Ready-to-use ELISA kits are available for the detection of EA2.1, an alias of the protein, major histocompatibility complex, class I, E. The official gene symbol is HLA-E. The protein, with a mass of 40.1 kDa and length of 358 residues, is reported to be membrane-associated and secreted. It is a member of the MHC class I family and may be known by other names, including: HLA-6.2, MHC class Ib antigen, MHC class I antigen E, and HLA class I histocompatibility antigen alpha chain E.