HLA-E (human leukocyte antigen E) is a non-classical MHC I antigen, which is important for dialogue with NK cells and their regulation through interaction with CD94/NKG2 receptor. Like other MHC I molecules, transmembrane HLA-E molecule (45 kDa) associates with beta2 microglobulin. Unlike HLA-G, expression of HLA-E molecules is not so restricted, but it has been detected at least at mRNA level in virtually all cells and tissues examined. In peripheral blood, HLA-E protein is expressed at least in all mononuclear cells, but in different quantity (B cells and monocytes more than T cells and NK cells).
