B cells mediate lung ischemia/reperfusion injury by recruiting classical monocytes via synergistic B cell receptor/TLR4 signaling
Khashayar Farahnak, … , Daniel Kreisel, Ruben G. Nava
Khashayar Farahnak, … , Daniel Kreisel, Ruben G. Nava
Published January 23, 2024
Citation Information: J Clin Invest. 2024;134(6):e170118. https://doi.org/10.1172/JCI170118.
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Research Article Immunology

B cells mediate lung ischemia/reperfusion injury by recruiting classical monocytes via synergistic B cell receptor/TLR4 signaling

Abstract

Ischemia/reperfusion injury–mediated (IRI-mediated) primary graft dysfunction (PGD) adversely affects both short- and long-term outcomes after lung transplantation, a procedure that remains the only treatment option for patients suffering from end-stage respiratory failure. While B cells are known to regulate adaptive immune responses, their role in lung IRI is not well understood. Here, we demonstrated by intravital imaging that B cells are rapidly recruited to injured lungs, where they extravasate into the parenchyma. Using hilar clamping and transplant models, we observed that lung-infiltrating B cells produce the monocyte chemokine CCL7 in a TLR4-TRIF–dependent fashion, a critical step contributing to classical monocyte (CM) recruitment and subsequent neutrophil extravasation, resulting in worse lung function. We found that synergistic BCR-TLR4 activation on B cells is required for the recruitment of CMs to the injured lung. Finally, we corroborated our findings in reperfused human lungs, in which we observed a correlation between B cell infiltration and CM recruitment after transplantation. This study describes a role for B cells as critical orchestrators of lung IRI. As B cells can be depleted with currently available agents, our study provides a rationale for clinical trials investigating B cell–targeting therapies.

Authors

Khashayar Farahnak, Yun Zhu Bai, Yuhei Yokoyama, Deniz B. Morkan, Zhiyi Liu, Junedh M. Amrute, Alejandro De Filippis Falcon, Yuriko Terada, Fuyi Liao, Wenjun Li, Hailey M. Shepherd, Ramsey R. Hachem, Varun Puri, Kory J. Lavine, Andrew E. Gelman, Ankit Bharat, Daniel Kreisel, Ruben G. Nava

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Figure 7

BCR-TLR4 synergistic activation drives classical monocyte recruitment to the lung after IRI.

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BCR-TLR4 synergistic activation drives classical monocyte recruitment to...
In Nur77GFP mice, there is GFP expression when the BCR is activated. (A) Flow cytometry gating strategy for GFP expression on activated B cells (CD25+ CD30+) in spleen and lung after hilar clamping of Nur77GFP mice. (B) Percentage and total number of GFP+ B cells per milligram of lung tissue. (C) Representative dot plots of flow cytometric analysis of B cell extravasation, which was determined by injecting fluorochrome-labeled B cell–specific anti-CD19 antibodies i.v. 5 minutes before sacrifice. The graph shows the mean percentage of B cell extravasation in the GFP– versus GFP+ populations. (D) IgM and IgD mean fluorescence intensity measured on lung-infiltrating GFP+ and GFP– B cells. (E) Splenic B cells from IgHEL mice were adoptively transferred to μMT mice 24 hours prior to hilar clamping. Lung function was assessed with ABG. μMT recipients of IgHEL B cells showed improved oxygenation compared with B6 WT B cells. (F and G) Flow cytometry was used to analyze the (F) percentage and total number per milligram of lung tissue of classical monocytes and (G) percentage of extravasated neutrophils in the lung after IRI. n = 4–7. Results are presented as mean ± SEM. P values were calculated by Mann-Whitney test. *P < 0.05, **P < 0.01.