Toll‐like receptor 4 agonists adsorbed to aluminium hydroxide adjuvant attenuate ovalbumin‐specific allergic airway disease: role of MyD88 adaptor molecule and interleukin‐12/interferon‐γ axis

Background Epidemiological and experimental data suggest that bacterial lipopolysaccharides (LPS) can either protect from or exacerbate allergic asthma. Lipopolysaccharides trigger immune responses through toll‐like receptor 4 (TLR4) that in turn activates two major signalling pathways via either MyD88 or TRIF adaptor proteins. The LPS is a pro‐Type 1 T helper cells (Th1) adjuvant while aluminium hydroxide (alum) is a strong Type 2 T helper cells (Th2) adjuvant, but the effect of the mixing of both adjuvants on the development of lung allergy has not been investigated. Objective We determined whether natural (LPS) or synthetic (ER‐803022) TLR4 agonists adsorbed onto alum adjuvant affect allergen sensitization and development of airway allergic disease. To dissect LPS‐induced molecular pathways, we used TLR4‐, MyD88‐, TRIF‐, or IL‐12/IFN‐γ‐deficient mice. Methods Mice were sensitized with subcutaneous injections of ovalbumin (OVA) with or without TLR4 agonists co‐adsorbed onto alum and challenged with intranasally with OVA. The development of allergic lung disease was evaluated 24 h after last OVA challenge. Results Sensitization with OVA plus LPS co‐adsorbed onto alum impaired in dose‐dependent manner OVA‐induced Th2‐mediated allergic responses such as airway eosinophilia, type‐2 cytokines secretion, airway hyper‐reactivity, mucus hyper production and serum levels of IgE or IgG1 anaphylactic antibodies. Although the levels of IgG2a, Th1‐affiliated isotype increased, investigation into the lung‐specific effects revealed that LPS did not induce a Th1 pattern of inflammation. Lipopolysaccharides impaired the development of Th2 immunity, signaling via TLR4 and MyD88 molecules and via the IL‐12/IFN‐γ axis, but not through TRIF pathway. Moreover, the synthetic TLR4 agonists that proved to have a less systemic inflammatory response than LPS also protected against allergic asthma development. Conclusion Toll‐like receptor 4 agonists co‐adsorbed with allergen onto alum down‐modulate allergic lung disease and prevent the development of polarized T cell‐mediated airway inflammation.     

Both FcγRIV and FcγRIII are essential receptors mediating type II and type III autoimmune responses via FcRγ‐LAT‐dependent generation of C5a

FcγRIV is a relatively new IgG Fc receptor (FcγR) that is reported to contribute to the pathogenesis of autoimmune diseases, although its specific role in relation to FcγRIII, complement and IgG2 subclasses remains uncertain. Here we define FcγRIV on macrophages as a receptor for soluble IgG2a/b complexes but not for cellular bound IgG2a and show that simultaneous activation of FcγRIV and FcγRIII is critical to mediate certain type II/III autoimmune responses. FcγRIII‐deficient mice display compensatory enhanced FcγRIV expression, are protected from lung inflammation after deposition of IgG complexes, and show reduced sensitivity to IgG2a/b‐mediated hemolytic anemia, indicating that increased FcγRIV alone is not sufficient to trigger these diseases in the absence of FcγRIII. Importantly, however, blockade of FcγRIV is also effective in inhibiting phagocytosis and cytokine production in IgG2b‐induced anemia and acute lung injury, processes that display a further dependence on C5a anaphylatoxin receptor. Using gene deletion and functional inhibition studies, we found that FcγRIII and FcγRIV are each essential to trigger an FcRγ‐linker for activation of T‐cell‐dependent signal that drives C5a production in the Arthus reaction. Together, the results demonstrate a combined requirement for FcγRIII and FcγRIV in autoimmune injury, and identify the linker for activation of T cells adaptor as an integral component of linked FcγR and C5a anaphylatoxin receptor activation to generate inflammation.     

