QUANTITATION OF CD62, SOLUBLE CD62, AND LYSOSOME-ASSOCIATED MEMBRANE-PROTEIN-1 AND MEMBRANE-PROTEIN-2 FOR EVALUATION OF THE QUALITY OF STORED PLATELET CONCENTRATES

Background: Platelets become activated during storage, which results in secretion of granules, vesiculation of microparticles, secretion of protein, and a number of other biochemical and morphologic processes that decrease the utility of platelet concentrates stored for transfusion. Study Design and Methods:To evaluate the quality of stored platelet concentrates, the cell surface expression of specific activation-dependent antigens (CD62 and lysosome-associated membrane proteins 1 and 2 [LAMP-1, LAMP-2]) on platelets stored in a hospital blood bank over a 7-day period was examined. Relative microparticle counts and the expression of CD62 by microparticles, as well as platelet concentrate supernatant levels of soluble CD62, were determined. Results: The percentage of platelets expressing CD62 increased significantly from Day 1 to Day 5 (p<0.05) of storage; the mean fluorescence Values for CD62 did not, In contrast, the mean fluorescence values of LAMP-I and LAMP-2 rose significantly (p<0.01 and p<0.05, respectively) between Days 1 and 5. Significant declines in CD62, LAMP-1, and LAMP-2 percent expression and mean fluorescence were seen on Day 6 of storage (p<0.001). Microparticle numbers increased significantly during storage and correlated with levels of CD62 protein (free and membrane-bound) (r = 0.95 vs. Day 2, p<0.05; r = 0.88 vs. Day 5, p<0.05). Conclusion: Flow cytometric evaluations of the expression of cell surface CD62, LAMP-1, and LAMP-2 are complementary tests that, especially when used in conjunction with the quantitation of CD62 protein, provide a simple and effective means of evaluating the quality of platelet concentrates stored for transfusion.