Some cancer cells lack or downregulate one or several MHC class I molecules and/or upregulate e.g. NKG2D ligands (NKG2DL) like the stress-inducible surface glycoproteins MHC class I-related chain A and B (MICA and MICB), and therefore provide no or not enough inhibitory stimulation [13, 21–23]. This evidence concerns the gene KLRK1 and cancer.