NKG2 also known as CD159 (Cluster of Differentiation 159) is a receptor for natural killer cells. There are 7 NKG2 types: A, B, C, D, E, F and H. NKG2D is an activating receptor on the NK cell surface. NIKG2A belongs to the NIKG2 family. It is also a type 2 film sub, and a member of the fifth group of c-type lectin superfamily. The relative molecular weight is 43000, which is composed of 233 amino acids. The extracellular region contains 135 amino acids, which are similar to CD94 and contain CDR.