Natural Cytotoxicity Triggering Receptor 3, NCR3, also known as NKp3, or CD337, is a natural cytotoxicity receptor, expressed on subsets of human peripheral blood NK cells, involved in NK cell killing of tumor cells and immature dendritic cells. The cellular ligand for NKp3 has remained elusive, but the membrane-associated heparan sulfate (HS) proteoglycans are involved in the recognition of cellular targets by NKp3 was recently reported. NKp3 is a member of the immunoglobulin superfamily and one of three existing natural cytotoxicity-triggering receptors. NKp3 is a glycosylated protein and is thought to be selectively expressed in resting and activated natural killer cells. NKp3 is a stimulatory receptor on human NK cells implicated in tumor immunity, and is capable of promoting or terminating dendritic cell maturation. NCR3 may play a role in inflammatory and infectious diseases.