Serum adenosine deaminase activity and its isoenzyme pattern in women with normal pregnancies

Adenosine deaminase (ADA) is a purine enzyme which is essential for the proliferation, maturation and function of lymphoid cells, and congenital deficiency of this enzyme is associated with severe combined immunodeficiency disease. The activity of ADA has changed in diseases characterized by the alteration of cell-mediated immunity such as rheumatoid arthritis, systemic lupus erythematosus and tuberculosis, so ADA has been considered as a nonspecific marker of cell-mediated immunity. In this study we examined changes in serum total ADA activity and the patterns of two ADA isoenzymes, ADA1 and ADA2 in normal pregnant women, and evaluated the possible role of the alteration of cell-mediated immunity during normal pregnancy as causes of changes in ADA activity. We measured serum activities of total ADA, ADA1 and ADA2 in normal pregnant women in the third trimester (n=24) and age-matched healthy nonpregnant women (n=24). Peripheral blood lymphocytes and monocytes were also measured. In normal pregnant women, serum total ADA activity averaged 10.5 +/- 0.5 U/L, which was significantly lower than in nonpregnant women (14.0 +/- 0.5 U/L ) (p<0.05), and mean serum ADA2 activity also significantly reduced that of nonpregnant women (p<0.05). There was no significant difference in ADA1 activity in normal pregnant and nonpregnant women. The decrease in total ADA activity was accompanied by the decrease in lymphocyte count. These results suggest that reduced serum total ADA activity reflects decrease in ADA2 activity, and which may be in part associated with depressed cell-mediated immunity during normal pregnancy.