Extractable nuclear antigens (ENA) are a group of autoantigens that were originally identified as antibody targets in people with autoimmune disorders. They are termed ENA because they can be extracted from the cell nucleus with saline. The ENAs consist of ribonucleoproteins and non-histone proteins, named by either the name of the donor who provided the prototype serum (Sm, Ro, La, Jo), or the name of the disease setting in which the antibodies were found (SS-A, SS-B, Scl-70).