Prolonged circulation of activated platelets following plasmapheresis

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Abstract
The extent and duration of in vivo platelet activation were determined in 12 volunteer donors undergoing automated plasmapheresis. Expression of P-selectin, activated GpIIb/IIIa, and platelet microparticle formation were measured by flow cytometry on peripheral blood samples obtained immediately before and after plasmapheresis and at 24 hour intervals thereafter for up to 3 days. Although no adverse effects were noted in any donor, immediately after apheresis 3 87% of circulating platelets expressed P-selectin: by 48 hours. 0.5 50% expressed P-selectin; and by 72 hours, all donors studied had fewer than 5% P-selectin expression on circulating platelets. Results were similar for the expression of the activated conformation of GpIIb/IIIa. There was a positive correlation with in vitro P-selectin expression in response to ADP in the pre-apheresis sample and the number of platelet microparticles detected in the donor following plasmapheresis. In addition, the percent expression of P-selectin and activated GpIIb/IIIa in response to ADP was reproducible in each individual studied on five separate occasions (CV ≤ 8%). Platelets activated during plasmapheresis using an automated device may circulate for at least 48 hours, and pre-plasmapheresis response of platelets to the agonist ADP correlated with platelet microparticle formation post-plasmapheresis.