Impact of MPs on the proadhesive phenotype of ECs. PS exposure by plasma PLT-MPs and RBC-MPs, which may facilitate the binding of SS MPs to ECs, is increased during crisis but decreased after treatment with HU for 2 years. These changes in MP quality explain, at least in part, why MPs of HU-treated SS patients decreased ICAM-1 expression levels, whereas crisis MPs increased the expression of this adhesion protein. Neutrophil adhesion was consistently decreased using plasma MPs from HU-treated SS patients, whereas crisis MPs triggered increased adhesion. ICAM-1 overexpression and increased adhesion of neutrophils with crisis MPs were abolished by AV and ICAM-1 blocking, respectively. AA MPs cause a decrease in ICAM-1 at the mRNA and protein levels in ECs, as well as neutrophil adhesion, compared with MPs from untreated SS patients.