Glossary
Apoptosis – Programmed cell death through various tightly regulated biological pathways.
Antibody – A specialized protein of the immune system that can identify and neutralize specific targets called antigens.
Area – The integral of the pulse.
Autofluorescence – Natural levels of fluorescence found within cells due to the presence of fluorescent compounds.
Backgating – A useful gating control to ensure you have identified the right cell population using traditional gating.
Band pass filter - Allow light through within a specified narrow range.
Cell sorting – The ability to separate cells, identified by specified characteristics, within droplets using an electrical charge.
Compensation – Mathematical algorithm for removing fluorescence spillover of one fluorophore into multiple detectors.
Doublets – Where two particles pass through the laser at the interrogation point.
Drop delay – The time between the interrogation and the point where a droplet breaks off during cell sorting.
Event – Any particle which generates enough signal when it passes through the laser to be recorded as a signal or pulse.
Fc receptors – Antibody receptors on certain cells which bind antibodies via their constant region to elicit immune responses.
Fixation – Crosslinking of cellular proteins to preserve from decay and allow permeabilization without loss of cell contents and structure for intracellular staining.
Forward scatter – Light that is scattered in the forward direction (up to 20o) after interacting with a particle.
Flow cytometer – Instrument which allows the measurement of properties of individual particles as they pass through a laser.
Fluorescence minus one control – Specific control, where one fluorophore is removed from the staining panel, to account for fluorescence spread.
Fluorescent protein – A protein which can accept light energy and re-emit at longer wavelengths and can be expressed in cells for live marking.
Fluorophore – Fluorescent markers that accept light energy at a given wavelength and re-emit at a longer wavelength.
Gating – Placing of regions around populations of cells with common characteristics to quantify and further investigate.
Height – The maximum amount of current output by the PMT of the pulse.
Histograms – Plots which display a single measurement parameter.
Hydrodynamic focusing – A faster outer sheath fluid around the sample stream allows narrowing of the stream creating a stream of single cells.
Immunophenotyping – Identification of cells in a population through the staining and identification of specific markers.
Instrument configuration – The set-up of lasers, optics and filters contained within the cytometer.
Isotype controls – Antibodies raised against an antigen not found on the cell being analyzed to help determine specific antibody binding.
Laser – A device that emits optically amplified light at a single wavelength.
Long pass filter – Allow light through above a certain wavelength.
Maximal emission – The wavelength at which a fluorophore emits the most photons.
Maximal excitation – The wavelength at which a fluorophore is excited by the most photons.
Parameter – The measurement from any given detector which can be displayed in height, area or width.
Photo multiplier tube - A photoemissive detection device in which the absorption of a photon results in the emission of an electron.
Permeabilization – Creation of holes in the cell membrane using detergents to allow large molecules (such as antibodies) to enter the cell for intracellular staining.
Resolution – The ability to separate a positive from a negative population.
Short pass filter - Allow light through below a certain wavelength.
Side scatter – Light that is scattered at 90o after interacting with a particle.
Spillover – The overlap of one fluorophore emission spectra with another.
Spread – The increase in a population’s fluorescence into another channel after compensation.
Stain index – The point where there is maximal separation between the positive and negative population on stained samples.
Stokes Shift – The difference between the maximal excitation and emission wavelengths of a fluorescent molecule.
Tandem dye – A fluorescent dye which is two molecules covalently coupled together.
Threshold – Signal intensity below which the flow cytometer does not record an event.
Titration – Dilution of an antibody to the concentration at which there is an optimal stain index.
Viability dye – Dye which allows identification of dead cells through a reduction in cell membrane integrity.
Width – The time interval during which the pulse occurs.