Z serum clot activator

Blood was collected from the jugular vein and transferred to a Vacuette tube with Z serum clot activator (Greiner Bio-One). Shortly after blood collection, tubes were centrifuged at 3000 rpm for 20 minutes. The resulting serum, approximately 4 ml, was aliquoted in labeled Eppendorf tubes and stored at -20°C until analysis.

Venous blood was drawn into vacutainers containing 3.8% trisodium citrate or silica microparticles (Z serum clot activator, Greiner Bio-One, Kremsmünster, Austria). Platelet-rich plasma (PRP) was obtained from the whole citrated blood by centrifugation at 200× g, 10 min, and 23 °C. Platelet-poor plasma (PPP) was obtained from PRP by centrifugation at 1500× g for 5 min; it was aliquoted and stored at −20 °C until use. The frozen samples of PPP were thawed at 37 °C for 60 min and used within 2 h. A portion of each citrated blood sample was used for standard immunological, hematological, and biochemical tests.

Individual human serum from 10 anonymous healthy donors was provided by Sanquin Research, Amsterdam, The Netherlands. Plasma samples were obtained after informed consent and in accordance to the ethics board of Sanquin. The whole blood from each individual was collected in a 9-ml Vacuette tube (Greiner Bio-One, Kremsmunster, Austria) containing Z Serum Clot Activator. The whole blood was then left undistributed at room temperature for 30–60 min. The clotted material was removed by centrifugation at 1800 × g for 20 min at room temperature and the sera were transferred as 1 ml aliquots to clean 1.5 ml Eppendorf tubes, snap froze in liquid nitrogen and stored at −80 °C. Human serum samples from 10 septic patients were acquired from Discovery Life Science, Columbus, OH, USA. All serum samples were stored at −80 °C until analysis.