Demonstration of Binding Sites for IgG Fc and the Third Complement Component (C3) on Isolated Hepatocytes

Abstract

Isolated hepatocytes from rabbits with experimental acute serum sickness showed immune complexes bound to the hepatocellular membrane with a coarse granular fluorescent pattern. Also in vitro preformed immune complexes (BSA-anti-BSA) or aggregated γ-globulin from human and rabbit could be bound to the surface of isolated hepatocytes. In contrast, immune complexes with F(ab′)₂ anti-BSA were not fixed on the membranes. Hepatocytes incubated in fresh serum showed membrane-fixed C3 in a coarse granular pattern. This deposition could be abolished by heating (56°C, 30 min) the serum or by adding EDTA (0.02 M). Also, purified human or guinea pig C3 could be bound to the hepatocellular membrane but in a linear fluorescent pattern. Thus, fixation of immune complexes on hepatocytes appears to operate through binding sites for IgG Fc and, possibly, also through binding sites for C3. It is suggested that these hepatocellular-binding sites may have a physiologic clearance function. In vivo fixed IgA could be detected on the membranes of isolated hepatocytes from healthy persons. It is assumed that the membrane-fixed IgA has a carrier function for antigens from the gut.