A new centrifuge system is developed for continuous cell separation according to their densities. It uses a centrifuge bowl equipped with a circular channel (3 cm wide and 5 mm deep with an about 160 ml capacity) around the periphery which is interrupted by a septum so that the liquid introduced from one terminal is quantitatively collected from the other end. The channel is equipped with 6 inlets and 6 outlets each connected to flow tubes which are led to the outside of the centrifuge system using a rotary-seal-free device. A set of polymer suspensions of different densities is introduced through inlets 2 to 6 at 1 ml/min and collected through the respective outlets at the same flow rates. The sample cell suspension is continuously fed through the first channel at a higher flow rate of 2 - 5 ml/min and collected through the respective outlet which is open to the air. Being subjected to a centrifugal force cells in the sample suspention gradually migrate into the polymer layers and are finally suspended in the polymer layer of the same density before reaching the outlet of the channel. The preliminary results obtained from human blood buffy coat revealed that the lymphocyts and granulocytes are well resolved and erythrocytes are completely separated from white cells. CD34 cells are mainly distributed in the lymphocyte fraction (density 1.060-1070) suggesting that they may be enriched by finely focusing the dendity gradient around 1.065. The time required to process 1,000,000,000 cells are about 3 hours. More recently we have made a similar but much smaller capacity column with only a 8 ml total capacity. The system can be used for the separation of a small number of cells with much less cost for the polymer suspension.
