Abstract
Thrombomodulin (TM) is a surface glycoprotein that forms a stoichiometric complex with thrombin thereby serving as a natural anticoagulant on endothelium of arteries, veins, capillaries, and lymphatics. Recently, it was shown that monocytes and macrophages express TM in vitro (McCachren et al, 1991). We here studied immunohistochemical expression of TM on inflammatory exudating cells in granulomatous inflammation. Tissue sections from sarcoidosis were reacted with anti-human recombinant TM polyclonal rabbit antiserum, and stained with avidin-biotin peroxidase complex immunohistochemistry or indirect immunofluorescence techniques. Results clearly showed that a subpopulation of CD11b-positive monocytic histiocytes infiltrating into the tissue is TM-positive. The TM-positive inflammatory cells are round, cuboidal and dendritic in cell morphology and they surround the granulomas but not observed in the center of organized granulomas where lysozyme-positive and CD68-positive epithelioid and multinucleated cells were accumulated. The results indicate that TM is potentially a unique and useful immunomarker of monocytic histiocytes particularly in the study of chronic granulomatous inflammation.
