Decreased 5′nucleotidase activity in suppressor (OKT₈) T lymphocytes from homosexuals with AIDS-related complex: Nonassociation with enhanced deoxynucleoside toxicity

The purine metabolic enzymes adenosine deaminase (ADA), purine nucleoside phosphorylase (PNP), and 5′nucleotidase (5NT) have been shown to be important for normal lymphocyte maturation. Abnormalities of these enzymes have been associated with hereditary as well as acquired immunodeficiency states. Enzyme activity was measured in helper (OKT₄) and suppressor (OKT₈) lymphocyte subsets from 10 homosexuals with AIDS-related complex (ARC) and in 10 healthy controls. There were no significant differences in either mean ADA activity or mean PNP activity between ARC OKT₄ cells and control OKT₄ cells and between ARC OKT₈ cells and control OKT₈ cells. By contrast, mean 5NT activity was slightly decreased in OKT₄ cells from ARC patients compared with that of controls and more significantly diminished in ARC OKT₈ cells compared with that of controls. Both deoxyadenosine and deoxyguanosine, when incubated separately with OKT₄ and OKT₈ cells in the presence of EHNA, and ADA inhibitor, did not significantly inhibit lymphocyte blastogenesis to a greater extent in ARC patients than in controls. Hence, the decreases in 5NT activity most likely reflect lymphocyte immaturity and are not associated with biochemical abnormalities leading to increased deoxynucleoside toxicity.