Comparison of the level of cytokine mRNA in buffy coat-derived platelet concentrates prepared with or without white cell reduction by filtration

Evidence for de novo synthesis of cytokines and chemokines in platelet concentrates

BACKGROUND AND OBJECTIVES

Inflammatory cytokines in platelet concentrates (PC) may cause side-effects such as febrile non-haemolytic transfusion reactions. The maximum white blood cell (WBC) content tolerable to avoid the accumulation of cytokines, and whether these cytokines originate from degranulating leucocytes or de novo synthesis during storage, had not been investigated prior to this study.

MATERIAL AND METHODS

We investigated the secretion of interleukin (IL)-1beta, IL-2, IL-6, IL-8, tumour necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) and quantified the appropriate expression of corresponding mRNA in PC with regard to different levels of WBC contamination and storage times. In addition we tested the viability of WBCs during PC storage (by staining with 7-aminoactinomycin D) and their ability to perform de novo cytokine synthesis (by using superantigen stimulation).

RESULTS

We detected a statistically significant increase of IL-1beta, IL-6, IL-8 and TNF-alpha in PC with > or = 108 WBCs. Quantitative reverse transcription-polymerase chain reaction (RT-PCR) showed increasing mRNA expression of the respective cytokines depending on the number of WBC present. On day 5 of storage, WBC viability was > 80% and the leucocytes were still able to produce cytokines de novo.

CONCLUSIONS

These data show clear evidence for de novo synthesis of cytokines in PC. The cytokine pattern supports the hypothesis that activated monocytes are responsible for this cytokine synthesis. PC with a WBC contamination of > or = 108 contain inflammatory mediators in clinically relevant concentrations.

Febrile and allergic transfusion reactions after the transfusion of white cell-poor platelet preparations

BACKGROUND

Nonhemolytic transfusion reactions (NHTRs) frequently occur after platelet transfusions. White cell (WBC)-derived inflammatory cytokines can cause these reactions, but they are rarely found in WBC-poor platelet preparations. Transfusion reactions were investigated with regard to the residual WBC content in the stored platelet concentrate in two consecutive study periods.

STUDY DESIGN AND METHODS

In the first study period, platelet concentrates were WBC-reduced by bedside filtration. In the second period, all platelet concentrates were filtered before storage. Recipients who experienced transfusion reactions were examined with regard to their main clinical symptoms during and after transfusion. In the supernatant of the involved platelet concentrates, concentrations of interleukin (IL)-1beta, IL-6, IL-8, tumor necrosis factor (TNF)alpha, macrophage inflammatory protein 1alpha, and RANTES were analyzed.

RESULTS

The incidence of transfusion reactions remained steady when the transfusion regimen was changed from bedside filtration to prestorage WBC filtration (1.63% and 1.56%; p = 0.84). In both periods, NHTRs were predominantly of allergic origin. Inflammatory mediators IL-1beta, IL-6, IL-8, and TNFalpha were detectable in only a minority of platelet components involved in NHTRs. Platelet concentrates involved in allergic reactions contained high concentrations of RANTES (668 +/- 223 ng/mL).

CONCLUSIONS

Prestorage WBC filtration did not reduce the incidence of these reactions, and inflammatory cytokines were of minor relevance. The proinflammatory platelet-derived chemokine RANTES, which accumulates even in WBC-reduced platelet concentrates, was associated with allergic transfusion reactions. Platelet-derived mediators may be a key to understanding NHTRs.

Pathophysiology of febrile nonhemolytic transfusion reactions

Most febrile nonhemolytic transfusion reactions (FNHTR) to platelets are caused by cytokines that accumulate in the product during storage. There have been numerous studies that have demonstrated high concentrations of leukocyte- and platelet-derived cytokines in stored platelet products. The mechanism of cytokine accumulation is not understood; however, recent studies have suggested that leukocyte apoptosis and/or monocyte activation during the manufacturing process may play a role. Additional support of cytokines as a cause of FNHTR is provided by a recently published randomized controlled trial that shows that removal of the supernatant plasma from platelets before transfusion significantly lowers the frequency of reactions and eliminates most of the severe reactions associated with platelet transfusions. Although cytokines appear to play a major role in causing platelet reactions, there is little evidence to support their role in causing erythrocyte reactions. Hence, it appears that most febrile nonhemolytic transfusion reactions to erythrocytes are probably the result of an incompatibility between leukocytes in the erythrocyte product and antibodies in the recipient's plasma. Recent studies have confirmed that the concentrations of proinflammatory cytokines in a wide variety of stored erythrocyte products are low. Also, there is no clinical evidence to suggest that the small quantities of cytokines present in stored erythrocyte products contribute to acute reactions to these products when transfused.