A rapid method for isolation of human mononuclear cells free of significant platelet contamination

In order to obtain mononuclear cells from peripheral human blood for the study of cell surface receptors, it was necessary to effectively eliminate contaminating platelets. The usual Hypaque-Ficoll isolation procedures were found to produce mononuclear cells contaminated with 10-1000 platelets per mononuclear cell (by phase microscopy). Multiple slow speed centrifugations reduced the contamination to 5-10 platelets per mononuclear cell. However, centrifugation of EDTA-anticoagulated blood through Hypaque (D20(20) 1.060) at 400 X g for 5 min at 22 degrees C followed by the usual Hypaque-Ficoll gradient reduced platelet contamination to less than 1 platelet per 2 mononuclear cells. Thus, a rapid and simple gradient procedure is capable of significantly reducing platelet contamination of mononuclear cell preparations and should facilitate the analysis of mononuclear cell receptors and functions.