Rapid clearance of small human platelets. (A) Representative flow cytometric studies of surface receptor level for CD41, CD42a, and CD42b on infused human platelets (gray graph) or young and old platelets after AMC EV-megakaryocytes (dashed and solid line graph, respectively) at 1 hour after infusion. (B) Data summary of flow cytometric studies of isolated human donor platelets (top) or EV-PLPs (bottom) stained for the indicated surface markers or Annexin V binding. Mean ± SEM for each subpopulation. N = 3 separate studies for donor platelets and N = 4 for EV-PLPs, each in duplicate. (C) Human platelets either nonactivated (open diamonds) or after TRAP (filled squares) or CVX activation (gray circles) were infused into recipient NSG mice that were or were not preinfused with clodronate-ladened liposomes. The counts in the activated studies were normalized to parallel studies with nonactivated donor platelets. Mean ± SEM is shown. N = 5 studies, each done in duplicate.