Dr. Arne Bøyum reported in 1968 a simple and efficient method for the isolation of mononuclear cells from human blood. For more than 45 years, a commercial medium known as Lymphoprep has been widely used to isolate these cells.
Mononuclear cells (monocytes and lymphocytes) have a lower buoyant density than erythrocytes and polymorphonuclear leukocytes (PMN) (granulocytes). The vast majority of mononuclear cells have densities less than 1.077 g/mL.
Therefore, these cells can be isolated by centrifugation in an isoosmotic medium with a density of 1.077 g/mL, which allows the erythrocytes and PMNs to settle in the medium while retaining the mononuclear cells at the sample/medium interface.
The method described is fast, simple and reliable and gives excellent results with blood samples from normal individuals and patients.