HU treatment or PS capping effects contrast with crisis MP–mediated increase in ICAM-1 level. At 4 hours, the percentage of ICAM-1⁺ cells (A) and their MFIs (B) were decreased with HU24 MPs or AVHU0 MPs (plasma MPs of untreated SS patients preincubated with AV to cap their exposed PS) compared with HU0 MPs (n = 15 for this cohort). *P < .05, **P < .01 vs corresponding HU0 MP level. For the other cohort of SS patients (n = 16), the percentage of ICAM-1⁺ cells (C) and their MFIs (D) were increased with crisis MPs vs steady-state MPs or AVcrisis MPs (plasma MPs of SS patients collected during crisis and preincubated with AV). Dotted lines represent control level (without MPs) at 4 hours. *P < .05, **P < .01.