5'-Nucleotidase activity in subjects with abnormal lymphocyte function.

5'-Nucleotidase (5'N) activity was determined in lymphocytes from patients with immunodeficiency diseases and in T-lymphocyte subpopulations from normal subjects. Cells from two patients with DiGeorge syndrome, with normal levels of B cells, and one patient with partial DiGeorge syndrome were found to have diminished 5'N activity. Utilizing monoclonal antibodies to deplete T-lymphocyte subpopulations, we found similar levels of 5'N in the cells remaining after depletion of OKT4- or OKT8-positive cells when 5'N values were determined after overnight incubation. If 5'N activity was determined on the day of the fractionation, however, OKT4-depleted cells had approximately threefold greater enzyme activity. These studies indicate that 5'N activity may vary in T lymphocyte subpopulations depending upon cell culture conditions. Diminished levels of 5'N activity are seen in patients with abnormal T-lymphocyte differentiation, as well as abnormalities of B-lymphocyte differentiation.