Markers of Platelet Activation and Granule Secretion

Platelet activation results in a complex series of changes including a physical redistribution of receptors, changes in the molecular conformation of receptors, secretion of granule contents, development of a procoagulant surface, generation of platelet-derived microparticles, and formation of leukocyte-platelet aggregates. Each of these changes can potentially be used as a marker of platelet activation. Whole blood flow cytometry ( 1 ) is the method of choice for the measurement of all these changes, except the secretion of soluble molecules, which are usually measured by enzyme-linked immunosorbent assay (ELISA). Whole blood flow cytometry has many advantages, including: only minuscule volumes (∼5 µL) of blood are required; platelets are directly analyzed in their physiological milieu of whole blood; the minimal manipulation of samples prevents artifactual in vitro activation and potential loss of platelet subpopulations; both the activation state of circulating platelets and the reactivity of circulating platelets can be determined; and a spectrum of different activation-dependent changes can be determined. The specific methodological details of the use of flow cytometry to measure platelet activation are described elsewhere ( 1 – 3 ). These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.