The cluster of differentiation (CD) system is commonly used as cell markers in immunophynotyping. Different kinds of cells in the immune system can be identified through the surface CD molecules which associating with the immune function of the cell. The CD155 ligand CD96 is a member of the Ig superfamily. It's a immunoglobulin-like protein tentatively allocated to the repertoire of human NK receptors. NK cells recognize poliovirus receptor (PVR), anectins and nectin-like protein family member serve to mediate cell-cell adhesion, cell migration, with the presence of an additional receptor, CD96. CD96 promotes NK cell adhesion to target cells expressing PVR, stimulates cytotoxicity of activated NK cells, and mediates acquisition of PVR from target cells.