Structural characteristics of RBC-MVs. (A) RBC-MVs visualized by electron microscopy after negative staining. (B) PS expression on RBC-MVs or sPL vesicles (15% PS, 41% PE, 44% PC) measured using a prothrombinase activity assay. (C) Representative donor sample of the number of MVs per milliliter (of liquid fraction of transfusion unit) over storage time in days. (D) Size distribution and concentration of MVs per milliliter at the day of storage noted, from a representative donor sample.