T(H)17 cells mediate pulmonary collateral priming

Interleukin‑27 ameliorates allergic asthma by alleviating the lung Th2 inflammatory environment

Interleukin (IL)‑27 can inhibit the differentiation of Th2 cells and plays a role in the development of asthma. However, whether the therapeutic administration of IL‑27 in a mouse model of asthma can inhibit allergic responses remains a matter of debate. Additionally, the mechanisms through which IL‑27 ameliorates inflammatory responses in asthma are not yet fully understood. Thus, the aim of the present study was to examine the effects of IL‑27 on asthma using a mouse model and to elucidate the underlying mechanisms. For this purpose, mice received an intranasal administration of IL‑27 and the total and differential cell counts, levels of cytokines and type 1 regulatory T (Tr1) cells in the lungs were detected. The protein and mRNA levels of signal transducer and activator of transcription (STAT)1 and STAT3 were analyzed and airway remodeling was assessed. The results indicated that IL‑27 did not ameliorate airway inflammation, airway hyperresponsiveness, and airway remolding when administrated therapeutically. Preventatively, the administration of IL‑27 decreased the concentrations of Th2 cytokines and increased the number of Tr1 cells. The protein and mRNA levels of STAT1 and STAT3 were increased. Taken together, these findings demonstrate that the prophylactic administration of IL‑27 ameliorates asthma by alleviating the lung Th2 inflammatory environment through the restoration of both the STAT1 and STAT3 pathways. IL‑27 may thus prove to be useful as a novel agent for the prevention of asthma.

IL‑27 suppresses airway inflammation, hyperresponsiveness and remodeling via the STAT1 and STAT3 pathways in mice with allergic asthma

Type 2 cytokine-associated immunity may be involved in the pathogenesis of allergic asthma. Although interleukin 27 (IL-27) has been reported as an initiator and suppressor of T-helper 1 (Th1) and T-helper 2 (Th2) responses, respectively, its effects on the development of asthma remain unclear. In the present study, mice were induced and challenged with ovalbumin and received subsequent intranasal administration of IL-27. Total and differential cell counts were determined from Wright-Giemsa-stained cytospins, whereas the cytokine levels were detected using ELISA. In addition, the expression levels of signal transducer and activator of transcription (STAT) 1, STAT3, GATA-binding protein-3 (GATA3) and T-bet (T-box transcription factor) were analyzed in T cells by western blot analysis. Their corresponding mRNA expression levels were determined by quantitative PCR. Airway remodeling was assessed by conventional pathological techniques. The results indicated that intranasal administration of IL-27 ameliorated airway inflammation and hyperresponsiveness in an acute model of asthma. Furthermore, IL-27 prevented airway remodeling in a chronic model of asthma. Following administration of IL-27, the mRNA expression levels of STAT1 and T-bet were upregulated, while those of GATA3 were downregulated. Moreover, the phosphorylation levels of STAT1 and STAT3 were increased. Taken together, these findings demonstrated that intranasal administration of IL-27 ameliorated Th2-related allergic lung inflammation and remodeling in mouse models of asthma by repairing both the STAT1 and STAT3 pathways.

IL-17 regulates DC migration to the peribronchial LNs and allergen presentation in experimental allergic asthma

IL-17 is associated with different phenotypes of asthma, however, it is not fully elucidated how it influences induction and maintenance of asthma and allergy. In order to determine the role of IL-17 in development of allergic asthma, we used IL-17A/F double KO (IL-17A/F KO) and WT mice with or without neutralization of IL-17 in an experimental allergic asthma model and analyzed airway hyperresponsiveness, lung inflammation, T helper cell polarization, and DCs influx and activation. We report that the absence of IL-17 reduced influx of DCs into lungs and lung draining LNs. Compared to WT mice, IL-17A/F KO mice or WT mice after neutralization of IL-17A showed reduced airway hyperresponsiveness, eosinophilia, mucus hypersecretion, and IgE levels. DCs from draining LNs of allergen-challenged IL-17A/F KO mice showed a reduction in expression of migratory and costimulatory molecules CCR7, CCR2, MHC-II, and CD40 compared to WT DCs. Moreover, in vivo stimulation of adoptively transferred antigen-specific cells was attenuated in lung-draining LNs in the absence of IL-17. Thus, we report that IL-17 enhances airway DC activation, migration, and function. Consequently, lack of IL-17 leads to reduced antigen-specific T cell priming and impaired development of experimental allergic asthma.

