SCD neutrophil adhesion is decreased by HU24 MPs but potentiated by crisis MPs. After a 4-hour incubation of ECs with MPs, fluorescently labeled SCD neutrophils (green) had a significantly decreased adhesion level using HU24 MPs vs HU0 MPs (A), whereas crisis MPs increased the adhesion level compared with steady-state MPs from the same SS patients (n = 11 and 9 per cohort, respectively) (D). Combination of crisis MPs and blocking anti–ICAM-1 antibody (α–ICAM-1) led to a stark decrease in adhesion level compared with crisis MPs or steady-state MPs. Levels in the HU0 MPs or the steady-state MPs were used for normalization. The mean level for each group is shown in red. Representative photomicrographs of each condition are shown: HU0 MPs (B) or HU24 MPs (C) for the same SS patients or with steady-state MPs (E), crisis MPs (F), or crisis MPs from the same SS patients but in combination with a blocking anti–ICAM-1 antibody (G) (original magnification ×400). Nuclei of ECs and of neutrophils were labeled using DAPI (data not shown). ^#P < .05 vs crisis MPs, *P < .05, ***P < .001 vs HU0 MPs or steady-state MPs.