Binding parameters of antibodies reacting with multivalent antigens: functional affinity or pseudo-affinity

Abstract

For antibodies binding bivalently to multivalent antigens, including the cell surface, it has been common to determine the `functional affinity', even though it is clear that the equations describing true affinity only apply to monovalent interactions. We here summarize evidence that `functional affinities' are not valid, because they do not accurately describe the interactions that occur. A basic discrepancy is that dissociation, in practice, is generally not a first-order reaction. A more useful approach to compare antibodies is to determine the kinetics of dissociation over a long time period, until near-complete dissociation has occurred.