Residual antigen presentation after influenza virus infection affects CD8 T cell activation and migration

Activated virus-specific CD8 T cells remain in the lung airways for several months after influenza virus infection. We show that maintenance of this cell population is dependent upon the route of infection and prolonged presentation of viral antigen in the draining lymph nodes (DLN) of the respiratory tract. The local effects on T cell migration have been examined. We show retention of virus-specific CD8 T cells in the mediastinal lymph node (MLN) and continuing recruitment of blood-borne migrants into the lung airways during antigen presentation. These data show that antigen that is retained after pulmonary influenza virus infection controls the migratory pattern and activation state of virus-specific CD8 T cells near the site of virus amplification.     

Lack of lymphoid chemokines CCL19 and CCL21 enhances allergic airway inflammation in mice

Lymphoid chemokines CCL19 and CCL21 are crucial for the recruitment of circulating naive T cells into lymph nodes. However, it is not completely known how they contribute to the development of allergic diseases. To determine whether the lack of CCL19 and CCL21 affects allergic airway inflammation, CCL19- and CCL21-deficient [paucity of lymph node T cells (plt/plt)] and wild-type (WT) mice were immunized intra-peritoneally and then challenged intra-nasally with chicken ovalbumin (OVA). Plt/plt mice developed more severe allergic airway inflammation characterized by increased eosinophils and lymphocytes in bronchoalveolar lavage (BAL) and profound inflammation in peribronchiolar and perivascular regions than did WT mice. CD4+ alpha4 integrin+ and CD4+ beta7 integrin+ T cells were significantly increased in the BAL of OVA-immunized and OVA-challenged (OVA/OVA) plt/plt mice compared with OVA/OVA WT mice. Moreover, there were higher levels of IL-4 and IL-13 mRNAs and lower levels of IL-2 and IFN-gamma mRNAs in inflamed lungs of OVA/OVA plt/plt mice compared with OVA/OVA WT mice. Plt/plt mice produced higher levels of total and OVA-specific IgE antibody. Thus, our results suggest that lack of lymphoid chemokines CCL19 and CCL21 enhances allergic airway inflammation by modulating the recruitment of CD4+ T cells into the lung, the balance between Th1 and Th2 cytokines and the IgE production.     

Respiratory syncytial virus, pneumonia virus of mice, and influenza A virus differently affect respiratory allergy in mice

BACKGROUND: Respiratory viral infections in early childhood may interact with the immune system and modify allergen sensitization and/or allergic manifestations. In mice, respiratory syncytial virus (RSV) infection during allergic provocation aggravates the allergic T helper (Th) 2 immune response, characterized by the production of IL-4, IL-5, and IL-13, and inflammatory infiltrates. However, it is unclear whether the RSV-enhanced respiratory allergic response is a result of non-specific virus-induced damage of the lung, or virus-specific immune responses. OBJECTIVE: In the present study we investigated whether RSV, pneumonia virus of mice (PVM) and influenza A virus similarly affect the allergic response. METHODS: BALB/c mice were sensitized and challenged with ovalbumin (OVA), and inoculated with virus during the challenge period. Pulmonary inflammation, lung cytokine mRNA responses, and IgE production in serum were assessed after the last OVA-challenge. RESULTS: Like RSV, PVM enhanced the OVA-induced pulmonary IL-4, IL-5, and IL-13 mRNA expression, which was associated with enhanced perivascular inflammation. In addition, PVM increased the influx of eosinophils in lung tissue. In contrast, influenza virus decreased the Th2 cytokine mRNA expression in the lungs. However, like PVM, influenza virus enhanced the pulmonary eosinophilic infiltration in OVA-allergic mice. CONCLUSION: The Paramyxoviruses RSV and PVM both are able to enhance the allergic Th2 cytokine response and perivascular inflammation in BALB/c mice, while the Orthomyxovirus influenza A is not.     

