Different topographical distribution of fibrin on ATRA-treated NB4 cells undergoing apoptosis and ETosis. (A) On the third day of ATRA treatment, NB4 cells undergoing ETosis were stained with lactadherin (Lact; green) and PI (red). Decondensed extracellular chromatin could be seen enclosed by a thin layer of membrane (arrowhead) or spilled out of the ruptured cell (arrow). (B) Fibrin deposited on the diffuse decondensed chromatin within the bubble and also along the thin membrane around the bubble (arrowhead) and on the remaining broken cell membrane (arrow), similar to the binding sites for lactadherin. (C) On day 5, ATRA treatment led to diffuse rim staining by lactadherin on most cells undergoing early apoptosis (arrowhead). Late apoptotic cells stained with lactadherin and had condensed nuclei stained with PI (arrow). (D) Fibrin deposited at the same position as condensed chromatin inside the apoptotic cells (arrow) and also colocalized with externalized PS on the membrane that could be identified by strong staining with lactadherin (arrowhead). (E) FXa (red) and FVa (green) had patchy coherent distributions that overlapped on apoptotic NB4 cell membrane (arrow). FVa staining was observed on the thin membrane around ETs releasing cells (arrowhead). (F) A large amount of fibrin (red) strands deposited on the adjacent late apoptotic APL cells (arrow) and formed a net of fibrin (arrowhead). Representative images of 6 independent experiments are shown. Bars represent 10 μm in panels A, C, E; 20 μm in panels B, D, F.