The isolation of human peripheral blood mononuclear cells (PBMCs) presented in OptiPrep™ Application Sheets C03 and C04 represent two approaches to PBMC purification in a non-ionic medium without polysaccharide. 

Application Sheet C03 describes a “traditional” approach of layering the blood over a ρ = 1.077 g/ml density barrier. Application Sheet C04 describes a simpler (“mixer”) approach in which the blood is adjusted to ρ = 1.077-1.078 g/ml and the PBMCs allowed to float to the surface. 

This Application Sheet presents a third alternative in which the blood is adjusted to a density considerably higher than that of the PBMCs (ρ = 1.095 g/ml) and layered beneath a ρ = 1.078 g/ml density barrier. As with the mixer technique, the PBMCs float to the surface, but this is the only system in which the cells do not band adjacent to the plasma-containing sample layer. 

The low-density barrier acts as a "buffer-zone" which "washes” the PBMCs free of soluble plasma proteins and particulate contaminants such as platelets at the same time as they are purified from other blood cells.