FIXATION WITH FORMALDEHYDE INDUCES EXPRESSION OF ACTIVATION-DEPENDENTPLATELET MEMBRANE-GLYCOPROTEINS, P-SELECTIN (CD62) AND GP53 (CD63)

Platelet activation in vivo is important in the pathogenesis of thromb osis. Accurate measurement is difficult due to artefactual in vitro pr eparation related activation. This can be overcome by using whole bloo d techniques, such as flow cytometry. However, there is little consens us on methods of platelet preparation, procedures for use of fixation, or the optimal types/amounts of fixative. The use of unfixed platelet s has received little attention. We describe a series of experiments c omparing platelet activation antigen expression detected by flow cytom etry tn fixed and unfixed samples. Formaldehyde increased the expressi on of both CD62 and CD63. We recommend that fixation with formaldehyde should not be used when studying platelet activation.