Plasminogen inhibits U937 cell apoptosis in a dose-dependent manner. U937 cells were either untreated (♦) or incubated with 10 ng/mL TNFα (□; A-C) or 50 μg/mL cycloheximide (○; D-F), in either the absence or presence of increasing concentrations of plasminogen for 24 hours at 37°C. Cell viability status was determined by dual-color FACS analysis with annexin V–FITC and PI as described in “Materials and methods,” and the percentage of viable (annexin V negative, PI negative), early apoptotic (annexin V positive, PI negative), and late apoptotic/necrotic (annexin V positive, PI positive) cells within the entire cell population is shown. Data are shown as mean ± SE, n = 3, for a representative of 6 independent experiments.