Multiple laser wavelengths are used in order to increase the amount or type of information that can be detected from the cell sample. The more laser wavelengths the cytometer is equipped with, the more fluorescence colors, and thereby more cellular properties of the sample can be characterized simultaneously.
The laser beams in a flow cytometer are often formed into a stack of light sheets with highly elliptical or top-hat shaped intensity cross-sections, in order to make sure that every cell is illuminated with the same light intensity, even if they do not hit the laser beam at exactly same position. This is important for the instrument’s CV (coefficient of variation) value, which is a measure of repeatability and reliability, and how small or dim cell populations can be resolved. Other important laser parameters for highest cytometer performance include; low intensity noise, stable power and beam pointing and perfect beam quality.
Flow cytometry is an important tool in hematology and immunology and has allowed detailed studies of the dozens of cells types that make up the immune system. This is possible by using antibodies targeted against specific protein receptors on the cell surfaces. When the antibodies are coupled to a fluorescence label tag they can be detected on the cell surface when illuminated with the specific laser wavelength and thereby enabling rapid diagnosis of various autoimmune and disease conditions. There are also fluorescence sensors that can measure cell membrane integrity, electric potential, mitochondrial function and calcium concentration. Other labels, such as fluorescent proteins, can be used to detect the gene expression in cells. Other applications of cytometry technology include virology, stem cell therapy, sperm sorting, plant biology and marine biology.