Effect of mAb against IAIPs on IAIP-induced induction of spherical shape in neutrophils. (A) Anti-IAIP mAb (69.26; 10 μg/mL) or control IgG1 was added simultaneously with IAIPs (100 μg/mL) and the incubation continued for 1 hour. The form factors were determined. The results shown are the means ± SEM of 7 experiments. **P < .001 vs HBSS; ##P < .001 compared with IAIPs + IgG1. (B) Typical picture from each group is shown (calcein stain; scale bars, 20 μm). (C) FACS analysis of IAIP binding on isolated human neutrophils. Purified human neutrophils were incubated with fluorescein-labeled IAIPs (100 and 200 μg/mL) in the presence or absence of unlabeled IAIPs (400 μg/mL) for 30 minutes at 37°C. After washing once, the fluorescein-labeled IAIPs were fixed by 0.5% PFA. The fluorescence intensity of the binding of IAIPs on neutrophils was analyzed by a FACS caliber. (i) Fluorescein-labeled IAIPs, 100 µg/mL; (ii) fluorescein-labeled IAIPs, 200 µg/mL. Buffer control is shown in red, fluorescein-labeled IAIPs is shown in blue, and fluorescein-labeled IAIPs in the presence of unlabeled IAIPs is shown in yellow. The data are representative of 2 independent experiments.