Table 1 Structures, expression patterns and receptors of B7 ligands
Ligand name (alternative names) | Structure | Protein expression pattern in lymphoid cells* | mRNA expression in non-lymphoid tissues or cells | Receptor | Function of ligand-receptor interaction |
|---|---|---|---|---|---|
B7.1 (CD80) |
| Induced in T, B, DCs, and monocytes | Not detected | CD28 CTLA-4 (CD152) | Costimulation Coinhibition |
B7.2 (CD86) |
| Constitutive and upregulated upon activation in B, DCs, and monocytes; induced in T | Not detected | CD28 CTLA-4 (CD152) | Costimulation Coinhibition |
ICOS-L (GL-50, B7 h, B7RP-1, B7H-2) |
| Constitutive in B, DCs, macrophages, and a subset of T | Lung, liver, kidney, and testes | ICOS | Costimulation |
PD-L1 (B7-H1) |
| Constitutive and upregulated upon activation in B, DCs, and monocytes; induced in T | Placenta, heart, pancreas, lung, liver, and tumor cells (carcinomas and melanomas) | PD-1 Unknown? | Coinhibition Costimulation |
PD-L2 (B7-DC) |
| Induced in DCs and monocytes | Heart, placenta, lung, liver keratinocytes, and epithelial cells | PD-1 Unknown? | Coinhibition Costimulation |
B7-H4 (B7x, B7S1) |
| Induced in T, B, NK, DCs, and monocytes | Placenta, uterus, testis, kidney, lung, heart, and brain | Unknown | Coinhibition |
B7-H3 |
| Induced in T, B, DCs, and monocytes | Heart, kidney, testes, lung, liver, pancreas, prostate, colon, and osteoblasts | Unknown Unknown | Costimulation Coinhibition |
