NETs in VITT patient cerebral sinus vein thrombi. (A) Cell-free DNA serum levels of VITT patients and controls using fluorescent DNA-intercalating dye Sytox Green. Statistical comparison by unpaired Student t test; (B) Serum citrullinated histone H3 (CitH3) levels in VITT patients and healthy controls measured by ELISA. Statistical comparison by unpaired Student t test; (C) Serum MPO levels in VITT patients and healthy controls quantified using an ELISA. Mann-Whitney nonparametric test compared the 2 groups. (D) Hematoxylin and eosin (H&E) stained histologic section of a cerebral venous sinus thrombus of a VITT patient. Arrows indicate amorphous fibrin (green) and granulocyte-rich areas (white) in the thrombus core, respectively (E-J). Immunohistochemistry images of the VITT patient cerebral sinus vein thrombus shown in panel A. The section assessed in more detail in panels C, E, and G are given as small rectangles in panels B, D, and F. Markers for NETs and neutrophils include NE (red) in panels E and F, and MPO (red) in panels G and H. Von Willebrand factor (vWF, red) is shown in panels I and J for comparison. DAPI stains DNA in blue while chromatin (antihistone H2A/H2B/DNA-complexes) is shown in green.