NK Receptors Corresponding Ligand/Cell Receptors Inhibitory signals KIR2DL1 HLA-C group 2 KIR2DL2/3 HLA-C  group 1  KIR3DL1 HLA-Bw4 KIR3DL2 HLA-A3 and HLA –A11 LIR-1 HLA class I molecules NKG2A HLA-E Activating signals KIR2DS1 HLA-C NKG2D ULBP-1-ULBP4, MICA and MICB NKp46 Viral heamagglutinin CD16 igG BY55 HLA-c

Table 2: NK cells harbour two sets of receptors; inhibitory and activating. Depending on the interaction of the ligand with the corresponding receptor, NK will signal the activating or inhibitory downstream cascade. In addition to the ligand/receptor interaction, debris from apoptotic and tumour cells, cytokines and costimulatory ligands as well dendritic cells can potentially skew the relevant signal, the interaction and hence the immune outcome.