CD11b suppresses TLR activation of nonclassical monocytes to reduce primary graft dysfunction after lung transplantation
Melissa Querrey, … , Ankit Bharat, G.R. Scott Budinger
Melissa Querrey, … , Ankit Bharat, G.R. Scott Budinger
Published July 15, 2022
Citation Information: J Clin Invest. 2022;132(14):e157262. https://doi.org/10.1172/JCI157262.
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Research Article Immunology

CD11b suppresses TLR activation of nonclassical monocytes to reduce primary graft dysfunction after lung transplantation

Abstract

Primary graft dysfunction (PGD) is the leading cause of postoperative mortality in lung transplant recipients and the most important risk factor for development of chronic lung allograft dysfunction. The mechanistic basis for the variability in the incidence and severity of PGD between lung transplant recipients is not known. Using a murine orthotopic vascularized lung transplant model, we found that redundant activation of Toll-like receptors 2 and 4 (TLR2 and -4) on nonclassical monocytes activates MyD88, inducing the release of the neutrophil attractant chemokine CXCL2. Deletion of Itgam (encodes CD11b) in nonclassical monocytes enhanced their production of CXCL2 and worsened PGD, while a CD11b agonist, leukadherin-1, administered only to the donor lung prior to lung transplantation, abrogated CXCL2 production and PGD. The damage-associated molecular pattern molecule HMGB1 was increased in peripheral blood samples from patients undergoing lung transplantation after reperfusion and induced CXCL2 production in nonclassical monocytes via TLR4/MyD88. An inhibitor of HMGB1 administered to the donor and recipient prior to lung transplantation attenuated PGD. Our findings suggest that CD11b acts as a molecular brake to prevent neutrophil recruitment by nonclassical monocytes following lung transplantation, revealing an attractive therapeutic target in the donor lung to prevent PGD in lung transplant recipients.

Authors

Melissa Querrey, Stephen Chiu, Emilia Lecuona, Qiang Wu, Haiying Sun, Megan Anderson, Megan Kelly, Sowmya Ravi, Alexander V. Misharin, Daniel Kreisel, Ankit Bharat, G.R. Scott Budinger

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Figure 5

HMGB1 activates TLR2 and TLR4 to induce the expression of CXCL2 in NCMs.

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HMGB1 activates TLR2 and TLR4 to induce the expression of CXCL2 in NCMs....
(A) Splenic NCMs were flow cytometry sorted from wild-type (C57BL/6J) mice and stimulated with putative DAMPs as indicated for 4 hours, after which the supernatants were collected for ELISA analysis. ****P < 0.0001 by 1-way ANOVA with Tukey’s multiple comparisons test. Mitochondrial DNA (mtDNA), S100 proteins (S100), and HMGB1 were administered at a dose of 1 μg. (B) Splenic NCMs were flow cytometry sorted from wild-type (C57BL/6J), Tlr2–/–, Tlr4–/–, and Tlr2–/– Tlr4–/– mice and treated with HMGB1 (1 μg), and CXCL2 was measured in the supernatant 4 hours later. **P = 0.0022, ****P < 0.0001 by 1-way ANOVA with Tukey’s multiple comparisons test. NS, not significant. (C) Schematic for human sera collection in D. (D) Blood samples from patients undergoing lung transplantation were obtained immediately prior to and 24 hours after reperfusion and analyzed for HMGB1. ****P < 0.0001 by 2-tailed, paired t test. (E) Schematic for murine sera collection. (F) HMGB1 serum concentrations in native, allogeneic, and syngeneic lung transplants. **P = 0.0073 by 1-way ANOVA with Dunnett’s correction for multiple comparisons. In A and B, each symbol represents 50,000 NCMs, and approximately 100,000 to 200,000 NCMs were isolated from an individual mouse; each symbol in D and F represents an individual mouse or human.