Autoimmunity, environmental exposure and vaccination: is there a link?

Although the wide clinical experience shows that vaccines are generally safe, concern has been expressed for a causal link between vaccines and autoimmune diseases. Even though the mechanisms of autoimmunity are ill-elucidated, the role of pre-existing risk factors including genetic predisposition and environmental factors is largely accepted. The present study was undertaken to test the hypothesis that vaccines can promote autoimmunity in genetically-prone individuals when simultaneously exposed to a chemical known to induce autoimmune reactions. Female lupus-prone (NZB x NZW) F(1) mice were given 1 microg or 10 microg of a hepatitis B vaccine at 2-week intervals in conjunction with 40 microg of mercuric chloride three times per week for 6 weeks. A marked increase in serum IgG levels and a slight increase in anti-nuclear autoantibody (ANA) levels were seen in the mice given 10 microg of the vaccine plus mercuric chloride. No straightforward conclusion can be drawn from these results because of the extreme experimental conditions of this study. Nevertheless, the results tend to support the hypothesis that vaccination could enhance the risk of autoimmunity in genetically susceptible individuals when exposed to certain environmental chemicals.