What is flow cytometry?
Flow cytometry is sometimes just called flow, or FACS (Flourescence Activated Cell Sorting), or Flow cytofluorometry, or flow cytometric analysis. Basically they all refer to the same technique – and that is, placing cells in a laminar flow so that they can be rapidly run through an investigative process in a single cell suspension. The investigative process involves hitting the cells with two or more lasers and translating those events into a digital record (an FCS file) which can be manipulated later in software programs such as FlowJo. Metric criteria can be cell size, cell granularity, cell contents (e.g. DNA, intracellular protiens), levels of specific cell surface receptors, and signaling events.
The primary objective in flow cytometry is identify cell subpopulations. Initially, the objective is just to differentiate cell types: CD4 T cells, CD8 T cells, dendritic cells, macrophages, neutrophils, etc. Then the challenge becomes to define subpopulations within those cell types.
What are they displaying on their cell surface?
What is their activation state?
Are these cells living or dead?
Are they dividing?
What will be the fate of these cells?
These are just a few of the questions that you can start to ask
through flow cytometry. Hence, it is a vital tool in the study of
Immunology since one of the hardest mysteries to unravel is just
who is doing what and when during the immune response.