Optimal detection of apoptosis by flow cytometry depends on cell morphology

Flow cytometry has recently become a choice technique for the quantitative analysis of apoptosis. Monoparametric DNA analysis usually allows identification of apoptotic cells as a “subdiploid” peak. Progression through apoptosis leads to chromatin condensation, nuclear fragmentation and eventually to cell disruption. Thus, a major problem for the flow cytometric analysis of apoptotic populations is discrimination between debris and apoptotic cells. Here we demonstrate that the best parameter on which to make such a distinction is the DNA content, no matter what type of cell is studied. In contrast, discrimination between apoptotic, non‐apoptotic cells, and debris is possible on the basis of scattering signals only in few selected cases, depending on the morphology of the intact cells. © 1993 Wiley‐Liss, Inc.