Effect of TNFR55 and TNFR75 blocking antibodies on TNF-α–induced apoptosis in human neutrophils. Human neutrophils (5 × 10⁶/mL) were preincubated with antihuman TNFR55 or TNFR75 MoAbs for 30 minutes at 37°C before a 6-hour incubation in the presence or absence of 12.5 ng/mL TNF-α. The extent of apoptosis was then assessed by morphological examination of cytocentrifuge preparations. Data represent mean ± SEM of three separate experiments each performed in triplicate. Where not shown, SEM values are less than 5% of means.