The chemicals, called phthalates, don't cause lupus in normal mice. And it's not at all clear that the mouse findings are relevant to humans.
Even so, the study raises questions about the link between the ubiquitous compounds and autoimmune disease, says researcher Swapan K. Ghosh, PhD, professor and interim chair of life sciences at Indiana State University.
In some autoimmune diseases, the immune system makes antibodies that attack the body's own cells. These are called anti-self antibodies. Mouse antibodies against phthalates, Ghosh found, are nearly identical to certain anti-self antibodies.
"We found out the antibody to phthalate is 98% the same as the anti-self antibody found in mouse lupus," Ghosh tells WebMD. "Then we started a more vigorous investigation to find out why not every strain of mouse gets disease. And we found it is genetic susceptibility."
Mouse Exposure Not Same as Human Exposure
To raise antiphthalate antibodies in mice, Ghosh injected the animals with several potent doses of phthalates to boost antibody reactions.
In their report, published in the current issue of the Journal of Autoimmunity, Gosh and colleague So-Yon Lim, PhD, report that all commonly used types of phthalates are harmful to susceptible strains of mice. Normal mice, however, soon block the antiphthalate antibodies and suffer no ill effects.
Ghosh is quick to point out that the doses of phthalates given to mice in this study have no relation to human exposure to the phthalate compounds that leach into the environment from plastics, cosmetics, dyes, flexible PVC products, artificial leather, adhesives, and many other products.
While noting that the study has no direct relevance to humans, the findings are quite interesting, says lupus expert Jennifer Anolik, MD, PhD, assistant professor of medicine and an investigator at the autoimmunity center of excellence at the University of Rochester in New York.
"In autoimmune diseases and in lupus, we know there are strong genetic and environmental influences -- but we do not know what the environmental factors are," Anolik tells WebMD. "Because that is such an unknown, it makes this paper interesting. There might be chemical exposures in the susceptible individual that might contribute to autoimmunity."
WebMD asked the phthalate esters panel of the American Chemical Council -- an industry group that includes many major phthalate manufacturers -- to comment. The panel was unable to comment before publication.