Targeting SIRP‐α protects from type 2‐driven allergic airway inflammation

The interplay between innate and adaptive immune responses is essential for the establishment of allergic diseases. CD47 and its receptor, signal regulatory protein α (SIRP‐α), govern innate cell trafficking. We previously reported that administration of CD47^+/+ but not CD47^−/− SIRP‐α⁺ BM‐derived DC (BMDC) induced airway inflammation and Th2 responses in otherwise resistant CD47‐deficient mice. We show here that early administration of a CD47‐Fc fusion molecule suppressed the accumulation of SIRP‐α⁺ DC in mediastinal LN, the development of systemic and local Th2 responses as well as airway inflammation in sensitized and challenged BALB/c mice. Mechanistic studies highlighted that SIRP‐α ligation by CD47‐Fc on BMDC did not impair Ag uptake, Ag presentation and Ag‐specific DO11.10 Tg Th2 priming and effector function in vitro, whereas in vivo administration of CD47‐Fc or CD47‐Fc‐pretreated BMDC inhibited Tg T‐cell proliferation, pinpointing that altered DC trafficking accounts for defective Th priming. We conclude that the CD47/SIRP‐α axis may be harnessed in vivo to suppress airway SIRP‐α⁺ DC homing to mediastinal LN, Th2 responses and allergic airway inflammation.     

Blockade of cysteinyl leukotriene‐1 receptors suppresses airway remodelling in mice overexpressing GATA‐3

Background We demonstrated previously that GATA‐3 overexpression markedly enhanced allergen‐induced airway inflammation and airway remodelling, including subepithelial fibrosis, and smooth muscle cell hyperplasia, in transgenic mice. Objective Because cysteinyl leukotrienes (cysLTs) have been shown to be involved in such structural changes, the effects of a specific cysLT1 receptor antagonist, montelukast, were evaluated in a mouse model of chronic asthma. Methods GATA‐3‐overexpressing mice and wild‐type Balb/c mice were sensitized and repeatedly challenged by ovalbumin (OVA) or saline. The effects of montelukast on the development of airway remodelling were compared between the two mouse genotypes. Results CysLTs in the lung were increased after repeated allergen challenges, and significantly enhanced in GATA‐3‐overexpressing mice. The enhanced cysLT levels were accompanied by the development of eosinophilia, smooth muscle cell hyperplasia, and increased stromal cell‐derived factor‐1 gene expression with a small increase in pro‐collagen gene expression in OVA‐challenged GATA‐3‐overexpressing mice, but not in wild‐type mice. Montelukast significantly decreased lung cysLT levels and inhibited the GATA‐3‐overexpression‐related airway remodelling, potently preventing smooth muscle cell hyperplasia, but partially suppressed the increased pro‐collagen gene expression and eosinophilic inflammation. Increases in the levels of IL‐4, IL‐5, IL‐13, and eotaxin in bronchial lavage and TGF‐β gene expression in the lungs were induced by OVA in both mouse genotypes. Montelukast treatment also significantly reduced these levels to the levels seen after saline challenges in GATA‐3‐overexpressing mice. Conclusion Montelukast efficaciously prevented airway inflammation and remodelling in a GATA‐3‐overexpression antigen challenge mouse model by decreasing the cysLT‐driven Th2 cytokine cycle of amplification of airway pathologies. Cite this as: T. Kiwamoto, Y. Ishii, Y. Morishima, K. Yoh, N. Kikuchi, N. Haraguchi, H. Masuko, M. Kawaguchi, A. Nomura, T. Sakamoto, S. Takahashi and N. Hizawa, Clinical & Experimental Allergy, 2011 (41) 116–128.     

Respiratory syncytial virus protects against the subsequent development of ovalbumin‐induced allergic responses by inhibiting Th2‐type γδ T cells

