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Soluble human leukocyte antigen G5 polarizes differentiation of macrophages toward a decidual macrophage-like
Cheuk-Lun Lee1, YiFan Guo2, Kam-Hei So3
1Department of Obstetrics and Gynaecology, The University of Hong Kong, Pokfulam Road, Hong Kong, China Centre for Reproduction, Development and Growth, LKS Faculty of Medicine, The University of Hong Kong, Pokfulam Road, Hong Kong, China Shenzhen Key Laboratory of Fertility Regulation, Department of Obstetrics and Gynecology, The University of Hong Kong-Shenzhen Hospital, Shenzhen, China.
Study Question:
What are the actions of soluble human leukocyte antigen G5 (sHLAG5) on macrophage differentiation?
Summary Answer:
sHLAG5 polarizes the differentiation of macrophages toward a decidual macrophage-like phenotype, which could regulate fetomaternal tolerance and placental development.
What Is Known Already:
sHLAG5 is a full-length soluble isoform of human leukocyte antigen implicated in immune tolerance during pregnancy. Low or undetectable circulating level of sHLAG5 in first trimester of pregnancy is associated with pregnancy complications such as pre-eclampsia and spontaneous abortion. Decidual macrophages are located in close proximity to invasive trophoblasts, and are involved in regulating fetomaternal tolerance and placental development.
Study Design, Size, Duration:
Human peripheral blood monocytes were differentiated into macrophages by treatment with granulocyte macrophage colony-stimulating factor in the presence or absence of recombinant sHLAG5 during the differentiation process. The phenotypes and the biological activities of the resulting macrophages were compared.
Participants/Materials, Setting, Methods:
Recombinant sHLAG5 was produced in Escherichia coli BL21 and the protein identity was verified by tandem mass spectrometry. The expression of macrophage markers were analyzed by flow cytometry and quantitative PCR. Phagocytosis was determined by flow cytometry. Indoleamine 2,3-dioxygenase 1 expression and activity were measured by western blot analysis and kynurenine assay, respectively. Cell proliferation and cell cycling were determined by fluorometric cell proliferation assay and flow cytometry, respectively. Cytokine secretion was determined by cytokine array and ELISA kits. Intracellular cytokine expression was measured by flow cytometry. Cell invasion and migration were determined by trans-well invasion and migration assay, respectively.
Main Results And The Role Of Chance:
sHLAG5 drove the differentiation of macrophages with 'immuno-modulatory' characteristics, including reduced expression of M1 macrophage marker CD86 and increased expression of M2 macrophage marker CD163. sHLAG5-polarized macrophages showed enhanced phagocytic activity. They also had higher expression and activity of indoleamine 2,3-dioxygenase 1, a phenotypic marker of decidual macrophages, which inhibited proliferation of autologous T-cells via induction of G0/G1 cell cycle arrest. In addition, sHLAG5-polarized macrophages had an increased secretion of interleukin-6 and C-X-C motif ligand 1, which inhibited interferon-γ production in T-cells and induction of trophoblast invasion, respectively.
Limitations, Reasons For Caution:
Most information on the phenotypes and biological activities of human decidual macrophages are based on past literatures. A direct comparison between sHLAG5-polarized macrophages and primary decidual macrophages is required to verify the present observations.
Wider Implications Of The Findings:
This is the first study on the role of sHLAG5 in macrophage differentiation. Further study on the mechanism that regulates the differentiation process of macrophages would enhance our understanding on the physiology of early pregnancy.
Study Funding/Competing Interests:
This work was supported in part by the Hong Kong Research Grant Council Grant HKU774212 and the University of Hong Kong Grant 201309176126. The authors have no competing interests to declare.
Trial Registration Number:
Nil.
Insights
Soluble human leukocyte antigen G5 (sHLAG5) promotes macrophage differentiation into a decidual type, crucial for immune tolerance during pregnancy. This finding offers insights into regulating fetomaternal tolerance and placental development.
Area of Science:
- Immunology
- Reproductive Biology
- Cell Biology
Background:
- Soluble human leukocyte antigen G5 (sHLAG5) is vital for immune tolerance in pregnancy.
- Low sHLAG5 levels in early pregnancy correlate with complications like pre-eclampsia.
- Decidual macrophages are key to fetomaternal tolerance and placental development.
Purpose of the Study:
- To investigate the effects of sHLAG5 on macrophage differentiation.
- To determine if sHLAG5 influences macrophage phenotype and function.
Main Methods:
- Human monocytes were differentiated into macrophages with or without sHLAG5.
- Macrophage markers, phagocytosis, indoleamine 2,3-dioxygenase 1 (IDO1) activity, T-cell proliferation, cytokine secretion, and trophoblast invasion were analyzed.
Main Results:
- sHLAG5 induced an 'immuno-modulatory' macrophage phenotype (M2-like) with increased CD163 and reduced CD86 expression.
- sHLAG5-polarized macrophages exhibited enhanced phagocytosis and IDO1 activity, suppressing T-cell proliferation.
- These macrophages secreted IL-6 and CXCL1, inhibiting T-cell interferon-γ production and trophoblast invasion.
Conclusions:
- sHLAG5 polarizes macrophages towards a decidual macrophage-like phenotype.
- This polarization may play a role in regulating fetomaternal tolerance and placental development.
- Further research comparing sHLAG5-polarized macrophages with primary decidual macrophages is warranted.
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