Cytokines in sensitization to aeroallergens

Knowledge about the immunological mechanisms underlying asthma bronchiale is a prerequisite for development of new (causal) interventions. A large number of studies has proven asthma to be a complex disease with subtypes with different immunological features. Cytokines and chemokines, which are secreted by immune cells as well as structural cells play an important role not only in maintenance and amplification but have significant impact in the initiation of pulmonary inflammations – the asymptomatic sensitization phase. This article describes important immunological mediators in the context of the pulmonary sensitization phase. Moreover chances and constraints of intervention strategies aiming at these mediators are discussed. Several new aspects like classification of immunological phenotypes in bronchial asthma for individualized strategies and taking the sensitization phase into account, reveal possible targets among both “old acquaintances” like IL-4 and newly identified mediators (e.g. IL-17, IL-33).

Suppression of Th17-polarized airway inflammation by rapamycin

Because Th17-polarized airway inflammation correlates with poor control in bronchial asthma and is a feature of numerous other difficult-to-treat inflammatory lung diseases, new therapeutic approaches for this type of airway inflammation are necessary. We assessed different licensed anti-inflammatory agents with known or expected efficacy against Th17-polarization in mouse models of Th17-dependent airway inflammation. Upon intravenous transfer of in vitro derived Th17 cells and intranasal challenge with the corresponding antigen, we established acute and chronic murine models of Th17-polarised airway inflammation. Consecutively, we assessed the efficacy of methylprednisolone, roflumilast, azithromycin, AM80 and rapamycin against acute or chronic Th17-dependent airway inflammation. Quantifiers for Th17-associated inflammation comprised: bronchoalveolar lavage (BAL) differential cell counts, allergen-specific cytokine and immunoglobulin secretion, as well as flow cytometric phenotyping of pulmonary inflammatory cells. Only rapamycin proved effective against acute Th17-dependent airway inflammation, accompanied by increased plasmacytoid dendritic cells (pDCs) and reduced neutrophils as well as reduced CXCL-1 levels in BAL. Chronic Th17-dependent airway inflammation was unaltered by rapamycin treatment. None of the other agents showed efficacy in our models. Our results demonstrate that Th17-dependent airway inflammation is difficult to treat with known agents. However, we identify rapamycin as an agent with inhibitory potential against acute Th17-polarized airway inflammation.

IL-27 Is Essential for Suppression of Experimental Allergic Asthma by the TLR7/8 Agonist R848 (Resiquimod)

Different models of experimental allergic asthma have shown that the TLR7/8 agonist resiquimod (R848) is a potential inhibitor of type 2 helper cell-driven inflammatory responses. However, the mechanisms mediating its therapeutic effects are not fully understood. Using a model of experimental allergic asthma, we show that induction of IL-27 by R848 is critical for the observed ameliorative effects. R848 significantly inhibited all hallmarks of experimental allergic asthma, including airway hyperreactivity, eosinophilic airway inflammation, mucus hypersecretion, and Ag-specific Ig production. Whereas R848 significantly reduced IL-5, IL-13, and IL-17, it induced IFN-γ and IL-27. Neutralization of IL-27 completely reversed the therapeutic effect of R848 in the experimental asthma model, demonstrating dependence of R848-mediated suppression on IL-27. In vitro, R848 induced production of IL-27 by murine alveolar macrophages and dendritic cells and enhanced expression of programmed death-ligand 1, whose expression on monocytes and dendritic cells has been shown to regulate peripheral tolerance in both murine and human studies. Moreover, in vitro IL-27 enhanced secretion of IFN-γ whereas it inhibited IL-5 and IL-13, demonstrating its direct effect on attenuating Th2 responses. Taken together, our study proves that R848-mediated suppression of experimental asthma is dependent on IL-27. These data provide evidence of a central role of IL-27 for the control of Th2-mediated allergic diseases.

