January 16, 2012
Study Shows 32 Million Americans Now Have Antibodies That Target Their Own Tissues
More than 32 million people in the United States and millions more around the world now have autoantibodies, which are made by the immune system and target the body's tissues, defining a condition known as autoimmunity, a study shows. The cause is no surprise.
An autoantibody is an antibody (a type of protein) manufactured by the immune system that is directed against one or more of the individual's own proteins.
The causes of autoantibody production are specifically initiated by responses to foreign substances within the body. Foreign substances primarily enter the body through toxic foods, preservatives, additives, vaccinations, medications and environmental pollution among other triggers. Although there is no direct genetic link, researchers are now investigating how some autoantibody production is due to a genetic predisposition combined with an environmental trigger, such as a viral illness or a prolonged exposure to certain toxic chemicals.
While families may be susceptible to autoimmune conditions, individual family members may have different autoimmune disorders, or may never develop an autoimmune condition. Poisons introduced in the body in non-lethal doses, especially a proteins are capable of causing disease when introduced into the body tissues but they most often cause long-term disease by inducing autoantibodies or antitoxins. Other factors, including cancer and infections are also known to cause autoantibodies in some people.
Mercury chronically activates the immune system and leads to the development of autoantibodies. High mercury hair concentrations have been linked to metabolic syndrome; causing inefficient insulin function and imbalanced blood sugar levels which can ultimately lead to the development of type-2 diabetes mellitus.
Methylmercury is 5 to 10 times more toxic to developing embryos than it is to adults; in its 2000 report on the toxicological effects of methylmercury the National Research Council, concluded that the population at highest risk of mercury toxicity are children of women who consume large amounts of fish and seafood. The report estimated that more than 60,000 children born each year in the US are at risk for adverse neurodevelopmental effects due to exposure to methylmercury in the womb.
Various autoantibodies may also be present against thyroid peroxidase, thyroglobulin and TSH receptors, which can detrimentally alter thyroid functioning. All autoimmune thyroid diseases are mediated by autoantibodies to thyroid receptors.
The first nationally representative sample looking at the prevalence of the most common type of autoantibody, known as antinuclear antibodies (ANA), found that the frequency of ANA is highest among women, older individuals, and African-Americans.
The study was conducted by the National Institute of Environmental Health Sciences (NIEHS), part of the National Institutes of Health. Researchers in Gainesville at the University of Florida also participated.
Earlier studies have shown that ANA can actually develop many years before the clinical appearance of autoimmune diseases, such as type 1 diabetes, lupus, and rheumatoid arthritis. ANA are frequently measured biomarkers for detecting autoimmune diseases, but the presence of autoantibodies does not necessarily mean a person will get an autoimmune disease.
"Previous estimates of ANA prevalence have varied widely and were conducted in small studies not representative of the general population," said Frederick Miller, M.D., Ph.D., an author of the study and acting clinical director at NIEHS. "Having this large data set that is representative of the general U.S. population and includes nearly 5,000 individuals provides us with an accurate estimate of ANA and may allow new insights into the etiology of autoimmune diseases." The findings appear online in the Jan. 11 issue of the Journal Arthritis and Rheumatism.
A multi-disciplinary team of researchers evaluated blood serum samples using a technique called immunofluorescence to detect ANA in 4,754 individuals from the 1994-2004 National Health and Nutrition Examination Survey (NHANES). The overall prevalence of ANA in the population was 13.8 percent, and was found to be modestly higher in African-Americans compared to whites. ANA generally increased with age and was higher in women than in men, with the female to male ratio peaking at 40-49 years of age and then declining in older age groups.
"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," said Linda Birnbaum, Ph.D., director of NIEHS and an author on the paper.
The paper also found that the prevalence of ANA was lower in overweight and obese individuals than persons of normal weight. "This finding is interesting and somewhat unexpected," said Edward Chan, Ph.D., an author on the study and professor of the Department of Oral Biology at the University of Florida.
"It 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.
The researchers say the paper should serve as a useful baseline for future studies looking at changes in ANA prevalence over time and the factors associated with ANA development. The paper is the first in a series analyzing this data from the NHANES dataset, and exploring possible environmental associations with ANA.