Soybean agglutinin binds a 160-kDa rat macrophage membrane glycoprotein and enhances cell differentiation and activation.

Mature macrophages (M phi) differ from other rat leukocytes by their ability to bind soybean agglutinin (SBA). In this study we identify the SBA-binding structure on rat bone marrow-derived M phi (BMDM phi). Precipitation of iodinated membrane proteins from rat bone marrow cells (BMC) and BMDM phi with SBA revealed a major glycoprotein of Mr 160 kDa on BMDM phi but not on BMC. In addition minor 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 increase 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), Macl (CD11b/CR3) and Mac2 (galectin-3/IgE binding protein) antigen. Expression of other M phi differentiation antigens recognized by mAb MRC OX43 (M phi, endothelial cells) and ED9 (M phi/CD14 like) were not significantly altered. BMDM phi derived from cultures with M phi colony-stimulating factor (M-CSF) and SBA showed increased oxidative burst and phagocytic activity compared to cells cultured with M-CSF alone. Our data suggest that binding of a 160-kDa membrane glycoprotein on M phi by N-acetylgalactosamine-specific lectins stimulates M phi differentiation and activation.