FIGURE 2.

Natural killer (NK) cell activation/inhibition equilibrium. The relative number of engaged receptor types dictates the response. (a) Normal cells, expressing normal MHC‐I molecules (inhibitory ligands), do not trigger the cytolytic response of NK cells. (b) Stressed cells, such as tumour cells, engaging the same relative number of activating and inhibiting receptors of NK cells, induce a dynamic equilibrium that results in no cytolytic response of NK cells. (c) If the equilibrium is tipped over by engaging more activating receptors on NK cells, a cytolytic response will be triggered against the cells presenting the corresponding ligands