Respiratory syncytial virus (RSV) infection has been hypothesized to be a risk factor for the development of allergy and asthma, but epidemiologic studies in humans still remain inconclusive. The association between RSV infection and allergic diseases may be dependent on an atopic background and previous history of RSV infection. It has been reported that RSV infection before sensitization to an allergen decreased the production of Th2‐like cytokines in the lung and the levels of allergen‐specific Th2‐type antibodies in the serum. However, the underlying mechanisms are largely unknown. In the present study, the role of pulmonary γδ T cells in RSV‐affected, allergen‐induced airway inflammation was investigated. BALB/c mice were sensitized to or challenged with ovalbumin (OVA) and infected with RSV either before or after the sensitization period. It became clear that sensitization and challenge of mice with OVA induced a large influx of γδ T cells to the lungs. However, prior RSV infection inhibited the infiltration of γδ T cells as well as activated γδ T cells, characterized by expression of CD40L or CD69 molecular in the cell surface. Moreover, prior RSV infection elevated the type 1 cytokine gene expression but suppressed type 2 cytokine expression in the lung γδ T cells. Adoptive transfer of γδ T cells from OVA‐sensitized and challenged mice increased airway inflammation, suggesting that γδ T cells may play a proinflammatory role in allergic responses. These results described here support the idea of an unknown γδ T cell‐dependent mechanism in the regulation of RSV‐affected, allergen‐induced allergic airway responses. J. Med. Virol. 85:149–156, 2012. © 2012 Wiley Periodicals, Inc.     

Human Fcγ receptors compete for TGN1412 binding that determines the antibody's effector function

The first‐in‐human clinical trial of the CD28‐specific monoclonal antibody (mAb) TGN1412 resulted in a life‐threatening cytokine release syndrome. Although TGN1412 was designed as IgG4, known for weak Fc:Fcγ receptor (FcγR) interactions, these interactions contributed to TGN1412‐induced T‐cell activation. Using cell lines (TFs) expressing human FcγRI, ‐IIa, ‐IIb, or ‐III, we show that TGN1412 and TGN1412 as IgG1 and IgG2 are bound by FcγRs as it can be deduced from literature. However, upon coculture of TGN1412‐decorated T cells with TFs or human primary blood cells, we observed that binding capacities by FcγRs do not correlate with the strength of the mediated effector function. FcγRIIa and FcγRIIb, showing no or very minor binding to TGN1412, mediated strongest T cell proliferation, while high‐affinity FcγRI, exhibiting strong TGN1412 binding, mediated hardly any T‐cell proliferation. These findings are of biological relevance because we show that FcγRI binds TGN1412, thus prevents binding to FcγRIIa or FcγRIIb, and consequently disables T‐cell proliferation. In line with this, FcγRI^?FcγRII⁺ but not FcγRI⁺FcγRII⁺ monocytes mediate TGN1412‐induced T‐cell proliferation. Collectively, by using TGN1412 as example, our results indicate that binding of monomeric IgG subclasses does not predict the FcγR‐mediated effector function, which has major implications for the design of therapeutic mAbs.     

Antigen‐specific airway IL‐33 production depends on FcγR‐mediated incorporation of the antigen by alveolar macrophages in sensitized mice

Although interleukin (IL)‐33 is a candidate for the aggravation of asthma, the mechanisms underlying antigen‐specific IL‐33 production in the lung are unclear. Therefore, we analysed the mechanisms in mice. Intra‐tracheal administration of ovalbumin (OVA) evoked increases in IL‐33 and IL‐33 mRNA in the lungs of both non‐sensitized and OVA‐sensitized mice, and the increases in the sensitized mice were significantly higher than in the non‐sensitized mice. However, intra‐tracheal administration of bovine serum albumin did not increase the IL‐33 level in the OVA‐sensitized mice. Depletion of neither mast cells/basophils nor CD4⁺ cells abolished the OVA‐induced IL‐33 production in sensitized mice, suggesting that the antigen recognition leading to the IL‐33 production was not related with either antigen‐specific IgE‐bearing mast cells/basophils or memory CD4⁺ Th2 cells. When a fluorogenic substrate‐labelled OVA (DQ‐OVA) was intra‐tracheally administered, the lung cells of sensitized mice incorporated more DQ‐OVA than those of non‐sensitized mice. The lung cells incorporating DQ‐OVA included B‐cells and alveolar macrophages. The allergic IL‐33 production was significantly reduced by treatment with anti‐FcγRII/III mAb. Depletion of alveolar macrophages by clodronate liposomes significantly suppressed the allergic IL‐33 production, whereas depletion of B‐cells by anti‐CD20 mAb did not. These results suggest that the administered OVA in the lung bound antigen‐specific IgG Ab, and then alveolar macrophages incorporated the immune complex through FcγRII/III on the cell surface, resulting in IL‐33 production in sensitized mice. The mechanisms underlying the antigen‐specific IL‐33 production may aid in development of new pharmacotherapies.     

