Contact activation in vivo and treatment with HKH20. Mice were injected subcutaneously in the neck with 2 × 10⁷ CFU S pyogenes bacteria, plasma was collected at 0, 4, 6, 10, 12, 18, 24, and 42 hours after infection (n = 2-6/group), and aPTT (A) and PT (B) were measured immediately. *P < .05; ***P < .001. (C) Scanning electron microscopy of representative mouse lung tissue sections is shown. Mice were injected subcutaneously with 2 × 10⁷ CFU S pyogenes and treated intraperitoneally 8 hours after infection with 200 μg HKH20 (C) or 100 μL PBS (D). Lungs were taken 18 hours after infection. Bar represents 100 μm.