A novel method of cell separation based on dual parameter immunomagnetic cell selection

We describe a novel method of cell purification involving two stage immunom agnetic selection which permits isolation of cells based on a second cell s urface marker without the need for removal of beads used in the first selec tion step. This approach takes advantage of the size differences between co mmercially available immunomagnetic beads and/or particles and their differ ing properties in terms of attraction to magnetic fields of various strengt hs. The first stage of separation involves positive selection of cells usin g the Miltenyi MiniMacs system, utilising 50 nm MicroBeads and a MiniMacs m agnet. Cells obtained from this procedure-still rosetted with 50 nm MicroBe ads-can then be subjected to further positive or negative selection using e ither streptavidin M280 or anti-rat M450 Dynabeads, without the need for pr ior bead removal, since the strength of the magnetic field of the Dynal sep arator is sufficient to attract the larger Dynabeads but not the MicroBeads . Here, we show that this system can be used to isolate a number of cell ty pes including very rare target cell populations such as haemopoietic stem c ells, using two different surface markers without perturbing subsequent fun ctional capacity. (C) 1999 Elsevier Science B.V. All rights reserved.