Modulation of naive CD4+ T-cell responses to an airway antigen during pulmonary mycobacterial infection

During pulmonary mycobacterial infection, there is increased trafficking of dendritic cells from the lungs to the draining lymph nodes. We hypothesized that ongoing mycobacterial infection would modulate recruitment and activation of antigen-specific naive CD4+ T cells after airway antigen challenge. BALB/c mice were infected by aerosol with Mycobacterium bovis BCG. At peak bacterial burden in the lungs (4 to 6 weeks postinfection), carboxy-fluorescein diacetate succinimidyl ester-labeled naive ovalbumin-specific DO11.10 T cells were adoptively transferred into infected and uninfected mice. Recipient mice were challenged intranasally with soluble ovalbumin (OVA), and OVA-specific T-cell responses were measured in the lungs, draining mediastinal lymph nodes (MLN), and spleens. OVA challenge resulted in increased activation and proliferation of OVA-specific T cells in the draining MLN of both infected and uninfected mice. However, only BCG-infected mice had prominent OVA-specific T-cell activation, proliferation, and Th1 differentiation in the lungs. BCG infection caused greater distribution of airway OVA to pulmonary dendritic cells and enhanced presentation of OVA peptide by lung CD11c+ cells. Together, these data suggest that an existing pulmonary mycobacterial infection alters the phenotype of lung dendritic cells so that they can activate antigen-specific naive CD4+ T cells in the lungs in response to airway antigen challenge.     

Enhanced allergen-induced airway inflammation in paucity of lymph node T cell (plt) mutant mice

BACKGROUND: Dendritic cells and lymphocytes play a central role in allergic asthma. Chemokines for these cells include the CCR7 agonists secondary lymphoid chemokine/CCL21 and EBV-induced lymphoid chemokine/CCL19, but their role in allergic asthma is poorly understood. OBJECTIVE: We sought to determine the effects of abrogation of lymphoid tissue expression of CCR7 agonists on allergic airway responses. METHODS: Paucity of lymphocyte T cell (plt) mutant mice, deficient in EBV-induced lymphoid chemokine/CCL19 and the lymphoid form of secondary lymphoid chemokine/CCL21, were evaluated in an established ovalbumin (OVA)-induced asthma model (plt-OVA group) and compared with similarly immunized +/+ BALB/c mice (+/+OVA group). RESULTS: APTI responses to methacholine increased similarly in OVA-challenged plt and +/+ mice. However, airway inflammation was strikingly enhanced in plt-OVA mutants over +/+OVA mice and included increased numbers of eosinophils, CD4 and B cells, neutrophils, and total leukocytes in bronchoalveolar lavage fluid and inflammatory cell cuffing around pulmonary arterioles. Enhanced airway inflammation was accompanied by an increase in lung T(H)2 activity, with increased levels of IL-4 and monocyte-derived chemoattractant/CCL22. CONCLUSIONS: Induction of allergic asthma in mutant mice with impaired CCR7 responses results in characteristics that resemble severe asthma in human subjects, including severe bronchial lymphocytosis, eosinophilia, and neutrophilia, but not in enhancement in airway hyperreactivity. CLINICAL IMPLICATIONS: Disruption of chemokines responsible for trafficking of antigen-processing cells and lymphocytes to the draining lymph nodes might lead to enhanced allergic airway responses.     