Lack of Fc Gamma Receptor IIIA Promotes Rather than Suppresses Humoral and Cellular Immune Responses after Mucosal or Parenteral Immunization with Antigen and Adjuvants

The Fcγ receptor IIIA (FcγRIIIA) has traditionally been known as a positive regulator of immune responses. Consistent with this, mice deficient in FcγRIIIA are protected from various inflammation‐associated pathologies including several autoimmune diseases. In contrast to this accepted dogma, we show here that mice lacking FcγRIIIA developed increased rather than reduced both humoral and cellular immune responses to mucosal (sublingual) immunization with ovalbumin (OVA) given together with the strong mucosal adjuvant cholera toxin as well as to parenteral (subcutaneous) immunization with OVA in complete Freund's adjuvant. After either route of immunization, in comparison with concomitantly immunized wild‐type mice, FcγRIIIA^−/− mice had increased serum anti‐OVA IgG (IgG1 but not IgG2) antibody responses as well as augmented cellular responses that included memory B cells and effector T cells. The increments in immune responses in FcγRIIIA^−/− mice were similar to those seen in FcγRIIB^−/− mice. Furthermore, OVA‐pulsed FcγRIIIA^−/− DCs, similar to OVA‐specific FcγRIIB^−/− DCs, had enhanced capacity to activate OVA‐specific OT‐II T cells, which was even further pronounced when DCs were pulsed with IgG1‐complexed OVA. Our data support an inhibitory–regulatory role of FcγRIIIA on vaccine/adjuvant‐induced immune responses and demonstrate that lack of FcγRIIIA can promote rather than suppress both humoral and cellular immune responses.     

Anti‐Asthma Simplified Herbal Medicine Intervention‐induced long‐lasting tolerance to allergen exposure in an asthma model is interferon‐γ, but not transforming growth factor‐β dependent

Background Chronic allergic asthma is the result of a T‐helper type 2 (Th2)‐biased immune status. Current asthma therapies control symptoms in some patients, but a long‐lasting therapy has not been established. Anti‐Asthma Simplified Herbal Medicine Intervention (ASHMI^?), a Chinese herbal formula improved symptoms and lung function, and reduced Th2 responses in a controlled trial of patients with persistent moderate to severe asthma. Objective We evaluated the persistence of ASHMI^? beneficial effects following therapy in a murine model of chronic asthma and the immunological mechanisms underlying such effects. Methods BALB/c mice sensitized intraperitoneally with ovalbumin (OVA) received 3 weekly intratracheal OVA challenges to induce airway hyper‐reactivity (AHR) and inflammation (OVA mice). Additionally, OVA mice were treated with ASHMI^? (OVA/ASHMI^?) or water (OVA/sham) for 4 weeks, and then challenged immediately and 8 weeks post‐therapy. In other experiments, OVA mice received ASHMI^? treatment with concomitant neutralization of IFN‐γ or TGF‐β. Effects on airway responses, cytokine‐ and OVA‐specific IgE levels were determined 8 weeks post‐therapy. Results Before treatment, OVA mice exhibited AHR and pulmonary eosinophilic inflammation following OVA challenge, which was almost completely resolved immediately after completing treatment with ASHMI^? and did not re‐occur following OVA re‐challenge up to 8 weeks post‐therapy. Decreased allergen‐specific IgE and Th2 cytokine levels, and increased IFN‐γ levels also persisted at least 8 weeks post‐therapy. ASHMI^? effects were eliminated by the neutralization of IFN‐γ, but not TGF‐β, during therapy. Conclusion ASHMI^? induced long‐lasting post‐therapy tolerance to antigen‐induced inflammation and AHR. IFN‐γ is a critical factor in ASHMI^? effects. Cite this as: K. Srivastava, T. Zhang, N. Yang, H. Sampson and X. M. Li, Clinical & Experimental Allergy, 2010 (40) 1678–1688.     

