Abstract: The invention provides methods for treating inflammatory and autoimmune diseases by administering to the subject an effective amount of a cardiac glycoside, where the dose is effective to suppress or prevent initiation, progression, or relapses of the disease, including the progression of established disease. In some embodiments, the methods of the invention comprise administering to a subject determined to have rheumatoid arthritis or systemic lupus, or a pre-clinical disease state thereof, an effective amount of a cardiac glycoside, to suppress or prevent activity of the disease. In other embodiments, the methods of the invention comprise administering to a subject determined to have insufficient endogenous cardiac glycosides, an effective amount as a supplement to counteract the effects of cardiac glycoside deficiency.