As labeled cells divide, their intracellular fluorescent material is distributed between daughter cells, producing an approximately twofold reduction in fluorescence with each generation. Flow cytometry can therefore separate successive intensity levels and associate them with division history. This makes it possible to distinguish cells that have remained undivided from populations that have undergone multiple rounds of proliferation.
The dye forms stable fluorescent bonds with intracellular proteins after entering the cell. That retention preserves a measurable signal as cells progress through division, while the signal is apportioned between daughter cells. Without a persistent intracellular label, fluorescence would provide less reliable information about successive generations and the extent of proliferation in rapidly dividing populations.
CFSE analysis can indicate both the proportion of cells that respond and the number of divisions completed by those cells. These are different aspects of proliferation: one describes the size of the responding fraction, while the other describes its division history. Together, they provide a more detailed view of cellular responses than a simple activated-versus-inactive classification.
A typical workflow labels the cell population with CFSE, allows the cells to undergo the experimental condition being studied, and then measures fluorescence by flow cytometry. The resulting fluorescence distribution is interpreted as successive cellular generations. This workflow enables investigators to quantify responding cells and determine how many divisions occurred during the assay.
In antigen-specific studies, the assay can reveal whether a lymphocyte population responds to the antigen being examined and how extensively the responding cells divide. Measuring both response frequency and division number helps characterize the strength of the cellular immune response. This supports investigations of immune function and disease mechanisms in medicine.
The method allows investigators to compare lymphocyte proliferation under conditions involving immunosuppressive treatments or cellular therapies. Changes in the fraction of responding cells or in their division history provide quantitative evidence of altered cellular behavior. These measurements support therapeutic development by showing whether an intervention modifies immune activation or the performance of relevant cell populations.