Method for separating cells

1. A method for separating a first population of cells from a second population of cells in a sample comprising:

linking dense particles to the first population of cells in the sample;

layering the sample over a density separation medium (DSM) having a density at least about 0.001 g/cm 3 greater than the mean density of the second population of cells;

allowing the cells to settle,

wherein the particle-linked first population of cells having a density that is greater than the density of the DSM settles to below the interface between the DSM and the sample and the second population of cells settles to the interface between the DSM and the sample; and

recovering the second population of cells from the interface between the DSM and the sample, and/or recovering the first population of cells from below the interface between the DSM and the sample.

2. The method according to claim 1 , comprising recovering the second population of cells from the interference between the DSM and the sample.

3. The method according to claim 2 , wherein the second population of cells is selected from the group consisting of T cells, B cells, basophils, Natural Killer (NK) cells, dendritic cells, monocytes, macrophages, megakaryocytes, platelets, eosinophils, neutrophils, hematopoletic stems cells, mesenchymal stem cells, endothelial cells, epithelial cells, fibroblasts and tumour cells.

4. The method according to claim 1 , comprising recovering the first population of cells from below the interface between the DSM and the sample.

5. The method according to claim 4 , comprising removing the dense particles from the first population of cells.

6. The method according to claim 4 , wherein the first population of cells is selected from the group consisting of T cells, B cells, basophils, NK cells, dendritic cells, monocytes, macrophages, megakaryocytes, platelets, eosinophils, neutrophils, hematopoietic stem cells, mesenchymal stem cells, endothelial cells, epithelial cells, fibroblasts and tumour cells.

7. The method according to claim 1 , wherein the settling is accelerated by centrifugation.

8. The method according to claim 1 , wherein the dense particles are selected from the group consisting of red blood cells, silica particles, metal particles, metal oxide particles, polymer particles and glass particles.

9. The method according to claim 8 , wherein the dense particles are selected from the group consisting of red blood cells and silica particles.

10. The method according to claim 1 , wherein the osmolarity of the DSM is approximately the same as the osmolarity of the sample.

11. The method according to claim 1 , wherein the osmolarity of the DSM is about 270 to about 300 mOsm.

12. The method according to claim 1 , wherein the first population of cells are linked to the dense particles by drug-drug receptor, antibody-antigen, hormone-hormone receptor, growth factor-growth factor receptor, carbohydrate-lectin, nucleic acid sequence-complementary nucleic acid sequence, enzyme-cofactor or enzyme-inhibitor binding.

13. The method according to claim 1 , wherein the first population of cells have specific surface proteins and the dense particles are linked to these cells by antibodies specific for the cell surface proteins.

14. The method according to claim 1 , wherein the density separation medium (DSM) has a density at least about 0.002 g/cm 3 greater than the mean density of the second population of cells.

15. The method according to claim 1 , wherein the density separation medium (DSM) has a density at least about 0.004 g/cm 3 greater than the mean density of the second population of cells.