Flow cytometry is one of the most important tools in many scientific fields, including immunology. The ability to stain populations of cells and quantify these populations in a few hours has revolutionized the field of immunology. The identification of the complexity of the immune system is due in part to flow cytometry.
Besides labeling cells with various cell markers in order to identify the cells present in your sample, cells can also be labeled with carboxy-fluorescein diacetate, succimidyl ester, or CFSE, a small fluorescent dye. Although colorless outside of the cell, once a cellular esterase activates this compound, it will label your cells several logs above your control (brightness has been shown to be cell type specific). This dye is very photostable and thus allows for long term studies of cell proliferation, usually in the context of immunological cell activate (i.e., T cell proliferation after TCR receptor activation, etc.). Once the fluorescently labeled cells are manipulated and cultured (or put back into an animal), the fluorescent intensity will be diluted by approximately one half every time the cell divides, since two cells are now labeled instead of one. Several cell divisions can be observed in this assay (Some labs have seen up to eight generations).
Using this kit in our lab, we were able to measure cell proliferation easily without prior experience with the assay. We were only interested in a shorter time frame of 4 generations and did not try for the higher end of 8 generations. The reproducibility of ours results has been very robust. While the individual aliquots help keep our experiments straightforward and reproducible, they also add some cost to the assay. Our lab does not regularly perform cell proliferation experiments, but labs that do would be better off purchasing larger quantities of CFSE and troubleshooting the protocol with fresh solutions for each experiment.
Overall, this assay is robust and extremely straightforward. Until other companies turn to developing competing kits, Invitrogen’s kit is the only option, and it is well worth the money for most labs.