Adenosine deaminase levels in construction workers with asbestos contact dermatitis

Adenosine deaminase (ADA) activity was measured in the lymphocytes, red blood cells and plasma of twelve construction workers with cutaneous hypersensitivity reactions to asbestos. Lymphocyte ADA activity was significantly greater in exposed individuals than a control population (p less than 0.0001), whereas erythrocyte and plasma enzyme activity did not differ from control determinations. ADA catalyzes the conversion of adenosine to inosine. Since increased adenosine concentrations in tissue culture inhibit the growth of lymphoblastic cell lines, it has been postulated that decreased ADA activity can result in suppression of the immune response by the inhibition of cell division. Our results indicate that the converse also applies, such that an increase in lymphocyte ADA activity may reflect an increased immune response.