Bacillus‐derived poly‐γ‐glutamic acid attenuates allergic airway inflammation through a Toll‐like receptor‐4‐dependent pathway in a murine model of asthma

Background Asthma is an inflammatory disease of the airways that is mediated by Th2 responses. Poly‐γ‐glutamic acid (γ‐PGA) is an extracellular polymeric compound that is synthesized by Bacillus cells. Previously, we found that γ‐PGA promoted Th1 cell development in a manner dependent on antigen‐presenting cells, but inhibited Th2 cell development. Objective To investigate the effect of γ‐PGA on dendritic cells (DCs), and its potential for treating Th2‐mediated allergic asthma. Methods Wild‐type, Toll‐like receptor (TLR)‐2 deficient, and TLR‐4‐defective mice were used. DCs derived from the bone marrow and extracted from the lung were stimulated with γ‐PGA and assayed for the expression of signalling molecules, costimulatory molecules, and cytokines. Mice were sensitized and challenged with ovalbumin (OVA) to induce asthma. They were repeatedly injected intranasally with γ‐PGA before and during the challenge period, and inflammation and structural remodelling of the airways were examined. Results γ‐PGA selectively signalled conventional DCs to activate NF‐κB and mitogen‐activated protein kinase, leading to the up‐regulation of CD86, CD40, and IL‐12, but not IL‐10 and IL‐6. These effects of γ‐PGA were dependent on TLR‐4 and independent of TLR‐2. Importantly, the intranasal administration of γ‐PGA to OVA‐sensitized/challenged mice reduced the airway hyperresponsiveness and allergic inflammation such as leucocyte influx, goblet cell hyperplasia, eosinophilia, and Th2 cytokine production. In addition to lowered IgE titres, the treatment of mice with γ‐PGA significantly reduced the multiplication and Th2 polarization of mediastinal lymph node T cells upon allergen‐specific restimulation. These anti‐asthmatic effects of γ‐PGA were also abolished in TLR‐4‐defective mice. Conclusions and Clinical Relevance Our data indicate that γ‐PGA activates DCs to favour Th1 cell induction through a TLR‐4‐dependent pathway and alleviates pathologic symptoms in a Th2‐biased asthmatic model. These findings highlight the potential of γ‐PGA for the treatment of asthma and other allergic disease in which Th2 polarization plays an important role. Cite this as: K. Lee, S.‐H. Kim, H. J. Yoon, D. J. Paik, J. M. Kim and J. Youn, Clinical & Experimental Allergy, 2011 (41) 1143–1156.     

IgE/antigen‐mediated enhancement of IgE production is a mechanism underlying the exacerbation of airway inflammation and remodelling in mice

IgE is known to enhance some antibody responses to specific antigens, but whether this contributes to allergic asthma remains unclear. We have previously found that repeated antigen challenges in mice sensitized with antigen‐specific IgE monoclonal antibody (mAb) exacerbated airway inflammation and remodelling accompanied by increased levels of endogenous antigen‐specific IgE and IgG1. Here, we investigated whether IgE/antigen‐mediated enhancement of endogenous IgE production contributes to the exacerbation of airway inflammation and remodelling. BALB/c mice passively sensitized with ovalbumin (OVA) ‐specific IgE mAb were challenged with OVA intratracheally seven times; anti‐IgE mAb was intraperitoneally administered 1 day before the fourth challenge. Treatment with anti‐IgE mAb inhibited the increased level of endogenous OVA‐specific IgE in serum, but not OVA‐specific IgG1, and a biphasic increase in airway resistance at the fourth challenge. Furthermore, a biphasic increase in airway resistance, airway hyper‐responsiveness to methacholine, OVA‐specific IgE and IgG1 production, and infiltrations by neutrophils and eosinophils in the lungs at the seventh challenge were suppressed by treatment; airway remodelling, such as goblet cell hyperplasia and sub‐epithelial fibrosis, was also reduced. In addition, the production of interleukin‐17A, interleukin‐33 and CXCL1 in the lungs related to these IgE‐mediated responses was decreased by treatment. Collectively, we found that the mechanism leading to the exacerbation of allergic asthma is closely related to IgE/antigen‐mediated enhancement of IgE production, suggesting that this may create a vicious circle leading to the chronic status in asthmatic patients having levels of antigen‐specific IgE ready to form complexes with antigen.     

