I notice a brief flurry of questions on annexinV staining and whether it is "early" or "late". We showed (Cell Death and Diff. 1999, vol6, 624) that it precedes (only just) DNA fragmentation in thymocytes treated with three different agents to induce apoptosis with different kinetics (thapsigargin, gliotoxin and dexamethasone). I would not rate this as an "early" event in apoptosis. We also report in the same paper that necrosis can lead to PS(+)PI(-) cells (I'm talking a large population - 32%). In fact the FACS profile at 1 hr when treated with the necrosis inducer was the same as the FACS profile at 6 hrs of the same cells treated with dex! I would not use Annexin V staining (even with PI) as a primary assay for apoptosis hope this is some help Paul Waring NHMRC Senior Research Fellow Chemistry, The faculties ANU, Australia.
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