Role of platelet surface glycoprotein Ibalpha 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-GPIbalpha. 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( summation operator )) 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Correlations were analyzed between in vitro assays of PLT activation and in vivo clearance of conventional (Days 2-5), outdated (Days 7-8), and refrigerated PCs.
RESULTS: Binding of anti-CD62 to the PLT surface was significantly increased and of anti-GPIbalpha decreased in outdated and refrigerated PCs compared to conventional PCs.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( summation operator )) clearance correlated better with anti-GPIbalpha 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 GPIbalpha changes are involved in delayed GPIbalpha-mediated PC clearance.