A simple method for measuring the complement activities of both classical and alternative pathways by using rabbit γ-globulin-coupled liposomes

Abstract Rabbit γ-globulin (RGG) was covalently coupled to liposomes in which carboxyfluorescein was encapsulated as a marker. Lysis of the liposomes was observed under incubation with guinea pig complement. However, no lysis was observed with heat-inactivated complement. These results suggest that lysis of the liposomes is caused by the activation of complement with coupled RGG in particular, through the alternative parhway of complement (APC). By addition of anti-rabbit IgG antibodies to the RGG-coupled liposomes, lysis of the liposomes was remarkably enhanced. This may be due to the additional activation of the classical pathway of complement (CPC) by antigen-antibody complexes formed on the surface of liposomes. Thus, the activities of both the pathways can be measured easily in the same system by using RGG-coupled liposomes.