Major histocompatibility complex, class I, E (HLA-E)

Major histocompatibility complex, class I, E (HLA-E) is a **non-classical MHC class I molecule** that forms a heterodimer with beta-2 microglobulin and is expressed on the surface of most nucleated cells[1]. Unlike classical MHC class I molecules, HLA-E binds a restricted set of peptides typically derived from the leader sequences of other class I molecules, as well as some pathogen-derived peptides[1][4]. Its primary role is to act as a **ligand for natural killer (NK) cell receptors**, mainly inhibiting NK cytotoxicity via interaction with the CD94/NKG2A receptor and, under certain conditions, activating NK cells via CD94/NKG2C[1]. HLA-E also presents antigens to a subset of CD8-positive T cells, contributing both to host defense against infections and to immune regulation in contexts such as pregnancy or cancer[1]. HLA-E is being explored as a **therapeutic target and immune biomarker** in cancer immunology and infection, but specific drugs directly modulating its function are still under investigation.

Other names

HLA class I histocompatibility antigen, alpha chain ESoluble HLA class I histocompatibility antigen, alpha chain EHLA-6.2HLAEsHLA-EMHC class I antigen EQA1MHC class Ib antigenNon-classical MHC class I antigenNonclassical MHC class I antigen

Inhibition or activation of NK cell activity via interaction with NK cell receptors (e.g., KLRD1-KLRC1/CD94-NKG2A for inhibition, KLRD1-KLRC2/CD94-NKG2C for activation)[1]; Presentation of antigens to unconventional CD8-positive T cells; Modulation of immune recognition by peptide mimicry