, which was inhibited by AG1478. However AHR, OVA‐specific IgE and IL‐4 mRNA expression in CD4⁺ T cells were not affected by AG1478. BALF from OVA‐sensitized/challenged rats induced CD4⁺ T‐cell migration, which was inhibited by both AG1478 treatment in vivo and neutralization of IL‐6 in vitro. EGFR activation during sensitization may affect the subsequent influx of CD4⁺ T cells to airways, mainly mediated through IL‐6.     

Development of eosinophilic airway inflammation and airway hyperresponsiveness requires interleukin-5 but not immunoglobulin E or B lymphocytes.

We previously defined a role for B cells and allergen-specific immunoglobulins in the development of allergic sensitization, airway inflammation, and airway hyperresponsiveness (AHR), using a 10-d protocol in which allergen exposure occurred exclusively via the airways, without adjuvant. In the present protocol, normal and B-cell-deficient (microMt(-/-)) mice were sensitized intraperitoneally to ovalbumin (OVA) and challenged with OVA via the airways in order to examine the requirements for AHR with this protocol. T-cell activation (antigen-specific proliferative responses and Th2-type cytokine production) and eosinophil infiltration in the peribronchial regions of the airways, with signs of eosinophil activation and degranulation, occurred in both experimental groups. In contrast to the 10-d protocol, increased in vivo airway responsiveness to methacholine and in vitro tracheal smooth-muscle responses to electrical field stimulation were observed in both normal and B-cell-deficient mice, and these responses were inhibited by anti-interleukin (IL)-5 administration before airway challenge. These data show that IL-5, but not B cells or allergen-specific IgE, are required for eosinophil airway infiltration and the development of AHR following allergen/alum sensitization and repeated airway challenge with allergen. These results emphasize that the use of different sensitization and challenge protocols can influence the requirements for development of AHR.     

Effect of ozone exposure on allergic sensitization and airway inflammation induced by dendritic cells

BACKGROUND: Epidemiological studies suggest that ozone exposure is related to increased asthma symptoms. Dendritic cells (DCs) are the principal antigen-presenting cells in the airways. OBJECTIVE: We have examined whether ambient doses of ozone (100 ppb for 2 h) enhance allergic sensitization and/or airway inflammation in a mouse model. METHODS: C57BL/6 mice were sensitized to inhaled ovalbumin (OVA) by intratracheal instillation of OVA-pulsed DCs on day 0. Daily exposure to OVA aerosol on days 14-20 resulted in an eosinophilic airway inflammation, as reflected in bronchoalveolar lavage fluid and lung histology. In a first experiment, mice were exposed to ozone or room air immediately prior to and following sensitization. Subsequently, we tested the effect of ozone exposure during antigen challenge in DC-sensitized mice. RESULTS: Exposure to ozone during sensitization did not influence airway inflammation after subsequent allergen challenge. In contrast, in sensitized mice, challenge with OVA together with ozone (days 14-20) resulted in enhanced airway eosinophilia and lymphocytosis, as compared with mice exposed to OVA and room air (1.91 x 106 +/- 0.46 x 106 vs. 0.16 x 106 +/- 0.06 x 106 eosinophils/mL lavage fluid; P = 0.015; 0.49 x 106 +/- 0.11 x 106 vs. 0.08 x 106 +/- 0.03 x 106 lymphocytes/mL lavage fluid; P = 0.004). Ozone exposure without subsequent OVA exposure did not cause airway inflammation. CONCLUSION: Ozone exposure does not increase allergic sensitization but enhances antigen-induced airway inflammation in mice that are sensitized via the airways.     

Interleukin (IL)-5 but not immunoglobulin E reconstitutes airway inflammation and airway hyperresponsiveness in IL-4-deficient mice

We studied the role of interleukin (IL)-4, IL-5, and allergen-specific immunoglobulin (Ig) E in the development of allergen-induced sensitization, airway inflammation, and airway hy-perresponsiveness (AHR). Normal, IL-4-, and IL-5-deficient C57BL/6 mice were sensitized intraperitoneally to ovalbumin (OVA) and repeatedly challenged with OVA via the airways. After allergen sensitization and airway challenge, normal and IL-5-deficient, but not IL-4-deficient, mice developed increased serum levels of total and antigen-specific IgE levels and increased IL-4 production in the lung tissue compared with nonsensitized control mice. Only normal mice showed significantly increased IL-5 production in the lung tissue and an eosinophilic infiltration of the peribronchial regions of the airways, whereas both IL-4- and IL-5-deficient mice had little or no IL-5 production and no significant eosinophilic airway inflammation. Associated with the inflammatory responses in the lung, only normal mice developed increased airway responsiveness to methacholine after sensitization and airway challenge; in both IL-4- and IL-5-deficient mice, airway responsiveness was similar to that in nonsensitized control mice. Reconstitution of sensitized, IL-4-deficient mice before allergen airway challenge with IL-5, but not with allergen-specific IgE, restored eosinophilic airway inflammation and the development of AHR. These data demonstrate the importance of IL-4 for allergen-driven airway sensitization and that IL-5, but not allergen-specific IgE, is required for development of eosinophilic airway inflammation and AHR after this mode of sensitization and challenge.     

