Ficoll-separated mononuclear cells from sepsis patients are contaminated with granulocytes

Objective: To determine the cell content and purity of Ficoll-separated peripheral blood mononuclear cells and granulocyte isolates in sepsis patients compared to healthy controls. Design and setting: Prospective study in the adult and pediatric intensive care departments of the Erasmus University Medical Center in the Netherlands. Patients: Three sepsis patients (two adults, one child) and four healthy controls. Measurements and results: Blood leukocytes were separated by Ficoll into an interface and a bottom fraction. The cell content and purity was analyzed by cytospin and flow-cytometric immunofluorescence. In sepsis patients, the interface consisted of 11-52% mononuclear cells only, due to high contamination with granulocytes (48-89%). This was in contrast to a high proportion of mononuclear cells (88-100%) in healthy controls. The bottom fraction showed a cell purity of >= 92% polymorphonuclear granulocytes in sepsis patients as well as in healthy controls. Conclusions: Ficoll-separated leukocytes of sepsis patients are not suitable for studying mononuclear cells but can be used for studying granulocytes with high purity. The mononuclear cell fraction is highly contaminated with granulocytes. Additional separation techniques are necessary to obtain a pure cell fraction.