Characterization of immunogenic properties of haptenated liposomal model membranes in mice.

This paper describes the specificity of delayed-type hypersensitivity (DH) and antibody formation in the mouse to the tripeptide-enlarged hapten, 3-(p-azobenzenearsonate)-N-acetyl-L-tyrosylglycylglycine (A). Hapten A was coupled to phosphatidylethanolamine (PE) and incorporated into liposomal membranes (A-PE-liposomes). DH was measured as footpad swelling and antibody formation by the enumeration of direct plaque-forming cells in the spleen. A-PE-liposomes mixed with the cationic, surface-active lipid, dimethyl dioctadecyl ammonium bromide (DDA) induce, on intracutaneous injection in mice, hapten-specific DH without a contribution by the carrier. With other haptenated liposomes it was not possible to induce DH to those haptens, including the closely related hapten 3-(p-azobenzenesulphonate)-N-acetyl-L-tyrosylglycylglycine (S). A-PE- and S-PE-liposomes evoke, after intravenous injection in mice, a humoral response. The antibody formation to A-PE-liposomes was thymus-independent. In this response a considerable cross reaction between haptens A and S was observed.