Publisher Correction: An engineered human Fc domain that behaves like a pH-toggle switch for ultra-long circulation persistence.

An amendment to this paper has been published and can be accessed via a link at the top of the paper

Controlled depolymerisation, as assessed by analytical ultracentrifugation, of low molecular weight chitosan for potential use in archaeological conservation

The heterogeneity and molecular weight of a chitosan of low molecular weight (molar mass) and low degree of acetylation (0.1), for potential use as a consolidant for decayed archaeological wood, has been examined by sedimentation velocity and sedimentation equilibriumin the analytical ultracentrifuge before and after depolymerisation. Sedimentation velocity before polymerisation revealed a uniform distribution of sedimentation coefficient with little concentration dependence. SEDFIT-MSTAR analysis revealed a weight average molecular weight Mw of (14.2 + 1.2) kDa, and polydispersity index of ~ 1.2. Further analysis using MULTISIG revealed a distribution of material between 2-20 kDa and consistent with the weight average Mw. Controlled depolymerisation using hydrogen peroxide and UV in an acetic acid medium reduced this to (4.9 + 0.7) kDa, with a similar polydispersity. The depolymerised material appears to be within the range that has been predicted to fully penetrate into archaeological wood. The consequences for this and the use of the analytical ultracentrifuge in wood conservation strategies is considered

Un nouveau modèle de souris pour comprendre le rôle des neutrophiles

Les polynucléaires neutrophiles jouent un rôle important dans les défenses contre les pathogènes et la réponse inflammatoire. L’utilisation de souris déficientes en ces cellules a permis de démontrer que les neutrophiles peuvent également participer aux réponses immunitaires adaptatives et à la résolution de l’inflammation. Nous décrivons ici un nouveau modèle d’étude, les souris PMNDTR, qui permet une élimination sélective des neutrophiles par injection de toxine diphtérique, et qui a déjà conduit à la mise en évidence d’un rôle protecteur des neutrophiles dans le choc endotoxinique. Ses principaux avantages par rapport à d’autres modèles couramment utilisés sont décrits

Epitope-specific CD4+, but not CD8+, T-cell responses induced by recombinant influenza A viruses protect against Mycobacterium tuberculosis infection

Tuberculosis remains a global health problem, in part due to failure of the currently available vaccine, BCG, to protect adults against pulmonary forms of the disease. We explored the impact of pulmonary delivery of recombinant influenza A viruses (rIAVs) on the induction of Mycobacterium tuberculosis (M. tuberculosis)-specific CD4(+) and CD8(+) T-cell responses and the resultant protection against M. tuberculosis infection in C57BL/6 mice. Intranasal infection with rIAVs expressing a CD4(+) T-cell epitope from the Ag85B protein (PR8.p25) or CD8(+) T-cell epitope from the TB10.4 protein (PR8.TB10.4) generated strong T-cell responses to the M. tuberculosis-specific epitopes in the lung that persisted long after the rIAVs were cleared. Infection with PR8.p25 conferred protection against subsequent M. tuberculosis challenge in the lung, and this was associated with increased levels of poly-functional CD4(+) T cells at the time of challenge. By contrast, infection with PR8.TB10.4 did not induce protection despite the presence of IFN-γ-producing M. tuberculosis-specific CD8(+) T cells in the lung at the time of challenge and during infection. Therefore, the induction of pulmonary M. tuberculosis epitope-specific CD4(+), but not CD8(+) T cells, is essential for protection against acute M. tuberculosis infection in the lung

Mechanisms of anaphylaxis in human low-affinity IgG receptor locus knock-in mice

International audienceBACKGROUND:Anaphylaxis can proceed through distinct IgE- or IgG-dependent pathways, which have been investigated in various mouse models. We developed a novel mouse strain in which the human low-affinity IgG receptor locus, comprising both activating (hFcγRIIA, hFcγRIIIA, and hFcγRIIIB) and inhibitory (hFcγRIIB) hFcγR genes, has been inserted into the equivalent murine locus, corresponding to a locus swap.OBJECTIVE:We sought to determine the capabilities of hFcγRs to induce systemic anaphylaxis and identify the cell types and mediators involved.METHODS:hFcγR expression on mouse and human cells was compared to validate the model. Passive systemic anaphylaxis was induced by injection of heat-aggregated human intravenous immunoglobulin and active systemic anaphylaxis after immunization and challenge. Anaphylaxis severity was evaluated based on hypothermia and mortality. The contribution of receptors, mediators, or cell types was assessed based on receptor blockade or depletion.RESULTS:The human-to-mouse low-affinity FcγR locus swap engendered hFcγRIIA/IIB/IIIA/IIIB expression in mice comparable with that seen in human subjects. Knock-in mice were susceptible to passive and active anaphylaxis, accompanied by downregulation of both activating and inhibitory hFcγR expression on specific myeloid cells. The contribution of hFcγRIIA was predominant. Depletion of neutrophils protected against hypothermia and mortality. Basophils contributed to a lesser extent. Anaphylaxis was inhibited by platelet-activating factor receptor or histamine receptor 1 blockade.CONCLUSION:Low-affinity FcγR locus-switched mice represent an unprecedented model of cognate hFcγR expression. Importantly, IgG-related anaphylaxis proceeds within a native context of activating and inhibitory hFcγRs, indicating that, despite robust hFcγRIIB expression, activating signals can dominate to initiate a severe anaphylactic reaction

Influenza A virus infection impairs mycobacteria-specific T cell responses and mycobacterial clearance in the lung during pulmonary coinfection.

