Long-term reconstitution of lymphoid progenitors and mature lymphocytes in unconditioned X-SCID mice after fetal transplantation of LMPPs and HSCs. (A-G) Fetal X-SCID mice transplanted with 200 LSK CD34⁺FLT3^hi LMPPs () or 200 LSK CD34⁻FLT3⁻ HSCs () were analyzed for donor-derived lymphoid progenitors and mature lymphocytes in PB, thymus, BM, and spleen 36 weeks after transplantation. (A) Mean (SEM) donor-derived contribution to total nucleated blood cells (top left panel), B cells (B220⁺C19⁺; top right panel), and T cells (CD4⁺ and CD8⁺; bottom panel) from 5 reconstituted mice. (B) FACS profiles of PB analysis from typical fetal X-SCID recipient transplanted with 200 LMPPs (top FACS plots) and 200 HSCs (bottom FACS plots). For each of the 2 populations, top panels show donor-derived CD45.1 (top left) B220⁺CD19⁺ B cells (top right). Bottom left panel shows frequency of TCR β⁺ T cells among total CD45.1⁺ cells, and bottom right panel shows distribution of TCR β⁺ cells into CD4⁺ and CD8⁺ blood cells. Gated numbers represent frequencies of total donor cells. (C) Mean (SEM) donor contribution to total B220 cells (B220⁺), pre B (B220⁺CD43⁻IgM⁻), and immature/mature B cells (B220⁺CD43⁻IgM⁺) in BM (per 2 femurs and 2 tibias) of 5 reconstituted mice. (D) Mean (SEM) donor contribution to DP, SP CD4, and SP CD8 cells in thymus from 5 mice, transplanted 36 weeks earlier. (E) Representative CD4 and CD8 FACS profiles of thymus (gated on CD45.1⁺ donor cells) in mice transplanted with LMPPs (ii) and HSCs (iii) 36 weeks earlier, showing variable reconstitution of CD4⁺CD8⁺ DP thymocytes, and compared with same profiles in WT control (nontransplanted) mouse (i). Percentages for LMPP and HSC transplanted mice are relative to total donor cells. (F,G) TCR V-beta rearrangement of (F) CD4⁺ and (G) CD8⁺ donor (CD45.1⁺) derived cells in spleen. Bar graphs represent mean (± SEM) percentage of cells (of 6 mice analyzed) expressing different V-β subtypes of total donor (F) CD4 and (G) CD8 cells. For all panels, all differences between LMPP and HSC transplanted mice were nonsignificant (P > .05).