References of "Marichal, Thomas"
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See detailHost DNA released by NETosis promotes rhinovirus-induced type-2 allergic asthma exacerbation.
Toussaint, Marie; Jackson, David J.; Swieboda, Dawid et al

in Nature Medicine (2017)

Respiratory viral infections represent the most common cause of allergic asthma exacerbations. Amplification of the type-2 immune response is strongly implicated in asthma exacerbation, but how virus ... [more ▼]

Respiratory viral infections represent the most common cause of allergic asthma exacerbations. Amplification of the type-2 immune response is strongly implicated in asthma exacerbation, but how virus infection boosts type-2 responses is poorly understood. We report a significant correlation between the release of host double-stranded DNA (dsDNA) following rhinovirus infection and the exacerbation of type-2 allergic inflammation in humans. In a mouse model of allergic airway hypersensitivity, we show that rhinovirus infection triggers dsDNA release associated with the formation of neutrophil extracellular traps (NETs), known as NETosis. We further demonstrate that inhibiting NETosis by blocking neutrophil elastase or by degrading NETs with DNase protects mice from type-2 immunopathology. Furthermore, the injection of mouse genomic DNA alone is sufficient to recapitulate many features of rhinovirus-induced type-2 immune responses and asthma pathology. Thus, NETosis and its associated extracellular dsDNA contribute to the pathogenesis and may represent potential therapeutic targets of rhinovirus-induced asthma exacerbations. [less ▲]

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See detailExposure to Bacterial CpG DNA Protects from Airway Allergic Inflammation by Expanding Regulatory Lung Interstitial Macrophages.
Sabatel, Catherine ULg; Radermecker, Coraline ULg; Fievez, Laurence ULg et al

in Immunity (2017), 46(3), 457-473

Living in a microbe-rich environment reduces the risk of developing asthma. Exposure of humans or mice to unmethylated CpG DNA (CpG) from bacteria reproduces these protective effects, suggesting a major ... [more ▼]

Living in a microbe-rich environment reduces the risk of developing asthma. Exposure of humans or mice to unmethylated CpG DNA (CpG) from bacteria reproduces these protective effects, suggesting a major contribution of CpG to microbe-induced asthma resistance. However, how CpG confers protection remains elusive. We found that exposure to CpG expanded regulatory lung interstitial macrophages (IMs) from monocytes infiltrating the lung or mobilized from the spleen. Trafficking of IM precursors to the lung was independent of CCR2, a chemokine receptor required for monocyte mobilization from the bone marrow. Using a mouse model of allergic airway inflammation, we found that adoptive transfer of IMs isolated from CpG-treated mice recapitulated the protective effects of CpG when administered before allergen sensitization or challenge. IM-mediated protection was dependent on IL-10, given that Il10-/- CpG-induced IMs lacked regulatory effects. Thus, the expansion of regulatory lung IMs upon exposure to CpG might underlie the reduced risk of asthma development associated with a microbe-rich environment. [less ▲]

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See detailLung resident eosinophils represent a distinct cell subset with homeostatic functions
Mesnil, Claire ULg; Raulier, Stéfanie ULg; Paulissen, Geneviève et al

Conference (2016, October 21)

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See detailCpG-DNA expand immunosuppressive interstitial macrophages from Ly6c+ local precursors
Sabatel, Catherine ULg; Radermecker, Coraline ULg; Fievez, Laurence ULg et al

in Proceeding of Cell Symposia: 100 years of phagocytes (2016, September)

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See detailKeratinocyte RabGEF1 maintains skin homeostasis in vivo.
Marichal, Thomas ULg

Conference (2016, April 22)

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See detailLung-resident eosinophils represent a distinct regulatory eosinophil subset
Mesnil, Claire ULg; Raulier, Stéfanie ULg; Paulissen, G et al

in Journal of Clinical Investigation (2016), 126(9), 3275-3295

Increases in eosinophil numbers are associated with infection and allergic diseases, including asthma, but there is also evidence that eosinophils contribute to homeostatic immune processes. In mice, the ... [more ▼]

Increases in eosinophil numbers are associated with infection and allergic diseases, including asthma, but there is also evidence that eosinophils contribute to homeostatic immune processes. In mice, the normal lung contains resident eosinophils (rEos), but their function has not been characterized. Here, we have reported that steady-state pulmonary rEos are IL-5–independent parenchymal Siglec-FintCD62L+CD101lo cells with a ring-shaped nucleus. During house dust mite–induced airway allergy, rEos features remained unchanged, and rEos were accompanied by recruited inflammatory eosinophils (iEos), which were defined as IL-5–dependent peribronchial Siglec-FhiCD62L–CD101hi cells with a segmented nucleus. Gene expression analyses revealed a more regulatory profile for rEos than for iEos, and correspondingly, mice lacking lung rEos showed an increase in Th2 cell responses to inhaled allergens. Such elevation of Th2 responses was linked to the ability of rEos, but not iEos, to inhibit the maturation, and therefore the pro-Th2 function, of allergen-loaded DCs. Finally, we determined that the parenchymal rEos found in nonasthmatic human lungs (Siglec-8+CD62L+IL-3Rlo cells) were phenotypically distinct from the iEos isolated from the sputa of eosinophilic asthmatic patients (Siglec-8+CD62LloIL-3Rhi cells), suggesting that our findings in mice are relevant to humans. In conclusion, our data define lung rEos as a distinct eosinophil subset with key homeostatic functions. [less ▲]

