Table 1.
Examples of suppressive (negative) and stimulatory (positive) immune checkpoint ligand–receptor pairs with cellular distribution of these molecules under physiological conditions.
| Ligand | Cellular Distribution of the Ligand Expression | Immune Checkpoint Receptor | Cellular Expression of the Receptor Expression |
|---|---|---|---|
| Suppressive (negative) immune checkpoints | |||
| CD80 or CD86 | Antigen-presenting cells | CTLA4 | Activated T cells, Tregs |
| PD-L1 (CD274) or PD-L2 (CD273) | DCs, macrophages, peripheral non-lymphoid tissues | PD-1 | Activated B and T cells, APCs, NK cells |
| MHC class II/Lectins | Antigen-presenting cells | LAG3 | Activated T cells, Tregs, NK cells, B cells, DCs |
| CD155/CD112 | Normal epithelial, endothelial, neuronal, and fibroblastic cells | TIGIT | Activated T cells, Tregs, NK cells |
| Galectin 9/ PtdSer /HMGB1 | Multiple tissues | TIM3 | Activated T cells |
| VSIG-3 | Neurons and glial cells | VISTA | Naïve and activated T cells |
| CEACAM1 | T and NK cells | CEACAM1 | Activated T and NK cells |
| Stimulatory (positive) immune checkpoints | |||
| B7 molecules: CD80 or CD86 | Antigen-presenting cells | CD28 | T cells |
| OX40L | DCs, macrophages, B cells, endothelial cells, smooth muscle cells | OX40 | Activated T cells, Tregs, NK cells, neutrophils |
| CD137L | Antigen-presenting cells | CD137 (4-1BB) | Activated Tcells, NK cells, B cells, DCs, endothelial cells |
| GITRL | Antigen-presenting cells and endothelium | GITR | T and NK cells, Tregs |
| ICOSLG | APCs, B cells, DCs and macrophages | ICOS | Naïve and activated T cells |
| CD70 | Activated lymphocytes | CD27 | Activated T and NK cells |