Comparison of annexin 1 expression, and localization, in microparticles derived from resting or adherent PMNs. Flow cytometry of resting PMN (20 minutes at 37°C in suspension)–derived microparticles, with acquisition of 5 to 10 000 events per sample. (A) Dot plot showing the heterogeneity in microparticle sizes. (B-D) Histograms demonstrating detection of L-selectin (CD62L), phosphatidylserine (using FITC-labeled annexin V), but not AnxA1 in microparticles prepared from resting PMNs. (E,F) EDTA wash of microparticles prepared from adherent PMNs markedly reduces AnxA1 immunostaining. Left panel shows histogram of intact microparticles; right panel, histogram of microparticles washed with EDTA. Data are representative from 3 independent microparticle preparations.