Reduced stimulating effect on one-way mixed lymphocyte culture by parturient's and neonatal cord blood cells.

One-way mixed lymphocyte culture (MLC), using the peripheral blood T, B cells and monocytes of 16 unmarried women who were never pregnant (i.e. nulligravidas) and 18 parturients, and the umbilical venous blood T, B cells and monocytes of 18 newborns as stimulating cells, were used to react with the peripheral mononuclear cells of a type "O" blood of a 29-year-old healthy man. We demonstrated that the stimulating effects were much lower in the parturients and the newborns than in the unmarried nulligravidas. The stimulating indices were significantly different, especially in the B cells. Mean stimulation index was 4.843 in unmarried nulligravidas, 1.249 in parturients and 1.284 in newborns. Our results seem to suggest that pregnancy produces some alternations on both the maternal and the fetal cells, making the maternal and the fetal immune systems fail to recognize each other.