Apoptosis increased membrane PR3 expression without degranulation of isolated human neutrophils. (A) Flow-cytometry analysis of membrane expression of PR3, HNE, MPO, CD63, CD66b, and CD35 (bold lines) or control IgG (thin lines) on isolated resting neutrophils (basal) or after f-MLP plus CB-triggered degranulation or physiologic apoptosis induction. This representative experiment used neutrophils from 1 donor; comparable results were obtained with neutrophils from 4 others. (B) Evaluation of PS externalization on apoptotic neutrophils. This typical experiment shows PS externalization detected with PE-conjugated annexin-V binding, plotted versus cell necrosis evaluated by 7-AAD labeling. (C) Variations of the membrane PR3, CD63, CD66b, or CD35 expression before and after apoptosis. After inducing apoptosis, mean fluorescence intensity (MFI) of membrane PR3 expression increased significantly compared with basal conditions (**P < .01 using ANOVA), whereas MFI of CD63, CD66b, or CD35 remained unchanged. Results are means (± SEM) from 5 independent experiments with neutrophils from 5 different healthy donors.