Further evidence that hepatic sources confer biliary antibody in the rat

The notion that bile-dedicated antibody is made within the liver by migratory antibody-forming cells (AFC) was examined further in rats. Livers from immunized animals were removed to perfusion in isolation so that plasma influences on bile antibody would be obviated. Antibody was secreted for at least 5 hr by the livers of rats that had received intravenous (i.v.) or intra-Peyer's patch (IPP) immunization with horse erythrocytes. After initially declining, the titres stabilized at 5-8% of the starting value for IPP-immunized rats and at 0.8% for i.v.-immunized animals, levels that were then sustained. In other experiments, the biliary antibody output was measured in immunized rats in the period immediately following splenectomy, an expedient that would deny the liver any newly formed AFC. Splenectomy during spleen-based, IgM antibody responses led to bile titres falling, over about 12 hr, to 21% of initial values. This level was then maintained for at least another 12 hr. Serum titres over this period remained static. Lastly, the bile ducts of immunized rats were ligated to test whether locally made antibody that was destined for bile could be forced instead to reflux to blood. Biliary obstruction during IgM responses to horse erythrocytes and pneumococcal polysaccharide, type 3, was found to raise significantly serum antibody titres. For pneumococcal polysaccharide, the serum response was also noticeably prolonged. These findings are consistent with the biliary antibody of immunized rats being constituted, in part, from local sources and not from plasma alone.