Deposition of cross-linked fibrin in tissues of hyperfibrinogenemic mice. Equivalent amounts (normalized to initial wet tissue weight) of the urea-insoluble fraction of tissue extracts from wild-type (wt), thrombomodulin-deficient (TMPro), and hyperfibrinogenemic mice (Hifib and Hifib/TMPro) were subjected to SDS-PAGE (sodium dodecyl sulfate–polyacrylamide gel electrophoresis), and the fibrin β-chain (arrows) was detected with fibrin-specific antibodies recognizing the neoepitope generated by thrombin-mediated fibrinopeptide B release. Each lane represents analysis of one organ from one mouse; 6 lanes per mouse strain shown. Total protein content loaded in each lane was roughly equivalent, as ascertained by Poinceau S staining of blots (not shown). Excess fibrin is found only in the spleen of Hifib mice and not in other organs, including liver. Mice with combined hyperfibrinogenemia and thrombomodulin-deficiency (Hifib/TMPro) show excess fibrin in the liver but not in the spleen or other organs (heart, lung, kidney, brain not shown).