LIVER-CELL UPTAKE AND DEGRADATION OF SOLUBLE IMMUNOGLOBULIN-G IMMUNE-COMPLEXES IN-VIVO AND IN-VITRO IN RATS

Immune complexes were formed between dinitrophenylated human serum alb umin (DNP-HSA) and polyclonal rabbit immunoglobulin G (IgG) anti-DNP a ntibodies at antibody excess, The antigen was labelled with isotope (I -125-tyramine-cellobiose) or fluorochrome, (6-[fluorescein-5-(and-6)-c arboxamido] hexanoic-acid, succinimidyI ester). The radiolabelled anti gen, native or antibody complexed, was given intravenously to rats. Ra dioactivity was measured in various organs at 1 hour following injecti on, The liver was the main site for removal of the antigen as well as of the immune complexes, Within the liver, immune complexes were mainl y associated with nonparenchymal liver cells, the total recovery from Kupffer cells being about 10 times greater than from the liver endothe lial cells, The uncomplexed radiolabelled antigen was readily degraded by both cell types. After IgG complexing, the degradation decreased, both in Kupffer cells and in liver endothelial cells, In vitro experim ents with isolated liver cells, showed that IgG complexing increased a ntigen uptake to about the same extent in Kupffer cells and in liver e ndothelial cells, The degradation of both antigen and immune complexes was less efficient in vitro than in vivo, Immune complex uptake in vi tro was shown also by confocal fluorescence microscopy in Kupffer cell s and in liver endothelial cells, Also in vitro, only minor uptake was found in the hepatocytes, We conclude that both liver endothelial cel ls and Kupffer cells are involved in the hepatic handling of soluble I gG immune complexes, but we found no evidence for substantial uptake b y hepatocytes.