Hepatic production of biliary IgM in the rat

Drainage of the thoracic duct resulted in a decrease in the IgA level in rat bile, but at the same time there was an increase in both the total IgM level and the specific IgM antibody activity to Escherichia coli 06 in the bile of animals immunized in the Peyer's patches with these bacteria. The increase in total IgM was significantly higher in animals immunized with the E. coli 06 than in unimmunized rats. The level of total IgG was not altered during the drainage. IgM antibodies to E. coli 04 given intravenously during lymph drainage did not appear in the bile, whereas specific IgM antibodies to E. coli 06 occurring after active immunization increased in the bile of the same animal. The data elucidate two aspects of the hepatic IgM turnover. First IgM could take the place of IgA in cases of IgA deficiency, and second the IgM might originate from intrahepatic production.