Recognition by macrophages and liver cells of opsonized phospholipid vesicles and phospholipid headgroups.

The interaction of liposomes with blood proteins is believed to play a critical role in the clearance pharmacokinetics and tissue distribution of intravenously injected liposomes. In this article we have focused our discussion on the interaction of liposomes with key blood proteins, which include immunoglobulins, complement proteins, apolipoproteins, fetuin, von Willebrand factor, and thrombospondin, and their role in liposome recognition by professional phagocytes and nonmacrophage hepatic cells. Alternatively, macrophages as well as hepatocytes and liver endothelial cells may phagocytose/endocytose liposomes via direct recognition of phospholipid headgroups. A number of plasma membrane receptors such as lectin receptors, CD14, various classes of scavenger receptors (e.g., classes A, B, and D), Fc-gammaRI and FcgammaRII-B2 may participate in phospholipid recognition. These concepts are also discussed.