Immune lysis assay of antibodies by use of antigen-coupled liposomes

Abstract

The concentrations of antibodies were measured by the use of immunoliposomes coupled with the corresponding antigens. The addition of complement under conditions of the existence of the antigen-antibody complex on the surface of the liposomes caused lysis of the liposomes. The degree of marker release from the liposomes was increased with the concentration of the antibodies, as well as the amount of antigen coupled to the liposomes, and was proportional to the amount of antigen-antibody complex formed. The liposomes made of 1,2-di(3RS,7R,11R-phytanyl)-sn-glycero-3-phosphocholine (DPhyPC) showed excellent stability and consequently could bind large amounts of antigen on the surface of the liposomes in comparison with liposomes made of ordinary lipids such as dipalmitoylphosphatidylcholine (DPPC). Although the characteristics of liposomal membranes consisting of DPhyPC in lysis by the classical pathway of complement were similar to those of DPPC liposomes, the DPhyPC liposomes showed higher resistance against non-specific lysis caused by the complement activity in serum samples, which may be effective to reduce false-positive errors in liposome immune lysis assay.