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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.

Asthma is a widespread chronic multifactorial disease of the airways which is often triggered by the perennial allergen house dust mite (HDM). Next to regulatory T cells (Tregs), IL10 producing regulatory B cells are crucial to substantially counteract inflammatory responses. However, their regulatory impact in asthma is inadequately known so far. To better understand the regulatory influence of B cells in allergic asthma, we employed a HDM-based experimental asthma model using wildtype (WT) and B cell deficient (µMT) mice. Compared to WT counterparts, HDM-sensitized µMT mice developed a significantly increased airway hyperreactivity (AHR), a cardinal feature of asthma, measured by invasive lung function. This observation was confirmed by independent precision cut lung slices (PCLS) technique, demonstrating stronger bronchoconstriction of explanted lung tissue slices of allergic µMT mice after methacholine provocation. Furthermore, allergic µMT mice displayed diminished levels of Tregs and Th2 cytokines, especially IL10, as determined by flow cytometry and immunoassays. Adoptive transfer of naive WT B cells followed by HDM-sensitization substantially attenuated AHR in µMT mice and boosted IL10 production and Treg expansion. To test the impact of IL10, B cells from IL10 deficient (IL10-/-) mice were transferred, but failed to improve lung function of allergic µMT mice. Furthermore, transfer of WT and IL10-/- B cells provoked comparable amounts of IL10 and Tregs. Taken together, our data indicate that B cells are critical in HDM-induced AHR, and that IL10 competent B cells may be central in regulating AHR in allergic airway inflammation.

Allergic asthma is a widespread chronic inflammatory disease of the airways. The role of different B cell subsets in developing asthma and respiratory tolerance is not well known. Especially regulatory B (Breg) cells are proposed to be important in asthma regulation. Using wild-type (WT) and B cell-deficient (μMT) mice we investigated how B cells are affected by induction of allergic airway inflammation and respiratory tolerance and whether they are necessary to develop these conditions. WT mice with an asthma-like phenotype, characterized by increased airway hyper reactivity, eosinophilic airway inflammation, mucus hypersecretion and elevated Th2 cytokines, exhibited increased MHCII and CD23 expression on follicular mature B cells in lung, bronchial lymph nodes (bLN) and spleen, which contributed to allergen-specific T cell proliferation in vitro. Germinal center B cell numbers were elevated and associated with increased production of allergen-specific immunoglobulins especially in bLN. In contrast, respiratory tolerance clearly attenuated these B cell alterations and directly enhanced marginal zone precursor B cells, which induced regulatory T cells in vitro. However, μMT mice developed asthma-like and tolerized phenotypes like WT mice. Our data indicate that although B cell subsets are affected by asthma-like and respiratory tolerant phenotypes, B cells are not required for tolerance induction.

Regulatory T cells (Treg) maintain immunological self-tolerance and their functional or numerical deficits are associated with progression of several neurological diseases. We examined the effects of Treg absence on the structure and integrity of the unchallenged murine brain. When compared to control, Treg-deficient FoxP3sf mutant mice showed no differences in brain size, myelin amount and oligodendrocyte numbers. FoxP3sf strain displayed no variations in quantity of neurons and astrocytes, whereas microglia numbers were slightly reduced. We demonstrate lack of neuroinflammation and parenchymal responses in the brains of Treg-deficient mice, suggesting a minor Treg role in absence of blood-brain barrier breakdown.

The increased susceptibility to infections of neonates is caused by an immaturity of the immune system as a result of both qualitative and quantitative differences between neonatal and adult immune cells. With respect to B cells, neonatal antibody responses are known to be decreased. Accountable for this is an altered composition of the neonatal B cell compartment towards more immature B cells. However, it remains unclear whether the functionality of individual neonatal B cell subsets is altered as well. In the current study we therefore compared phenotypical and functional characteristics of corresponding neonatal and adult B cell subpopulations. No phenotypic differences could be identified with the exception of higher IgM expression in neonatal B cells. Functional analysis revealed differences in proliferation, survival, and B cell receptor signaling. Most importantly, neonatal B cells showed severely impaired class-switch recombination (CSR) to IgG and IgA. This was associated with increased expression of miR-181b in neonatal B cells. Deficiency of miR-181b resulted in increased CSR. With this, our results highlight intrinsic differences that contribute to weaker B cell antibody responses in newborns.

Cellular therapy with chimeric antigen receptor (CAR)-redirected cytotoxic T cells has shown impressive efficacy in the treatment of hematologic malignancies. We explored a regulatory T cell (Treg)-based therapy in the treatment of allergic airway inflammation, a model for asthma, which is characterized by an airway hyper-reactivity (AHR) and a chronic, T helper-2 (Th2) cell-dominated immune response to allergen. To restore the immune balance in the lung, we redirected Tregs by a CAR toward lung epithelia in mice upon experimentally induced allergic asthma, closely mimicking the clinical situation. Adoptively transferred CAR Tregs accumulated in the lung and in tracheobronchial lymph nodes, reduced AHR and diminished eosinophilic airway inflammation, indicated by lower cell numbers in the bronchoalveolar lavage fluid and decreased cell infiltrates in the lung. CAR Treg cells furthermore prevented excessive pulmonary mucus production as well as increase in allergen-specific IgE and Th2 cytokine levels in exposed animals. CAR Tregs were more efficient in controlling asthma than non-modified Tregs, indicating the pivotal role of specific Treg cell activation in the affected organ. Data demonstrate that lung targeting CAR Treg cells ameliorate key features of experimental airway inflammation, paving the way for cell therapy of severe allergic asthma.

