Abstract
The supernatant of phytohemagglutinin (PHA)-stimulated lymphocyte culture derived from pregnant women in the first two trimesters inhibited DNA synthesis of normal human lymphocytes after PHA induction. This soluble factor was heat-labile and the same factor could not be found in the supernatant generated from lymphocytes of pregnant women in 3rd trimester as well as from those of the non-pregnant. In contrast, the heatstable factor in the supernatant generated from lymphocytes of non-pregnant and pregnant women in all trimesters contained an stimulating factor on the DNA synthesis of normal human lymphocytes after PHA induction. An endogenous alternation in lymphocyte competence or an alternation in subpopulation of lymphocytes was suggested at the early stage of pregnancy.