Synthesized OVA323-339MAP octamers mitigate OVA-induced airway inflammation by regulating Foxp3 T regulatory cells

ABSTRACT: BACKGROUND: Antigen-specific immunotherapy (SIT) has been widely practiced in treating allergic diseases such as asthma. However, this therapy may induce a series of allergic adverse events during treatment. Peptide immunotherapy (PIT) was explored to overcome these disadvantages. We confirmed that multiple antigen peptides (MAPs) do not cause autoimmune responses, which led to the presumption that MAPs intervention could alleviate allergic airway inflammation without inducing adverse effects. RESULTS: In this study, synthesized OVA323-339MAP octamers were subcutaneously injected into ovalbumin (OVA)-sensitized and -challenged Balb/c mice to observe its effect on allergic airway inflammation, Th2 immune response, and immune regulating function. It was confirmed that OVA sensitization and challenge led to significant peritracheal inflammatory, cell infiltration, and intensive Th2 response. Treatment of OVA323-339MAP octomers in the airway inflammation mice model increased CD4+CD25+Foxp3+ T regulatory (Treg) cells and their regulatory function in peripheral blood, mediastinal draining lymph nodes, and the spleen. Furthermore, OVA323-339MAP increased IL-10 levels in bronchial alveolar lavage fluid (BALF); up-regulated the expression of IL-10,membrane-bound TGF-beta1, as well as Foxp3 in lung tissues; and up-regulated programmed death-1 (PD-1) and cytotoxic T lymphocyte associated antigen 4 (CTLA-4) on the surface of Treg cells. These results were further correlated with the decreased OVA specific immunoglobulin E (sIgE) level and the infiltration of inflammatory cells such as eosinophils and lymphocytes in BALF. However, OVA323-339 peptide monomers did not show any of the mentioned effects in the same animal model. CONCLUSIONS: Our study indicates that OVA323-339MAP had significant therapeutic effects on mice allergic airway inflammation by regulating the balance of Th1/Th2 response through Treg cells in vivo. Key words Allergic airway inflammation; Specific immunotherapy; Multiple antigen peptide.     

Endothelial amine oxidase AOC3 transiently contributes to adaptive immune responses in the airways

Amine oxidase, copper containing 3 (AOC3, also known as vascular adhesion protein‐1 (VAP‐1)) is an endothelial adhesion molecule that contributes to the extravasation of neutrophils, macrophages, and lymphocytes to sites of inflammation. However, the role of AOC3/VAP‐1 in allergic responses remains unknown. Here, we studied eosinophil and CD4⁺ T‐cell recruitment to the airways using AOC3/VAP‐1‐deficient mice. In an OVA‐triggered asthma model, AOC3/VAP‐1 slightly contributed to the accumulation of leukocytes in lungs in an age‐dependent manner. We then established a new model to kinetically measure recruitment of OVA‐specific CD4⁺ T cells to different airway immune compartments during the priming and effector phases of an adaptive immune response. The results showed that in the absence of AOC3/VAP‐1, recruitment of antigen‐specific CD4⁺ T cells to draining bronchial lymph nodes is reduced by 89% on day 3 after tracheal allergen exposure, but this difference was not observed on day 6. The dispersal of effector cells to lung and tracheal mucosa is AOC3/VAP‐1 independent. Thus, in allergic airway reactions, AOC3/VAP‐1 transiently contributes to the antigen‐specific, CD4⁺ T‐cell traffic to secondary lymphatic tissues, but not to airway mucosa or lung parenchyma. Our results suggest a largely redundant function for AOC3/VAP‐1 in allergic inflammatory responses of the airways.     

Antigen-stimulated lung CD4+ cells produce IL-5, while lymph node CD4+ cells produce Th2 cytokines concomitant with airway eosinophilia and hyperresponsiveness

OBJECTIVE AND DESIGN: We investigated whether airway inflammation in a mouse model of allergic asthma is related to antigen-specific T cell responses in the effector organ, the lung, and in the lung draining lymph nodes (LN). MATERIALS AND SUBJECTS: In BALB/c mice pathophysiological parameters were measured in vivo, and lung draining LN and lung cells were restimulated in vitro. TREATMENT: Mice were sensitized with ovalbumin and repeatedly challenged with ovalbumin or saline inhalation. METHODS: Airway reactivity, inflammation in the airways, serum levels of IgE were measured, and cytokine levels and proliferative responses were determined in antigen-stimulated lymphocyte cultures. RESULTS AND CONCLUSIONS: Sensitization results in antigen-specific Th0-like LN cells, despite the presence of antigen-specific IgE. Repeated antigen inhalation induced airway hyperresponsiveness and eosinophil infiltration concomitant with a shift towards Th2 cytokine production exclusively by lung draining LN T cells. Furthermore, these airway symptoms are associated with antigen-specific CD4+ effector T cells in the airway tissue producing only IL-5, but not IL-4, which are unable to proliferate.     