Effect of ageing on pulmonary inflammation, airway hyperresponsiveness and T and B cell responses in antigen-sensitized and -challenged mice

BACKGROUND: The effect of ageing on several pathologic features of allergic asthma (pulmonary inflammation, eosinophilia, mucus hypersecretion), and their relationship with airway hyperresponsiveness (AHR) is not well characterized. OBJECTIVE: To evaluate lung inflammation, mucus metaplasia and AHR in relationship with age in murine models of allergic asthma comparing young and older mice. METHODS: Young (6 weeks) and older (6, 12, 18 months) BALB/c mice were sensitized and challenged with ovalbumin (OVA). AHR and bronchoalveolar fluid (BALF), total inflammatory cell count and differential were measured. To evaluate mucus metaplasia, quantitative PCR for the major airway mucin-associated gene, MUC-5AC, from lung tissue was measured, and lung tissue sections stained with periodic acid-Schiff (PAS) for goblet-cell enumeration. Lung tissue cytokine gene expression was determined by quantitative PCR, and systemic cytokine protein levels by ELISA from spleen-cell cultures. Antigen-specific serum IgE was determined by ELISA. RESULTS: AHR developed in both aged and young OVA-sensitized/challenged mice (OVA mice), and was more significantly increased in young OVA mice than in aged OVA mice. However, BALF eosinophil numbers were significantly higher, and lung histology showed greater inflammation in aged OVA mice than in young OVA mice. MUC-5AC expression and numbers of PAS+ staining bronchial epithelial cells were significantly increased in the aged OVA mice. All aged OVA mice had increased IL-5 and IFN-gamma mRNA expression in the lung and IL-5 and IFN-gamma protein levels from spleen cell cultures compared with young OVA mice. OVA-IgE was elevated to a greater extent in aged OVA mice. CONCLUSIONS: Although pulmonary inflammation and mucus metaplasia after antigen sensitization/challenge occurred to a greater degree in older mice, the increase in AHR was significantly less compared with younger OVA mice. Antigen treatment produced a unique cytokine profile in older mice (elevated IFN-gamma and IL-5) compared with young mice (elevated IL-4 and IL-13). Thus, the airway response to inflammation is lessened in ageing animals, and may represent age-associated events leading to different phenotypes in response to antigen provocation.     

Interferon-γ and pulmonary macrophages contribute to the mechanisms underlying prolonged airway hyperresponsiveness

Background Airway hyperresponsiveness (AHR) in asthmatics includes a variable component that persists following an allergen challenge. This may be dissociated from inflammatory cell recruitment, implying a role for resident pulmonary cells in regulating the response. Objective Using improved methods of assessing AHR in a mouse model of allergic airway disease, to investigate the basis of the development of prolonged AHR. Method BALB/c mice were systemically sensitized and then challenged with aerosolized ovalbumin (OVA). Airway and tissue responsiveness were measured at baseline and at 1 day, and 1, 2 and 3 weeks after the last OVA challenge. Inflammatory cell numbers in BALF and levels of mRNA for eotaxin‐1 and ‐2, IFN‐γ, IL‐5 and ‐13 in the lung were measured at each time‐point. In further experiments, the roles of IFN‐γ and of CCR3⁺ and CD4⁺ cells in the development of prolonged AHR were assessed by blockade or depletion with monoclonal antibodies. The role of pulmonary macrophages was assessed by selective chemical depletion of these cells. Results Airway responsiveness was increased above baseline at 1 day after the last OVA challenge, and this was sustained for 1 week. In contrast, tissue‐specific responsiveness was only significantly increased above baseline at 1 day. Development of prolonged AHR was inhibited by neutralization of IFN‐γ or by depletion of pulmonary macrophages, but not by depletion of either CD4⁺ T cells or CCR3⁺ eosinophils. Conclusion An interaction between IFN‐γ and pulmonary macrophages contributed to the prolongation of airway hyperresponsiveness. In contrast, T cells and eosinophils did not contribute to prolongation of AHR. These findings emphasize the importance of the innate host response in the development of manifestations of asthma, as well as its potential relevance as a target for therapeutic intervention. Cite this as: M. Yang, R. K. Kumar and P. S. Foster, Clinical & Experimental Allergy, 2010 (40) 163–173.