Skin transplantation on nonirradiated NSG-Tg(hu-mSCF) mice that were non-HSC–engrafted or engrafted with human HSCs as newborns. Nonirradiated NSG-Tg(hu-mSCF) mice were non-HSC–engrafted (left panels) or engrafted with human HSCs as newborns (right panels) as described in “Engraftment of mice with human HSCs.” At 12 to 14 weeks of age, all mice were transplanted and monitored for rejection of human skin allografts. Left side indicates the stain used for each row. (A-B) H&E indicates hematoxylin and eosin. (C-D) CD45 indicates all human hematolymphoid cells. (E-F) CD31 indicates human endothelium. (G-H) INV indicates human involucrin. (I-J) VIM indicates human vimentin.