|Budget Amount *help
¥2,400,000 (Direct Cost : ¥2,400,000)
Fiscal Year 1996 : ¥1,700,000 (Direct Cost : ¥1,700,000)
Fiscal Year 1995 : ¥700,000 (Direct Cost : ¥700,000)
Liposomes were previously shown to activate mouse peritoneal macrophages, thus enhancing the Fcgamma receptor (FcgammaR) -mediated ingestion of IgG-opsonized sheep red blood cells (SRBCs) in vivo and in vitro. During this activation, liposomes do not activate macrophages directly, but rather to serum and B cells, and a macrophages activating serum factor has been purified by affinity chromatography using a concanavalin A-Sepharose column and identified as modified alpha_2-macroglobulin (alpha_2M) with mannose residues at termini of the sugar chains by immunochemical methods. Modified alpha_2M was shown to increase the number of FcgammaR and activate macrophages, base on the results of the phagocytosis of IgG-opsonized SRBCs. By the addition of mannose, macrophage activation induced by modified alpha_2M was inhibited and ingestion activity and the number of FcgammaR decreased to that of the control.
In this project, thus, activation mechanism of B cell membranous glycosidase by liposomes and contribution of tyrosine kinase following the binding of modified alpha_2M to the mannose receptor which activates FcgammaR-mediated phagocytosis were studied, and the following findings are clarified. Liposomes would appear to interact with B cells via cell-surface IgM,with a consequent decrease in membrane fluidity, as well as the activation of B cell membranous glycosidase, causing alpha_2M to be converted into a macrophage activationg factor. The binding of modified alpha_2M to mannose receptors was demonstrated by the inducement of tyrosine kinase activation which is sensitive to herbimycin A followed by increase in Fcgamma receptors and consequently greater phagocytosis. Mannose receptors would thus appear to be essential to signal transduction in FcgammaR expression in macrophages induced by modified alpha_2M.