Based on the recently proposed correlation between circulating nucleosomes, granulocyte activation and ETosis, MPO-DNA or elastase–DNA complexes content in serum was measured as an indirect marker of in vivo ET formation.31, 32 We found that the elevated ET release in treated APL cells was paralleled by an increased abundance of plasma elastase–DNA complexes (Figure 3b), which was also seen in APL patients in comparison with healthy controls (data not shown). Here, MPO is linked to acute promyelocytic leukemia.