Cell sorting separates different types of cells from a mixed sample. This process isolates specific cell populations based on their unique characteristics. Its purpose is to obtain pure groups of cells for various studies and applications. Cell sorting is a tool in many biological disciplines, enabling a clearer understanding of cellular functions and behaviors.
What is Cell Sorting
Cell sorting isolates specific cell populations from a heterogeneous mixture, such as blood, tissue, or cell cultures. Researchers separate cells to reduce experimental complexity and attribute observed effects to a particular cell type. For instance, a bone marrow extract contains various immune cells, but research might only require a specific type, like B-cells, identifiable by markers such as CD19/CD20.
Obtaining pure populations of cells is beneficial for accurate analysis and detailed studies. This isolation allows for molecular analysis, including RNA expression and epigenetic studies of a single cell type. Pure cells can also be genetically modified and expanded for disease modeling or cell therapy research, such as T-cell therapy.
How Cell Sorting Works
Cell sorting distinguishes cells based on their physical or biological properties. Cells can be separated by differences in size, morphology, density, or viability. These physical attributes allow for initial discrimination among various cell types within a sample.
Cells can also be identified and isolated based on biological differences, such as the expression of specific surface markers or intracellular proteins. Fluorescent tags or antibody-coated magnetic beads are used to label target cells, enabling their separation from unwanted cells.
Major Cell Sorting Technologies
Fluorescence-Activated Cell Sorting (FACS) is a common technology that sorts cells based on their light scattering and fluorescent properties. In FACS, cells are first tagged with fluorescent antibodies that bind to specific proteins on their surface, or by using fluorescent proteins or dyes. The suspended cells then flow one by one through a laser beam, which excites the fluorescent tags. Detectors measure the emitted fluorescence, as well as forward-scattered light (indicating cell size) and side-scattered light (indicating granularity or internal complexity). Based on these measurements, an electronic system applies an electrical charge to droplets containing the desired cells, which are then deflected into separate collection containers by an electric field.
Magnetic-Activated Cell Sorting (MACS) uses magnetic beads to separate cells. This method involves coating magnetic particles with antibodies, lectins, or enzymes that specifically bind to surface markers of the target cells. Once the target cells are labeled with these magnetic beads, the solution is passed through a column placed within a strong magnetic field. Cells bound to the magnetic beads are retained in the column due to the magnetic force, while unlabeled cells flow through. After removing the magnetic field, the isolated, bead-carrying cells can be released and collected.
Where Cell Sorting is Used
Cell sorting has many applications across various scientific and medical fields. In biomedical research, it allows scientists to isolate specific cell populations, such as T cells and leukocytes from blood or tumor tissues, for in-depth study. This capability has led to advancements in understanding disease mechanisms, including the detailed characterization of tumor-infiltrating leukocytes in cancer.
The technique is also used in clinical diagnostics and therapeutic applications. Cell sorting can identify rare cell populations, like circulating tumor cells, for non-invasive diagnostic purposes, and assist in diagnosing conditions such as immunodeficiency disorders and leukemias. In therapeutic contexts, cell sorting helps in isolating stem cells for regenerative medicine, purifying immune cells for immunotherapy, and preparing cells for gene therapy methods targeting specific cell types.