Stability of glycoproteins Ib/IX and IIb/IIIa during preparation and storage of platelet concentrates: detection by binding assays with epitope-defined monoclonal antibodies and physiological ligands.

Preservation of the glycoprotein (GP) complexes Ib/IX and IIb/IIIa, because of their role as specific platelet receptors for adhesive proteins, is essential for the haemostatic efficacy of transfusions of platelet concentrates (PCs). We have combined binding assays with epitope-defined monoclonal antibodies, and with the physiological ligands von Willebrand factor and fibrinogen (Fo), to investigate the total expression and functional status of these receptors, in PCs stored for up to 9 days. Routine preparation and storage for up to 5 days have no apparent effect on the surface expression and the functional status of GPs Ib/IX and IIb/IIIa. However, after prolonged storage for up to 9 days we found a 50% decrease in the level of the total and functional GP Ib/IX content of platelets. This finding parallelled a significant rise in plasma glycocalicin, a proteolytic fragment of GP Ib. In addition, long-term storage promoted an impairment in the exposure of GP IIb/IIIa to Fo, and a 50% decrease in Fo binding capacity, without affecting the complex quantitatively. Finally, we also noticed a storage-induced increase in the platelet surface expression of GMP 140, and after 9 days of storage there was a rise in mean platelet volume, and a significant reduction in pH levels.