IgG Immune Complex Binding to and Activation of Liver Cells

BACKGROUND/AIMS: The aim was to study IgG immune complex (IC) binding to isolated hepatocytes, Kupffer cells (KCs) and sinusoidal endothelial cells (SECs). Further, we wished to analyze the capacity of IgG ICs to induce release of reactive oxygen metabolites by the IC-binding liver cells. METHODS: ICs were formed between (125)I-tyramine-cellobiose-labelled dinitrophenyl-conjugated human serum albumin ((125)I-TC-DNP(10)HSA) and polyclonal rabbit IgG antibodies. Binding of ICs to different rat liver cells in suspension was studied at 4 degrees C. Production of reactive oxygen metabolites was measured by luminol-enhanced chemiluminescence at 37 degrees C. RESULTS: IgG mediated binding of (125)I-TC-DNP(10)HSA to both KCs and SECs, but not to hepatocytes. The binding showed saturation kinetics and was blocked by an excess of unlabelled IgG-ICs. IgG-ICs activated KCs, but not SECs, to a chemiluminescence response. CONCLUSIONS: Both KCs and SECs bind IgG-ICs in vitro, probably via Fc receptor interaction. IgG-ICs activate KCs to produce reactive oxygen metabolites. The binding of IgG-ICs to isolated hepatocytes is small.