Flow cytometry is a critical technology for both clinical medicine and basic research in the life sciences. Flow cytometers use lasers, hydrodynamically focused streams of single cells and photon detectors (usually photomultiplier tubes) to rapidly analyze large numbers of cells for a variety of physical characteristics.
The technology has allowed detailed study of immunology, characterizing the dozens of individual cell types that make up a normal immune system. This is possible through the use of monoclonal antibodies targeted against specific protein receptors on thesurface of immune cells; when the antibodies are coupled to fluorescent tags, they can be detected on the cell surface using the correct laser wavelength, enabling rapid diagnosis of a variety of autoimmune and disease conditions.
Thousands of fluorescent probes are available that, theoretically, could be used for flow cytometry. Some could be attached to antibodies and other proteins that can target specific markers on the cell surface. Others, including the expressible fluorescent proteins (such as GFP), could be used to detect gene expression in cells. Fluorescent sensors can be used to measure the health and function of a cell, including cell membrane integrity and electrical potential, mitochondrial function, calcium concentration and DNA content; all of these probes are important for basic cell biology studies.