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IgG subclasses determine pathways of anaphylaxis in mice.

ABSTRACT: BACKGROUND:Animal models have demonstrated that allergen-specific IgG confers sensitivity to systemic anaphylaxis that relies on IgG Fc receptors (Fc?Rs). Mouse IgG2a and IgG2b bind activating Fc?RI, Fc?RIII, and Fc?RIV and inhibitory Fc?RIIB; mouse IgG1 binds only Fc?RIII and Fc?RIIB. 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 Fc?Rs injected with mediator antagonists or in which basophils, monocytes/macrophages, or neutrophils had been depleted. Fc?R expression was evaluated on these cells before and after anaphylaxis. RESULTS:Activating Fc?RIII 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 Fc?RIIB to negatively regulate these models of anaphylaxis. CONCLUSION:We propose that the differential expression of inhibitory Fc?RIIB 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.

SUBMITTER: Beutier H

PROVIDER: S-EPMC5081282 | biostudies-literature | 2017 Jan

REPOSITORIES: biostudies-literature

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IgG subclasses determine pathways of anaphylaxis in mice.

Beutier Héloïse H Gillis Caitlin M CM Iannascoli Bruno B Godon Ophélie O England Patrick P Sibilano Riccardo R Reber Laurent L LL Galli Stephen J SJ Cragg Mark S MS Van Rooijen Nico N Mancardi David A DA Bruhns Pierre P Jönsson Friederike F

The Journal of allergy and clinical immunology 20160426 1

<h4>Background</h4>Animal models have demonstrated that allergen-specific IgG confers sensitivity to systemic anaphylaxis that relies on IgG Fc receptors (FcγRs). Mouse IgG<sub>2a</sub> and IgG<sub>2b</sub> bind activating FcγRI, FcγRIII, and FcγRIV and inhibitory FcγRIIB; mouse IgG<sub>1</sub> 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.<h4>Objective</h4>We ...[more]

PMID: 27246523

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Project description:Membranous nephropathy (MN) is an autoimmune disease caused by binding of circulating antibodies to podocyte antigens in the kidney. For decades and still today primary MN has been considered to have an unspecified IgG4-driven autoimmune genesis, while secondary MN has been associated with other diseases, most notably cancer, and not linked to IgG4. Immunologic mechanisms of primary and malignancy-associated MN are assumed to be different, however, this has never been systematically evaluated. The identification of Phospholipase A2 Receptor 1 (PLA2R1) and Thrombospondin Type-1 Domain-Containing 7A (THSD7A) as target antigens in MN allows a pathogenesis-driven differential diagnosis. Recent data showing a molecular link between increased THSD7A-expression in tumors and THSD7A-antibody positive MN suggest a similar pathogenesis of malignancy-associated and primary MN. In order to better define the underlying immunologic processes, we systematically analyzed circulating antigen-specific IgG subclasses in the serum of 76 patients with PLA2R1-associated MN and 41 patients with THSD7A-associated MN in relationship to concurrent malignancy and disease outcome. Twenty-three patients in the study had malignancy-associated MN. We analyzed antigen-specific IgG subclasses in the serum of all patients at baseline and in 55 patients during follow-up by Western blot applying antigens derived from human kidney and lung. At baseline all 117 patients were positive for IgG4-antibodies against either PLA2R1 or THSD7A, while IgG3, IgG1, and IgG2-antibodies were found in 87, 72, and 26% of patients, respectively. There were no differences in the IgG subclass distribution between patients with primary vs. cancer-associated MN and no association with disease outcome. Moreover, levels of antigen-specific IgG4-antibodies were not different between primary and malignancy-associated MN and levels of all IgG subclasses did not differ between these groups. Both podocytes and lung bronchioles showed expression of both PLA2R1 and THSD7A when analyzed by immunofluorescence and Western blot. Every antigen-specific IgG subclass showed identical binding in both organs and autoantibodies bound the respective antigen only under non-reducing conditions. We conclude that antigen-specific IgG subclasses do not differentiate primary from malignancy-associated MN or predict disease prognosis. These data support the view that one common pathway may lead to primary and cancer-associated MN induced by PLA2R1- or THSD7A-antibodies.

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IgG subclasses determine pathways of anaphylaxis in mice.

Publications

IgG subclasses determine pathways of anaphylaxis in mice.

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