Changes in lymphocyte function during pregnancy.

A gradual increase in spontaneous lymphocyte DNA synthesis was demonstrated in each trimester of pregnancy. Autoradiographic studies indicated that lymphocytes were primarily responsible for this activity. PHA-induced lymphocyte transformation in both fetal calf serum and autologous serum was significantly reduced in the second and third trimesters of pregnancy. Spontaneous lymphocyte DNA synthesis was significantly reduced in patients with mild pre-eclampsia. However, no significant differences were seen in patients with severe pre-eclampsia in the third trimester of pregnancy compared with the normal control subjects. No evidence was adduced to implicate inhibitory humoral factors affecting the peripheral blood lymphocytes in pregnany patients in experiments in which washed lymphocytes were cultured in medium containing heterologous serum. In vitro experiments demonstrated that cortisol, progesterone and HPL caused a significant reduction in lymphocyte DNA synthesis, and HGH and HCG had a variable effect. However, only cortisol was regularly inhibitory at physiological concentrations. The progesterone effect was dose-related, producing 90 per cent inhibition of activity at a concentration of 10 mug/ml. No synergism could be shown between HPL and progesterone on lymphocyte transformation. The increase in activity of circulating immunoreactive cells during pregnancy and its depression with the onset of pre-eclampsia is discussed.