SURVIVAL OF FRESH HUMAN PLATELETS IN A RABBIT MODEL AS TRACED BY FLOW-CYTOMETRY

BACKGROUND: In the event of hemorrhage and blood loss, platelets play a vital role in the coagulation process. However. there are currently no acceptable protocols far long-term storage of platelets. As a first step toward testing the efficacy of stored platelets or platelet subs titutes in vivo, a flow cytometric technique was developed to detect h uman platelets in rabbit blood. STUDY DESIGN AND METHODS: Human platel ets were transfused to rabbits whose reticuloendothelial system was in hibited by the administration of ethyl palmitate. Because human and ra bbit platelets display surface molecules with different epitopes, huma n platelets were selectively labeled with antibodies specific for glyc oprotein IX (CD42a). As this antibody does not label rabbit platelets, it allows discrimination of human from rabbit platelets in samples of rabbit blood containing both types of platelets. RESULTS: Survival of human platelets in rabbits was monitored by flow cytometry and fluore scence microscopy in blood drawn at various times after the platelet t ransfusion. Fresh human platelets transfused to untreated control rabb its (n = 3) were removed from circulation within 10 minutes of the com pletion of the transfusion. Fresh platelets (1 day old) transfused to rabbits treated with ethyl palmitate (n = 5) survived for 24 hours wit h an average half-life of 8.6 hours. In contrast, 8-day-old platelets were cleared from the circulation sooner with an average half-life of 2.9 hours (n = 4). CONCLUSION: This report describes a rapid and effic ient method of assessing the survival of human platelets in a rabbit m odel using flow cytometry. This technique will enable.the monitoring i n rabbits of human platelets prepared by various preservation protocol s.