Platelet surface p-selectin, platelet-granulocyte heterotypic aggregates, and plasma-soluble p-selectin during plateletpheresis

BACKGROUND: Plateletpheresis components have been shown to contain p-select in-positive platelets after collection and storage. P-selectin mediates bin ding of activated platelets to granulocytes and monocytes. This study was u ndertaken to assess platelet activation, granulocyte activation, platelet-g ranulocyte heterotypic aggregate formation, and the plasma-soluble p-select in level during plateletpheresis performed on a particular instrument (MCS, Haemonetics). STUDY DESIGN AND METHODS: Flow cytometry was used to assay platelet surface p-selectin, granulocyte iC3b receptor, and platelet-granulocyte aggregates in the platelet component, residual blood in the disposable polycarbonate bowl of the MCS+, and in the donor blood with and without the addition of i n vitro agonists before, during, and after plateletpheresis. The plasma-sol uble p-selectin levels in the platelet component, disposable bowl, and dono r venous blood were measured by an enzyme-linked immunosorbent assay. RESULTS: Levels of p-selectin-positive platelets, activated granulocytes, a nd platelet-granulocyte aggregates were greater in the disposable bowl than in the preapheresis donor blood. Levels of p-selectin-positive platelets, activated granulocytes, and platelet-granulocyte aggregates in the postaphe resis donor blood were similar to those in the preapheresis donor blood. Th e platelet components contained no activated granulocytes or detectable pla telet-granulocyte heterotypic aggregates, and only about 10-percent activat ed platelets. The plasma-soluble p-selectin level in the platelet component was significantly greater than that in the preapheresis donor blood, the r esidual blood in the disposable bowl, or the postapheresis donor blood. CONCLUSIONS: Measurements of platelet surface p-selectin, platelet-granuloc yte heterotypic aggregates, and plasma-soluble p-selectin can be used to de tect platelet activation during plateletpheresis.