Long-term persistence of semiallogeneic donor-derived ETPs is detected only after intrathymic transplantation of BM progenitors. (A) Bar graph quantification of the percentages of donor-derived DP cells (CD4+CD8+) detected in the thymi of mice 28 weeks after transplantation of intravenous- or intrathymic-administered semiallogeneic progenitors, in the absence or presence of a preconditioning regimen. Data are presented as mean ± SD (***P < .0001). (B) Representative dot plots showing the percentages of ETPs in the thymi of C57Bl/6 (WT) and ZAP-70^−/− mice. ETPs were assessed by CD44/c-Kit staining on gated donor-derived CD25^-TN thymocytes. The percentages (n = 6) as well as absolute numbers (n = 8) of ETPs were determined, and mean ± SD are presented (P = .003 for percentages and P = .006 for absolute numbers). (C) Representative dot plots showing the percentages of ETPs detected in the thymi of mice transplanted by intravenous or intrathymic administration, in the absence or presence of prior conditioning. Bar graph quantification of the percentages of donor and host ETPs in the thymi of conditioned and nonconditioned recipient mice 28 weeks after intravenous and intrathymic transplantation of semiallogeneic progenitors. Mean ± SD are presented (*P < .05).