Table 1.
Major NK cell inhibitory receptors that may act as immune checkpoint molecules and their ligands.
| Receptor Family | Inhibitory Natural Killer (NK) Cell Receptors | Ligands |
|---|---|---|
| Killer immunoglobulin-like receptors (KIR) | KIR2DL1 | Human leukocyte antigen (HLA)-C2 group |
| KIR2DL2/3 | HLA-C1 group | |
| KIR3DL1 | HLA-Bw4 serotypes | |
| KIR3DL2 | HLA-A3/11 serotype | |
| Leucocyte immunoglobulin-like receptors (LILR) | LILRB1 | HLA-A, -B, -C, -G |
| Cluster of differentiation (CD) 94/Natural killer G2 (NKG2) | NKG2A | HLA-E |
| Natural killer receptor P1 (NKRP1) | NKRP1A | Lectin-like transcript 1 (LLT1) |
| Programmed death 1 (PD-1) | Programmed death ligand 1 (PDL-1) |