Inhibition of cytokine accumulation and bacterial growth during storage of platelet concentrates at 4° C with retention of in vitro functional activity

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Abstract
The potential for bacterial contamination limits the storage of platelet concentrates (PCs) at 22 degrees C to 5 days. In addition, storage of platelets under conventional protocols for longer times (> 3 days), in the absence of white cell filtration, has been correlated with incidents of cytokine-associated febrile reaction in recipients. It has been demonstrated that the addition of a reagent mixture of second-messenger effectors allows platelets stored at 4 degrees C to maintain significant in vitro functional activity. Thus, the effects of 4 degrees C storage on the growth of bacteria and the accumulation of cytokines by the white cell fraction of PCs were analyzed to demonstrate the benefits of this refrigerated storage system. The platelet storage solution was added directly to PCs obtained from the blood bank, and these treated PCs were stored at 4 degrees C without agitation. In parallel, control PCs were stored according to standard blood-banking procedures. On Days 1, 3, 5, and 9, the PCs were measured for the plasma concentrations of cytokines. Treated and control PCs stored at 4 degrees C and 22 degrees C were inoculated with low-titer Staphylococcus aureus, and bacterial growth was measured over a 5-day period. Control PCs displayed a time-dependent increase in the plasma concentration of interleukin 6, interleukin 1 beta, and tumor necrosis factor alpha. These conventionally stored PCs also displayed a time-dependent increase in the bacteria titer. In contrast, the treated PCs stored at 4 degrees C displayed no accumulation of the above cytokines in the plasma fraction and no increase in bacteria titer above the initial inoculation. The storage of PCs at refrigerated temperatures inhibits the accumulation of white cell-produced cytokines in the PCs, an effect that could alleviate cytokine-associated febrile transfusion reactions The 4 degrees C storage was also bacteriostatic, which indicates that the storage of PCs at that temperature increases safety by decreasing the potential for sepsis. Thus, the ability to store PCs at 4 degrees C may allow extension of the storage limit beyond 5 days.