Antibody and ADC saturation binding. Binding of cAC10, irrelevant cIgG, and their respective ADCs to CD30⁺ Karpas 299 cells. Cells were combined with increasing concentrations of cAC10, cAC10-vcMMAE, an irrelevant isotype-matched IgG, or this IgG linked to vcMMAE. Cells were incubated for 20 minutes, washed with 2% FBS/PBS (staining medium) to remove free mAb, and incubated with goat-antihuman-FITC. Labeled cells were washed again with staining medium and examined by flow cytometry. The resultant mean fluorescence intensities were plotted versus mAb concentration, as described in “Materials and methods.”