Studies of of the irradiation protection effect of fetal liver in mice. I. Influence of the gestational age of the donor tissue.

I)r 1lemn. Tilese late (leatils usually occur between the 30th and 90th day aild n any investigators believe that immunologic rejection of the host by the grafted reticuloendotilelial cells may be the cause. It has been suggested that fetal hematopoietic donor tissue might I)e less likely to cause tiliS immunologic reaction since tolerance can he induced in fetal animals.2 Thus, reticuloendothehial cells from an immature fetus might