Studies on platelets contained in eluates following filtration leukapheresis

Platelets eluted from nylon fiber filters after filtration leukapheresis have been studied. The platelet yield from 61 routine donations was 1.25 +/- 0.18 x 10(11), (mean +/- SEM) corresponding to 1.78 x 10(10) per 500 ml blood processed. Filtered platelets labeled with radiochromate demonstrated reduced recovery in vivo 15 minutes after infusion (38.5 +/- 1.7%) when compared to the control value (68.5 +/- 6.8, p less than 0.001). The survival of those platelets remaining in the circulation after 15 minutes did not however differ from the control value. ADP (10 micrometer, 1 mM), adrenaline (100 micrometer) and collagen (7.25 mg/ml) added in vitro induced less aggregation of filtered platelets than normal control platelets and electron microscopy revealed structural abnormalities. It is concluded that recipients of granulocyte transfusions obtained by filtration leukapheresis are unlikely to be benefited by the platelets contained in these transfusions.