PLATELET STORAGE LESIONS - ANALYSIS OF PLATELET MEMBRANE-GLYCOPROTEINS AND PLATELET-DERIVED MICROPARTICLES BY FLUORESCENCE-ACTIVATED FLOW-CYTOMETRY

We have used recently developed flow cytometric techniques in combinat ion with specific monoclonal antibodies (MoAbs): (i) to study the memb rane expression of two major platelet glycoprotein (GP) complexes, GP Ib-IX and GP Hb-IIIa, and the appearance of activation-dependent membr ane epitopes, and (ii) to evaluate the relative proportion of platelet -derived microparticles and their GP pattern during storage of platele t-rich plasma. Binding of fluoresceinated (FITC) LJ-P3, an anti-GP Iba lpha MoAb, to platelets continuously decreased by 50% during storage f or 6 days. Binding of FITC-LJ-P4, directed to the GP IIb-IIIa complex on the platelet surface, also decreased during day 1-3, but increased again to baseline levels from day 4-6 of storage. The re-increase of G P IIb-IIIa was associated with the exposure of secretion-dependent gra nule membrane proteins, GMP-140 and GP-53, and the presence of thrombo spondin at the platelet surface. These neoantigens are indicative of p latelet activation. Moreover, the proportion of platelet-derived micro particles increased from 6 to 22% (p<0.001), whereby a predominant sub population of GP Ib-negative microparticles was identified. Thus, sign ificant changes in platelet membrane GP occur during standard platelet preservation. These changes, resulting from time-dependent platelet a ctivation and/or proteolysis in vitro may affect platelet GP receptor function upon transfusion