5?-Nucleotidase activity in subjects with abnormal lymphocyte function

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Abstract
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.