Expression of P-Selectin and Platelet-Neutrophil (PMN) Interactions In Untreated and Mirasol^® PRT Treated Platelet Concentrates During Routine Storage.

Platelet concentrates develop biologically active compounds during storage which may play a role in adverse events of transfusion. Although many studies have focused on release of soluble pro-inflammatory compounds, changes in cells such as platelets may contribute to the pro-inflammatory effects of transfusion products. We evaluated untreated and Mirasol Pathogen Reduction Technology (PRT) treated platelet concentrates for expression of P-selectin and interactions between platelets and PMNs.

Four, double apheresis platelet products were collected from healthy volunteers with TRIMA system under an IRB approved protocol. One product of each pair was PRT treated with Mirasol PRT and both were stored under standard conditions. At various times, aliquots were sterilely removed from products. Expression of P-selectin on platelets was defined with a specific antibody. Neutrophils, isolated from ABO type specific peripheral blood of volunteers, were incubated with platelet concentrates for 3 min at 37° C, and labeled CD41 was added. PMNs were identified with flow cytometry by forward/side scatter and platelets by fluorescence and the % of PMNs associated with platelets determined. Inhibition of platelet/neutrophil interaction with antibodies to adhesion molecules was also examined. In parallel experiments, activation of neutrophils after incubation with platelets was determined by oxidation of dihydrorhodamine (DHR).

During storage, platelet expression of P-selectin increased in both untreated and Mirasol treated platelet concentrates (p<0.05) with greater expression on treated products (p<0.05). On day 0 of storage, PMNs associated with platelets was 9.7±1.1% (mean±SEM, n=4, untreated) and 12.1±1.3% (treated products), and on day 5 results were 16.8±4.3% and 27.1±4.3% respectively (significant, p<0.05). Platelet-PMN interactions were inhibited by ≥90% by antibodies to P-selectin or its PMN adhesion partner PSGL-1, but not Mac1, LFA-1, GPIb or ICAM-1. Platelet-PMN interactions were directly related to the stored platelets, not the effects of stored plasma. Activation of the PMN respiratory burst by oxidation of DHR was not shown in any product type over storage time.

During storage, platelets exhibit increased P-selectin expression and the capability to adhere to PMNs. These effects were greater after Mirasol PRT treatment. The cell association depended on the interaction between P-selectin (platelets) and PSGL-1 (PMNs). These changes occurring during storage of platelet concentrates may explain platelet recovery patterns in patients requiring repeated transfusions with untreated and PRT treated products and could play a potential role in adverse events for either product type.

Goodrich:CaridianBCT Biotechnologies: Employment, Patents & Royalties, Research Funding. Marschner:CaridianBCT Biotechnologies: Employment, Research Funding.