Mouse and human FcR effector functions Bruhns, Pierre; Jönsson, Friederike
Immunological reviews,
November 2015, Letnik:
268, Številka:
1
Journal Article
Recenzirano
Summary
Mouse and human FcRs have been a major focus of attention not only of the scientific community, through the cloning and characterization of novel receptors, and of the medical community, ...through the identification of polymorphisms and linkage to disease but also of the pharmaceutical community, through the identification of FcRs as targets for therapy or engineering of Fc domains for the generation of enhanced therapeutic antibodies. The availability of knockout mouse lines for every single mouse FcR, of multiple or cell‐specific—‘à la carte’—FcR knockouts and the increasing generation of hFcR transgenics enable powerful in vivo approaches for the study of mouse and human FcR biology. This review will present the landscape of the current FcR family, their effector functions and the in vivo models at hand to study them. These in vivo models were recently instrumental in re‐defining the properties and effector functions of FcRs that had been overlooked or discarded from previous analyses. A particular focus will be made on the (mis)concepts on the role of high‐affinity IgG receptors in vivo and on results from antibody engineering to enhance or abrogate antibody effector functions mediated by FcRs.
Mechanisms of human drug-induced anaphylaxis Bruhns, Pierre; Chollet-Martin, Sylvie
Journal of allergy and clinical immunology,
April 2021, 2021-Apr, 2021-04-00, 20210401, 2021-04, Letnik:
147, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Drug-induced anaphylaxis is a hyperacute reaction affecting multiple organs that can be of fatal consequence. Its incidence is increasing, consistent with a global increased sensitization to various ...allergens and drugs in the population. Few risk factors and mechanisms have been identified from human studies due to the rarity of anaphylactic events and their unpredictability. This systemic reaction is caused by the rapid release of a large range of functionally diverse mediators, including histamine and platelet-activating factor as the main drivers identified. Mechanisms defined from models of experimental anaphylaxis identify drug-specific antibodies of the IgE and IgG class that link the drug to antibody receptors on multiple cell types, causing their activation and mediator release. In the case of drugs with peculiar chemical structures, antibodies may not be necessary because drug-binding receptors, such as Mas-related G protein–coupled receptor member X2, have been identified. This review describes the complex reaction leading to drug-induced anaphylaxis that can involve various antibody classes, various cell types—including mast cells, neutrophils, platelets, basophils, macrophages, and monocytes—and their mediators and receptors that, importantly, can be activated alone or in association to participate in the severity of the reaction.
Antibody-secreting cells (ASC), plasmablasts and plasma cells, are terminally differentiated B cells responsible for large-scale production and secretion of antibodies. ASC are derived from activated ...B cells, which may differentiate extrafollicularly or form germinal center (GC) reactions within secondary lymphoid organs. ASC therefore consist of short-lived, poorly matured plasmablasts that generally secrete lower-affinity antibodies, or long-lived, highly matured plasma cells that generally secrete higher-affinity antibodies. The ASC population is responsible for producing an immediate humoral B cell response, the polyclonal antibody repertoire, as well as in parallel building effective humoral memory and immunity, or potentially driving pathology in the case of autoimmunity. ASC are phenotypically and transcriptionally distinct from other B cells and further distinguishable by morphology, varied lifespans, and anatomical localization. Single cell analyses are required to interrogate the functional and transcriptional diversity of ASC and their secreted antibody repertoire and understand the contribution of individual ASC responses to the polyclonal humoral response. Here we summarize the current and emerging functional and molecular techniques for high-throughput characterization of ASC with single cell resolution, including flow and mass cytometry, spot-based and microfluidic-based assays, focusing on functional approaches of the secreted antibodies: specificity, affinity, and secretion rate.
Impressive advances in defining the properties of receptors for the Fc portion of immunoglobulins (FcR) have been made over the past several years. Ligand specificities were systematically analyzed ...for both human and mouse FcRs that revealed novel receptors for specific IgG subclasses. Expression patterns were redefined using novel specific anti-FcR mAbs that revealed major differences between human and mouse systems. The in vivo roles of IgG receptors have been addressed using specific FcR knockout mice or in mice expressing a single FcR, and have demonstrated a predominant contribution of mouse activating IgG receptors FcγRIII and FcγRIV to models of autoimmunity (eg, arthritis) and allergy (eg, anaphylaxis). Novel blocking mAbs specific for these activating IgG receptors have enabled, for the first time, the investigation of their roles in vivo in wild-type mice. In parallel, the in vivo properties of human FcRs have been reported using transgenic mice and models of inflammatory and allergic reactions, in particular those of human activating IgG receptor FcγRIIA (CD32A). Importantly, these studies led to the identification of specific cell populations responsible for the induction of various inflammatory diseases and have revealed, in particular, the unexpected contribution of neutrophils and monocytes to the induction of anaphylactic shock.
Background 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.
The SARS-CoV-2 Omicron variant can escape neutralization by vaccine-elicited and convalescent antibodies. Memory B cells (MBCs) represent another layer of protection against SARS-CoV-2, as they ...persist after infection and vaccination and improve their affinity. Whether MBCs elicited by mRNA vaccines can recognize the Omicron variant remains unclear. We assessed the affinity and neutralization potency against the Omicron variant of several hundred naturally expressed MBC-derived monoclonal IgG antibodies from vaccinated COVID-19-recovered and -naive individuals. Compared with other variants of concern, Omicron evaded recognition by a larger proportion of MBC-derived antibodies, with only 30% retaining high affinity against the Omicron RBD, and the reduction in neutralization potency was even more pronounced. Nonetheless, neutralizing MBC clones could be found in all the analyzed individuals. Therefore, despite the strong immune escape potential of the Omicron variant, these results suggest that the MBC repertoire generated by mRNA vaccines still provides some protection against the Omicron variant in vaccinated individuals.
