The term extractable nuclear antigens (ENAs) is a historical denomination, though still in use, derived from the observation that several antigens from the cell nuclei are soluble and can be isolated or “extracted” in isotonic buffers, which facilitated the characterisation of several autoantibodies. Nowadays, the term has broadened and it also includes other antibodies directed against antigens from the cytoplasm and other cell compartments, such as ribonucleoproteins, histones or antigens only expressed when the cell is found in its mitotic state.
