Antibodies coating paramagnetic beads will bind to antigens present on the surface of cells thus capturing the cells and facilitate the concentration of these bead-attached cells. The concentration process is created by a magnet placed on the side of the test tube bringing the beads to it.
MACS systems (Magnetic Cell Separation system):
Through the usage of smaller super paramagnetic beads (<100 nm), which requires a stronger magnetic field to separate cells. Cells are labeled with primary antibodies and then MACS beads are coated with specific- specific antibodies. These labeled cell suspension is then put into a separation column in a strong magnetic field. The labeled cells are contained, magnetized, while in the magnetic field and the unlabeled cells are suspended, un-magnetized, to be collected. Once removed from magnetic field positive cells are eluted. These MACS beads are then incorporated by the cells allowing them to remain in the column because they do not intrude with the cell attachment to the culture surface to cell-cell interactions. A bead removal reagent is then applied to have an enzymatically release of the MACS beads allowing those cells to become relabeled with some other marker, which then is sorted.