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•Omicron evaded a large fraction of memory B cell (MBC)-derived antibodies•Only 30% of the MBCs retained high affinity against Omicron•Omicron neutralization by MBCs was reduced even more in all individuals•Neutralizing antibodies still represented more than 10% of the MBC repertoire
Whether memory B cells (MBCs) elicited by SARS-CoV-2 mRNA vaccines can recognize the Omicron variant remains unclear. Sokal et al. show that compared with other variants of concern, Omicron evaded recognition and neutralization by a larger proportion of MBC-derived antibodies elicited after infection and/or vaccination. Nonetheless, Omicron-neutralizing MBC clones could be found in the repertoire of all the analyzed individuals.
Allergic asthma is characterized by elevated levels of IgE antibodies, type 2 cytokines such as interleukin-4 (IL-4) and IL-13, airway hyperresponsiveness (AHR), mucus hypersecretion and ...eosinophilia. Approved therapeutic monoclonal antibodies targeting IgE or IL-4/IL-13 reduce asthma symptoms but require costly lifelong administrations. Here, we develop conjugate vaccines against mouse IL-4 and IL-13, and demonstrate their prophylactic and therapeutic efficacy in reducing IgE levels, AHR, eosinophilia and mucus production in mouse models of asthma analyzed up to 15 weeks after initial vaccination. More importantly, we also test similar vaccines specific for human IL-4/IL-13 in mice expressing human IL-4/IL-13 and the related receptor, IL-4Rα, to find efficient neutralization of both cytokines and reduced IgE levels for at least 11 weeks post-vaccination. Our results imply that dual IL-4/IL-13 vaccination may represent a cost-effective, long-term therapeutic strategy for the treatment of allergic asthma as demonstrated in mouse models, although additional studies are warranted to assess its safety and feasibility.
Tumor engraftment followed by monoclonal antibody (mAb) therapy targeting tumor antigens represents a gold standard for assessing the efficiency of mAbs to eliminate tumor cells. Mouse models have ...demonstrated that receptors for the Fc portion of immunoglobulin G (FcγRs) are critical determinants of mAb therapeutic efficacy, but the FcγR-expressing cell populations responsible remain elusive. We show that neutrophils are responsible for mAb-induced therapy of both subcutaneous syngeneic melanoma and human breast cancer xenografts. mAb-induced tumor reduction, abolished in neutropenic mice, could be restored in FcγR-deficient hosts upon transfer of FcγR+ neutrophils or upon human FcγRIIA/CD32A transgenic expression. Finally, conditional knockout mice unable to perform FcγR-mediated activation and phagocytosis specifically in neutrophils were resistant to mAb-induced therapy. Our work suggests that neutrophils are necessary and sufficient for mAb-induced therapy of subcutaneous tumors, and represent a new and critical focal point for optimizing mAb-induced immunotherapies that will impact on human cancer treatment.
•Neutrophils are necessary and sufficient for mAb-induced therapy of subcutaneous syngeneic or xenograft tumors in mice.•Antitumor immunoglobulin G mAb therapy requires a Syk-dependent FcγR-induced killing of tumors by neutrophils.
Neutrophils have crucial antimicrobial functions but are also thought to contribute to tissue injury upon exposure to bacterial products, such as lipopolysaccharide (LPS). To study the role of ...neutrophils in LPS-induced endotoxemia, we developed a new mouse model,
mice, in which injection of diphtheria toxin induces selective neutrophil ablation. Using this model, we found, surprisingly, that neutrophils serve to protect the host from LPS-induced lethal inflammation. This protective role was observed in conventional and germ-free animal facilities, indicating that it does not depend on a particular microbiological environment. Blockade or genetic deletion of myeloperoxidase (MPO), a key neutrophil enzyme, significantly increased mortality after LPS challenge, and adoptive transfer experiments confirmed that neutrophil-derived MPO contributes importantly to protection from endotoxemia. Our findings imply that, in addition to their well-established antimicrobial properties, neutrophils can contribute to optimal host protection by limiting the extent of endotoxin-induced inflammation in an MPO-dependent manner.
Induced pluripotent stem cells (iPSCs) have considerably impacted human developmental biology and regenerative medicine, notably because they circumvent the use of cells of embryonic origin and offer ...the potential to generate patient-specific pluripotent stem cells. However, conventional reprogramming protocols produce developmentally advanced, or primed, human iPSCs (hiPSCs), restricting their use to post-implantation human development modeling. Hence, there is a need for hiPSCs resembling preimplantation naive epiblast. Here, we develop a method to generate naive hiPSCs directly from somatic cells, using OKMS overexpression and specific culture conditions, further enabling parallel generation of their isogenic primed counterparts. We benchmark naive hiPSCs against human preimplantation epiblast and reveal remarkable concordance in their transcriptome, dependency on mitochondrial respiration and X-chromosome status. Collectively, our results are essential for the understanding of pluripotency regulation throughout preimplantation development and generate new opportunities for disease modeling and regenerative medicine.
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