Purification of Human Leukocytes.∗

Summary Methods for preparing human leukocytes from venous blood have been investigated. Sedimentation of erythrocytes by fibrinogen or phytohemagglutinin of Phaseolus vulgaris have given best results. With white cell purity as a goal, the phytohemagglutination method has been clearly superior, giving preparations of 72.7% and 96.5% from normal and leukemic bloods, respectively. These values have been increased to 93.8% and 98.8% by utilization of a phosphate buffer which preferentially lyses red cells while leaving white cells intact.