Glycoengineered CD20 antibodies mediate phagocytosis of CLL targets by PMNs. CLL targets were labeled with PKH26 and incubated for 24 hours with either purified PMNs (panels A,B,D) or whole blood from healthy donors (panel C), in the presence or absence of 10 µg/mL of the indicated antibodies. Phagocytosis was measured as the percentage of CD15⁺/PKH26⁺/CD19^- cells with respect to total CD15⁺ cells. The data are the means and standard deviations of 4 to 6 experiments. In some experiments with purified PMNs, cytospins were prepared to visualize CD15-FITC–labeled PMNs (green) having engulfed PKH26⁺ CLL targets (red). Slides were mounted in medium containing 4,6 diamidino-2-phenylindole to visualize the nuclei (blue) under a fluorescence microscope (original magnification ×20). Statistical significance was calculated for antibody treated vs control. In panel D, the statistical significance was calculated for samples treated with HS or heat-inactivated HS with respect to no serum (no HS).