Human CD96, also known as haptic (late expression of increased T cell activation), is a 160 kDa type I transmembrane glycoprotein of the Ig superfamily, with CD226, CD96 and TIGIT sharing the ligand CD155, which plays an important role in the regulation of NK cell function. Mature human CD96 contains an extracellular region of 498 aa, including three Igg-like domains. The two n-terminal domains are V-type structures, and the distal domains are C-type structures. Studies have shown that NK cells recognize the poliovirus receptor (PVR), a member of the connectin and connectin-like protein family that mediates cell-cell adhesion and cell migration in the presence of the CD96 receptor.