The Role of the Non‐Classical HLA Class I Molecule HLA ‐E in Health and Haematological Malignancies

ABSTRACT The ability of the non‐classical HLA Class I molecule HLA‐E to both activate and suppress the immune response allows it to play an important role in both health and disease. Under normal conditions, HLA‐E includes not only tolerance to self‐antigens but also activating immune responses against intracellular pathogens and regulation of immune activation processes. Numerous studies confirm that increased HLA‐E expression on tumour cells is associated with cancer progression. As a significant component of the tumour microenvironment, HLA‐E facilitates tumour evasion from the immune response. By interacting with inhibitory receptors on immune cells, HLA‐E can induce local immune suppression. However, there is also evidence for activation of the immune response by HLA‐E. In this review, we summarise data on HLA‐E expression in various cells and the role of this expression in regulating the immune response in health, solid tumours, and blood cancers.