Annexin 1–rich microparticles inhibit PMN/HUVEC interaction under flow. Microparticles (between 30 and 50 × 10³) were generated from resting or adherent PMNs and added to fresh PMNs for 8 minutes prior to the flow experiment. PMNs (5 × 10⁶) were then flown for 15 minutes at 1 dyne/cm², prior to quantifying the degree of PMN interaction with the HUVECs, as (A) PMN capture, (B) PMN rolling, or (C) PMN adhesion. Data are mean plus or minus SEM of from 3 or more independent experiments (with distinct microparticles, PMN, and HUVEC preparations). *P < .05 versus respective control group.