Plasma nucleosomes, DNA, LDH, MPO, and S100A8/A9 are markers of acute TMAs. (A-F) Analysis of plasma samples of the learning cohort including healthy controls (Ctrl; n = 10) and from patients with acquired TTP (n = 6), D+HUS (n = 4), tumor-associated TMA (Tumor; n = 8), and TMAs that are not otherwise specified ([NOS]; n = 11). (A) Quantification of nucleosomes by ELISA. Quantification of DNA by a fluorescent DNA probe (B) and LDH activity using a chromogenic substrate (C). (D) Quantification of myeloperoxidase by ELISA, a marker of granules in neutrophils and monocytes. (E) Quantification of S100A8/A9, a cytosolic protein complex present in neutrophils. (F) Correlation of DNA with MPO and S100A8/A9 in plasma from TMA patients and healthy controls. The symbol color indicates the level of S100A8/A9 compared with healthy controls. In most patients with acute TMA, all 3 markers were elevated, indicating that inflammation, and neutrophils, monocytes, or both contributed to the release of nucleosomes in acute TMA. (G-J) Comparison of DNA (G), LDH (H), MPO (I), and S100A8/A9 (J) in plasma from 5 patients with acquired TTP collected at presentation with acute disease (Acute) or in remission (Remission). All 4 markers were elevated in acute disease and normalized in remission, indicating that they reflect disease activity in TMA patients. Shaded area indicates the range of nucleosomes, DNA, LDH, MPO, or S100A8/A9 in plasma from healthy controls (*P < .05, **P < .01,***P < .001).