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.     

Basophils as a primary inducer of the T helper type 2 immunity in ovalbumin‐induced allergic airway inflammation

Antigen‐induced allergic airway inflammation is mediated by T helper type 2 (Th2) cells and their cytokines, but the mechanism that initiates the Th2 immunity is not fully understood. Recent studies show that basophils play important roles in initiating Th2 immunity in some inflammatory models. Here we explored the role of basophils in ovalbumin (OVA) ‐induced airway allergic inflammation in BALB/c mice. We found that OVA sensitization and challenge resulted in a significant increase in the amount of basophils in blood and lung, along with the up‐regulation of activation marker of CD200R. However, depletion of basophils with MAR‐1 or Ba103 antibody attenuated airway inflammation, represented by the significantly decreased amount of the Th2 subset in spleen and draining lymph nodes, interlukin‐4 level in lung and OVA‐special immunoglobulin E (sIgE) levels in serum. On the other hand, adoptive transfer of basophils from OVA‐challenged lung tissue to naive BALB/c mice provoked the Th2 immune response. In addition, pulmonary basophils from OVA‐challenged mice were able to uptake DQ‐OVA and express MHC class II molecules and CD40 in vivo, as well as to release interleukin‐4 following stimulation by IgE–antigen complexes and promote Th2 polarization in vitro. These findings demonstrate that basophils may participate in Th2 immune responses in antigen‐induced allergic airway inflammation and that they do so through facilitating antigen presentation and providing interleukin‐4.     

Respiratory syncytial virus infection does not increase allergen-induced type 2 cytokine production, yet increases airway hyperresponsiveness in mice

Severe respiratory syncytial virus (RSV)-induced disease is associated with childhood asthma and atopy. We combined murine models of allergen-sensitization and RSV infection to explore the interaction of allergic and virus-induced airway inflammation and its impact on airway hyperresponsiveness (AHR). We found that RSV infection during ova-sensitization (OVA/RSV) increased and prolonged AHR compared to mice only RSV-infected (RSV) or ova-sensitized (OVA). AHR is known to be associated with an increase in Type 2 cytokines (IL-4, IL-5, and IL-13) in allergen-sensitized mice. Therefore, we hypothesized that RSV-induced enhancement of AHR was a result of potentiating the Type 2 cytokine profile promoted by ova-sensitization. Surprisingly, we found that Type 2 cytokines induced by ova-sensitization were not increased by RSV infection despite the increase in AHR, and in some cases were diminished. RNAse protection assay revealed no difference in IL-4 and IL-5 mRNA levels between the OVA and OVA/RSV groups, and IL-13 mRNA was significantly decreased in the OVA/RSV mice compared to the OVA group. Flow cytometric analysis of Type 2 cytokines demonstrated the same frequency of IL-4 and IL-5 production in lung-derived T lymphocytes from the OVA/RSV and OVA groups. Direct cytokine ELISA measurements of lung supernatant showed the level of IL-13 was significantly decreased in the OVA/RSV group compared to OVA mice, while there was no difference in either IL-4 or IL-5 between these two groups. These data indicate that the enhanced and prolonged AHR caused by the interaction of allergic airway inflammation and virus-induced immune responses is a complex process that can not be explained simply by augmented production of Type 2 cytokines.     

