The theory of competitive ligand-receptor binding has been used to analyze the effect of afucosylation-based antibody heterogeneity on Fc-Fc gamma RIIIa ligand-receptor binding activity. In vitro activity is found to represent a linear combination of the component antibody activities, weighted by the relative concentrations of the different afucosylated antibody forms. An analysis of ELISA binding activity data has allowed for the dissection of the activity contributions of the different afucosylated antibodies, revealing that the heterogeneous afucosylated antibody exhibits greater activity, on a per mole basis, when compared to the homogeneous afucosylated antibody. The ratio of the afucosylated antibody equilibrium dissociation constants is computed to be K-AF/K-A approximate to 0.6-0.9, where K-AF and K-A denote the dissociation equilibrium constant of the heterogeneous and the homogeneous afucosylated antibodies, respectively. Our analysis also reveals that, in general, activity scales quadratically with the afucosylated glycan content of a sample. Linear activity-afucosylated glycan fraction correlations reported in the literature are shown to represent specific cases of this general scaling and result from oversimplifying the underlying antibody concentration distributions. The implications of our findings for drug development are also discussed. (C) 2015 American Institute of Chemical Engineers