Fluorescence-activated cell sorting separates and collects individual cells from a mixed population based on light scattering and fluorescent labeling measured by flow cytometry.
Explanation
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FACS is a type of flow cytometry that physically separates cells based on characteristics detected by lasers. In this system, cells suspended in a stream of fluid pass one at a time through a laser beam. Detectors measure forward and side light scatter along with fluorescence emitted from antibodies or dyes attached to cell markers. Each event is processed in real time, and when a cell matches a preset signal pattern, an electrical charge is applied to the droplet containing that cell. Charged plates then deflect the droplet into a collection tube for isolation. This process can sort thousands of cells per second while maintaining viability. The method is routinely used to purify specific immune cell populations, isolate stem cells for experimental use and analyse heterogeneous tumour samples. In contrast to standard flow cytometry, which only measures cells, FACS adds the ability to collect selected cells for downstream applications.
ace markers, to isolate stem cells for transplantation and to study heterogeneous tumor samples. Unlike standard flow cytometry, which only analyzes cells, FACS adds the sorting capability, making it a valuable tool for experiments that require purified cells.
Research applications and key facts
Researchers often use FACS to isolate T lymphocytes, B lymphocytes or hematopoietic stem cells based on combinations of CD markers. For example, in immunology studies, fluorescent antibodies targeting CD4 and CD8 allow separation of helper and cytotoxic T cells. In cancer biology, FACS can sort tumor cells expressing specific oncogenic proteins from non-malignant cells. The technique can also enrich rare cell populations, such as circulating tumor cells, by capturing cells that express epithelial markers. Sorting speeds can exceed ten thousand cells per second, and sorting purity can reach above ninety per cent under optimal conditions. However, sorting requires careful instrument calibration and may subject cells to stress from pressure and sheath fluid. Despite these considerations, FACS remains one of the most precise methods for obtaining defined cell populations for downstream assays such as RNA sequencing, proteomics or functional assays.
FACS refers both to the technology and to the instruments that perform this type of sorting. It has transformed cell biology by enabling the isolation of specific cells from complex mixtures. Because it combines analysis and physical separation, FACS will continue to be a core technique in biomedical research.
Related Terms: Flow cytometry, Fluorescence microscope, Immunophenotyping, Cell sorting, Cytometry