HLA-E and neoplasm: As mentioned previously, the ligand of the heterodimer CD94:NKG2A is HLA‐E, a non‐classical HLA class I molecule, expressed by virtually all cells.35 Because the most relevant peptides presented by HLA‐E derive from the classical HLA class I leader sequences,27 the level of HLA‐E expression mirrors the overall amount of HLA class I. Thus, NK cells, through CD94:NKG2A/HLA‐E interactions, monitor possible HLA class I decreases caused by infection or tumor transformation.