Potentiation of the humoral response of intravenous antigen by splenotropic liposomes.

We have recently described that large liposomes composed of egg phosphatidylcholine (PC), cholesterol (chol) and monosialoganglioside GM1 show elevated accumulation in the red pulp of the spleen when they are i.v. administered into mice. Up to 50% of the injected dose was found in spleen at 4 h post injection. In this report, we have investigated the potential application of such liposomes in the stimulation of anti-lysozyme response in mice. Lysozyme entrapped in the splenotropic liposomes composed of PC/chol/GM1 showed higher efficiency in potentiating the humoral response than that of either free lysozyme or lysozyme entrapped in hepatotropic liposomes composed of PC/chol. The results demonstrate that high levels of i.v. antigen delivery by liposomes to the splenic macrophage instead of the liver Kupffer cells is important in the liposomal adjuvanticity. The antibody elicited by the liposome entrapped antigen was mainly IgG1 subtype.