KIR2DS4 and cytomegalovirus infection: CMV infection promotes clonal expansion of NK cells expressing the activating receptors NKG2C and members of killer cell immunoglobulin‐like receptors (KIR) (KIR2DS2, KIR2DS4, KIR3DS1), and a bias for self‐specific inhibitory KIRs (educated/licensed NK cell subsets) [18, 46].