Transgenic expression of survivin compensates for OX40‐deficiency in driving Th2 development and allergic inflammation

Survivin, an inhibitor of apoptosis family molecule, has been proposed as a crucial intermediate in the signaling pathways leading to T‐cell development, proliferation, and expansion. However, the importance of survivin to T‐cell‐driven inflammatory responses has not been demonstrated. Here, we show that survivin transgenic mice exhibit an increased antigen‐driven Th2 lung inflammation and that constitutive expression of survivin reversed the defective lung inflammation even in the absence of OX40 costimulation. We found that OX40‐deficient mice were compromised in generating Th2 cells, airway eosinophilia, and IgE responses. In contrast, OX40‐deficient/survivin transgenic mice generated normal Th2 responses and exhibited strong lung inflammation. These results suggest that OX40 costimulation crucially engages survivin during antigen‐mediated Th2 responses. These findings also promote the notion that OX40 costimulation regulates allergic responses or lung inflammation by targeting survivin thereby enhancing T‐cell proliferation and resulting in more differentiated Th2 cells in the allergic inflammatory response.     

United airways: circulating Th2 effector cells in an allergic rhinitis model are responsible for promoting lower airways inflammation

Background Allergic rhinitis (AR) and asthma often coexist and are referred to as ‘united airways’ disease. However, the molecular and cellular pathways that are crucially involved in the interaction between upper and lower airways remain to be identified. Objective We sought to assess whether and how AR exacerbates lower airway inflammation upon allergen challenge in mice. Methods We previously developed an intranasal ovalbumin (OVA)‐driven AR model, characterized by nasal eosinophilic inflammation, enhanced serum levels of OVA‐specific IgE and Th2 cytokine production in cervical lymph nodes. In OVA‐sensitized mice with or without AR, a lower airway challenge was given, and after 24 h, lower airway inflammation was analysed. Results We found that AR mice were more susceptible to eosinophilic inflammation following a lower airway OVA challenge than OVA‐sensitized controls. AR mice manifested increased numbers of eosinophils in bronchoalveolar lavage fluid and increased inter‐cellular adhesion molecule‐1 (ICAM‐1) expression on lung endothelium, when compared with OVA‐sensitized controls. Depletion of T cells in OVA‐challenged AR mice completely abrogated all hallmarks of lower airway inflammation, including enhanced IL‐5 and tissue eosinophilia. Conversely, adoptive transfer of Th2 effector cells in naïve animals induced lower airway eosinophilic inflammation after challenge with OVA. Blocking T cell recirculation during AR development by the spingosine‐1 analogue FTY720 also prevented lower airway inflammation including ICAM‐1 expression in AR mice upon a single lower airway challenge. Conclusion Our mouse model of ‘united airways’ disease supports epidemiological and clinical data that AR has a significant impact on lower airway inflammation. Circulating Th2 effector cells are responsible for lung priming in AR mice, most likely through up‐regulation of ICAM‐1. Cite this as: A. KleinJan, M. Willart, M. van Nimwegen, K. Leman, H. C. Hoogsteden, R.W. Hendriks and B.N. Lambrecht, Clinical & Experimental Allergy, 2010 (40) 494–504.     

Administration of polysaccharides from Antrodia camphorata modulates dendritic cell function and alleviates allergen‐induced T helper type 2 responses in a mouse model of asthma

Asthma is a chronic disease characterized by airway inflammation caused by the dysregulated production of cytokines secreted by allergen‐specific type 2 T helper (Th2) cells. Antrodia camphorata is a commonly used fungus in Asian folk medicine, and A. camphorata polysaccharides are reported to possess anti‐cancer activities. In this study, the immunomodulatory effects of purified fractionated polysaccharides (GF2) from A. camphorata on dendritic cells (DCs) and their potential preventive effects against ovalbumin (OVA) ‐induced asthma were investigated. In the presence of GF2, lipopolysaccharide (LPS) ‐activated DCs exhibited up‐regulated expression of major histocompatibility complex (MHC) class II and co‐stimulatory molecules, as well as enhanced interleukin‐10 (IL‐10) and IL‐12 production. GF2 treatment on LPS‐activated DCs suppressed naïve CD4⁺ T‐cell proliferation and Th2 cell polarization with IL‐10 production in an allogeneic mixed lymphocyte reaction. In animal experiments, a high dose of GF2 efficiently reduced expression levels of OVA‐specific immunoglobulin G1 (IgG1) and IgE. However, lower doses of GF2 significantly enhanced OVA‐specific IgG2a production. Our data also showed that administration of GF2 dose‐dependently inhibited the development of airway hyperresponsiveness, airway eosinophilia and Th2 responses. OVA‐specific CD4⁺ T cells from higher doses of GF2‐treated mice had significantly lower proliferative capacities compared with control mice. Moreover, treatment with GF2 significantly increased the high levels of IL‐10 and low levels of interferon‐γ produced by T cells. Taken together, these data indicate that administration of A. camphorata polysaccharides (GF2) may have therapeutic potential when used as an adjuvant for the immunomodulatory treatment of allergic asthma.     

