KLRK1 and carcinoma: The major histocompatibility complex class I chain related-protein A (MICA) and B (MICB) act as activation ligands, which are plentifully expressed on various carcinomas and can interact with natural killer group 2D receptors (NKG2D), thus triggering the cytolytic responses of NK cells and eventuating the eradication of tumors [33].