Flow cytometric analysis of SmANX 18 or annexin A5 staining. (a) Representative dot plots of double-stained Jurkat apoptotic cells were assayed by FITC-annexin 18/PI or FITC-annexin A5/PI binding. (b) The double-parameter apoptotic cell scatter diagram of RAW264.7 cells was evaluated by FITC-annexin 18/PI or FITC-annexin A5/PI binding. Ten thousand events were collected for each histogram. The bottom left region of each quadrant (Q4) shows normal living cells, which exclude PI and are negative for FITC-annexin 18 (or A5) binding. The bottom right region (Q3) represents the early apoptotic cells, FITC-annexin 18 (or A5)-positive and PI-negative, demonstrating cytoplasmic membrane integrity. The top right region (Q2) contains necrotic or late apoptotic cells, both positive for FITC-annexin 18 (or A5) binding and PI. The top left region (Q1) may be cell fragments without a cell membrane or dead cells caused by other reasons.