CD96 (also Tactile) is a 160 kDa member of the Ig-Superfamily. It is expressed on CD4 ⁺ and CD8 ⁺ T cells, plus NK cells and select B cells. Human CD96 binds to CD155 and presumably participates in NK cell killing of CD155-expressing target cells. Mature human CD96 is a 564 amino acid (aa), type I transmembrane glycoprotein. It contains a 498 aa extracellular region (aa 22-519) that contains three Ig-like domains. The two N-terminal domains are V-type (aa 38-238), while the distal domain is a C-type structure (aa 269-375). There is one isoform that shows a deletion of aa 183-192. This deletion converts the second V-type domain into an I-like domain, and generates the most common form of CD96. An additional isoform shows the same deletion coupled to a nine aa substitution for aa 410-585. Over aa 1-536, human CD96 shares 59% aa identity with mouse CD96.