Immunocytological Demonstration of Lysozyme (Muramidase) in Human Leukaemic Cells

Summary. Using the immunofluorescent method the intracytoplasmic lysozyme content of leukaemic cells in the various forms of leukaemia was compared with the biochemically assayed serum and urinary lysozyme levels. This enzyme was demonstrated in mature leukaemic monocytes, in promyelocytes and in myelo‐monocytic cells in concentrations varying according to the particular case under study, in the myelogeneous forms of patients with chronic granulocytic leukaemia, but not in immature leukaemic monocytes, myeloblasts or lymphoblasts. Thus the lysozyme content of a single leukaemic cell depends not only upon the type of cell involved but also upon the degree of cellular maturation as evaluated by morphological and histochemical methods. There was an excellent correlation between the amount of cellular lysozyme demonstrated immunocytologically, and the lysozyme level in serum and urine.