Influence of an Allergen-Specific Th17 Response on Remodeling of the Airways

We showed previously that sensitization of mice with dendritic cells (DCs) via the airways depends on activation of these cells with LPS. Allergen-pulsed DCs that were stimulated with low doses of LPS induce a strong Th2 response in vivo. Our objective was to investigate whether airway sensitization of mice by the application of DCs with a phenotype that is able to induce Th17 cells results in increased remodeling of the airways. We generated DCs from the bone marrow of mice and pulsed them with LPS-free ovalbumin. Subsequently, cells were activated with LPS with or without ATP for inflammasome activation. The activated cells were used to sensitize mice via the airways. Intranasal instillation of DCs that were activated with 0.1 ng/ml LPS induced a Th2 response with airway eosinophilia. High doses of LPS, particularly when given in combination with ATP, led to induction of a mixed Th2/Th17 response. Interestingly, we found a correlation between IL-17A production and the remodeling of the airways. Stimulation of mouse fibroblasts with purified IL-17A protein in vitro resulted in transforming growth factor-β1 secretion and collagen transcription. Interestingly, we found enhanced secretion of transforming growth factor-β1 by fibroblasts after costimulation with IL-17A and the profibrotic factor wingless-type MMTV integration site family, member 5A (Wnt5a). We showed that an allergen-specific Th17 response in the airway is accompanied by increased airway remodeling. Furthermore, we revealed that increased remodeling is not only based on neutrophilic inflammation, but also on the direct impact of IL-17A on airway structural cells.

Delineating the role of histamine-1- and -4-receptors in a mouse model of Th2-dependent antigen-specific skin inflammation

BACKGROUND

Histamine drives pruritus in allergic skin diseases which clinically constitutes a most disruptive symptom. Skin pathology in allergic skin diseases is crucially influenced by different T-helper subsets. However, the contribution of different histamine-receptors to T-helper cell dependent skin pathology has not been definitively answered. Models which can specifically address the functional role of T-helper subsets and the mediators involved are therefore valuable to gain further insights into molecular pathways which contribute to allergic skin disease. They might also be helpful to probe amendable therapeutic interventions such as histamine-receptor antagonism.

OBJECTIVE

Establishing an adoptive transfer model for antigen-specific Th cells, we aimed to delineate the role of histamine H1- and H4-receptors in Th2-dependent skin inflammation.

METHODS

In-vitro differentiated and OVA primed Th2 cells were adoptively transferred into congenic recipient mice. In vivo treatment with specific histamine H1- and H4-receptor antagonists was performed to analyze the contribution of these histamine-receptors to Th2-dependent skin pathology in our model. Analysis four days after epicutaneous challenge comprised skin histology, flow cytometric detection of transferred T-helper cells and analysis of antigen-cytokine profiles in skin-draining lymph nodes.

RESULTS

Use of specific H1- and H4-receptor antagonists revealed a crucial role for H1- and H4-receptors for Th2 migration and cytokine secretion in a Th2-driven model of skin inflammation. While H1- and H4-receptor antagonists both reduced Th2 recruitment to the site of challenge, local cytokine responses in skin-draining lymph nodes were only reduced by the combined application of H1- and H4-receptor antagonists and mast cell counts remained altogether unchanged by either H1R-, H4R- or combined antagonism.

CONCLUSION

Our model demonstrates a role for H1- and H4-receptors in Th2 cell infiltration and cytokine secretion in allergic skin diseases and suggests further studies to evaluate these findings for therapeutic approaches.

Advances in mechanisms of asthma, allergy, and immunology in 2011

2011 was marked by rapid progress in the identification of basic mechanisms of allergic disease and the translation of these mechanisms into human cell systems. Studies published in the Journal of Allergy and Clinical Immunology this year provided new insights into the molecular determinants of allergenicity, as well as the environmental, cellular, and genetic factors involved in sensitization to allergens. Several articles focused on mechanisms of allergen immunotherapy and the development of novel strategies to achieve tolerance to allergens. Additional studies identified substantial contributions from T(H)17-type cells and cytokines to human disease pathogenesis. Finally, new therapeutic applications of anti-IgE were identified. The highlights of these studies and their potential clinical implications are summarized in this review.