The natural cytotoxicity receptors (NCRs) are a recently characterized family of Ig-like activation receptors that appear to be major triggering receptors in tumor cell recognition. NCR1 is a glycoprotein that has two extracellular Ig-like domains followed by a ~40 amino acid residue stalk region, a type I transmembrane domain, and a short cytoplasmic tail. NCR1 has been shown to represent a novel NK cell-specific molecule involved in human NK cell activation. NCR1 has been implicated in NK ce