Human histocompatibility leukocyte antigen(HLA)-E is a nonclassical major histocompatibility complex (MHC)class I molecule,which is the 4th major histocompatibility complex (MHC)class I molecule that human have found following up that of HLA-A ,B,C. HLA-E is distinguished from the classical MHC class I molecule by limited allelic polymorphism,low expression on the cell surface and extensive tissue distribution.Human have paid great attention to the important role of HLA-E that it plays in maternal-placental immunological tolerance,transplantation immunization. as well as antitumor and antiviral immunity .