The Interaction of Liposomes with the Complement System: In Vitro and In Vivo Assays

This chapter describes some basic principles and details of the most widely used experimental methods in studying the interaction of liposomes with the complement (C) system. Liposomes can interact with all four “rms” of the immune system: the cellular and humoral arms of acquired immunity and the corresponding parts of native immunity. The first two interactions underlie the attempts to use ‘‘immune’’ or ‘‘adjuvant’’ liposomes as antigen carriers to augment T-cell and antibody responses to liposomal vaccines. The third interaction is studied widely as the major clearance mechanism of most ‘‘non-stealth’’ drug carrier liposomes. The fourth type of interaction of liposomes with the immune system, referred to as “nonspecific humoral,” is manifested in liposome-induced C activation with consequent opsonization of vesicles by C split products, mainly C3b and its by-products.