Background Allergic asthma is a chronic lung disease resulting from inappropriate immune responses to environmental antigens. Early tolerance induction is an attractive approach for primary prevention of asthma. Objective We analyzed the mechanisms of perinatal tolerance induction to allergens, with particular focus on the role of B cells in preconception and early intrauterine immune priming. Methods Wild-type (WT) and B cell–deficient mice received ovalbumin (OVA) intranasally before mating. Their offspring were analyzed in a murine model of allergic airway inflammation. Results Although antigen application before conception protected WT progeny from allergy, it aggravated allergic airway inflammation in B cell–deficient offspring. B-cell transfer restored protection, demonstrating the crucial role of B cells in perinatal tolerance induction. Effective diaplacentar allergen transfer was detectable in pregnant WT mice but not in pregnant B-cell knockout dams, and antigen concentrations in WT amniotic fluid (AF) were higher than in IgG-free AF of B cell–deficient dams. Application of OVA/IgG immune complexes during pregnancy boosted OVA uptake by fetal dendritic cells (DCs). Fetal DCs in human subjects and mice expressed strikingly higher levels of Fcγ receptors compared with DCs from adults and were highly efficient in taking up OVA/IgG immune complexes. Moreover, murine fetal DCs effectively primed antigen-specific forkhead box P3 + regulatory T cells after in vitro coincubation with OVA/IgG-containing AF. Conclusion Our data support a decisive role for B cells and immunoglobulins during in utero tolerance priming. These findings improve the understanding of perinatal immunity and might support the development of effective primary prevention strategies for allergy and asthma in the future.

The iron-sulfur cluster containing protein mitoNEET is known to modulate the oxidative capacity of cardiac mitochondria but its function during myocardial reperfusion injury after transient ischemia is unknown. The purpose of this study was to analyze the impact of mitoNEET on oxidative stress induced cell death and its relation to the glutathione-redox system in cardiomyocytes in an in vitro model of hypoxia and reoxygenation (H/R). Our results show that siRNA knockdown (KD) of mitoNEET caused an 1.9-fold increase in H/R induced apoptosis compared to H/R control while overexpression of mitoNEET caused a 53% decrease in apoptosis. Necrosis was not affected. Apoptosis of both, mitoNEET-KD and control cells was diminished to comparable levels by using the antioxidants Tiron and glutathione compound glutathione reduced ethyl ester (GSH-MEE), indicating that mitoNEET-dependent apoptosis is mediated by oxidative stress. The interplay between mitoNEET and glutathione redox system was assessed by treating cardiomyocytes with 2-acetylamino-3-[4-(2-acetylamino-2-carboxyethylsulfanylthio-carbonylamino) phenylthiocarbamoylsulfanyl] propionic acid (2-AAPA), known to effectively inhibit glutathione reductase (GSR) and to decrease the GSH/GSSG ratio. Surprisingly, inhibition of GSR-activity to 20% by 2-AAPA decreased apoptosis of control and mitoNEET-KD cells to 23% and 25% respectively, while at the same time mitoNEET-protein was increased 4-fold. This effect on mitoNEET-protein was not accessible by mitoNEET-KD but was reversed by GSH-MEE. In conclusion we show that mitoNEET protects cardiomyocytes from oxidative stress-induced apoptosis during H/R. Inhibition of GSH-recycling, GSR-activity by 2-AAPA increased mitoNEET-protein, accompanied by reduced apoptosis. Addition of GSH reversed these effects suggesting that mitoNEET can in part compensate for imbalances in the antioxidative glutathione-system and therefore could serve as a potential therapeutic approach for the oxidatively stressed myocardium. peerReviewed

Foxp3(+) regulatory T (Treg) cells play a pivotal role in maintaining immunological tolerance. Loss-of-function mutations in the Foxp3 gene result in multiorgan inflammation known as immunodysregulation, polyendocrinopathy, enteropathy, X-linked syndrome in humans and scurfy (Sf) disease in mice. While the impact of missing Treg cells on adaptive immune cells is well documented, their role in regulation of myeloid cells remains unclear. Here we report that Sf mice exhibit an altered composition of stem and progenitor cells, characterized by increased numbers of myeloid precursors and higher efficiency of macrophage generation ex vivo. The proportion of monocytes/macrophages in the bone marrow, blood, and spleen was significantly elevated in Sf mice, which was accompanied with tissue-specific monocyte expression of homing receptor and phagocytic activity. Sf mice displayed high levels of M-CSF and other inflammatory cytokines, including monocyte-recruiting chemokines. Adoptive transfer of WT CD4(+) cells and in vivo neutralization of M-CSF normalized frequencies of monocyte subsets and their progenitors and reduced high levels of monocyte-related cytokines in Sf mice, while Treg cell transfer to RAG2(-/-) mice had no effect on myelopoiesis and monocyte/macrophage counts. Our findings illustrate that deregulated myelopoiesis in Sf mice is mainly caused by the inflammatory reaction resulting from the lack of Treg cells.