Abstract
The specific activity of 5'-nucleotidase was determined in lymphocyte plasma membranes from 14 normal subjects and 10 patients with chronic lymphocytic leukemia (CLL). Whereas the enzyme was present in the preparation from normal lymphocytes, in 7 out of 10 CLL patients the membranes had markedly decreased or no detectable 5'-nucleotidase activity. The lack of this activity from the lymphocytes of most patients with CLL constitutes an alteration in a plasma membrane enzyme from the normal cell. The presence of the enzyme in the lymphocytes of some patients with CLL and its decrease in others provide further evidence for biochemical heterogeneity among patients with this disorder.