Methods for enriching specific cell-types by density gradient centrifugation

A method of enriching for a population of desired cells from a cell mixture containing multiple cell populations, comprising:

• layering a cell mixture containing the desired cells onto a gradient density solution contained in a centrifuge tube;
• said tube having a first closed end defining an inner bottom wall and an opposite open end;
• an annular member disposed in said tube and defining an opening therethrough, wherein said opening has an area less than the area of a cross section of said tube, said annular member defining a lower portion of the tube extending between said member and said tube bottom wall and upper portion above said annular member;
• said tube containing a density gradient solution which fills said lower portion and a part of said top portion to a level above said annular member;
• said density gradient solution having an osmolality of 280.+-.10 mOsm/kg H.sub.2 O and a specific density within 0.0005 gr/ml of the specific density of the desired cell;
• centrifuging said tube at a gravitational force sufficient to pellet cells having specific densities greater than the specific density of the density gradient material in said tube;
• and
• collecting from upper portion of said tube an enriched fraction of said population of cells.