Identification of the serum factor required for liposome-primed activation of mouse peritoneal macrophages. Modified alpha 2-macroglobulin enhances Fc gamma receptor-mediated phagocytosis of opsonized sheep red blood cells.
Culture supernatant, prepared by incubating fetal calf serum and liposome-treated B cells, augments mouse peritoneal macrophage Fc gamma receptor-mediated phagocytosis of IgG-opsonized sheep red blood cells. The activation process was hypothesized to be as follows. B-cell membranous glycosidases stimulated by liposomes, convert serum factor to a macrophage-stimulating active serum factor. As the active serum factor loses its activation potential by the addition of mannose or by digestion with alpha-mannosidase, mannose residues at the terminal present in the active serum factor are hypothesized to contribute to macrophage activation. The active serum factor was purified on a concanavalin A-Sepharose 4B column, and identified as a modified form of alpha 2-macroglobulin by immunochemical analysises. On non-denaturing polyacrylamide gel electrophoresis, modified alpha 2-macroglobulin showed a slow form, while alpha 2-macroglobulin-trypsin and alpha 2-macroglobulin-methylamine complexes, which bind specifically to alpha 2-macroglobulin receptors, showed a fast form and did not activate macropahges. These findings demonstrate that alpha 2-macroglobulin is the essential serum factor in liposome-primed macrophage activation, and that modified alpha 2-macroglobulin with mannose residues at the terminal sugar chain binds to macrophage mannose receptors, but not alpha 2-macroglobulin receptors, and increases Fc gamma receptor-mediated phagocytosis of IgG-opsonized sheep red blood cells.
Murai
M
M
School of Pharmacy, Tokyo University of Pharmacy and Life Science, Hachioji, Japan.
Aramaki
Y
Y
Tsuchiya
S
S
D000818:Animals; D001402:B-Lymphocytes / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D017077:Culture Media, Conditioned; D004912:Erythrocytes; D007122:Immunoelectrophoresis; D037181:Lectins, C-Type; D008081:Liposomes / Q000378:metabolism*; D008262:Macrophage Activation; D016215:Macrophage-Activating Factors / Q000378:metabolism*; D008297:Male; D008358:Mannose / Q000378:metabolism; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins; D051379:Mice; D008807:Mice, Inbred BALB C; D009895:Opsonin Proteins; D010587:Phagocytosis; D011956:Receptors, Cell Surface / Q000378:metabolism; D017452:Receptors, IgG / Q000378:metabolism*; D012756:Sheep; D000511:alpha-Macroglobulins / Q000737:chemistry / Q000378:metabolism*
D017077:Culture Media, Conditioned; D037181:Lectins, C-Type; D008081:Liposomes; D016215:Macrophage-Activating Factors; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins; D009895:Opsonin Proteins; D011956:Receptors, Cell Surface; D017452:Receptors, IgG; D000511:alpha-Macroglobulins; D008358:Mannose