The rapid one-step gradient centrifugation procedure for simultaneous isolation of granulocytic and mononuclear leukocytes from human blood: Biological, physical and chemical bases

When anti-coagulated blood is layered over a ficoll-hypaque gradient of special chemical composition and optimal density of 1.114 gm per ml, the leukocytes resolve into two distinct bands at the interface after centrifugation at 400G for 20-30 minutes. These two bands are usually at least 0.9 mm apart, and can be easily removed separately. The top band consists of predominantly mononuclear cells, while granulocytes predominate in the lower band. This simple, rapid method for the isolation of blood leukocytes of high purity is now available as Mono-Poly Resolving Medium (Flow Laboratories, Virginia), but the curious phenomenon on which it is based has yet to be satisfactorily explained. In this paper, we report on preliminary observations which indicate that both the erythrocytes and chemical composition of the separation medium play crucial roles in the process