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