An antibody that is directed against the structures within the nucleus of a cell and that is characteristic of autoimmunity. Abbreviated ANA. ANAs are found in the blood of patients whose immune systems attack their own body tissues (autoimmunity), such as patients with systemic lupus erythematosus, rheumatoid arthritis, juvenile diabetes mellitus, and Hashimoto disease. ANAs can also be found in patients with chronic infections and cancer, and many medications— including procainamide (brand name- Procan SR), hydralazine, and phenytoin (brand name- Dilantin)—can stimulate their production.