BACKGROUND: Blood platelets (PLTs) link the processes of hemostasis and inflammation. Recent studies have demonstrated that PLTs promote immunity and inflammation mainly by means of the CD40/CD40L pathway. Our objective was to describe the accumulation of cytokines in PLT concentrates during storage.
STUDY DESIGN AND METHODS: Pools of PLT concentrates were prepared, separated from plasma, and resuspended in clinical-grade storage medium; samples were taken on Days 0, 1, 2, 3, and 5 for analysis, without replacement (i.e., without soluble protein dilution). Interleukin (IL)-6, IL-8, PLT-derived growth factor (PDGF)-AA, soluble CD40 ligand (sCD40L), RANTES, and transforming growth factor-β production were measured by specific enzyme-linked immunosorbent assays.
RESULTS: Over time, the levels of RANTES, IL-8, and IL-6 were stable. In contrast, the levels of PDGF-AA and sCD40L increased. Ex vivo production of sCD40L was quantified at levels sufficient to induce B-cell effects based on previous studies of in vitro induced B-cell activation and differentiation by sCD40L. Cytokine and/or chemokine levels were generally higher in PLT concentrate supernatants and/or PLT lysates in comparison to PLT-free plasma, allowing the determination of which cytokine and/or chemokine was absorbed or secreted by transfusion-grade PLTs over time.
CONCLUSION: Our data provide evidence that stored PLTs contain molecules with known immunomodulatory competence and secrete them differentially over time during storage for transfusion purposes.