Individuals infected with mycobacteria are likely to experience episodes of concurrent infections with unrelated respiratory pathogens, including the seasonal or pandemic circulating influenza A virus strains. We analyzed the impact of influenza A virus and mycobacterial respiratory coinfection on the development of CD8 T cell responses to each pathogen. Coinfected mice exhibited reduced frequency and numbers of CD8 T cells specific to Mycobacterium bovis bacille Calmette-Guérin (BCG) in the lungs, and the IFN-γ CD8 T cell response to BCG-encoded OVA was decreased in the lungs of coinfected mice, when compared with mice infected with BCG alone. Moreover, after 2 wk of infection, mice coinfected with both pathogens showed a significant increase in the number of mycobacteria present in the lung compared with mice infected with BCG only. Following adoptive transfer into coinfected mice, transgenic CD8 T cells specific for OVA257–264 failed to proliferate as extensively in the mediastinal lymph nodes as in mice infected only with BCG-OVA. Also noted was a reduction in the proliferation of BCG-specific CD4 transgenic T cells in mice coinfected with influenza compared with mice infected with BCG alone. Furthermore, phenotypic analysis of CD11c+ dendritic cells from mediastinal lymph nodes of the infected mice showed that coinfection was associated with decreased surface expression of MHC class II and class I. Thus, concurrent pulmonary infection with influenza A virus is associated with decreased MHC expression on dendritic cells, reduced activation of BCG-specific CD4 and CD8 T cells, and impaired clearance of mycobacteria

In vivo effector functions of high-affinity mouse IgG receptor FcγRI in disease and therapy models

International audienceBACKGROUND:Anaphylaxis can proceed through distinct IgE- or IgG-dependent pathways, which have been investigated in various mouse models. We developed a novel mouse strain in which the human low-affinity IgG receptor locus, comprising both activating (hFcγRIIA, hFcγRIIIA, and hFcγRIIIB) and inhibitory (hFcγRIIB) hFcγR genes, has been inserted into the equivalent murine locus, corresponding to a locus swap.OBJECTIVE:We sought to determine the capabilities of hFcγRs to induce systemic anaphylaxis and identify the cell types and mediators involved.METHODS:hFcγR expression on mouse and human cells was compared to validate the model. Passive systemic anaphylaxis was induced by injection of heat-aggregated human intravenous immunoglobulin and active systemic anaphylaxis after immunization and challenge. Anaphylaxis severity was evaluated based on hypothermia and mortality. The contribution of receptors, mediators, or cell types was assessed based on receptor blockade or depletion.RESULTS:The human-to-mouse low-affinity FcγR locus swap engendered hFcγRIIA/IIB/IIIA/IIIB expression in mice comparable with that seen in human subjects. Knock-in mice were susceptible to passive and active anaphylaxis, accompanied by downregulation of both activating and inhibitory hFcγR expression on specific myeloid cells. The contribution of hFcγRIIA was predominant. Depletion of neutrophils protected against hypothermia and mortality. Basophils contributed to a lesser extent. Anaphylaxis was inhibited by platelet-activating factor receptor or histamine receptor 1 blockade.CONCLUSION:Low-affinity FcγR locus-switched mice represent an unprecedented model of cognate hFcγR expression. Importantly, IgG-related anaphylaxis proceeds within a native context of activating and inhibitory hFcγRs, indicating that, despite robust hFcγRIIB expression, activating signals can dominate to initiate a severe anaphylactic reaction

