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 (TIR-FPR) has been used to examine the dissociation kinetics between monomeric mouse IgG and a mouse Fc receptor (moFc gamma RII) reconstituted into substrate-supported planar membranes. IgG1, IgG2a, and IgG2b exhibited similar dissociation kinetics, whereas IgG3 did not bind. The fluorescence recovery curves for the IgG-moFc gamma RII interactions were 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 kinetic parameters for a mouse anti-dinitrophenyl (DNP) IgG1 antibody were equivalent in the absence and presence of saturating amounts of DNP-glycine, demonstrating that possible allosteric changes which might occur in IgG1 upon hapten binding do not appreciably affect the kinetic characteristics of moFc gamma RII binding. The fluorescence recovery curves for polyclonal mouse IgG Fc were similar to those for intact IgG, showing that decreasing the size of the IgG 3-fold does not alter the dissociation rate. The dissociation kinetics of IgG1 decreased considerably in a low ionic strength buffer, indicating that the IgG1-moFc gamma RII interaction has significant electrostatic components.