OBJECTIVE: To evaluate the relationship between plasma adenosine deaminase activity and the proportion of cytokine‐secreting T cells as causes of changes in adenosine deaminase activity in normal pregnancy.
METHODS: Plasma adenosine deaminase activity and the proportions of cytokine‐secreting T cells were measured in the peripheral blood of 26 nonpregnant and normal pregnant women in the third trimester. The proportion of CD4‐positive T cells secreting interferon‐γ derived from T helper 1 cells, and interleukin‐4 derived from T helper 2 cells, were analyzed by flow cytometry. The ratio of interferon‐γ–secreting cells to interleukin‐4–secreting cells was taken as the T helper 1/T helper 2 ratio.
RESULTS: Mean plasma adenosine deaminase activity in normal pregnant women, averaged, was significantly lower than that in nonpregnant women (10.3 ± 0.6 U/L versus 13.8 ± 0.5 U/L, P < .05). In normal pregnant women, the proportion of interferon‐γ–secreting cells was significantly lower than that in nonpregnant women (20.5% ± 1.0% versus 24.7% ± 1.2%, P < .05), but the proportion of interleukin‐4–secreting cells did not differ from that of nonpregnant women. Consequently, the T helper 1/T helper 2 ratios were significantly decreased during normal pregnancy. A significant correlation was found between adenosine deaminase activity and the proportion of interferon‐γ–secreting cells (r = .54, P < .05).
CONCLUSION: Decreased plasma adenosine deaminase activity in normal pregnant women may be in part associated with changes in the immunological status, especially the decrease of the proportion of interferon‐γ–secreting cells.