Neutrophils contribute to cerebral thrombosis in experimental thromboinflammation and exhibit enhanced extracellular DNA activity. Schematic representation of neutrophil transfer from donor control and STM into neutropenic ANS recipient STM followed by light/dye-induced thrombosis (A1-3) time of flow cessation was quantified in cerebral arterioles (B) and venules (C). (D) Cerebral microvessels were analyzed after DNase (2000 U) treatment (n = 4-6 mice/group). (E) Plasma levels of circulating annexin A1 (n = 6 each) were also determined in control mice and STM. (F) NE DNA complex (NE-DNA) levels were determined by ELISA in plasma from saline (vehicle) and AnxA1_Ac2-26-treated mice (n = 12 saline-treated and n = 6 AnxA1_Ac2-26–treated control and STM). Two values for control-AnxA1_Ac2-26 and 1 value for STM-AnxA1_Ac2-26 were under detectable levels and are not included. (G) Percentage of histone H3 (H3Cit⁺)–positive unstimulated (n = 10 [1 outlier removed]; n = 10 STM [1 outlier removed]) and ionomycin-stimulated (n = 10 control; n = 7 STM; 4 µM) neutrophils. Data are as means ± SEM from independent experiments. *P < .05; **P < .01 vs control mice. ^#P < .05; ^###P < .001 vs STM. ^@@P < .01 vs unstimulated STM neutrophils. ^$P < .05 vs stimulated STM neutrophils. ^ØP < .05 vs STM+ANS. ^ΦP < .05 vs STM+ANS+ control neutrophils.