Confocal microscopy confirms higher cytotoxicity through ATG-mediated phagocytosis by neutrophils after G-CSF treatment. Neutrophils were obtained from a healthy donor who received 10 mg/kg Filgrastim for 5 days and from a healthy donor who served as control. Neutrophils were incubated with CD14⁻ allogeneic PBMCs in the absence or presence of 20 μg/mL ATG for 2 hours or overnight. Neutrophils were stained with CD64⁻ APC (red), and target cells were CTV+ labeled (blue) for confocal microscopy visualization. Pictures were taken with same Z-resolution (in 1 slice). Original magnification ×65. (A,E) Control neutrophils and target cells without ATG, incubated for 2 hours (A) or overnight (E). (B,F) Neutrophils from G-CSF recipient and target cells without ATG, incubated for 2 hours (B) or overnight (F). (C,G) Control neutrophils and target cells with ATG, incubated for 2 hours (C) or overnight (G). (D,H) Neutrophils from G-CSF recipient and target cells with ATG, incubated for 2 hours (D) or overnight (H). For neutrophils from the G-CSF recipient, shown are target cells within neutrophils. Z-stack analyses were applied to ensure target cells were contained within neutrophils.