Hepatic uptake of autologous immune complexes in the rat

The hepatic uptake of autologous immune complexes (ICx) was studied in Wistar rats immunized with bovine serum albumin (BSA). After attaining a suitable serum titre of rat anti-BSA Ig (RatABSA) they were injected intravenously with 2 mg BSA. The antibody levels were measured with an ELISA and the rate of disappearance of BSA from the circulation was studied by labelling the antigen with FITC. At various times after injection of BSA the uptake of ICx in the different types of liver cells was studied with the immunoperoxidase technique at the light microscope and ultrastructural levels. Within 5 min of injection with BSA ICx appeared to be bound and internalized by Kupffer cells, endothelial cells, and hepatocytes. After 2 h hepatocytes showed many large vacuoles containing ICx, whereas most microvilli had disappeared from the sinusoidal plasma membrane of these cells. In rats with a high antibody titre BSA had disappeared almost completely (92%) from the blood within 2 h. Rats with low antibody titre showed a lower disappearance rate of BSA, whereas a considerable amount of antibody was still present in the blood after 2 h. We conclude that autologous ICx are bound and endocytosed by Kupffer cells, endothelial cells and hepatocytes of the liver. The affinity for the antigen from the circulation. Uptake of autologous ICx by hepatocytes occurs only in the presence of large amounts of circulating ICx.