HLA class I antibody-activated endothelium promotes CD206+ M2-macrophage polarization and MMP9 secretion through TLR4 signaling and P-selectin in a model of antibody-mediated rejection and allograft vasculopathy

Jessica Nevarez-Mejia; Yi-Ping Jin; Harry Pickering; Rajesh Parmar; Nicole M Valenzuela; Rebecca A Sosa; Sebastiaan Heidt; Gregory A Fishbein; Enrique Rozengurt; M Baldwin William 3rd; Robert L Fairchild; Elaine F Reed

doi:10.1016/j.ajt.2023.10.020

HLA class I antibody-activated endothelium promotes CD206+ M2-macrophage polarization and MMP9 secretion through TLR4 signaling and P-selectin in a model of antibody-mediated rejection and allograft vasculopathy

Am J Transplant. 2023 Oct 27:S1600-6135(23)00822-5. doi: 10.1016/j.ajt.2023.10.020. Online ahead of print.

Affiliations

¹ Department of Pathology and Laboratory Medicine, University of California, Los Angeles, CA.
² Department of Immunology, Leiden University Medical Center, Leiden, the Netherlands.
³ Division of Digestive Diseases, Department of Medicine, University of California, Los Angeles, CA.
⁴ Department of Inflammation & Immunity, Lerner Research Institute, Cleveland Clinic, Cleveland Clinic, OH.
⁵ Department of Pathology and Laboratory Medicine, University of California, Los Angeles, CA. Electronic address: [email protected].

PMID: 39491096
DOI: 10.1016/j.ajt.2023.10.020

Abstract

HLA donor-specific antibodies (DSA) elicit alloimmune responses against the graft vasculature, leading to endothelial cell (EC) activation and monocyte infiltration during antibody-mediated rejection (AMR). AMR promotes chronic inflammation and remodeling, leading to thickening of the arterial intima termed transplant vasculopathy (TV) or cardiac allograft vasculopathy (CAV) in heart transplants. Intragraft-recipient macrophages serve as a diagnostic marker in AMR however, their polarization and function remain unclear. In this study, we utilized an in vitro transwell co-culture system to explore the mechanisms of monocyte-to-macrophage polarization induced by HLA I DSA activated ECs. Anti-HLA I (IgG or F(ab')₂) antibody-activated ECs induced the polarization of M2-macrophages with increased CD206 expression and MMP9 secretion. However, inhibition of TLR4 signaling or PSGL-1-P-selectin interactions significantly decreased both CD206 and MMP9. Monocyte adherence to Fc-P-selectin coated plates induced M2-macrophages with increased CD206 and MMP9. Moreover, Fc-receptor and IgG interactions synergistically enhanced active-MMP9 in conjunction with P-selectin. Transcriptomic analysis of arteries from DSA+CAV+ rejected cardiac allografts and multiplex-immunofluorescent staining illustrated the expression of CD68+CD206+CD163+MMP9+ M2-macrophages within the neointima of CAV affected lesions. These findings reveal a novel mechanism linking HLA I antibody-activated endothelium to the generation of M2-macrophages which secrete vascular remodeling proteins contributing to AMR and CAV pathogenesis.