Immunohistochemical Demonstration of the Reticuloendothelial Clearance of Circulating Fibrin Aggregates

In rabbits given an intravenous infusion of thrombin or an injection of endotoxin, immunohistochemical examination of the tissues, using conjugated antiserum against rabbit fibrin, showed bright intracytoplasmic staining in many of the phagocytic cells of the liver and spleen. In normal rabbits as well as in animals injected with large doses of heparin prior to thrombin or endotoxin administration, no such intracellular staining was observed. The findings of this study substantiate the hypothesis that fibrin aggregates formed in the circulating blood during low grade intravascular coagulation are largely removed by the reticuloendothelial system.