Immunohistochemical demonstration of cathepsin B in the macrophages of benign and malignant lymphoid tissues.

Cathepsin B has been demonstrated by immunohistochemical means in the macrophages of palatine tonsils, reactive lymph nodes and in specimens of Hodgkin's disease (HD) and non-Hodgkin's lymphomas (NHL). Two cases of genuine histiocytic lymphoma showed strong staining for the enzyme in most cells. In Hodgkin's disease, many Reed-Sternberg cells and Hodgkin cells were positive. Branching and 'tingible body' macrophages (histiocytic reticulum cells, HRCs) were strongly positive in all of the specimens. In reactive lymph nodes, the sinus-lining cells and intrasinusoidal macrophages were positive for cathepsin B. True dendritic reticulum cells (DRCs) appeared to be negative. Unlike muramidase (lysozyme), cathepsin B is not seen in neutrophil polymorph leucocytes.