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Published on: May 1, 2015
Expression and regulation of the PD-L1 immunoinhibitory molecule on microvascular endothelial cells
Michael J Eppihimer1, Jason Gunn, Gordon J Freeman
1Discovery Research: Respiratory Diseases, Wyeth/Genetics Institute, Andover, MA 01810, USA. meppihimer@genetics.com
Insights
Programmed death-ligand 1 (PD-L1) is expressed on endothelial cells (ECs) and upregulated by interferons (IFNs). This suggests a mechanism for ECs to regulate T-cell responses.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- Endothelial cells (ECs) play a crucial role in regulating immune responses.
- Programmed death-1 (PD-1) is an inhibitory receptor on T-cells, and its ligand, PD-L1, is a B7-like protein.
- Understanding PD-L1 expression on ECs is key to deciphering immune modulation in microvasculature.
Purpose of the Study:
- To investigate the expression and regulation of PD-L1 on microvascular endothelial cells (ECs).
- To determine the role of interferons (IFNs) and IL-12 in modulating PD-L1 expression on ECs.
Main Methods:
- Quantified PD-L1 expression on ECs in vitro and in vivo using a dual radiolabeled antibody technique.
- Assessed PD-L1 mRNA levels via reverse transcription-polymerase chain reaction (RT-PCR).
- Measured PD-L1 expression in mouse tissues following IL-12 challenge, comparing wild-type and IFN-gamma-deficient models.
Main Results:
- PD-L1 was constitutively expressed on ECs.
- IFN-alpha, -beta, and -gamma, but not lipopolysaccharide (LPS), significantly increased PD-L1 mRNA and surface expression on ECs.
- IL-12 challenge in mice led to a significant increase in tissue PD-L1 expression, peaking at 72 hours.
- IL-12 failed to induce PD-L1 expression in IFN-gamma-deficient mice, highlighting the critical role of IFN-gamma.
Conclusions:
- Murine ECs express a novel B7-like molecule, PD-L1.
- IFN-alpha, -beta, and -gamma mediate the expression of PD-L1 on ECs.
- ECs may modulate T-cell function through PD-L1 expression, representing a significant immunoregulatory pathway.
Objective:
To evaluate the expression and regulation of a novel B7-like protein, PD-L1, the ligand for the immunoinhibitory receptor PD-1 expressed on activated T-cells, on microvascular endothelial cells (ECs)
Methods:
PD-L1 expression on ECs in vitro and in vivo was quantified by using a dual radiolabeled antibody technique after treatment with interferons (IFN) and IL-12, respectively. Changes in the level of PD-L1 mRNA were determined by using RT-PCR.
Results:
PD-L1 was observed to be present on ECs under basal conditions. Treatment of ECs with IFN-alpha, -beta and -gamma, but not LPS, was observed to induce elevations in the mRNA and surface expression of PD-L1 on ECs. By using a dual radiolabeled monoclonal antibody (mAb) technique, PD-L1 expression in various tissues of control and IL-12 challenged wild-type and IFN-gamma-deficient mice was measured. A significant increase in PD-L1 expression was observed in tissues at 24 hours after IL-12-challenge, with peak levels of PD-L1 occurring 72 hours after IL-12 challenge. IL-12 was not effective at inducing PD-L1 expression in tissues of IFN-gamma-deficient mice.
Conclusions:
These data show the expression of a novel B7-like molecule on murine ECs that is mediated by IFN-alpha, -beta, and -gamma, and suggest a potential pathway by which ECs may modulate T-cell function.
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