Surface-linked liposomal antigen induces IgE-selective unresponsiveness regardless of the lipid components of liposomes

We have previously reported that antigen coupled with liposomes induced ant igen-specific and IgE-selective unresponsiveness in mice. This antigen prep aration was investigated for application in a novel vaccine protocol to ind uce minimal IgE synthesis. In this study, ovalbumin (OVA)-liposome conjugat es were made using liposomes of four different lipid components, including unsaturated carrier lipid and three different saturated carrier lipids, aft er which the induction of anti-OVA antibody production was investigated in mice. All of the OVA-liposome conjugates induced IgE-selective unresponsive ness. The membrane fluidity of liposomes, as measured by detecting changes in the fluorescence polarization of a 1,6-diphenyl-1,3,5-hexatriene (DPH) p robe located in the bilayers, was significantly higher in liposomes consist ing of unsaturated carrier lipids than those of the other liposomes consist ing of saturated carrier lipids. The highest titer of anti-OVA IgG was obse rved in mice immunized with OVA-liposomes made using liposomes consisting o f unsaturated carrier lipids. In addition, among these OVA-liposomes, the o ne possessing the longest carbon chain induced the lowest IgG antibody prod uction. These results suggest that the membrane fluidity of liposomes might affect the adjuvant effect of liposomes but not the induction of IgE-selec tive unresponsiveness in immunizations with surface-linked liposomal antige ns.