Type 1 IFN signaling mediates the activation of coagulation cascades in endotoxemia. (A-D) WT and IFN-α/βR1 KO mice were administered LPS intraperitoneally (4 mg/kg) for 6 hours. Heparin (200 IU/kg) was injected subcutaneously 30 minutes before LPS injection. (A) Representative SD-IVM images of thrombin generation (green), platelet aggregation (blue), fibrin deposition (dark red), and albumin (red) within the liver microvasculature or representative multiphoton microscopy images of albumin (red) within lung microvasculature. AF647-albumin (red) was represented as a contrast material to identify perfused vessels; the occluded vessels exhibited weak fluorescent signals. Quantitative analysis was conducted of thrombin and platelets (B), occluded vessels (C), and fibrin deposition (D) within the liver microcirculation by using ImageJ software. (E-H) Mice were primed with 0.4 mg/kg of LPS for 7 hours and then challenged with 10 mg/kg of LPS for 8 hours. (E) Representative images of hematoxylin and eosin and immunohistochemical staining of fibrin in livers and lungs of WT mice vs IFN-α/βR1 KO mice (400×). The black arrow indicates thrombus in liver and lung capillaries from WT mice challenged with LPS. (F) Plasma levels of TAT complexes, PAI-1, fibrinogen (Fib), and D-dimer were detected in WT mice vs IFN-α/βR1 KO mice. (G) Time course of thrombocytopenia in WT mice vs IFN-α/βR1 KO mice after administration of 10 mg/kg of LPS treated at time 0, 8, and 14 hours. (H) Kaplan-Meier survival plots for WT mice vs IFN-α/βR1 KO mice treated with saline or LPS or LPS plus heparin (n = 11 mice per group). (I) Representative images of FeCl₃-induced mesenteric arteriole thrombosis in WT mice and IFN-α/βR1 KO mice (left). Occlusion time of the mesenteric arteriole was analyzed (right). All data are shown as mean ± standard error of the mean. *P < .05; **P < .01; ***P < .001. N = 3 to 11 mice per group. Scale bar, 50 μm. NS, not significant.