Role of platelet surface glycoprotein Ibα and P-selectin in the clearance of transfused platelet concentrates

BACKGROUND: Role of P-selectin (CD62) and glycoprotein (GP) Ibalpha in posttransfusion clearance of platelet concentrates (PCs) is unclear. STUDY DESIGN AND METHODS: Platelet (PLT) activation in vitro was determined by flow cytometry using anti-CD62 and anti-GPlbalpha. PC clearance in vivo was evaluated in an animal model using rabbits with an inhibited reticuloendothelial system, as measured by 0.5-hour (R-0.5), 24-hour (R-24), and total (R-Sigma) PLT recoveries, and survival time (ST). Correlations were analyzed between in vitro assays of PLT activation and in vivo clearance of conventional (Days 2-5), outdated (Days 7-8), and refrigerated PCs. RESULTS: Binding of anti-CD62 to the PLT surface was significantly increased and of anti-GPlba decreased in outdated and refrigerated PCs compared to conventional PCs. Negative correlation was observed between in vitro anti-CD62 binding and the fast (R-0.5) PLT clearance, but not with delayed (R-24 and ST) clearance. In contrast, anti-GPIbalpha binding showed positive correlations with delayed but not with fast PLT clearance. Overall (R-Sigma) clearance correlated better with anti-GPlba than with anti-CD62 binding. CD62 density on the PLT surface was decreased after PC transfusion, whereas GPIbalpha density remained unchanged. CONCLUSION: These data suggest that CD62 exposure on the PLT surface during PC storage triggers fast CD62-mediated PC clearance, whereas in vitro GPIba changes are involved in delayed GPIbalpha-mediated PC clearance.