Loss of DNA content in PMN undergoing apoptosis as measured by flow cytometry of prodium iodide–stained PMN. Original recordings of fluorescence histograms of PMN freshly isolated from the circulation, aged for 2, 6, or 22 hours in culture without further stimulation (control), or treated with 300 U/mL TNF- or 300 U/mL GM-CSF, respectively. Numbers indicate apoptotic PMN in percent of total cell number. Results are representative of 12 independent experiments.