High-fat feeding redirects cytokine responses and decreases allergic airway eosinophilia

Background Dietary fat intake has been associated with obesity and obesity in its turn with attenuated airway function and asthma, but it is unclear whether or how high-fat intake per se alters immune function relevant to development of allergic asthma.
Objective To use a non-obese mouse model of mild to moderate allergic asthma to compare effects of high-fat with isocaloric control-diet on allergic immune responses.
Methods C57BL/6 mice weaned and maintained on control (11% fat calories) or isocaloric high-fat diet (58% fat calories) were systemically sensitized with ovalbumin and challenged in the lungs. Allergic airway inflammation was assessed by measuring lung inflammation; serum antibodies; and, cytokines in serum, bronchoalveolar lavage (BAL) fluid and in supernatants of in vitro stimulated lung draining lymph node and spleen lymphocytes.
Results There was a significant reduction in lung eosinophilia and IL-5 in high-fat fed mice. Lung draining lymph node cells from these mice showed reduced pro-inflammatory cytokine (MCP-1 and TNF-α) release after ovalbumin re-stimulation and reduced release of IL-13 after concanavalin-A stimulation, indicating a general rather than just an antigen-specific change. There was no difference in IFN-γ release. In contrast, pro-inflammatory cytokine release was increased from splenocytes. Decreased eosinophilia was not due to increased regulatory T cell or IL-10 induction in draining lymph nodes or spleen, nor to changes in antibody response to ovalbumin. However, decreased levels of serum and BAL eotaxin were found in high-fat fed animals.
Conclusions The data indicate that high-fat dietary content redirects local immune responses to allergen in the lungs and systemic responses in the spleen and serum. These effects are not due to changes in regulatory T cell populations but may reflect a failure to mobilize eosinophils in response to allergic challenge.     

Staphylococcus aureus enterotoxin B facilitates allergic sensitization in experimental asthma

Background Staphylococcus aureus Enterotoxin B (SEB) has immunomodulatory effects in allergic airway disease. The potential contribution of SEB to the sensitization process to allergens remains obscure. Objective In order to study the effects of staphylococcal‐derived toxins on the sensitization to ovalbumin (OVA) and induction of allergic airway inflammation, we have combined the nasal application of OVA with different toxins. Methods Nasal applications of OVA and saline, SEA, SEB, toxic shock syndrome toxin (TSST)‐1, protein A or lipopolysaccharide (LPS) were performed on alternate days from day 0 till 12. On day 14, mice were killed for the evaluation of OVA‐specific IgE, cytokine production by mediastinal lymph node (MLN) cells and bronchial hyperreactivity (BHR) to inhaled metacholine. The effect of SEB on dendritic cell (DC) migration and maturation, and on T cell proliferation was evaluated. Results Concomitant endonasal application of OVA and SEB resulted in OVA‐specific IgE production, whereas this was not found with SEA, TSST‐1, protein A, LPS or OVA alone. Increased DC maturation and migration to the draining lymph nodes were observed in OVA/SEB mice, as well as an increased T cell proliferation. Bronchial inflammation with an influx of eosinophils and lymphocytes was demonstrated in OVA/SEB mice, together with hyperresponsiveness and the production of IL‐4, IL‐5, IL‐10 and IL‐13 by MLN stimulated with OVA. Conclusions Our data demonstrate that SEB facilitates sensitization to OVA and consecutive bronchial inflammation with features of allergic asthma. This is likely due to augmentation of DC migration and maturation, as well as the allergen‐specific T cell proliferation upon concomitant OVA and SEB application. Cite this as: W. Huvenne, I. Callebaut, M. Plantinga, J. A. J. Vanoirbeek, O. Krysko, D. M. A. Bullens, P.Gevaert, P. Van Cauwenberge, B. N. Lambrecht, J. L. Ceuppens, C. Bachert and P. W. Hellings, Clinical & Experimental Allergy, 2010 (40) 1079–1080.     

