Fcγ and β2 integrin receptor requirement for PMN ADCC with hu14.18 alone, hu14.18 mixed with GM-CSF, and hu14.18/GM-CSF.
(A) ADCC was mediated by hu14.18 alone (5 μg/mL), hu14.18 (5 μg/mL) mixed with GM-CSF (100 ng/mL) (hu14.18 + GM-CSF), or hu14.18/GM-CSF (5 μg/mL). Anti-FcγRII (CD32) IV.3 Fab, anti-FcγRIII (CD16) 3G8 F(ab) 2 (10 μg/mL of each), or the same volume of PBS was added to the cell mixture just before the initiation of ADCC. (B) ADCC with hu14.18/GM-CSF (control; 5 μg/mL) and with the addition of anti-CD18 7E4, anti-CD11a R7.1, anti-CD11b 2LPM19C, anti-CD11c 3.9, or mouse IgG1 isotype control antibody (10 μg/mL of each) to the cell mixture just before the initiation of ADCC. Retained calcein fluorescence was quantified after 4 hours with DIMSCAN, and results are expressed as tumor cell viability index (mean ± SD for 6 replicate wells). ***Significant difference (P < .001, ANOVA) compared to controls. Data are from 1 of 4 experiments that gave similar results.