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.     

Activation of invariant natural killer T cells in regional lymph nodes as new antigen‐specific immunotherapy via induction of interleukin‐21 and interferon‐γ

Invariant natural killer T (iNKT) cells play important immunoregulatory functions in allergen‐induced airway hyperresponsiveness and inflammation. To clarify the role of iNKT cells in allergic rhinitis (AR), we generated bone marrow‐derived dendritic cells (BMDCs), which were pulsed by ovalbumin (OVA) and α‐galactosylceramide (OVA/α‐GalCer‐BMDCs) and administered into the oral submucosa of OVA‐sensitized mice before nasal challenge. Nasal symptoms, level of OVA‐specific immunoglobulin (IgE), and T helper type 2 (Th2) cytokine production in cervical lymph nodes (CLNs) were significantly ameliorated in wild‐type (WT) mice treated with OVA/α‐GalCer‐BMDCs, but not in WT mice treated with OVA‐BMDCs. These anti‐allergic effects were not observed in Jα18^–/– recipients that lack iNKT cells, even after similar treatment with OVA/α‐GalCer‐BMDCs in an adoptive transfer study with CD4⁺ T cells and B cells from OVA‐sensitized WT mice. In WT recipients of OVA/α‐GalCer‐BMDCs, the number of interleukin (IL)‐21‐producing iNKT cells increased significantly and the Th1/Th2 balance shifted towards the Th1 dominant state. Treatment with anti‐IL‐21 and anti‐interferon (IFN)‐γ antibodies abrogated these anti‐allergic effects in mice treated with α‐GalCer/OVA‐BMDCs. These results suggest that activation of iNKT cells in regional lymph nodes induces anti‐allergic effects through production of IL‐21 or IFN‐γ, and that these effects are enhanced by simultaneous stimulation with antigen. Thus, iNKT cells might be a useful target in development of new treatment strategies for AR.     

Pulmonary eosinophilia correlates with allergen deposition to the lower respiratory tract in a mouse model of asthma

Background Eosinophilic infiltration into the airways is frequently associated with allergic asthma; however, the role of antigen deposition in mediating this phenomenon has not been studied in detail.
Objective Using a murine model of ovalbumin (OVA) allergy, we examined how differential deposition of OVA during antigen challenge affects pulmonary eosinophilia, immune response and airway hyper-reactivity (AHR).
Methods Differential allergen deposition to the upper respiratory tract (URT) alone or combined upper and lower respiratory tract (ULRT) was accomplished by administering OVA intranasally to either anaesthetized or unanaesthetized mice, respectively. BALB/c mice (6–7 weeks old) were sensitized with OVA–alum via the intraperitoneal route, and then challenged intranasally using OVA, with or without anaesthesia. AHR, enumeration of inflammatory cells and quantitative measurement of inflammatory cytokines and chemokines in bronchoalveolar lavage fluid (BALF), lung histopathology and immune responses were subsequently assessed.
Results In sensitized animals challenged via the ULRT route, a profound eosinophilia and goblet cell hyperplasia was observed in lung tissue. Conversely, sensitized mice receiving an identical challenge dose via the URT route alone exhibited only negligible levels of inflammation. Interestingly, AHR and OVA-specific IgG₁ and IgE systemic responses were comparable between the two groups.
Conclusion This study indicates that direct exposure of allergen in the deep lung is highly correlated with airway eosinophilia and lung inflammation, but does not correlate with AHR or immune response.