Concentration-response relationships for TNF-α–induced apoptosis, priming, and direct superoxide anion generation. Human neutrophils were prepared and incubated at 5 × 10⁶/mL with 0 to 100 ng/mL TNF-α for 6 hours for assessment of apoptosis (A) or at 10⁷/mL with 0 to 100 ng/mL TNF-α for 30 minutes before assessment of fMLP-stimulated (100 nmol/L, 10 minutes) (B) or direct superoxide anion generation (10 minutes) (C) using a cytochrome C reduction assay (see Materials and Methods). Values represent mean ± SEM of n = 3 separate experiments, each performed in triplicate. Where not shown, SEM values are less than 2% and fall within the symbols.