Antibody responses in the liver and bile of rats injected with horse erythrocytes.

The intravenous injection of 1 ml of a 0.1% (or higher %) suspension of horse red blood cells (HRBC) into rats results in the appearance of high levels of agglutinating activity in bile as well as serum. Lower doses of HRBC induce reduced responses in both fluids, demonstrating that the biliary response is as dose-dependent as the serum response. The presence of IgM anti-HRBC antibody forming cells (AFC) in the liver in numbers equivalent to those detected in the spleen at day 6 of the study suggests them to be the most likely source of the biliary antibody. Also, the injection of HRBC into other parenteral sites (intramuscular [i.m.], intraperitoneal [i.p.] and intrathoracic cavity [i.t.]) results in a biliary response which is considered to originate from the IgM-, IgG- and IgA-anti-HRBC AFC detected in the liver, again in numbers approximating those detected in the spleen. Splenectomy of rats immunized i.p., i.m. and i.t. had only a minimal effect on the liver and biliary responses, indicating that AFC arising in peripheral lymphoid tissues can also relocate in liver. It is concluded that the liver is a major site of antibody synthesis following parenteral immunization leading to substantial levels of antibody being secreted into the gastrointestinal tract.