Age-dependency of lymphocyte ecto-5'-nucleotidase activity.

The activity of lymphocyte ecto-5'-nucleotidase (ecto-5'-NT) decreases with advancing age, T lymphocyte ecto-5'-NT activity begins to fall after the age of 40 and subjects in the 41 to 50, 51 to 60, 61 to 75, and 75 to 85 age ranges of life have 57, 52, 38, and 19%, respectively, of the T lymphocyte ecto-5'-NT activity of subjects under the age of 40. TG cells (suppressor cells) have 39% of the ecto-5'-NT activity of Tnon-G cells (helper cells) but the increase in numbers of TG cells that occurs with age explains only about 14% of the age-related fall in T lymphocyte ecto-5'-NT activity. B lymphocyte ecto-5'-NT activity remains stable until age 60 and subjects over 60 years of age have 42% of the B lymphocyte ecto-5'-NT activity of subjects under age 60.