Cepharanthine (CEP), a biscoclaurine alkaloid, is reported to be effective in prevention of immune suppression and leukopenia induced by the administration of antitumor agents. It is known that CEP inhibits a function of P-glycoprotein, and expected to reduce the multiple drug resistance of tumor cells. We reported some physico-chemical characteristics of CEP containing liposomes already. In this paper, we studied whether the efficacy of immuno-modulating action of CEP will be enhanced by using liposome as a drug carrier. Effects of liposome type and composition which contained CEP on the antigen-specific IgM production in mice were investigated. Liposomes composed of egg phosphatidylcholine and cholesterol in a molar ratio of 7 : 2. Multilamellar liposomes(MLV) were prepared by vortexing dried lipid films, and small unilamellar liposomes (SUV) were prepared by ultrasonication of MLV. Antigen(pneumococcal polysaccharides) and CEP-containing liposomes were injected i.p. to BALB/C mice. Blood was collected to obtain plasma, and the primary immune responsed was examined. The specific IgM antibody against antigen in plasma was measured by ELISA. Liposomes containing CEP enhanced the antigen-specific IgM antibody production compared to free CEP or vehicle liposomes. CEP contained in MLV enhanced specific IgM antibody production against pneumococcal polysaccharides more effectively than CEP contained in SUV. The increase in specific IgM antibody production was influenced by both the type and composition of liposomes. These results suggest that the efficacy of immuno-modulating action of CEP is enhanced by using appropriate liposome as a drug delivery system.
