CD335, also known as NKp46, is a member of the natural cytotoxicity receptor (NCR) family which triggers cytotoxicity in NK cells. CD335 is direct-ly involved in target cell recognition and lysis, and is exclusively expressed on CD3-CD56+ NK cells, suggesting it is a universal marker for NK cells. NKp46, along with NKp30 and NKp44, is referred to as a natural cytoxicity receptor (NCR) and plays a very important role in killing virus-infected tumor cells and MHC-class I-unprotected cells.