Inhibition of airway eosinophilia and pulmonary pathology in a mouse model of allergic asthma by the live vaccine strain of Francisella tularensis

Background It has been suggested that exposure to certain microbes and their products, particularly during neonatal and early childhood periods, may shift the immune response towards a T-helper cell (Th) 1 phenotype and thereby prevent the development of and/or alleviate the clinical symptoms of allergic airway diseases.
Objective We evaluated the ability of the live vaccine strain (LVS) of Francisella tularensis to suppress airway eosinophilia and pulmonary pathology in a murine model of allergic airway disease.
Methods C57BL/6 mice were sensitized by intraperitoneal injection of ovalbumin (OVA) on days 1 and 14, and challenged intranasally (i.n.) with OVA on day 21 or thereafter. Some sensitized mice were i.n. treated with live LVS or its cell-free sonicate extract (CFSE) before i.n. OVA challenge. Bronchoalveolar lavage fluid, regional lymph node cells, lung tissues and serum samples were collected 3–7 days after the i.n. challenge.
Results Intranasal and, to a lesser degree, intradermal immunization of OVA-sensitized mice with LVS suppressed the development of airway eosinophilia and associated pulmonary pathology induced by i.n. OVA challenge. Moreover, CFSE prepared from LVS showed a similar inhibitory effect whereas neither LPS nor DNA purified from F. tularensis LVS had such an effect. The inhibition was associated with the reduction in mRNA expression and protein levels of Th2 cytokines IL-5 and IL-13 in the lungs and the enhanced production of OVA-induced IFN-γ by local draining lymph node cells, but not with the serum levels of OVA-specific IgG1 or IgE.
Conclusion F. tularensis LVS is capable of suppressing allergic airway inflammation probably through a Th1-mediated suppression of an ongoing Th2 response mechanism, and raises the possibility of exploring LVS and its components as potential therapeutic modalities for human allergic asthma.     

Selective depletion of Foxp3+ Treg during sensitization phase aggravates experimental allergic airway inflammation

Recent studies highlight the role of Treg in preventing unnecessary responses to allergens and maintaining functional immune tolerance in the lung. We investigated the role of Treg during the sensitization phase in a murine model of experimental allergic airway inflammation by selectively depleting the Treg population in vivo. DEpletion of REGulatory T cells (DEREG) mice were depleted of Treg by diphtheria toxin injection. Allergic airway inflammation was induced using OVA as a model allergen. Pathology was assessed by scoring for differential cellular infiltration in bronchoalveolar lavage, IgE and IgG1 levels in serum, cytokine secretion analysis of lymphocytes from lung draining lymph nodes and lung histology. Use of DEREG mice allowed us for the first time to track and specifically deplete both CD25⁺ and CD25^? Foxp3⁺ Treg, and to analyze their significance in limiting pathology in allergic airway inflammation. We observed that depletion of Treg during the priming phase of an active immune response led to a dramatic exacerbation of allergic airway inflammation in mice, suggesting an essential role played by Treg in regulating immune responses against allergens as early as the sensitization phase via maintenance of functional tolerance.     

Effects of anti-inflammatory therapies on recurrent and low-grade respiratory syncytial virus infections in a murine model of asthma.

