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 μg Fe⁺³). ¹¹¹In-colloid is then added to 10 mL 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.