– Natural cytotoxicity triggering receptor 1(NKp46/NCR1) is a single-pass type I membrane protein. It consists of two extracellular Ig-like domains followed by a short stalk region, a transmembrane domain containing a positively charged amino acid residue, and a short cytoplasmictail. NKp46 is predominantly expressed in the embryo. It has a positive charge in its transmembrane domain that permits association with the ITAM-bearing signal adapter proteins, CD3 zeta and Fc epsilon RI gamma. These receptors are expressed almost exclusively by NK cells and play a major role in triggering some of the key lytic activities of NK cells. Studies with neutralizing antibodies indicate that the three NCR are primarily responsible for triggering the NK-mediated lysis of many human tumor celllines.