SOYBEAN AGGLUTININ BINDS A 16O-KDA RAT MACROPHAGE MEMBRANE GLYCOPROTEIN AND ENHANCES CELL-DIFFERENTIATION AND ACTIVATION

Mature macrophages (M phi) differ from other rat leukocytes by their a bility to bind soybean agglutinin (SBA). In this study we identify the SBA-binding structure on rat bone marrow-derived M phi (BMDM phi). Pr ecipitation of iodinated membrane proteins from rat bone marrow cells (BMC) and BMDM phi with SBA revealed a major glycoprotein of Mr 160 kD a on BMDM phi but not on BMC. In addition miner bands migrating at 70 and 26 kDa were seen. Stimulation of BMDM phi with 100 nM SBA induced a decrease in surface density of Thy1.1 (MRC OX7) and His54 and an inc rease in the expression of MRC OX6 (RT1.B/I-A), MRC OX17 (RT1.D/I-E), MRC OX41(gp 110/120), MRC OX42 (CD11b/c), Mad (CD11b/CR3) and Mac2 (ga lectin-3/IgE binding protein) antigen. Expression of other M phi diffe rentiation antigens recognized by mAb MRC OX43 (M phi, endothelial cel ls) and ED9 (M phi/CD14 like) were not significantly altered. BMDM phi derived from cultures with M phi colony-stimulating factor (M-CSF) an d SBA showed increased oxidative burst and phagocytic activity compare d to cells cultured with M-CSF alone. Our data suggest that binding of a 160-kDa membrane glycoprotein on M phi by N-acetylgalactosamine-spe cific lectins stimulates M phi differentiation and activation.