Prophylactic allergen immunotherapy with Der p 2 prevents murine asthma by regulating lung GM-CSF

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Myocardial infarction primes autoreactive T cells through activation of dendritic cells

Peripheral tolerance is crucial for avoiding activation of self-reactive T cells to tissue-restricted antigens. Sterile tissue injury can break peripheral tolerance, but it is unclear how autoreactive T cells get activated in response to self. An example of a sterile injury is myocardial infarction (MI). We hypothesized that tissue necrosis is an activator of dendritic cells (DCs), which control tolerance to self-antigens. DC subsets of a murine healthy heart consisted of IRF8-dependent conventional (c) DC1, IRF4-dependent cDC2, and monocyte-derived DCs. In steady state, cardiac self-antigen alpha-myosin was presented in the heart-draining mediastinal lymph node (mLN) by cDC1s, driving the proliferation of antigen-specific CD4(+) TCR-M T cells and their differentiation into regulatory cells (Tregs). Following MI, all DC subsets infiltrated the heart, whereas only cDCs migrated to the mLN. Here, cDC2s induced TCR-M proliferation and differentiation into interleukin-(IL)-17/interferon-(IFN) gamma-producing effector cells. Thus, cardiac-specific autoreactive T cells get activated by mature DCs following myocardial infarction

The ubiquitin-editing enzyme A20 controls NK cell homeostasis through regulation of mTOR activity and TNF

The ubiquitin-editing enzyme A20 is a well-known regulator of immune cell function and homeostasis. In addition, A20 protects cells from death in an ill-defined manner. While most studies focus on its role in the TNF-receptor complex, we here identify a novel component in the A20-mediated decision between life and death. Loss of A20 in NK cells led to spontaneous NK cell death and severe NK cell lymphopenia. The few remaining NK cells showed an immature, hyperactivated phenotype, hallmarked by the basal release of cytokines and cytotoxic molecules. NK-A20(-/-) cells were hypersensitive to TNF-induced cell death and could be rescued, at least partially, by a combined deficiency with TNF. Unexpectedly, rapamycin, a well-established inhibitor of mTOR, also strongly protected NK-A20(-/-) cells from death, and further studies revealed that A20 restricts mTOR activation in NK cells. This study therefore maps A20 as a crucial regulator of mTOR signaling and underscores the need for a tightly balanced mTOR pathway in NK cell homeostasis

Interleukin-33-activated basophils promote asthma by regulating Th2 cell entry into lung tissue

Asthma is characterized by lung eosinophilia, remodeling, and mucus plugging, controlled by adaptive Th2 effector cells secreting IL-4, IL-5, and IL-13. Inhaled house dust mite (HDM) causes the release of barrier epithelial cytokines that activate various innate immune cells like DCs and basophils that can promote Th2 adaptive immunity directly or indirectly. Here, we show that basophils play a crucial role in the development of type 2 immunity and eosinophilic inflammation, mucus production, and bronchial hyperreactivity in response to HDM inhalation in C57Bl/6 mice. Interestingly, conditional depletion of basophils during sensitization did not reduce Th2 priming or asthma inception, whereas depletion during allergen challenge did. During the challenge of sensitized mice, basophil-intrinsic IL-33/ST2 signaling, and not FcεRI engagement, promoted basophil IL-4 production and subsequent Th2 cell recruitment to the lungs via vascular integrin expression. Basophil-intrinsic loss of the ubiquitin modifying molecule Tnfaip3, involved in dampening IL-33 signaling, enhanced key asthma features. Thus, IL-33-activated basophils are gatekeepers that boost allergic airway inflammation by controlling Th2 tissue entry.</p

The ORMDL3 asthma susceptibility gene regulates systemic ceramide levels without altering key asthma features in mice

