NCR1 and viral infectious disease: NK cell activating receptors (NKARs), such as NK group 2, member D (NKG2D), DNAX accessory molecule 1 (DNAM1) as well as natural cytotoxicity receptors (NCRs) NKp30, NKp44, and NKp46, recognize stress-induced ligands expressed during cellular transformation or viral infection (4).