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See detailDifferent activation signals induce distinct mast cell degranulation strategies.
Gaudenzio, Nicolas; Sibilano, Riccardo; Marichal, Thomas ULg et al

in Journal of Clinical Investigation (2016), 126(10), 3981-3998

Mast cells (MCs) influence intercellular communication during inflammation by secreting cytoplasmic granules that contain diverse mediators. Here, we have demonstrated that MCs decode different activation ... [more ▼]

Mast cells (MCs) influence intercellular communication during inflammation by secreting cytoplasmic granules that contain diverse mediators. Here, we have demonstrated that MCs decode different activation stimuli into spatially and temporally distinct patterns of granule secretion. Certain signals, including substance P, the complement anaphylatoxins C3a and C5a, and endothelin 1, induced human MCs rapidly to secrete small and relatively spherical granule structures, a pattern consistent with the secretion of individual granules. Conversely, activating MCs with anti-IgE increased the time partition between signaling and secretion, which was associated with a period of sustained elevation of intracellular calcium and formation of larger and more heterogeneously shaped granule structures that underwent prolonged exteriorization. Pharmacological inhibition of IKK-beta during IgE-dependent stimulation strongly reduced the time partition between signaling and secretion, inhibited SNAP23/STX4 complex formation, and switched the degranulation pattern into one that resembled degranulation induced by substance P. IgE-dependent and substance P-dependent activation in vivo also induced different patterns of mouse MC degranulation that were associated with distinct local and systemic pathophysiological responses. These findings show that cytoplasmic granule secretion from MCs that occurs in response to different activating stimuli can exhibit distinct dynamics and features that are associated with distinct patterns of MC-dependent inflammation. [less ▲]

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See detailPathways of immediate hypothermia and leukocyte infiltration in an adjuvant-free mouse model of anaphylaxis.
Balbino, Bianca; Sibilano, Riccardo; Starkl, Philipp et al

in Journal of Allergy and Clinical Immunology (The) (2016)

BACKGROUND: Conflicting results have been obtained regarding the roles of Fc receptors and effector cells in models of active systemic anaphylaxis (ASA). In part, this might reflect the choice of adjuvant ... [more ▼]

BACKGROUND: Conflicting results have been obtained regarding the roles of Fc receptors and effector cells in models of active systemic anaphylaxis (ASA). In part, this might reflect the choice of adjuvant used during sensitization because various adjuvants might differentially influence the production of particular antibody isotypes. OBJECTIVE: We developed an "adjuvant-free" mouse model of ASA and assessed the contributions of components of the "classical" and "alternative" pathways in this model. METHODS: Mice were sensitized intraperitoneally with ovalbumin at weekly intervals for 6 weeks and challenged intraperitoneally with ovalbumin 2 weeks later. RESULTS: Wild-type animals had immediate hypothermia and late-phase intraperitoneal inflammation in this model. These features were reduced in mice lacking the IgE receptor FcepsilonRI, the IgG receptor FcgammaRIII or the common gamma-chain FcRgamma. FcgammaRIV blockade resulted in a partial reduction of inflammation without any effect on hypothermia. Depletion of monocytes/macrophages with clodronate liposomes significantly reduced the hypothermia response. By contrast, depletion of neutrophils or basophils had no significant effects in this ASA model. Both the hypothermia and inflammation were dependent on platelet-activating factor and histamine and were reduced in 2 types of mast cell (MC)-deficient mice. Finally, engraftment of MC-deficient mice with bone marrow-derived cultured MCs significantly exacerbated the hypothermia response and restored inflammation to levels similar to those observed in wild-type mice. CONCLUSION: Components of the classical and alternative pathways contribute to anaphylaxis in this adjuvant-free model, with key roles for MCs and monocytes/macrophages. [less ▲]

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See detailGuanine nucleotide exchange factor RABGEF1 regulates keratinocyte-intrinsic signaling to maintain skin homeostasis.
Marichal, Thomas ULg; Gaudenzio, Nicolas; El Abbas, Sophie ULg et al

in Journal of Clinical Investigation (2016), 126(12), 4497-4515

Epidermal keratinocytes form a structural and immune barrier that is essential for skin homeostasis. However, the mechanisms that regulate epidermal barrier function are incompletely understood. Here we ... [more ▼]

