Common Methods for Measuring Apoptotic Cell Death by Flow Cytometry

Apoptosis is a finely tuned mechanism for the control of cell number in eukariotes. The process is operative during embryo-genesis, in tumor regression and in the control of immune response1. In some cases, it consists in an ordered sequence of cellular events that start with the transcription of specific genomic sequences, synthesis of specific proteins, and activation of nucleases that cut DNA in the oligonucleosomal subunits. In other models the interaction of specific molecules with a widely expressed “death receptor” (Fas/Apo-1, CD95) activates a family of cysteine proteases (caspases) which are the executors of the apoptotic dissolution of the cell. The ordered series of events which characterize apoptotic death are paralleled by specific morphological changes in both the cell nucleus and cytoplasm (Fig. 1). Extensive literature exists regarding molecular, biochemical and morphological changes that occur during apoptosis (for review ref.2+)