SGN-30 mediates ADCP activity in vitro. (A) Representative flow cytometry analysis and fluorescence microscopy of SGN-30-mediated phagocytosis. For flow cytometry, L540cy, HDLM-2, Wil-2S, and HL-60 target cells were labeled with PKH26 lipophilic dye for tracking purposes, and treated with SGN-30 or non-binding control IgG and mixed with monocyte-derived macrophages (MΦ). MΦ were stained with PE-conjugated anti-CD11b. Cells present in the upper right quadrant (PKH26⁺CD11b⁺) are MΦ that internalized tumor cells. For microscopy, tumor cells were labeled with PKH67 (green), and the macrophages were detected with Alexa Fluor 568-conjugated antibody specific for CD11b (red). (B) Tumor targets were treated with various concentrations of SGN-30 before incubation with MΦ. The levels of MΦ that engulfed tumor cells were determined by flow cytometry (C). WIL2-S cells were incubated with SGN-30, SGN-30 F(ab′)2, or nonbinding control IgG before incubation with MΦ and analyzed by flow cytometry.