 The human HLA-E is a non-classical MHC class I molecule that is characterized by a limited polymorphism and a lower cell surface expression than its classical paralogues.The functional homolog in mice is called Qa-1b, officially known as H2-T23.Like other MHC class I molecules, HLA-E is a heterodimer consisting of an α heavy chain and a light chain (β-2 microglobulin).