32 Million Americans Have Autoantibodies

According to a study by the National Institute of Environmental Health Sciences (NIEHS), more than 32 million people in the United States have proteins created by the immune system that target the body’s tissues. Known as autoantibodies, these proteins are typically markers for autoimmunity, which can result in conditions such as type 1 diabetes and rheumatoid arthritis.

They also established that the most common category of autoantibody, known as antinuclear antibodies (ANA), are found most frequently in women, the elderly, and African-Americans.

ANA can be measured as a biomarker for detecting autoimmune diseases, as previous studies have discovered that ANA can found in an individual’s body years prior to clinical appearance of autoimmune diseases. The presence of autoantibodies, however, does not guarantee that a person will get an autoimmune disease, since other factors like drugs, cancer, and infections could also cause autoantibodies in a number of individuals.

Frederick Miller, MD, PhD, and author of the study and acting clinical director at NIEHS, worked with fellow researchers and assessed the blood samples of 4,754 individuals aged 12 and older from the National Health and Nutrition Examination Survey (NHANES) 1999-2004. They used a technique called immunofluorescence to detect ANA in the blood of the participants.

They found that the prevalence of ANA in the participants was 13.8%, though it was modestly higher in African-Americans in comparison to whites. Also, they found that ANA typically was higher in women and increased with age, peaking in women at age 40 to 49 and then declining.

“The peak of autoimmunity in females compared to males during the 40-49 age bracket is suggestive of the effects that the hormones estrogen and progesterone might be playing on the immune system,” Linda Birnbaum, PhD, director of NIEHS and one of the authors of the paper, said in a NIEHS press release.

Somewhat surprising to the researchers was the finding that ANA was lower in overweight and obese individuals than normal weight participants.

This finding “raises the likelihood that fat tissues can secrete proteins that inhibit parts of the immune system and prevent the development of autoantibodies, but we will need to do more research to understand the role that obesity might play in the development of autoimmune diseases,” said Minoru Satoh, M.D., Ph.D., another author on the study and associate professor of rheumatology and clinical immunology at the University of Florida.

Future studies assessing the alterations in ANA prevalence over time and the factors associated with ANA development are anticipated by the researchers.

This study appears online in the January 11, 2012 issue of the Journal Arthritis and Rheumatism.