KLRK1 and neoplasm: Relevant activating receptors for tumor cell recognition are NKG2D that recognizes MICA/B and ULBPs proteins, orthologs of the mouse RAE1 molecules, DNAM-1 that binds two ligands named poliovirus receptor (PVR/CD155) and Nectin-2 (CD112), and the receptors NKp30, NKp44, and NKp46 belonging to the natural cytotoxicity receptors and shown to interact with a broad spectrum of ligands (3).