In these CARs, the human NKG2D ECD recognize several distinct ligands, including the MIC (MHC class I-related chain) family and six members of the ULBP/RAET (UL16-binding protein, or retinoic acid early transcript) family [10], which are generally absent or expressed at low levels by healthy tissues but widely expressed on cancer cells. Here, KLRK1 is linked to cancer.