DEVINE ET AL. 724 TRANSFUSION Volume 39, July 1999 BACKGROUND: The introduction of prestorage white cell (WBC) reduction in random-donor platelet concen- trates in Canada has increased the occurrence of par- ticulate material in PCs. The effects of filtration on plate- let activation state and the activation of plasma enzyme systems were assessed. STUDY DESIGN AND METHODS: Particulate material was examined by light microscopy, electron microscopy, protein electrophoresis, and biochemical analysis. Thirty PCs (10 unfiltered, 20 filtered) were examined during processing and 5-day storage for pH, platelet count and mean volume, morphology, activation marker expres- sion, and hypotonic shock response. Complement acti- vation, thrombin generation, and fibrinolysis were as- sessed by using specific enzyme immunoassays or chromogenic assays. RESULTS: By all analyses, the particulate material ap- peared to be platelet aggregates. Platelets exposed to WBC-reduction filters expressed a significantly higher level of activation markers CD62 and CD63, altered morphology, and increased platelet microparticles throughout the storage period than did unfiltered plate- lets. Complement activation at the C3 level was signifi- cantly increased in filtered units with little evidence of coagulation or fibrinolytic system activation. CONCLUSION: Exposure of platelets to filters during prestorage WBC reduction increased platelet activation and mildly increased complement activation over the levels during the storage period. These alterations can contribute to the formation of irreversible platelet aggre- gates during processing. W hite cells (WBCs) in cellular blood compo- nents are associated with several negative side effects of transfusion. The development of technologies to WBC reduce cellular blood components has led to decreases in alloimmu- nization 1,2 and cytomegalovirus infection risk. 3,4 The re- moval of contaminating WBCs from random-donor plate- let concentrates (PCs) also reduces the level of cytokine pro- duction over the storage period, 5,6 with a concomitant reduction in the rate of nonhemolytic febrile transfusion re- action. 7 WBC reduction may also reduce immunomodulatory effects of transfusion other than alloimmunization. 8 While the benefits of WBC reduction are clinically im- portant, the exposure of PCs to WBC reduction filters has effects beyond the removal of WBCs. Negatively charged filter material has been reported to activate blood coagu- lation proteins and the kallikrein and bradykinin sys- tem. 9-11 On the other hand, WBC-reduction filters have been reported to remove already formed, activated comple- Effects of prestorage white cell reduction on platelet aggregate formation and the activation state of platelets and plasma enzyme systems D.V. Devine, A.J. Bradley, E. Maurer, E. Levin, S. Chahal, K. Serrano, and M.I.C. Gyongyossy-Issa ABBREVIATIONS: EIA(s) = enzyme immunoassay(s); GP = gly- coprotein; HSR = hypotonic shock response; PAP = plasmin– antiplasmin; PC(s) = random-donor platelet concentrate(s); PRP = platelet-rich plasma; SDS-PAGE = sodium dodecyl sulfate- polyacrylamide gel electrophoresis; TAT = thrombin–anti- thrombin; WBC(s) = white cell(s). From the Canadian Blood Services, Vancouver Centre; and the Departments of Pathology and Laboratory Medicine, Biochem- istry, and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada. Address correspondence to: Dana Devine, PhD, Canadian Blood Services, 4750 Oak Street, Vancouver, BC V6H 2N9, Canada; e-mail: ddevine@pathology.ubc.ca. No reprints avail- able. Supported in part by the Canadian Red Cross Society Blood Services. Received for publication July 23, 1998; revision received November 14, 1998, and accepted November 18, 1998. TRANSFUSION 1999;39:724-734. B L O O D C O M P O N E N T S