Complement activation on endothelium initiates antibody-mediated acute lung injury
Simon J. Cleary, … , James C. Zimring, Mark R. Looney
Simon J. Cleary, … , James C. Zimring, Mark R. Looney
Published July 30, 2020
Citation Information: J Clin Invest. 2020;130(11):5909-5923. https://doi.org/10.1172/JCI138136.
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Research Article Immunology Pulmonology

Complement activation on endothelium initiates antibody-mediated acute lung injury

Abstract

Antibodies targeting human leukocyte antigen (HLA)/major histocompatibility complex (MHC) proteins limit successful transplantation and transfusion, and their presence in blood products can cause lethal transfusion-related acute lung injury (TRALI). It is unclear which cell types are bound by these anti-leukocyte antibodies to initiate an immunologic cascade resulting in lung injury. We therefore conditionally removed MHC class I (MHC I) from likely cellular targets in antibody-mediated lung injury. Only the removal of endothelial MHC I reduced lung injury and mortality, related mechanistically to absent endothelial complement fixation and lung platelet retention. Restoration of endothelial MHC I rendered MHC I–deficient mice susceptible to lung injury. Neutrophil responses, including neutrophil extracellular trap (NET) release, were intact in endothelial MHC I–deficient mice, whereas complement depletion reduced both lung injury and NETs. Human pulmonary endothelial cells showed high HLA class I expression, and posttransfusion complement activation was increased in clinical TRALI. These results indicate that the critical source of antigen for anti-leukocyte antibodies is in fact the endothelium, which reframes our understanding of TRALI as a rapid-onset vasculitis. Inhibition of complement activation may have multiple beneficial effects of reducing endothelial injury, platelet retention, and NET release in conditions where antibodies trigger these pathogenic responses.

Authors

Simon J. Cleary, Nicholas Kwaan, Jennifer J. Tian, Daniel R. Calabrese, Beñat Mallavia, Mélia Magnen, John R. Greenland, Anatoly Urisman, Jonathan P. Singer, Steven R. Hays, Jasleen Kukreja, Ariel M. Hay, Heather L. Howie, Pearl Toy, Clifford A. Lowell, Craig N. Morrell, James C. Zimring, Mark R. Looney

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Figure 9

Anti–MHC I–mediated release of NETs into blood requires complement activation.

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Anti–MHC I–mediated release of NETs into blood requires complement activ...
Effect of cobra venom factor (CVF) pretreatment and anti–H-2d injections (1 mg/kg i.v., +5 minutes) on (A) lung neutrophil surface CD11b expression and (B) release of neutrophil elastase (NE)–DNA complexes (NETs) into plasma in LPS-primed BALB/c mice (n = 8). (C) Intravital lung imaging of release of NETs following anti–H-2d antibody injection into LPS-primed B6.H2d × PF4-Cre × mTmG mice (cells in lungs, red; SYTOX Green–dyed DNA, green; platelets, blue) (representative of imaging from 6 mice). (D–J) Blood was collected from LPS-primed B6.H2d mice, EDTA anticoagulated, and stimulated with anti–H-2d/isotype for 5 minutes before flow cytometric measurements of DAPI– neutrophil (E and F) CD11b and (G and H) CD62L surface expression (n = 4). (H–J) Blood was collected from LPS-primed B6.H2d mice, anticoagulated with EDTA or PPACK, and uptake of DAPI by neutrophils was assessed using flow cytometry following 5 minutes of anti–H-2d/isotype stimulation (n = 4). (K–M) Alternatively, PPACK-anticoagulated blood was used for (K and L) imaging of neutrophil uptake of DRAQ7 (neutrophil Ly6G, green; DRAQ7-DNA, magenta), and (M) ELISA measurements of release of NETs into plasma following 60 minutes of 0.01 mg/mL anti–H-2d stimulation (normalized to isotype controls). (N) Separate B6.H2d mice were given i.p. LPS and either CVF or vehicle, and blood plasma was collected for ELISA measurements of NE-DNA NETs following 60 minutes of 0.01 mg/mL anti–H-2d stimulation (normalized to isotype controls) (n = 10). Mean ± SEM. *P < 0.05; **P < 0.01; ***P < 0.001 by 2-way ANOVA with Holm’s test (A and B), 1-way ANOVA main effect of anticoagulant (J), paired t test (K and M), or unpaired t test (N).