Studies on the binding and phagocytic inhibition properties of antimacrophage globulin (AMG)

Ring fluorescence of mouse macrophages, seen following incubation at 4°C with rabbit anti macrophage globulin (AMG) and fluorescein conjugated goat anti rabbit globulin, was transformed into aggregate fluorescence after subsequent maintenance at 37°. Studies based on the saturation binding of radiolabelled AMG indicated that between 400,000 and 800,000 heterologous antigenic determinants are present on the macrophage surface. AMG and F(ab')₂ and Fab but not Fc fragments, could both bind to macrophages and inhibit phagocytosis; attachment of bacteria was however, unaffected. Kinetic experiments based on the assumption that phagocytosis is analogous to carrier mediated membrane transport indicated that non competitive inhibition is responsible for AMG impairment of macrophage phagocytic capacity. (Journal received: 30 May 1974)