KLRF1 and neoplasm: The ligands for these receptors, MICA/B (ligands for NKG2D), HLA-E (ligand for NKG2C), CD122, CD155 (both ligands for DNAM-1) (3–5), AICL (ligand for NKp80) (6, 7), and B7-H6 (ligand for NKp30) (8, 9), are frequently upregulated in tumor cells and can even be entirely absent in healthy cells, as is the case for B7-H6.