Forssman-Containing Liposomes: Complement-Dependent Damage due to Interaction with a Monoclonal IgM

Since 1968 liposomes have been employed as a model for studying the molecular basis of immune lysis (1). The liposomes consist of closed, concentric shells of lipid bilayers alternating with aqueous interspaces (2). The aqueous portions within the liposomes generally contain marker molecules (e.g., glucose) and the membrane damage is measured by release of the marker compound (2, 3). By using liposomes with various amphipathic lipids as antigens, a wide variety of specificities have been described (1, 4). Forssman substance was the first antigen used in these studies and its properties in liposomes have now been thoroughly investigated (5). The initial work demonstrated that liposomes containing Forssman hapten could bind anti-Forssman antibodies (hemolysin) and this led to membrane damage and glucose release due to complement fixation (6, 7). A subsequent report showed that this was a highly specific phenomenon, and anti-Forssman antibodies did not cross-react with globoside I, which is a closely related glycolipid (8).