Engraftment levels following IUHCT of congenic and allogeneic BM. E14 fetal mice were given injections of either congenic or allogeneic whole BM. The PB of recipients was assessed at 1, 2, 4, and 6 months of life for total donor chimerism (A) #P < .1, *P < .05. The PB of fetal recipients of both congenic and allogeneic BM transplants was assessed for multilineage engraftment at 4 months of age (B). GFP control mice refer to age-matched naive GFP mice and chimerism levels are expressed as the percentage of GFP⁺ cells that express the indicated lineage marker. Error bars represent the mean ± SEM.