Mixed lymphocyte culture reactions between parental cells in pregnancy and puerperium.

Mixed lymphocyte culture (MLC) reactions of maternal cells with paternal and control cells, inhibition of these reactions with maternal serum, and cytotoxic antibodies in maternal serum were studied in 36 couples through pregnancy and puerperium. Average MLC reactions of maternal cells with paternal and control cells were not significantly different, nor did the MLC responses of maternal cells clearly differ from those of other cells in their time-course kinetics. However, the response of maternal cells to paternal cells was weaker than to control cells in 15 of 18 couples studied during the first week postpartum; this may suggest some specific alteration in maternal immunity to paternal antigens. The sera of pregnant women suppressed MLC reactions. This suppressive effect disappeared during the first week postpartum, whereafter only about 20% of the sera studied caused clear inhibition of MLC reactions. Nine per cent of the postpartum sera studied contained cytotoxic antibodies against paternal cells.