Bacteria and human autoimmunity: the case of primary biliary cirrhosis

Purpose of review: Primary biliary cirrhosis is a chronic inflammatory disease of the intrahepatic bile ducts that eventually leads to liver cirrhosis and organ failure, in which several observations suggest an autoimmune origin. Similarly to other autoimmune diseases, microbial mediated molecular mimicry is the most widely studied trigger that may break immunologic tolerance in primary biliary cirrhosis. Recent findings: The hypothesis of a bacterial role in the cause of primary biliary cirrhosis has received recent attention, based on in vitro data and the identification of a unique xenobiotic-metabolizing bacterium that modulates naturally occurring environmental estrogens, namely, Novosphingobium aromaticivorans. Summary: The evidence indicates that bacteria, through different mechanisms, may precipitate autoimmunity in primary biliary cirrhosis and other autoimmune diseases. These data have several implications.