The liver: an integral part of the enteric mucosal immune system.

The inclusion of the liver and biliary tract as an integral part of the enteric mucosal immune defense has come about in the past 5 years as a result of experimental studies in laboratory animals. The importance of secretory IgA and IgA immune complexes in the generation of an immune response and their participation in the immune exclusion of potentially pathogenic molecules and organisms are areas of active investigation. The transport of IgA and IgA immune complexes by the liver from serum to bile may provide another means of immune-mediated host defense against enteric pathogens.