Antibody-coated liposomes. The role of non-specific antibody adsorption.

Incubation of small unilamellar liposomes composed of equimolar phospholipid and cholesterol with mouse IgG or mouse monoclonal IgG1 for up to 24 h resulted in considerable (34-89%) adsorption of the protein onto the liposomal surface. Immunoglobulin remained adsorbed after exposure to mouse plasma and, in the case of monoclonal (anti-HBSAg) IgG1, was able to mediate association of the liposomes with the antigen. Extensive immunoglobulin adsorption suggests caution in interpreting covalent linkage values obtained upon prolonged incubation of chemically modified antibodies with liposomes. It may also be a preferred alternative in preparing targeted liposomes for intravenous use when chemically modified antibodies promote premature clearance of the antibody-liposome complex from the circulation.