Table 1. Antigens included in Panel One and their functional roles with respect to the villous core.
Antigens are grouped by cell type (grey and white boxes).
| Antigen | Full name/s | Functional capacity/relevance | References |
|---|---|---|---|
| ITGβ4/CD104 | β4 integrin | Cell adhesion molecule that uniquely identifies cytotrophoblasts in the placenta. | James et al., 2015 |
| CD45 | Protein tyrosine phosphatase, receptor type, C. lymphocyte common antigen | Expressed on all nucleated haematopoietic cells. | Hermiston et al., 2003 |
| HLA-DR | Human Leukocyte Antigen – DR isotype | Expressed by antigen presenting cells i.e. macrophages, MHC class II cell surface receptor, involved in antigen presentation and adaptive immunity, | Cruz-Tapias et al., 2013 |
| CD235a/GPA | Glycophorin A | Red blood cell marker, identifies early emerging RBCs/erythroblasts from haemogenic endothelium | Garcia-Alegria et al., 2018; Mao et al., 2016 |
| CD41 | Integrin alpha-IIb | Platelet marker. Expressed by earliest emerging haematopoietic cells from haemogenic endothelium | Garcia-Alegria et al., 2018; Li et al., 2005 |
| CD117/cKIT | Mast/stem cell growth factor receptor | Receptor expressed on haematopoietic stem cells and involved in their differentiation | Rönnstrand, 2004 |
| CD144 /VE-cadherin | Vascular endothelial cadherin | Endothelial cell-cell adherens junctional marker, stabilises vessels, inhibits vascular growth, regulates vascular permeability. | Giannotta et al., 2013 |
| CD34 | Haematopoietic Progenitor Cell Antigen | Expressed by haematopoietic and vascular progenitors and adipose-derived MSCs. Transmembrane phosphoglycoprotein, thought to identify early placental progenitors | Brooks et al., 2020; Sidney et al., 2014; Yoder, 2009 |
| CD31/PECAM1 | Platelet endothelial cell adhesion molecule | Expressed by endothelial cells, platelets, macrophages and Kupffer cells, granulocytes, lymphocytes, megakaryocytes. Adhesion molecule found at endothelial intercellular junctions. | Marelli-Berg et al., 2013 |
| VEGFR2/KDR | Vascular Endothelial Growth Factor Receptor 2/Kinase Insert Domain Receptor | Expressed by endothelial cells and thought to identify placental core progenitors. Receptor for angiogenic VEGF, involved in vasculogenesis and angiogenesis. | Demir et al., 2007 |
| CD54/ICAM1 | Intercellular Adhesion Molecule 1 | Expressed at low levels on endothelial cells, monocytes and lymphocytes. Increased expression in response to inflammatory cytokines. | Hubbard and Rothlein, 2000 |
| CD36/FAT | Platelet glycoprotein 4/fatty acid translocase | Expressed by microvascular endothelial cells, and fibroblasts. Has an anti-angiogenic effect via binding Thrombospondin 1. Involved in fatty acid uptake. | Dye et al., 2001; Heinzelmann et al., 2018; Silverstein and Febbraio, 2009 |
| CD90 /Thy-1 | Thymocyte differentiation antigen 1 | Expressed by MSCs, haematopoietic stem cells, fibroblasts, myofibroblasts. | Viswanathan et al., 2019 |
| CD73 /NT5E | Ecto-5′-nucleotidase | Expressed by MSCs and endothelial cells. Works with CD39 to convert extracellular ATP to adenosine to create immunosuppressive effect. | Roh et al., 2020; Viswanathan et al., 2019 |
| CD39 /NTPDase | Ectonucleoside triphosphate diphosphohydrolase-1 | Upregulated by MSCs to suppress lymphocyte activation. Immunosuppressive actions via the conversion of extracellular ATP (inflammatory) into adenosine (anti-inflammatory) | Saldanha-Araujo et al., 2011; Zhao et al., 2017 |
| CD55/DAF | Decay-accelerating factor | Expressed by MSCs. Complement regulatory protein, inhibits C3 convertases thereby creating a threshold for complement activation, increased expression correlated with evasion of innate immune system | Ruiz-Argüelles and Llorente, 2007; Soland et al., 2013 |
| CD271 /NGFR / p75NTR | Low-affinity Nerve Growth Factor Receptor | Used in MSC and pericyte identification. Hypothesised to identify “stem-cell” or progenitor populations with superior differentiation and colony forming capacity. | Barilani et al., 2018; Kumar et al., 2017 |
| CD146/MCAM | Melanoma cell adhesion molecule | Adhesion molecule expressed by pericytes, endothelial cells and smooth muscle cells. Involved in the regulation of angiogenesis and vessel permeability. | Crisan et al., 2009; Leroyer et al., 2019 |
| CD248 | Endosialin/ tumor endothelial marker 1 | Pericyte and stromal cell marker. Involved in cell–cell adhesion, and host defence. | Lax et al., 2010; Tomkowicz et al., 2010 |
| CD142/TF | Tissue Factor/ thromboplastin | Expression correlated with pericytes, smooth muscle and fibroblasts. Activates blood clotting after injury, located outside the vasculature, | Abe et al., 1999; Morrissey, 2004 |
| CD26/DDP4 | Dipeptidyl peptidase-4, adenosine deaminase complexing protein 2 | Expressed by many tissues; T-cells, epithelial cells, ESCs, progenitor cells, placental myofibroblasts. Serine protease that cleaves a range of chemokines. Downregulation is correlated with increased stromal/myofibroblast proliferation. | Kohnen et al., 1996; Mezawa et al., 2019; Ou et al., 2013 |
| PDPN | Podoplanin | Lymphatic vascular marker. Expression is correlated with increased fibroblast migration. Binds to CLEC-2 receptor on platelets. | Astarita et al., 2012; Suchanski et al., 2017 |