BACKGROUND: Recurrent and subclinical viral respiratory tract infections could immunologically exacerbate allergic airway inflammation. However, the most appropriate treatment for virus-induced asthma exacerbation is yet to be established. The effects of glucocorticoids in virus-induced acute asthma are controversial. OBJECTIVE: To determine the effects of representative anti-inflammatory therapies for asthma--glucocorticoids and leukotriene receptor antagonists (LTRAs)--in mite allergen-sensitized and repeatedly low-grade respiratory syncytial virus (RSV)--infected mice. METHODS: Dermatophagoides farinae-sensitized mice were inoculated twice with low-grade RSV and subcutaneously injected with either a glucocorticoid or an LTRA for 4 consecutive days. Lung inflammation, cytokine profiles, LT production, and viral RNA in lung tissues were compared in 5 groups of 8 mice each: controls, D farinae allergen sensitized, D farinae sensitized and RSV infected, D farinae sensitized and RSV infected with dexamethasone, and D farinae sensitized and RSV infected with pranlukast, an LTRA. RESULTS: Allergic airway inflammation in D farinae mice was significantly enhanced by recurrent and low-grade RSV infections (RLRIs). The glucocorticoid attenuated allergic airway inflammation, which was associated with interleukin 5 (IL-5) and interferon-gamma (IFN-gamma) suppression in lung-draining lymph nodes without affecting viral quantity. The LTRA also attenuated allergic airway inflammation in D farinae-RSV mice with concomitant inhibition of IL-5 but not IFN-gamma. Dermatophagoides farinae allergen sensitization significantly increased LTs in the airway, whereas RLRIs did not further enhance LT production. CONCLUSIONS: Glucocorticoids and LTRAs significantly inhibit RLRI-induced exacerbation of allergic airway inflammation by distinct pathways. Dexamethasone suppressed nonspecific cytokines, whereas viral RNA did not increase via suppression of immunity. In contrast, pranlukast specifically inhibited IL-5 but not IFN-gamma.     

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.     

IgE-dependent enhancement of Th2 cell-mediated allergic inflammation in the airways

T helper 2 (Th2) cell-derived cytokines, including interleukin (IL)-4, IL-5 and IL-13, play important roles in causing allergic airway inflammation. In contrast to Th2 cells, however, the role of IgE and mast cells in inducing allergic airway inflammation is not understood fully. In the present study, we addressed this point using transgenic mice expressing trinitrophenyl (TNP)-specific IgE (TNP-IgE mice), which enable us to investigate the role of IgE without the influence of antigen-specific T cell activation and other immunoglobulins. When the corresponding antigen, TNP-BSA, was administered intranasally to TNP-IgE mice, a large number of CD4+ T cells were recruited into the airways. In contrast, TNP-BSA administration did not induce eosinophil recruitment into the airways or airway hyperreactivity. Furthermore, when ovalbumin (OVA)-specific Th2 cells were transferred to TNP-IgE mice and the mice were challenged with inhaled OVA, TNP-BSA administration increased OVA-specific T cell recruitment and then enhanced Th2 cell-mediated eosinophil recruitment into the airways. These results indicate that IgE-induced mast cell activation principally induces CD4+ T cell recruitment into the airways and thus plays an important role in enhancing Th2 cell-mediated eosinophilic airway inflammation by recruiting Th2 cells into the site of allergic inflammation.     

Regulatory T cells expressing granzyme B play a critical role in controlling lung inflammation during acute viral infection

The inflammatory response to lung infections must be tightly regulated, enabling pathogen elimination while maintaining crucial gas exchange. Using recently described "depletion of regulatory T cell" (DEREG) mice, we found that selective depletion of regulatory T cells (Tregs) during acute respiratory syncytial virus (RSV) infection enhanced viral clearance but increased weight loss, local cytokine and chemokine release, and T-cell activation and cellular influx into the lungs. Conversely, inflammation was decreased when Treg numbers and activity were boosted using interleukin-2 immune complexes. Unexpectedly, lung (but not draining lymph node) Tregs from RSV-infected mice expressed granzyme B (GzmB), and bone marrow chimeric mice with selective loss of GzmB in the Treg compartment displayed markedly enhanced cellular infiltration into the lung after infection. A crucial role for GzmB-expressing Tregs has not hitherto been described in the lung or during acute infections, but may explain the inability of children with perforin/GzmB defects to regulate immune responses to infection. The effects of RSV infection in mice with defective immune regulation closely parallel the observed effects of RSV in children with bronchiolitis, suggesting that the pathogenesis of bronchiolitis may involve an inability to regulate virus-induced inflammation.