Circulating platelet-leukocyte complexes Circulating activated platelets form complexes with leukocytes via CD62P-PSGL interaction. These complexes are quantified on a population of 5000 leukocytes. Complexes are identified by flow cytometry as the cell population stained with both anti-CD41-PE (platelet marker) and anti-CD45-FITC (leukocyte marker) and are expressed as a percentage of total leukocytes.