Background: Platelet products (PLT) are transfused both prophylactically and therapeutically to prevent and stop bleeding, respectively. United States (US) regulatory guidelines dictate PLT be stored at room temperature (20-24°C, “RTPLT”) for up to 5 days. However, cold storage of PLT (2-6°C, “CSPLT”) out to 21 days has been shown to improve PLT hemostatic function, prolong shelf life, and decrease contamination risks. CSPLT are now used in US Military combat hospitals and at one civilian institution via Food and Drug Administration (FDA) variance. While platelets are typically linked mechanistically to hemostasis, platelets are immunologically active and modulate leukocyte function. The immunological effects of CSPLT are poorly understood, and as such, need to be more clearly defined if CSPLT are to be transfused into patients with altered immune states (eg. immunocompromised or septic patients).

Aims: To use PLT:whole blood (WB) co-cultures to determine if CSPLT potentiate or dampen leukocyte function.

Methods: PLT (type O+) were stored in plasma with agitation at either 22°C (0, 5 days) or 4°C (0, 5, 10, 21 days) and then mixed with fresh donor WB (type O+). Co-cultures were assessed by flow cytometry for myeloid respiratory burst (DHR+) and degranulation (CD107a+), and by Luminex for cytokine secretion in response to lipopolysaccharide (LPS) stimulation.

Results: Upon PLT:WB co-culture, there was reduced monocyte respiratory burst with early-stored (D0, D5) CSPLT and RTPLT. However, as storage time increased (> 10 days), CSPLT lost the ability to suppress monocyte respiratory burst. Cold storage out to D21 increased PLT-mediated neutrophil degranulation. There were minimal changes in myeloid degranulation. The longer CSPLT were stored, the more they potentiated LPS-induced IL6 and IL8 production in PLT:WB co-cultures. IL8 induction was specific to monocytes and required intact platelets.

Conclusions: CSPLT promote proinflammatory leukocyte responses (increased IL8 secretion and cellular degranulation) upon co-culture with WB from healthy volunteers.

[Cold-stored platelets potentiate monocyte-specific IL8 secretion in LPS-stimulated PLT:whole blood cultures.]

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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/cold-storage-of-apheresis-platelets-promotes-il-8-release-in-platelet-leukocyte-co-cultures/