Table 4.
Major immune checkpoint inhibitory and stimulatory proteins.
| Immune Checkpoint Receptor | CD Number | Receptor Family | Cellular Expression of the Receptor | Ligand | CD Number | Cellular Expression of the Ligand |
|---|---|---|---|---|---|---|
| A. Immune Checkpoint Inhibitory Proteins | ||||||
| CTLA-4 | CD152 | CD28 | Activated T-cells and Tregs | CD80 | CD80 | APC |
| CD86 | CD86 | |||||
| PD-1 | CD279 | CD28 | Activated T and B-cells, NK cells and APCs | PD-L1 | CD274 | Activated DC, Macrophage and Tumors |
| PD-L2 | CD273 | APCs | ||||
| BTLA | CD272 | CD28 | T and B-cells, Macrophages, DCs and NK cells | HVEM | CD270 | T-cells and Macrophage |
| LAG3 | CD223 | - | Activated T-cells, Tregs, B cells, NK cells and Plasmacytoid DCs | MHC class II/Lectins | - | APC |
| TIGIT | - | CD28 | Activated T-cells, Tregs and NK cells | PVR | CD155 | DC, APCs and Tumors |
| Nectin-2 (PVRL2) | CD112 | |||||
| TIM3 | CD366 | - | Activated T-cells (Th1 cells), Treg | Gal9 | - | Variety of tissues |
| PtdSer | ||||||
| HMGB1 | ||||||
| CEACAM-1 | ||||||
| VISTA (B7-H5) |
- | CD28 | Macrophages, DCs, Naïve CD4+ T-cells, Tregs, Circulating Neutrophils and Monocytes | VSIG-3 | - | Neurons and glial cells |
| NKG2A | CD94 | NKG2 | NK | HLA-E | - | - |
| ecto-5′NT | CD73 | Ecto-nucleotidase | Many cell types, upregulated in Treg | - | - | - |
| NTPDase1 | CD39 | Ecto-nucleotidase | Many cell types, upregulated in Treg | - | - | - |
| CD47 | CD47 | Ig superfamily | Ubiquitous | SIRPα | CD172α | Myeloid, neurons |
| THBS1 (TSP-1) | - | Extracellular matrix | ||||
| B. Immune Checkpoint Stimulatory Proteins | ||||||
| CD27 | CD27 | TNFR | Activated T-cells, B-cells and NK cells | CD70 | CD70 | Activated T, B-cells and DC |
| CD28 | CD28 | CD28 | T-cells | B7 | CD80 | APC |
| CD86 | ||||||
| GITR | CD357 | TNFR | Tregs and Naïve and Memory T-cells | GITRL | - | DC, Macrophage and Activated B-cells |
| ICOS | CD278 | B7/CD28 | Activated T-cells | ICOSLG | CD275 | B-cells, Macrophage and DC |
| NKG2D | CD314 | NKG2 | NK cells, CD8+ T-cells and γδ T-cells | MHC class I | - | Epithelial and endothelial cells |
| UL16-binding protein | ||||||
| OX40 | CD134 | TNFR | Activated T cells, Tregs and NK cells | OX40L | CD252 | DC, Macrophage, B-cell and Endothelial cells |
| 4-1BB | CD137 | TNFR | Activated T and NK cells | 4-1BBL | CD137L | DC, Macrophage and B-cells |