Spontaneous human lymphocyte-mediated cytotoxicity against tumor target cells. IV. The suppressive effect of normal pregnancy.

The effects of pregnancy and other donor characteristics on spontaneous lymphocyte-mediated cytotoxicity (SLMC) were studied. Sex, age, and stage of the menstrual cycle had no significant effect on the SLMC of the control donors, the SLMC was significantly lower in pregnant donors in the second or third trimester. However, this lowered level of activity was still within the 95 per cent confidience limits of the normal population and parity had no cumulative effect. At delivery, fetal cord blood lymphocytes possessed substantial cytotoxic activity, further evidence that the fetus is immunologically competent at birth. The relevance of these data to the immunologic coexistence of the mother and fetus is discussed.