Flt3⁺CD150^– preGMs are T lineage-potent, but inefficient T progenitors. (A) Flt3⁺CD150^– preGMs or MPPs were sorted from WT B6 BM (CD45^B6) and intrathymically transferred at 1000 cells per mouse into sublethally irradiated congenic recipients (CD45^SJL). Recipient thymi were analyzed 3 weeks after transfer for donor chimerism at the DP stage. n = 4. (B) Graphic representations of donor chimerism after intrathymic transfer of MPPs or Flt3⁺CD150^– preGMs. *P = .01. (C) Flt3⁺CD150^– preGM (1000 cells), Flt3^–CD150^– preGMs (10 000 cells), and LMPPs (1000 Flt3^hi LSK cells) were sorted from WT B6 BM (CD45^B6) and intravenously transferred into sublethally irradiated congenic recipients (CD45^SJL). BM of recipient mice was analyzed on day 18 after transfer for donor chimerism in the B cell lineage (CD19⁺B220⁺). n = 4-5. (D) Donor chimerism in the B cell lineage after intravenous transfer of LMPPs, Flt3⁺CD150^– preGMs, and Flt3^–CD150^– preGMs. N.D. indicates not detected. (E) Thymi of the same recipient mice that received intratransfer of LMPPs, Flt3⁺CD150^– preGMs, and Flt3^–CD150^– preGMs were analyzed for donor chimerism at the DP stage on day 18 after transfer. (F) Donor chimerism at the DP stage after intravenous transfer of LMPPs, Flt3⁺CD150^– preGMs, and Flt3^–CD150^– preGMs. N.D. indicates not detected. *P = 2 × 10^–6 and **P = .01. P values were determined by Student t test. Error bars denote SEM. Results shown are from 2 independent experiments.