Tissue specific opsonins for phagocytic cells and their different affinity for cholesterol-rich liposomes

In accordance with the finding of our in vivo experiments reported earlier [(1983) Biochim. Biophys. Acta 761, 142-157; (1986) Biochim. Biophys. Acta 888, 184-190], the results of in vitro experiments show that Kupffer cells avidly take up cholesterol-poor but not cholesterol-rich liposomes, whereas splenic phagocytic cells take up preferentially cholesterol-rich rather than cholesterol-poor liposomes in the presence of serum. Evidence presented here suggests that serum contains opsonins specific for hepatic and splenic phagocytic cells and these opsonins have different affinities for cholesterol-rich and cholesterol-poor liposomes.