Background: Genome-wide association studies in asthma have repeatedly identified single nucleotide polymorphisms in the ORM (yeast)-like protein isoform 3 (ORMDL3) gene across different populations. Although the ORM homologues in yeast are well-known inhibitors of sphingolipid synthesis, it is still unclear whether and how mammalian ORMDL3 regulates sphingolipid metabolism and whether altered sphingolipid synthesis would be causally related to asthma risk. Objective: We sought to examine the in vivo role of ORMDL3 in sphingolipid metabolism and allergic asthma. Methods: Ormdl3-LacZ reporter mice, gene-deficient Ormdl3(-/-) mice, and overexpressing Ormdl3(Tg/wt) mice were exposed to physiologically relevant aeroallergens, such as house dust mite (HDM) or Alternaria alternata, to induce experimental asthma. Mass spectrometry-based sphingolipidomics were performed, and airway eosinophilia, T(H)2 cytokine production, immunoglobulin synthesis, airway remodeling, and bronchial hyperreactivity were measured. Results: HDM challenge significantly increased levels of total sphingolipids in the lungs of HDM-sensitized mice compared with those in control mice. In Ormdl3(Tg/wt) mice the allergen-induced increase in lung ceramide levels was significantly reduced, whereas total sphingolipid levels were not affected. Conversely, in liver and serum, levels of total sphingolipids, including ceramides, were increased in Ormdl3(-/-) mice, whereas they were decreased in Ormdl3(Tg/wt) mice. This difference was independent of allergen exposure. Despite these changes, all features of asthma were identical between wildtype, Ormdl3(Tg/wt), and Ormdl3(-/-) mice across several models of experimental asthma. Conclusion: ORMDL3 regulates systemic ceramide levels, but genetically interfering with Ormdl3 expression does not result in altered experimental asthma

CCR2-and Flt3-dependent inflammatory conventional type 2 dendritic cells are necessary for the induction of adaptive immunity by the human vaccine adjuvant system AS01

The Adjuvant System AS01 contains monophosphoryl lipid A (MPL) and the saponin QS-21 in a liposomal formulation. AS01 is included in recently developed vaccines against malaria and varicella zoster virus. Like for many other adjuvants, induction of adaptive immunity by AS01 is highly dependent on the ability to recruit and activate dendritic cells (DCs) that migrate to the draining lymph node for T and B cell stimulation. The objective of this study was to more precisely address the contribution of the different conventional (cDC) and monocyte-derived DC (MC) subsets in the orchestration of the adaptive immune response after immunization with AS01 adjuvanted vaccine. The combination of MPL and QS-21 in AS01 induced strong recruitment of CD26(+)XCR1(+) cDC1s, CD26(+)CD172(+) cDC2s and a recently defined CCR2-dependent CD64-expressing inflammatory cDC2 (inf-cDC2) subset to the draining lymph node compared to antigen alone, while CD26(-)CD64(+)CD88(+) MCs were barely detectable. At 24 h post-vaccination, cDC2s and inf-cDC2s were superior amongst the different subsets in priming antigen-specific CD4(+) T cells, while simultaneously presenting antigen to CD8(+) T cells. Diphtheria toxin (DT) mediated depletion of all DCs prior to vaccination completely abolished adaptive immune responses, while depletion 24 h after vaccination mainly affected CD8(+) T cell responses. Vaccinated mice lacking Flt3 or the chemokine receptor CCR2 showed a marked deficit in inf-cDC2 recruitment and failed to raise proper antibody and T cell responses. Thus, the adjuvant activity of AS01 is associated with the potent activation of subsets of cDC2s, including the newly described inf-cDC2s

STE20 kinase TAOK3 regulates type 2 immunity and metabolism in obesity

Healthy adipose tissue (AT) contains ST2(+) Tregs, ILC2s, and alternatively activated macrophages that are lost in mice or humans on high caloric diet. Understanding how this form of type 2 immunity is regulated could improve treatment of obesity. The STE20 kinase Thousand And One amino acid Kinase-3 (TAOK3) has been linked to obesity in mice and humans, but its precise function is unknown. We found that ST2(+) Tregs are upregulated in visceral epididymal white AT (eWAT) of Taok3(-/-) mice, dependent on IL-33 and the kinase activity of TAOK3. Upon high fat diet feeding, metabolic dysfunction was attenuated in Taok3(-/-) mice. ST2(+) Tregs disappeared from eWAT in obese wild-type mice, but this was not the case in Taok3(-/-) mice. Mechanistically, AT Taok3(-/-) Tregs were intrinsically more responsive to IL-33, through higher expression of ST2, and expressed more PPAR & gamma; and type 2 cytokines. Thus, TAOK3 inhibits adipose tissue Tregs and regulates immunometabolism under excessive caloric intake. Maes et al. reveal an unexpected role of TAOK3 in regulating ST2(+) regulatory T cells in mouse adipose tissue. Absence of TAOK3 sustains Tregs in obesity and improves metabolic dysfunction

