DECREASED IGG-FC-GAMMA-RII DISSOCIATION KINETICS IN THE PRESENCE OF APROTEIN ANTIGEN

Total internal reflection fluorescence microscopy has been used to exa mine the interaction of a mouse monoclonal IgG2b, in the absence and p resence of its protein antigen, with mouse Fc gamma RII in substrate-s upported planar membranes. Equilibrium association and kinetic dissoci ation constants were measured for the antibody S6-34.11, which is spec ific for bovine prothrombin fragment 1 (BF1). These measurements showe d that BFI induces a statistically significant decrease (30-40%) in th e IgG-Fc gamma RII dissociation kinetics. A corresponding increase in the equilibrium association constant was not observed, perhaps because the statistical accuracy of the equilibrium measurements is lower tha n that for the kinetic measurements. The consequences of these results for understanding the mechanism by which macrophages recognize and in gest opsonized targets are discussed. (C) 1997 Elsevier Science Ltd.