Sequential studies of NK cell activity in human pregnancy

We have assessed maternal NK cell function sequentially during and after 14 uncomplicated human pregnancies. As the pattern of response varied in different individuals, a single examination may not provide reliable information. Normally, there was depression of NK cell activity throughout pregnancy, most obvious in the first trimester. In one individual, no depression was seen at any stage. Cryopreservation of peripheral blood leucocytes had no effect on NK activity. In contrast to previous reports, we found no consistent effect of pregnancy serum or plasma on the NK cell activity of control normal lymphocytes.