Effects of anti-Fas IgM on apoptotic rates of activated neutrophils. Neutrophils (1 × 10⁶/mL) incubated with LPS (1 μg/mL), migrated through an endothelial cell/fibronectin monolayer, or cross-linked with antibodies to CD11b, were incubated with anti-Fas IgM (100 or 200 ng/mL) for 1 hour before being washed. Apoptosis was assessed after 18-hour incubation in medium alone by flow cytometry. *P < .05 versus control, ρP < .05 versus medium alone. Results are the mean ± SD for n = 5 experiments with four separate donors of neutrophils.