Detection of dead cells and measurement of cell killing by flow cytometry.

A flow cytometer can quickly perform numerous quantitative, sensitive measurements on each individual cell within a large, heterogeneous population. The modern commercially available analytical instruments, which can be found in most hospitals, pathology laboratories, and cell biology research laboratories in the industrially developed countries, can now routinely measure fluorescence simultaneously at four different wavelengths, in addition to light scatter in two directions, at rates of thousands of cells per second. Thus, flow cytometry provides a powerful and versatile approach to the measurement of cell death and cell killing. However, it is important to stress that the biological nature of the phenomenon under investigation will determine which assay is appropriate, and at what stage in the process of cell killing it should be applied. This consideration is particularly important in the study of drug- or cell-mediated cytotoxicity.