Method of separating cells from a sample
Rare cells are separated from a sample fluid by a positive selection or negative selection antibody by centrifuging in a tube containing a harvesting float. The harvesting float has an axial passage and a density to settle in the sample fluid and expand the layer of the target component. The positive selection antibody is preferably coupled to a particulate carrier, such as a microbead, to attach to the target component. The negative selection antibody forms a complex or conjugate with a contaminating component. In the positive separation, the particulate carrier is recovered in the axial passage of the float.
1. A method of separating at least one target component from a biological sample, said method comprising
a. placing said biological sample into a separation container, said separation container comprising
a focusing device, having an axial bore passage and being capable of vertical movement within said separation container upon centrifugation and a specific density
a set of selection microbeads having at least one target affinity binding agent bound to their surfaces, said at least one target affinity binding agent having a binding affinity for said at least one target component within said biological sample and
a negative selection binding agent having a binding affinity for a component other than said target component within said biological sample, such that a complex or conjugate is formed between said negative selection binding agent and said component other than said target component within said biological sample on contact with said biological sample, wherein the specific density of said focusing device is substantially equal to the density of said set of selection microbeads and the specific density of said complex or conjugate formed between said negative selection binding agent and said component other than said target component within said biological sample is different to that of said focusing device and said set of selection microbeads
b. centrifuging said separation container containing said biological sample to densitometrically separate components of said sample into layers such that separation of said set of selection microbeads and said complex or conjugate formed between said negative selection binding agent and said component other than said target component within said biological sample is induced, wherein an elongated target layer comprising said set of selection microbeads bound to said at least one target component is located within said axial bore passage of said focusing device and wherein said complex or conjugate formed between said negative selection binding agent and said component other than said target component within said biological sample is absent from said axial bore passage of said focusing device after centrifugation; and
c. aspirating said elongated target layer to remove said at least one target component from said separation container.
2. The method of claim 1 , further comprising mixing said biological sample with said set of selection microbeads and said negative selection binding agent prior to centrifugation.
3. The method of claim 2 , wherein said separation container is a cylindrical, closed-end tube with an inner surface, and said focusing device having an outer surface that complements said inner surface of said tube.
4. The method of claim 3 , wherein said biological sample is blood.
5. The method of claim 4 , wherein said focusing device comprises a single bore axial passage.
6. The method of claim 5 , wherein said selection microbeads have a density of between about 1.00 g/cc and about 1.06 g/cc.
7. The method of claim 6 , wherein said set of selection microbeads and said negative selection binding agent each comprise at least one antibody.
8. The method of claim 7 , wherein said negative selection binding agent binds to the surface of normal white blood cells.
9. The method of claim 7 , wherein said negative selection binding agent agglutinates white blood cells.
10. The method of claim 7 , wherein said negative selection binding binds white blood cells to red blood cells.
11. The method of claim 7 , wherein said negative selection binding agent comprises at least one leukocyte CD antibody.
12. The method of claim 7 , wherein said antibody of said set of selection microbeads binds to the surface of cells other than said normal white blood cells.
13. The method of claim 12 , wherein said cells other than normal white blood cells are selected from the group consisting of cancer cells and fetal cells.