The electrokinetic properties of artificial particles--microcapsules--were compared with those of the rat lymphocyte sub-populations, T and B cells, and similar results were obtained. The affinity of the microcapsules to the polyamine graft co-polymer, which was claimed to be capable of separating the cells efficiently, was measured and it revealed that not the magnitude of the surface negative charge and the kind of dissociable groups, but the balance of the anionic and cationic charges on the microcapsule surface played a key role in their adsorption to the co-polymer.