The association of the T hr715 P ro P ‐selectin genotype with levels of P ‐selectin in platelet concentrates

Background and Objectives P‐selectin is stored in the alpha granules of platelets and in the W eibel P alade 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 T hr715 P ro polymorphism, is strongly associated with the plasma levels of soluble P ‐selectin. In platelet concentrates soluble P ‐selectin can be regarded mainly platelet derived. Materials and Methods 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. Results 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 T hr715 T hr individuals ( P  < 0·0001), but not in heterozygotes ( T hr715 P ro, P  = 0·2). Conclusion The donors' genotype has only little influence on levels of soluble P ‐selectin in apheresis platelets suspended in 35% plasma/65% SSP +.