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Internalization of an anti-CD20 antibody drug-conjugate via clathrin-coated vesicles. Ramos B cells incubated with the conjugate rituximab-vcMMAE were fixed, permeabilized, and cell-associated rituximab-vcMMAE was detected using Alexa Fluor-568 conjugated mouse anti-human IgG (H) (red). Clathrin-coated vesicles were detected by a mouse antibody raised against clathrin heavy chain followed by an Alexa Fluor-488 conjugated goat anti-mouse IgG (H) antibody with minimal cross-reactivity to human IgG (green). Cell nuclei were counterstained with 4', 6-Diamidino-2-phenylindole (Blue). Co-localization of rituximab-vcMMAE to clathrin-coated vesicles is represented by yellow signals. For further details see Law et al., on page 7842 in this issue.