Leucocyte labeling with colloidal 111In in whole blood

A simple method of 111In leucocyte labeling in whole blood is described. 111In-colloid is initially formulated using iron (50 micrograms Fe+3). 111In-colloid is then added to 10mL of whole blood and leucocyte labeling is achieved by phagocytosis. Non-phagocytosed 111In-colloid is solubilized using a sodium citrate solution. Labeling efficiencies of 60-80% have been achieved with this method. If needed, excess 111In-soluble-complexes can be removed in the plasma fraction by appropriate centrifugation. The labeling method described is easy to use and has the advantage of selectively labeling leucocytes in a whole blood mixture.