Cross-Talk between HLA Class I and TLR4 Mediates P-Selectin Surface Expression and Monocyte Capture to Human Endothelial Cells

The Journal of Immunology, vol. 209, pp. 1359–1369

Abstract

Abstract Donor-specific HLA Abs contribute to Ab-mediated rejection (AMR) by binding to HLA molecules on endothelial cells (ECs) and triggering intracellular signaling, leading to EC activation and leukocyte recruitment. The molecular mechanisms involving donor-specific HLA Ab–mediated EC activation and leukocyte recruitment remain incompletely understood. In this study, we determined whether TLRs act as coreceptors for HLA class I (HLA I) in ECs. We found that human aortic ECs express TLR3, TLR4, TLR6, and TLR10, but only TLR4 was detected on the EC surface. Consequently, we performed coimmunoprecipitation experiments to examine complex formation between HLA I and TLR4. Stimulation of human ECs with HLA Ab increased the amount of complex formation between HLA I and TLR4. Reciprocal coimmunoprecipitation with a TLR4 Ab confirmed that the crosslinking of HLA I increased complex formation between TLR4 and HLA I. Knockdown of TLR4 or MyD88 with small interfering RNAs inhibited HLA I Ab–stimulated P-selectin expression, von Willebrand factor release, and monocyte recruitment on ECs. Our results show that TLR4 is a novel coreceptor for HLA I to stimulate monocyte recruitment on activated ECs. Taken together with our previous published results, we propose that HLA I molecules form two separate signaling complexes at the EC surface, that is, with TLR4 to upregulate P-selectin surface expression and capture of monocytes to human ECs and integrin β4 to induce mTOR-dependent firm monocyte adhesion via ICAM-1 clustering on ECs, two processes implicated in Ab-mediated rejection.

Authors 8

1. Yiping Jin

   University of California, Los Angeles

   Affiliation as printed

   Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California , Los Angeles, Los Angeles, CA

   *Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA;

2. Jessica Nevarez‐Mejia

   University of California, Los Angeles

   Affiliation as printed

   Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California , Los Angeles, Los Angeles, CA

   *Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA;

3. Allyson Q. Terry

   University of California, Los Angeles

   Affiliation as printed

   Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California , Los Angeles, Los Angeles, CA

   *Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA;

4. Rebecca A. Sosa

   University of California, Los Angeles

   Affiliation as printed

   Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California , Los Angeles, Los Angeles, CA

   *Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA;

5. Sebastiaan Heidt Aachen Department of Immunology, Leiden University Medical Center

   Leiden University Medical Center

   Affiliation as printed

   Department of Immunology, Leiden University Medical Center , Leiden,

   †Department of Immunology, Leiden University Medical Center, Leiden, the Netherlands; and

6. Nicole M. Valenzuela

   University of California, Los Angeles

   Affiliation as printed

   Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California , Los Angeles, Los Angeles, CA

   *Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA;

7. Enrique Rozengurt

   University of California, Los Angeles

   Affiliation as printed

   Department of Medicine, David Geffen School of Medicine, University of California , Los Angeles, Los Angeles, CA

   ‡Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA

8. Elaine F. Reed corresponding

   University of California, Los Angeles

   Affiliation as printed

   Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California , Los Angeles, Los Angeles, CA

   *Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA;