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 combination with specific monoclonal antibodies (MoAbs): (i) to study the membrane expression of two major platelet glyco-protein (GP) complexes, GP Ib-IX and GP IIb-IIIa, and the appearance of activation-dependent membrane epitopes, and (ii) to evaluate the relative proportion of platelet-derived microparticles and their GP pattern during storage of platelet-rich plasma. Binding of fluoresceinated (FITC) LJ-P3, an anti-GP Ibalpha MoAb, to platelets continuously decreased by 50% during storage for 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 GP IIb-IIIa was associated with the exposure of secretion-dependent granule membrane proteins, GMP-140 and GP-53, and the presence of thrombospondin at the platelet surface. These neoantigens are indicative of platelet activation. Moreover, the proportion of platelet-derived microparticles increased from 6 to 22% (p less than 0.001), whereby a predominant subpopulation of GP Ib-negative microparticles was identified. Thus, significant changes in platelet membrane GP occur during standard platelet preservation. These changes, resulting from time-dependent platelet activation and/or proteolysis in vitro may affect platelet GP receptor function upon transfusion.