The enzyme, 5'-nucleotidase (5'N) (E.C.-188.8.131.52) is present in lymphocytes isolated from the blood of normal subjects. This activity is markedly decreased or not detectable in the cells from three-quarters of patients with chronic lymphocytic leukemia (CLL), while supranormal levels are found in less than 10% of the cases. To determine whether the decreased 5'N value in CLL represents a lower activity per cell or fewer enzyme-containing cells than in the normal, conditions were established for the histochemical measurement of 5'N in human lymphocytes. It was found that the cells isolated from the blood of normal subjects or patients with CLL consist of 5'N-positive and 5'N-negative subpopulations. Normal subjects who had high 5'N specific activity were shown to have a greater percentage of 5'N-positive cells than individuals with low 5'N activity. Patients with CLL who had no activity by standard chemical assay had no 5'N-positive cells, while the exceptional patient with CLL with a higher than normal specific activity showed an percentage of 5'N-positive cells. It is suggested that the selective proliferation of 5'N-positive and 5'N-negative populations may account for the heterogeneity of 5'N in CLL.
R Silber, M Conklyn, G Grusky, D Zucker-Franklin