CCR2- and Flt3-Dependent Inflammatory Conventional Type 2 Dendritic Cells Are Necessary for the Induction of Adaptive Immunity by the Human Vaccine Adjuvant System AS01

The Adjuvant System AS01 contains monophosphoryl lipid A (MPL) and the saponin QS-21 in a liposomal formulation. AS01 is included in recently developed vaccines against malaria and varicella zoster virus. Like for many other adjuvants, induction of adaptive immunity by AS01 is highly dependent on the ability to recruit and activate dendritic cells (DCs) that migrate to the draining lymph node for T and B cell stimulation. The objective of this study was to more precisely address the contribution of the different conventional (cDC) and monocyte-derived DC (MC) subsets in the orchestration of the adaptive immune response after immunization with AS01 adjuvanted vaccine. The combination of MPL and QS-21 in AS01 induced strong recruitment of CD26+XCR1+ cDC1s, CD26+CD172+ cDC2s and a recently defined CCR2-dependent CD64-expressing inflammatory cDC2 (inf-cDC2) subset to the draining lymph node compared to antigen alone, while CD26-CD64+CD88+ MCs were barely detectable. At 24 h post-vaccination, cDC2s and inf-cDC2s were superior amongst the different subsets in priming antigen-specific CD4+ T cells, while simultaneously presenting antigen to CD8+ T cells. Diphtheria toxin (DT) mediated depletion of all DCs prior to vaccination completely abolished adaptive immune responses, while depletion 24 h after vaccination mainly affected CD8+ T cell responses. Vaccinated mice lacking Flt3 or the chemokine receptor CCR2 showed a marked deficit in inf-cDC2 recruitment and failed to raise proper antibody and T cell responses. Thus, the adjuvant activity of AS01 is associated with the potent activation of subsets of cDC2s, including the newly described inf-cDC2s

House dust mite-driven asthma and allergen-specific T cells depend on B cells when the amount of inhaled allergen is limiting

Background: Allergic asthma is a CD4 T(H)2-lymphocyte driven disease characterized by airway hyperresponsiveness and eosinophilia. B cells can present antigens to CD4 T cells and produce IgE immunoglobulins that arm effector cells; however, mouse models are inconclusive on whether B cells are necessary for asthma development. Objectives: We sought to address the role of B cells in a house dust mite (HDM)-driven T(H)2-high asthma mouse model. Methods: Wild-type and B cell-deficient muMT mice were sensitized and challenged through the airways with HDM extracts. The antigen-presenting capacities of B cells were studied by using new T-cell receptor transgenic 1-DER mice specific for the Der p 1 allergen. Results: In vitro-activated B cells from HDM-exposed mice presented antigen to 1-DER T cells and induced a T(H)2 phenotype. InvivoBcellswere dispensable for activation of naive 1-DERTcells but necessary for full expansion of primed 1-DER T cells. At high HDMchallenge doses, Bcells were not required for development of pulmonary asthmatic features yet contributed to T(H)2 expansion in themediastinal lymph nodes but not in the lungs. When theamount of challenge allergen was decreased, muMT mice had reduced asthma features. Under these limiting conditions, B cells contributed also to expansion of T(H)2 effector cells in the lungs and central memory T cells in the mediastinal lymph nodes. Conclusion: B cells are a major part of the adaptive immune response to inhaled HDM allergen, particularly when the amount of inhaled allergen is low, by expanding allergen-specific T cells

Canonical IRE1 function needed to sustain vigorous natural killer cell proliferation during viral infection

The unfolded protein response (UPR) aims to restore ER homeostasis under conditions of high protein folding load, a function primarily serving secretory cells. Additional, non-canonical UPR functions have recently been unraveled in immune cells. We addressed the function of the inositol-requiring enzyme 1 (IRE1) signaling branch of the UPR in NK cells in homeostasis and microbial challenge. Cell-intrinsic compound deficiency of IRE1 and its downstream transcription factor XBP1 in NKp46+ NK cells, did not affect basal NK cell homeostasis, or overall outcome of viral MCMV infection. However, mixed bone marrow chimeras revealed a competitive advantage in the proliferation of IRE1-sufficient Ly49H+ NK cells after viral infection. CITE-Seq analysis confirmed strong induction of IRE1 early upon infection, concomitant with the activation of a canonical UPR signature. Therefore, we conclude that IRE1/XBP1 activation is required during vigorous NK cell proliferation early upon viral infection, as part of a canonical UPR response.</p