Useful in a rapid staining method for identification of macrophages; counts by this method were confirmed by the more complex morphological criteria, by phagocytosis, and by the presence of Fc receptors. It is an inhibitor of Chymotrypsin and Trypsin. ,4 Dichloroisocoumarin also inhibits granzymes A, B, and H, cathepsin G, neutrophil elastase, proteinase and blocks apoptotic internucleosomal DNA cleavage in thymocytes without the involvement of endonucleases.