Provided herein are compositions comprising purified antibodies and fragments thereof that are specifically immunoreactive to only human leukocyte antigen E (HLA-E) but not to other HLA Ia and HLA-Ib alleles. Also provided are methods of their making and diagnostic and therapeutic applications. The monospecific HLA-E antibodies are highly specific and can be used for diagnosing or localizing the presence of HLA-E on normal or diseased cells or tissues. The monospecific HLA-E antibodies can also be used for cancer therapies, likely through regulation of the CD94/NKG2a on Cytotoxic and/or Natural Killer T cells.