Transmission of maternal blood cells to the fetus during pregnancy: detection in mouse neonatal spleen by immunofluorescence flow cytometry and polymerase chain reaction.

Mouse embryos were transferred to allogeneic pseudopregnant foster mothers and the cells of the resultant neonates were analyzed for the expression of maternal major histocompatibility complex (MHC) antigens to elucidate maternal cell transmission to the fetus during pregnancy. Expression of maternal-type MHC antigens was detected in the spleen but not in the liver or thymus of the neonates in analyses by immunofluorescence flow cytometry and polymerase chain reaction. These findings provide evidence, on the molecular basis, that maternal blood cells are transmitted to the fetus through the placenta.