Flow Cytometry

Flow cytometry analyzes a heterogeneous cell population such as white blood cells based on multiple parameters, like size and complexity.

When the suspension is loaded on a flow cytometer, the sheath fluid and vibrating nozzle form single-cell droplets that pass through a laser beam, scattering light in multiple directions.

The forward scatter measuring cell size, and the side scatter indicating cell complexity, are detected through different detector systems.

Plotting forward versus side scatter on a graph helps differentiate cell populations and their proportions in a sample. For instance, the forward and side scatter are higher for granulocytes, which are larger and more granular than lymphocytes.

Fluorescent activated cell sorter or FACS, a specialized flow cytometry, helps analyze and sort cells. It uses fluorescently tagged antibodies specific against certain cellular components -- such as CD4 or CD8 markers on T cells -- added to the sample.

An electrical charging ring adds a charge on single-cell droplets based on the fluorescent tag.

The electromagnets then use this charge to deflect different cell types into separate tubes.