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.
View: Text | PDF
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

×

Figure 2

Restoration of MHC I exclusively on endothelium is sufficient to induce susceptibility to anti–MHC I–mediated lung injury.

Options: View larger image (or click on image) Download as PowerPoint
Restoration of MHC I exclusively on endothelium is sufficient to induce ...
B2minv/inv mice were created in which exons 2 and 3 of the B2m locus were inverted and flanked by loxP and lox2272 sites to permit conditional restoration of B2m expression and therefore surface MHC I expression in response to Cre recombination. (A) Schematic showing WT and modified B2m loci with and without Cre recombination. Lungs from B6.H2d reference controls, B6.H2d-background B2minv/inv Cre-negative mice, and their VE-Cad–Cre × B2minv/inv littermates were dissociated for measurement of H-2Kd MHC I expression on CD41–, CD45–, CD31+ pulmonary endothelial cell surfaces. (B) Representative histograms showing pulmonary endothelial H-2Kd expression, and (C) quantification of median fluorescence intensity (MFI) of pulmonary endothelial surface H-2Kd (n = 6). Blood was also tested to confirm H-2Kd MHC I removal from CD45+ leukocytes in B2minv/inv mice. (D) Representative leukocyte H-2Kd histograms, and (E) quantification of leukocyte H-2Kd MFI (B6.H2d and VE-Cad–Cre–, n = 13; VE-Cad–Cre+, n = 5). Separate mice were primed with LPS and challenged with 1 mg/kg anti–H-2d i.v. for measurements of (F) lung vascular permeability and (G) extravascular lung water (both n = 6), or (H) 4.5 mg/kg anti–H-2d i.v. for survival assessment (B6.H2d and VE-Cad–Cre–, n = 10; VE-Cad–Cre+, n = 8). Mean ± SEM. Horizontal lines in F and G are reference data from Figure 1 from mice given isotype control i.v. *P < 0.05; **P < 0.01; ***P < 0.001 by 1-way ANOVA with Tukey’s test (C, E, F, and G) or log-rank test with Bonferroni’s correction (H).