Density gradient separation of lymphoid cells adhering to protein-A-containing staphylococci.

A cell separation technique was designed based on the interaction between cell-surface-bound IgG and protein A of Staphylococcus aureus. The density of lymphoid cells coated with IgG antibodies against one of the surface markers was increased by adherence of staphylococci. Cells with adhering bacteria were separated from cells without bacteria by density gradient centrifugation in 11.5% sodium metrizoate. Bacteria were removed from the lymphoid cells by lysostaphin digestion. The purity of separated cells was approximately 95% even when the proportion of a specific cell population was below 10% in the initial mixture. The viability and the ability of cells to multiply in vitro were not significantly impaired by the fractionating procedure. The technique can generally be applied for cell separation, provided antibodies of the IgG class against specific surface markers are available.