Fig. 2

Homotypic and heterotypic cell-cell fusion. Physiological homotypic cell-cell fusion is characterised by a highly efficient fusion frequency and the generation of multiple syncytia, which is most likely attributed to a high number of cells in a pro-fusogenic state (A). However, it is also possible that pro-fusogenic cells fuse with non-fusogenic cells in a homotypic manner. Heterotypic cell-cell fusion is different since it remains unclear, which cells provide fusogens and exhibit further fusion relevant properties (B). A pro-fusogenic cell fuses with a cell in a non-fusogenic state, which only expresses cognate receptors and phosphatidylserine (PS) (adapted from [166])