DISSOCIATION KINETICS BETWEEN A MOUSE FC RECEPTOR (FC-GAMMA-RII) AND IGG - MEASUREMENT BY TOTAL INTERNAL-REFLECTION WITH FLUORESCENCE PHOTOBLEACHING RECOVERY

Total internal reflection with fluorescence photobleaching recovery (T IR-FPR) has been used to examine the dissociation kinetics between mon omeric mouse IgG and a mouse Fc receptor (moFc gamma RII) reconstitute d into substrate-supported planar membranes. IgG1, IgG2a, and IgG2b ex hibited similar dissociation kinetics, whereas IgG3 did not bind. The fluorescence recovery curves for the IgG-moFc gamma RII interactions w ere best described by two reversible components (1.4 s(-1), 66% and 0. 06 s(-1), 18%) and an irreversible component (<0.01 s(-1), 16%). The k inetic parameters for a mouse anti-dinitrophenyl (DNP) IgG1 antibody w ere equivalent in the absence and presence of saturating amounts of DN P-glycine, demonstrating that possible allosteric changes which might occur in IgG1 upon hapten binding do not appreciably affect the kineti c characteristics of moFc gamma RII binding. The fluorescence recovery curves for polyclonal mouse IgG Fc were similar to those for intact I gG, showing that decreasing the size of the IgG 3-fold does not alter the dissociation rate. The dissociation kinetics of IgG1 decreased con siderably in a low ionic strength buffer, indicating that the IgG1-moF c gamma RII interaction has significant electrostatic components.