IgG subclasses determine pathways of anaphylaxis in mice

International audienceBACKGROUND:Animal models have demonstrated that allergen-specific IgG confers sensitivity to systemic anaphylaxis that relies on IgG Fc receptors (FcγRs). Mouse IgG2a and IgG2b bind activating FcγRI, FcγRIII, and FcγRIV and inhibitory FcγRIIB; mouse IgG1 binds only FcγRIII and FcγRIIB. Although these interactions are of strikingly different affinities, these 3 IgG subclasses have been shown to enable induction of systemic anaphylaxis.OBJECTIVE:We sought to determine which pathways control the induction of IgG1-, IgG2a-, and IgG2b-dependent passive systemic anaphylaxis.METHODS:Mice were sensitized with IgG1, IgG2a, or IgG2b anti-trinitrophenyl mAbs and challenged with trinitrophenyl-BSA intravenously to induce systemic anaphylaxis that was monitored by using rectal temperature. Anaphylaxis was evaluated in mice deficient for FcγRs injected with mediator antagonists or in which basophils, monocytes/macrophages, or neutrophils had been depleted. FcγR expression was evaluated on these cells before and after anaphylaxis.RESULTS:Activating FcγRIII is the receptor primarily responsible for all 3 models of anaphylaxis, and subsequent downregulation of this receptor was observed. These models differentially relied on histamine release and the contribution of mast cells, basophils, macrophages, and neutrophils. Strikingly, basophil contribution and histamine predominance in mice with IgG1- and IgG2b-induced anaphylaxis correlated with the ability of inhibitory FcγRIIB to negatively regulate these models of anaphylaxis.CONCLUSION:We propose that the differential expression of inhibitory FcγRIIB on myeloid cells and its differential binding of IgG subclasses controls the contributions of mast cells, basophils, neutrophils, and macrophages to IgG subclass-dependent anaphylaxis. Collectively, our results unravel novel complexities in the involvement and regulation of cell populations in IgG-dependent reactions in vivo

IgG Subclass-Dependent Pulmonary Antigen Retention during Acute IgG-Dependent Systemic Anaphylaxis in Mice

Mouse models of active systemic anaphylaxis rely predominantly on IgG Abs forming IgG-allergen immune complexes that induce IgG receptor-expressing neutrophils and monocytes/macrophages to release potent mediators, leading to systemic effects. Whether anaphylaxis initiates locally or systemically remains unknown. In this study, we aimed at identifying the anatomical location of IgG-allergen immune complexes during anaphylaxis. Active systemic anaphylaxis was induced following immunization with BSA and i.v. challenge with fluorescently labeled BSA. Ag retention across different organs was examined using whole-body fluorescence imaging, comparing immunized and naive animals. Various mouse models and in vivo deletion strategies were employed to determine the contribution of IgG receptors, complement component C1q, myeloid cell types, and anaphylaxis mediators. We found that following challenge, Ag diffused systemically, but specifically accumulated in the lungs of mice sensitized to that Ag, where it formed large Ab-dependent aggregates in the vasculature. Ag retention in the lungs did not rely on IgG receptors, C1q, neutrophils, or macrophages. IgG2a-mediated, but neither IgG1- nor IgG2b-mediated, passive systemic anaphylaxis led to Ag retention in the lung. Neutrophils and monocytes significantly accumulated in the lungs after challenge and captured high amounts of Ag, which led to downmodulation of surface IgG receptors and triggered their activation. Thus, within minutes of systemic injection in sensitized mice, Ag formed aggregates in the lung and liver vasculature, but accumulated specifically and dose-dependently in the lung. Neutrophils and monocytes recruited to the lung captured Ag and became activated. However, Ag aggregation in the lung vasculature was not necessary for anaphylaxis induction

Necroptosis signalling promotes inflammation, airway remodelling and emphysema in COPD

Rationale: Necroptosis, mediated by RIPK3 and MLKL, is a form of regulated necrosis that can drive tissue inflammation and destruction, however its contribution to COPD pathogenesis is poorly understood. Objectives: To determine the role of necroptosis in COPD. Methods: Levels of RIPK3, MLKL and activated phospho-MLKL were measured in lung tissues of COPD patients and non-COPD controls. Necroptosis-related mRNA and proteins and cell death were examined in the lungs and pulmonary macrophages of mice with cigarette smoke (CS)-induced experimental COPD. The responses of Ripk3- and Mlkl-deficient (-/-) mice to CS exposure were compared to wild-type mice. Combined inhibition of apoptosis (pan-caspase inhibitor qVD-OPh) and necroptosis (Mlkl-/- mice) was assessed. Measurements and main results: Protein levels of MLKL and pMLKL but not RIPK3 were increased in lung tissues of COPD patients compared to never smokers or smoker non-COPD controls. Necroptosis-related mRNA and protein levels were increased in lung tissue and macrophages in CS-exposed mice/experimental COPD. Ripk3 or Mlkl deletion prevented airway inflammation in response to acute CS-exposure. Ripk3 deficiency reduced airway inflammation and remodelling and development of emphysematous pathology following chronic CS-exposure. Mlkl deletion and qVD-OPh treatment reduced chronic CS-induced airway inflammation, but only Mlkl deletion prevented airway remodelling and emphysema. Ripk3 or Mlkl deletion and qVD-OPh treatment reduced CS-induced lung cell death. Conclusions: Necroptosis is induced by CS exposure and increased in COPD patient lungs and experimental COPD. Inhibiting necroptosis attenuates CS-induced airway inflammation, airway remodelling and emphysema. Targeted inhibition of necroptosis is a potential therapeutic strategy in COPD