Immunohistochemical localization of cathepsin G in human tissues

An antiserum to human cathepsin G has been raised in sheep and its reactivity with human tissues has been tested. The indirect immunoperoxidase staining sequence was employed and was applied to routinely processed paraffin sections. Mature granulocytes, especially those of the neutrophil variety, were intensely and consistently stained. Activity was not observed in other cell or tissue types. Many of the cells of acute and chronic myeloid leukemia were strongly stained, in contrast to those of acute lymphoblastic or chronic lymphocytic leukemias. The results of the technique are compared with those described with staining for muramidase (lysozyme), alpha 1-antitrypsin, leukocyte elastase, and naphthol-AS-D-chloroacetate esterase, and with certain monoclonal antisera directed against granulocyte determinants.