Dead cells in freshly isolated lymph node cell suspensions lack apoptotic DNA fragmentation and hypodiploidy. A single-cell suspension was obtained from a lymph node (patient #2) by the grinding technique described in Materials and Methods. (A1) Forward scatter (FSC) analysis revealed two distinct cell populations, one composed of abnormally small lymphocytes with a size comparable to that of apoptotic cells,10 and one of normal-sized lymphocytes. (A2) The cell suspension contained 10.9% dead cells, gated in R1, permeable to 7-AAD and stainable with anti-CD45. (A3) Electronic gating on these cells revealed that they corresponded to the population of abnormally small apoptotic-like cells. Only 0.5% of these freshly isolated lymph node cells had an hypodiploid DNA content (B1) and no fragmented DNA was detected by gel electrophoresis (2 × 106 cells) (C1). By contrast, after 24-hour in vitro culture 23% of lymph node cells were hypodiploid (B2) and fragmented DNA could be revealed (C2).
