Lymphocyte Lysosomes and Lysosomal Enzymes in Chronic Lymphocytic Leukemia

Electron microscopic cytochemical and biochemical studies of lysosomal markers have been performed in unstimulated normal and chronic lymphotic leukemia (CLL) lymphocytes. Decreased activities of the lysosomal enzymes acid phosphatase and β-glucuronidase but not of the nonlysosomal enzyme malate dehydrogenase were observed in CLL lymphocytes as compared to normal cells. At the electron microscopic level, the number of membrane-bounded acid phosphatase-positive organelles was diminished in CLL cells. (Average 1.07 per cell profile in normal cells and 0.17 in CLL lymphocytes). The findings indicate that the diminution of acid hydrolase activities in CLL lymphocytes is most likely due to a reduced number of lysosomes, rather than to a diminished enzyme content of these organelles.