Due to this covalent coupling reaction, fluorescent CFSE can be retained within cells for extremely long periods.

As CFDA-SE, which is non-fluorescent, enters the cytoplasm of cells, intracellular esterases remove the acetate groups and convert the molecule to the fluorescent ester.

CFSE was originally developed as a fluorescent dye that could be used to stably label lymphocytes and track their migration within animals for many months.

Thus CFSE represents an extremely valuable fluorescent dye for immunological studies, allowing lymphocyte proliferation, migration and positioning to be simultaneously monitored.

Since the initial description of CFSE it has been used in thousands of immunological studies, an example of an early proliferation study in animals being described by Kurts et al.[5] However, perhaps the most important CFSE investigations have been those demonstrating that many of the effector functions of lymphocytes, such as cytokine production by T lymphocytes,[6][7] and antibody class switching by B cells,[8] are division dependent.