Table 1.
Expression and function of the B7 family ligands and their receptors of the CD28 family
| The B7 family ligands | The CD28 family receptors | ||||
|---|---|---|---|---|---|
| Expression | Name | Name | Expression | Function | |
| Group I | |||||
| APC | B7-1 |  | CD28 | T cells | Costimulation |
| APC | B7-2 | CTLA-4 | Activated T cells | Coinhibition | |
| APC, tissue | B7h |  | ICOS | Activated T cells | Costimulation |
| Group II | |||||
| APC, tissue, tumors | PD-L1 |  | PD-1 | Activated T, B, and myeloid cells | Coinhibition |
| APC | PD-L2 |  | PD-1 | Activated T, B, and myeloid cells | Coinhibition |
| Group III | |||||
| APC, tissue, tumors | B7-H3 |  | Unidentified receptor | Activated T cells | Coinhibition |
| Tissue, tumors | B7x |  | Unidentified receptor | Activated T cells | Coinhibition |