What is an antinuclear antibody?

An antibody is a protein made by white blood cells (B cells). Antibodies help defend against invaders (for example, viruses and bacteria) that cause disease or infection in the body. When antibodies make a mistake by recognizing our “self” cells as being “foreign,” they are called autoantibodies.

Most of us have autoantibodies, but usually a very small amount. If there are enough autoantibodies present, a cascade of inflammation (swelling) is started. This causes our immune system to attack our own body (autoimmune disease).

An antinuclear antibody (ANA) is an autoantibody that mistakenly binds to normal protein within the nucleus of a cell. ANAs are usually found in people who have autoimmune conditions such as systemic lupus erythematosus. They may also be seen in other autoimmune diseases, such as mixed connective tissue disease, Sjogren's syndrome, dermatomyositis, polymyositis and scleroderma.

However, not everybody who has ANAs has an autoimmune disease. For instance, ANAs could be found in 10-15 percent of completely healthy children. They could be briefly present in the setting of intercurrent infection (an infection that occurs while the person already has another infection) or in people who are taking certain drugs (for example, hydralazine, isoniazid, procainamide, and some anticonvulsants).

Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy