Mast cells are augmented in deep vein thrombosis and express a profibrinolytic phenotype

A number of recent data suggest that mast cells (MC) and their products are involved in the pathophysiology of thrombosis. In the current study, we ha ve evaluated the number, distribution, and phenotype of MC in patients with deep vein thrombosis of the lower limb (DVT) (n = 15). Contralateral nonth rombosed limb veins served as control (CO). MC were examined by Giemsa stai ning and by immunohistochemistry using antibodies against tryptase, chymase , tissue-type plasminogen activator (tPA), urokinase (uPA), urokinase recep tor (uPAR), and plasminogen activator inhibitors (PAI-1, PAI-2). We found a n increase in the number of tryptase-positive MC in DVT compared with CO (D VT: 9.1 +/- 1.0 v CO: 4.7 +/- 0.6 MC/mm(2) P <.05). Most of these MC appear ed to accumulate in the adventitia of the thrombosed veins, in vicinity of the vasa vasorum. In both DVT and CO, MC reacted with monoclonal antibodies to c-kit, tryptase, and chymase. MC also stained positive for tPA and urok inase receptor, but did not express detectable PAI-1 or PAI-2. As compared with CO, a decreased proportion of MC in DVT was found to stain positive fo r chymase and tPA. Together, our results show that MC increase in number in DVT and express a profibrinolytic phenotype. We hypothesize that MC and MC -derived profibrinolytic molecules play a role in the pathophysiology of DV T. HUM PATHOL 30:188-194. Copyright (C), 1999 by W.B. Saunders Company.