The association of the Thr715Pro P‐selectin genotype with levels of P‐selectin in platelet concentrates

Abstract

P-selectin is stored in the alpha granules of platelets and in the Weibel Palade bodies of endothelial cells; upon activation, it is translocated to the cell surface and released into the plasma in soluble form. One variant of the P-selectin gene, the Thr715Pro polymorphism, is strongly associated with the plasma levels of soluble P-selectin. In platelet concentrates soluble P-selectin can be regarded mainly platelet derived. The relation of the genotype with soluble P-selectin, platelet expressed P-selectin and the sum of all forms of P-selectin - comprising soluble P-selectin, platelet surface P-selectin and P-selectin from the alpha granules - was assessed in fresh whole blood and in apheresis platelets suspended in 35% plasma/65% SSP+ obtained from 89 platelet donors. Levels of total P-selectin were genotype associated (P=0·025); likewise, in fresh whole blood there was an association of soluble P-selectin with genotype (P=0·02). In platelets suspended in additive solution, however, levels of the storage-associated or TRAP-6 agonist induced increase of platelets' P-selectin were not associated with the genotype. A correlation between levels of soluble P-selectin and surface expression of P-selectin was observed on day 3 of storage in Thr715Thr individuals (P<0·0001), but not in heterozygotes (Thr715Pro, P=0·2). The donors' genotype has only little influence on levels of soluble P-selectin in apheresis platelets suspended in 35% plasma/65% SSP+.