Epidermal keratinocytes form a structural and immune barrier that is essential for skin homeostasis. However, the mechanisms that regulate epidermal barrier function are incompletely understood. Here we have found that keratinocyte-specific deletion of the gene encoding RAB guanine nucleotide exchange factor 1 (RABGEF1, also known as RABEX-5) severely impairs epidermal barrier function in mice and induces an allergic cutaneous and systemic phenotype. RABGEF1-deficient keratinocytes exhibited aberrant activation of the intrinsic IL-1R/MYD88/NF-kappaB signaling pathway and MYD88-dependent abnormalities in expression of structural proteins that contribute to skin barrier function. Moreover, ablation of MYD88 signaling in RABGEF1-deficient keratinocytes or deletion of Il1r1 restored skin homeostasis and prevented development of skin inflammation. We further demonstrated that epidermal RABGEF1 expression is reduced in skin lesions of humans diagnosed with either atopic dermatitis or allergic contact dermatitis as well as in an inducible mouse model of allergic dermatitis. Our findings reveal a key role for RABGEF1 in dampening keratinocyte-intrinsic MYD88 signaling and sustaining epidermal barrier function in mice, and suggest that dysregulation of RABGEF1 expression may contribute to epidermal barrier dysfunction in allergic skin disorders in mice and humans. Thus, RABGEF1-mediated regulation of IL-1R/MYD88 signaling might represent a potential therapeutic target. [less ▲]

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See detailRole of double-stranded DNA in allergic airway inflammation.
Marichal, Thomas ULg

Conference (2016)

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See detailIgE and mast cells in host defense against parasites and venoms.
Mukai, Kaori; Tsai, Mindy; Starkl, Philipp et al

in Seminars in Immunopathology (2016)

IgE-dependent mast cell activation is a major effector mechanism underlying the pathology associated with allergic disorders. The most dramatic of these IgE-associated disorders is the fatal anaphylaxis ... [more ▼]

IgE-dependent mast cell activation is a major effector mechanism underlying the pathology associated with allergic disorders. The most dramatic of these IgE-associated disorders is the fatal anaphylaxis which can occur in some people who have developed IgE antibodies to otherwise innocuous antigens, such as those contained in certain foods and medicines. Why would such a highly "maladaptive" immune response develop in evolution and be retained to the present day? Host defense against parasites has long been considered the only beneficial function that might be conferred by IgE and mast cells. However, recent studies have provided evidence that, in addition to participating in host resistance to certain parasites, mast cells and IgE are critical components of innate (mast cells) and adaptive (mast cells and IgE) immune responses that can enhance host defense against the toxicity of certain arthropod and animal venoms, including enhancing the survival of mice injected with such venoms. Yet, in some people, developing IgE antibodies to insect or snake venoms puts them at risk for having a potentially fatal anaphylactic reaction upon subsequent exposure to such venoms. Delineating the mechanisms underlying beneficial versus detrimental innate and adaptive immune responses associated with mast cell activation and IgE is likely to enhance our ability to identify potential therapeutic targets in such settings, not only for reducing the pathology associated with allergic disorders but perhaps also for enhancing immune protection against pathogens and animal venoms. [less ▲]

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See detailImmunoglobulin E enhances host resistance to venoms.
Marichal, Thomas ULg

Conference (2015, September 07)

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See detailRole of double stranded DNA in allergic inflammation.
Marichal, Thomas ULg

Conference (2015, June 06)

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See detailApproaches for analyzing the roles of mast cells and their proteases in vivo.
Galli, Stephen J.; Tsai, Mindy; Marichal, Thomas ULg et al

in Advances in immunology (2015), 126

The roles of mast cells in health and disease remain incompletely understood. While the evidence that mast cells are critical effector cells in IgE-dependent anaphylaxis and other acute IgE-mediated ... [more ▼]

The roles of mast cells in health and disease remain incompletely understood. While the evidence that mast cells are critical effector cells in IgE-dependent anaphylaxis and other acute IgE-mediated allergic reactions seems unassailable, studies employing various mice deficient in mast cells or mast cell-associated proteases have yielded divergent conclusions about the roles of mast cells or their proteases in certain other immunological responses. Such "controversial" results call into question the relative utility of various older versus newer approaches to ascertain the roles of mast cells and mast cell proteases in vivo. This review discusses how both older and more recent mouse models have been used to investigate the functions of mast cells and their proteases in health and disease. We particularly focus on settings in which divergent conclusions about the importance of mast cells and their proteases have been supported by studies that employed different models of mast cell or mast cell protease deficiency. We think that two major conclusions can be drawn from such findings: (1) no matter which models of mast cell or mast cell protease deficiency one employs, the conclusions drawn from the experiments always should take into account the potential limitations of the models (particularly abnormalities affecting cell types other than mast cells) and (2) even when analyzing a biological response using a single model of mast cell or mast cell protease deficiency, details of experimental design are critical in efforts to define those conditions under which important contributions of mast cells or their proteases can be identified. [less ▲]

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