NKG2, also known as NKG2A(CD159A), is a member of the killer cell lectin-like receptor family. This family is a group of transmembrane proteins preferentially expressed in NK cells. Members of this fmaily are characterized by the type II membrane orientation and the presence of a C-type lectin domain. NKG2 contains 1 C-type lectin domain and forms a complex with another family member, KLRD1/CD94. It is expressed only in NK-cells, but not in T-cells or B-cells. It has been shown that NKG2 represents a family of related cDNA clones, designated NKG2A, NKG2B, NKG2C, and NKG2D, which encode type 2 integral membrane proteins (extracellular C-terminus) containing a C-type lectin domain. Natural killer (NK) cells are lymphocytes that can mediate lysis of certain tumor cells and virus-infected cells without previous activation. They can also regulate specific humoral and cell-mediated immunity. NKG2 functions as a receptor for the recognition of MHC class I HLA-E molecules by NK cells and some cytotoxic T-cells.