Binding of macrophages and phospholipid flip-flop in supported lipid bilayers

Subclass-specific antibody-dependent interactions (binding and triggering) between macrophages and supported lipid bilayers have been studied. Percentages of mouse macrophage binding (J774 cell line) to the lipid bilayers were dependent on mouse monoclonal IgG subclasses. The efficiencies were as follows: IgG1 = IgG2a greater than IgG2b greater than IgG3. Furthermore, macrophage triggering (spreading) was more efficient on IgG2a- or IgG1-coated lipid bilayers than on IgG2a, IgG3, or non-specific rabbit IgG. The present experiments show also that phospholipid molecules are able to flip-flop from one side of a supported planar bilayer membrane to the other with a half-life of 10 h-1 day at 25 degrees C.