When cells are threatened, for example by viral infection, special sensors are activated to kick-start the immune system. Now, new genetic techniques are increasing our knowledge about how this response mechanism actually unfolds.
The genetic material of more biologically advanced organisms, such as humans, is normally to be found in the cell nucleus and the mitochondria (membrane-bounded organelles). Therefore, DNA found in the surrounding cytoplasm is likely to be due to nucleus or mitochondria damage or the result of bacterial or viral infection.