The most commonly used technique for the isolation of peripheral blood mononuclear cells (PBMCs) from human blood is to centrifuge whole blood (diluted 1:1 with saline) over an isoosmotic 1.077 g/ml density barrier. 

For more information see Application Sheet C03. An alternative strategy devised by Ford and Rickwood [1] simplifies the procedure. A 19% (w/v) Nycodenz® solution (ρ = 1.100 g/ml), produced commercially as NycoPrep™ Mixer, was added to an equal volume of whole blood to raise the density of the plasma to 1.077 g/ml. 

During centrifugation at 1500 g for 30 min at 20°C the erythrocytes and polymorphonuclear leukocytes (PMNs) sediment while the PBMCs float to the top and are recovered from the meniscus and the medium below it. NycoPrep™ Mixer is no longer available but the technique has been adapted very successfully to the use of OptiPrep™ and is described below.