Role of the newborn's sex in mixed maternal-newborn lymphocyte culture reactivity.

One-way-stimulated mixed mother-newborn lymphocyte cultures (MMNLC) from male and female newborns were evaluated and compared shortly after delivery. Newborn sex-correlated differences were observed in the strength of the MMNLC reactivity with responding maternal as well as newborn cells. The reactivity of MMNLC with responding maternal cells from male as compared to female newborns was significantly less inhibited in maternal and newborn serum. The inhibitory effect of maternal serum on maternal and male newborn lymphocytes in MMNLC seems to be correlated to the sex of the previous child delivered and was significantly lower when the present as well as the previous baby were of the same sex, e.g. 2 boys. The results suggest that fetal-male-specific Y-chromosome-correlated histocompatibility antigens may specifically influence the maternal immune response to her fetus.