IgG hexamers initiate complement-dependent acute lung injury
Simon J. Cleary, … , James C. Zimring, Mark R. Looney
Simon J. Cleary, … , James C. Zimring, Mark R. Looney
Published March 26, 2024
Citation Information: J Clin Invest. 2024;134(11):e178351. https://doi.org/10.1172/JCI178351.
View: Text | PDF
Research Article Pulmonology

IgG hexamers initiate complement-dependent acute lung injury

Abstract

Antibodies can initiate lung injury in a variety of disease states such as autoimmunity, in reactions to transfusions, or after organ transplantation, but the key factors determining in vivo pathogenicity of injury-inducing antibodies are unclear. Harmful antibodies often activate the complement cascade. A model for how IgG antibodies trigger complement activation involves interactions between IgG Fc domains driving the assembly of IgG hexamer structures that activate C1 complexes. The importance of IgG hexamers in initiating injury responses was not clear, so we tested their relevance in a mouse model of alloantibody- and complement-mediated acute lung injury. We used 3 approaches to block alloantibody hexamerization (antibody carbamylation, the K439E Fc mutation, or treatment with domain B from staphylococcal protein A), all of which reduced acute lung injury. Conversely, Fc mutations promoting spontaneous hexamerization made a harmful alloantibody into a more potent inducer of acute lung injury and rendered an innocuous alloantibody pathogenic. Treatment with a recombinant Fc hexamer “decoy” therapeutic protected mice from lung injury, including in a model with transgenic human FCGR2A expression that exacerbated pathology. These results indicate an in vivo role of IgG hexamerization in initiating acute lung injury and the potential for therapeutics that inhibit or mimic hexamerization to treat antibody-mediated diseases.

Authors

Simon J. Cleary, Yurim Seo, Jennifer J. Tian, Nicholas Kwaan, David P. Bulkley, Arthur E.H. Bentlage, Gestur Vidarsson, Éric Boilard, Rolf Spirig, James C. Zimring, Mark R. Looney

×

Figure 6

Acute lung injury is complement dependent in a model incorporating human FCGR2A–mediated pathology.

Options: View larger image (or click on image) Download as PowerPoint
Acute lung injury is complement dependent in a model incorporating human...
(A) Lung vascular permeability, (B) excess lung water, and (C) survival readouts from LPS-primed B6.H2d:hFCGR2aTg/0 mice and littermate controls lacking hFCGR2A expression that were given i.v. hIgG1-34-1-2S at 1 mg/kg. (D) Immunofluorescence images of platelet sequestration (CD41, red, with Acta2 in cyan) and (E) neutrophils (S100a8, red, with Acta2 in cyan) in lungs from LPS-primed B6.H2d:hFCGR2aTg/0 mice and littermates without hFCGR2A expression, fixed at 20 minutes after hIgG1-34-1-2S injections and (F and G) quantification. Scale bars: 50 μm. (H) SpO2 measurements from LPS-primed B6.H2d:hFCGR2aTg/0 mice and littermate controls without hFCGR2A expression before and after hIgG1-34-1-2S injections. (I) Lung vascular permeability, (J) excess lung water, and (K) survival readouts for LPS-primed B6.H2d C1qa+/+ and B6.H2d C1qa–/– mice, as well as for hFCGR2A-expressing littermates of each genotype, that were given i.v. hIgG1-34-1-2S at 1 mg/kg. Data in A, B, F, G, H, I, and J show the mean ± SEM, with horizontal gray lines showing values from the no-injury controls (baseline readings or values from B6.H2d mice given LPS i.p. plus hIgG1 isotype control i.v.), and were log10 transformed prior to analysis. *P < 0.05, **P < 0.01 and ***P < 0.0001, by unpaired, 2-tailed t tests (A, B, F, and G); 2-way ANOVA with Šídák’s multiple-comparison test (I and J); log-rank test (C and K); or 2-way, repeated-measures mixed-model approach with tests for main effect of the genotype and for post-baseline effects of the genotype within time levels with Holm’s adjustment for multiple comparisons (H). n = 4/group (D–G); n = 10/group (H); n = 12/group (other graphs).