Flow cytometry

Flow cytometry measures physical and fluorescent properties of individual cells or particles as they pass through a focused light beam, enabling rapid analysis of mixed populations.

Hydrodynamic focusing: A fluid-flow technique that confines a sample stream within a surrounding sheath fluid. It lines cells up so they pass the interrogation point individually.
Fluorescence: Light emitted by a substance after it absorbs photons, usually at a longer wavelength. Fluorescent labels make otherwise invisible cell features measurable.
Complete blood count: A laboratory test that measures blood-cell counts and related indices. Automated blood analyzers use flow-based optical measurements to classify cells.
Immunohistochemistry: A tissue-staining method that uses antibodies to reveal specific antigens in their spatial context. Unlike flow cytometry, it preserves where markers occur within tissue architecture.
Laser-induced fluorescence: Light emitted by a substance after it absorbs energy from a laser. Fluorophores on cells emit signals that reveal selected molecular features.
Fluorophore: A molecule or molecular group that absorbs light and emits fluorescence. Each fluorophore supplies a signal tied to a chosen cellular target.
CD4 count: A measurement of CD4-positive T lymphocytes in blood, used to assess immune status. Flow cytometry can quantify these cells in HIV care and immune monitoring.
Fluorescence microscopy: Microscopy that forms images from fluorescent light emitted by labeled specimens. It reveals spatial structure, while flow cytometry rapidly measures suspended events.
Forward scatter: Light scattered at small angles in the forward direction by a particle in an optical instrument. Its signal is commonly used as an approximate indicator of cell size.
Monoclonal antibody: An antibody population produced from one cell clone and directed against a single epitope. Fluorescently labeled antibodies identify specific cell-surface or intracellular markers.

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