Transfer, tissue localization and proliferation of fetal cells in pregnant mice.

Matings between Rb7-Rb7 male mice, possessing the Rb7 chromosomal marker, with CBA, C57/B1, Swiss or F1 BALB/SJL females were carried out to determine whether fetal cells transferred into maternal tissues. Rb7 cells undergoing spontaneous mitosis were sought in maternal blood, bone marrow, thymus, para-aortic lymph nodes, Peyer's patches and liver. Proliferation fetal cells were unequivocally demonstrated in maternal spleen and bone marrow, 12-21 days after mating.