HLA antibody (Ab)-mediated rejection (AMR) is often characterized by graft-infiltrating macrophages, which correlate with tissue fibrosis. Recent studies suggest they may mainly represent M2-polarized macrophages. Our earlier studies showed that HLA class I Ab (HLA I)can enhance monocyte recruitment by increasing the expression of P-selectin and ICAM-1 clustering on endothelial cell (ECs) surface. The aim of the current study is to investigate whether and how HLA I Ab-activated ECs affect monocyte differentiation. We co-cultured human primary monocytes from 4 donors with HLA I Ab (intact and F(ab')2) stimulated primary aortic ECs from four different donors for five days. Monocytes exposed to IFNγ, IL-4, hIgG+LPS, or IL-10 served as controls for M1, M2a, M2b and M2c, respectively. Monocytes and supernatants were collected for phenotype and cytokine assessments. We found that ECs alone can drive human monocyte differentiation into M2a-like macrophages with enhanced expression of CD206. HLA I Ab-stimulated ECs further promote polarization into M2a/c-like macrophages with increased expression of CD206, CD163 and CD68. HLA I F(ab')2-stimulated ECs promote a different phenotype of macrophages compared with intact antibody. We also found that several cytokines and chemokines, including IL-6, IL-8, IL-10, MCP-1 and GRO, are significantly increased in the supernatant from HLA I Ab-stimulated co-cultures. These findings uncover the role of ECs in monocyte differentiation, and demonstrate the ability of HLA I Ab to promote this polarization.

CITATION INFORMATION: Wei X, Valenzuela N, Rossetti M, Reed E. Anti-HLA I Antibody Enhances Endothelial Cell-Induced Polarization of Human Monocytes to M2a/c-Like Macrophages. Am J Transplant. 2017;17 (suppl 3).

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