Comparison of cytofluorometric methods for quantifying apoptotic cells.

B-CLL cells were subjected to one of the 4 assays for apoptosis quantitation after incubation for 48 hours in CM and ECCM. (A, B) Gate R1 was drawn around apoptotic cells, which can be distinguished from living cells through their decreased FSC and increased SSC characteristics. (C, D) The upper left quadrant (annexin-V⁺/PI⁻) represents the early apoptotic cells, and the upper right quadrant (annexin-V⁺/PI) contains the late apoptotic cells. M1 defines the percentages of B-CLL cells with hypodiploid DNA content (E, F) and TUNEL⁺ signal (G, H). Dotted lines show control staining. Numbers at the top of each cytogram represent the percentages of apoptotic cells. Data are representative of 5 experiments.