Gross hemorrhage in Mx⁺fII^lox/− mice after Cre-mediated recombination of the fII^lox allele. (A) Normal brain in a control mouse. (B,C) Dural-based hemorrhage in Mx⁺fII^lox/− animals after administration of poly I:C. CNS hemorrhage was observed in dural, ventricular, and parenchymal areas of poly I:C-treated Mx⁺fII^lox/− mice. Additional sites of hemorrhage after recombination of the fII^lox allele include thigh (D), testes (E), and skin (F). Mx⁺fII^lox/− treated with poly I:C would often have multiple sites of subcutaneous hemorrhage in addition to other more life-threatening areas of hemorrhage.