Figure 1.

Natural killer (NK) cell activating and inhibitory signaling mediates phenotypic outcomes. (A) When NK cell inhibitory receptors bind MHC class I on the target cell, this interaction suppresses NK cell activation and lysis of the target cell. (B) In some circumstances, the activating receptor on NK cells will bind the activating ligand on the target cell, while the inhibitory receptor does not bind MHC Class I, leading to NK cell activation and lysis of the target cell. (C) When the target cell expresses both MHC Class I and activating ligands, the fate of the target cell is determined by a balance of signals.