Adenosine deaminase and purine nucleoside phosphorylase activities in lymphocytes from patients with lung cancer.

The activity of adenosine deaminase (EC 3.5.4.4.) was significantly lower in lymphocytes from patients with lung cancer than in those from healthy subjects, whereas the activity of purine nucleoside phosphorylase (EC 2.4.2.1.) was significantly higher in lymphocytes from the patients than in those from normal controls. When the one activity was plotted against the other, the plots for patients with lung cancer were all outside the frame formed by the lower and higher limits of the standard deviation of the mean of normal activities of the two enzymes. The ratio of adenosine deaminase activity to purine nucleoside phosphorylase activity was lower in patients with lung cancer than in controls. The possible effect of this ratio on the function of lymphocytes was briefly discussed. These enzyme activities were suggested to be useful measures of the immune responsiveness of patients with lung cancer.