Sorting-out process in the offspring of female rats injected during pregnancy with allogeneic cells

The foetal consequences of transplacental transmission of maternal cells and allogeneic cells injected into the maternal circulation were studied. Female outbred rats, mated with outbred males, were injected with hyaluronidase (group H) or hyaluronidase and Lewis splenocytes (group SH) in the last period of pregnancy. In the group H 73% of the offspring were highly tolerant to maternal skin grafts, the percentage being much higher than in group SH. Lewis grafts survived significantly longer in group SH than in the control group. There was no difference in the mean survival times of maternal and Lewis grafts in group SH. The only difference was the finding of highly tolerant offspring (24%) to maternal grafts. The analysis of individual results of skin graft survival in group SH showed the existence of individual differences between maternal and Lewis grafts. The tolerance to simultaneously transplanted maternal and Lewis grafts was alternative, but some of the offspring rejected both grafts as if they were sensitized (particularly to maternal tissue antigens). The results show that simultaneous transplacental transmission of two different kinds of allogeneic cells leads to a temporary or a permanent establishment of one cell line only, i.e. that a sorting-out process takes place.