IgG Subclass-Dependent Pulmonary Antigen Retention during Acute IgG-Dependent Systemic Anaphylaxis in Mice [ALLERGY AND OTHER HYPERSENSITIVITIES]

Key Points

Active systemic anaphylaxis in mice shows Ag retention specifically in the lung.

Ag is predominantly captured by neutrophils and monocytes.

Neutrophils and monocytes activate locally in the lung during anaphylaxis.

Abstract

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.

Footnotes

This work was supported by European Research Council (ERC)–Seventh Framework Program Grant ERC-2013-CoG 616050; additional support was provided by the Institut Pasteur and the Institut National de la Santé et de la Recherche Médicale (INSERM). C.M.G. was supported partly by a stipend from the Pasteur–Paris University International PhD program and by the Institut Carnot Pasteur Maladies Infectieuses. F.J. is an employee of the CNRS. None of the sources of funding has an interest in the subject matter or materials discussed in the submitted manuscript.

B.T. performed most experiments, with contributions from O.G., E.C., C.M.G., D.F., B.I., and O.R.-L.G.; A.J.M., L.E.M., and J.H.W.L. designed mouse targeting and/or generated mouse strains; L.T.R. provided mouse strains; B.T., L.L.R., F.J., and P.B. analyzed and discussed results; L.L.R., F.J., and P.B. supervised the research. P.B. and B.T. prepared the figures. P.B. designed the research and secured funding. P.B. wrote the manuscript with the help of C.M.G. All authors read and reviewed the manuscript before submission.

The online version of this article contains supplemental material.

Abbreviations used in this article:

alumaluminum hydroxideASAactive systemic anaphylaxisDCdendritic cellEGFPenhanced GFPGfi-1growth factor independence 1KOknockoutMHC-IIMHC class IIMPOmyeloperoxidaseNDDnondescanned detectorPAFplatelet-activating factorTNPtrinitrophenylVT680VivoTag 680WTwild-typeReceived March 31, 2022.Accepted July 25, 2022.Copyright © 2022 by The American Association of Immunologists, Inc.

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