Only ETPs differentiating from intrathymically administered hematopoietic progenitors retain significant ex vivo myeloid potential. Mice reconstituted with intrathymically injected WT BM progenitors were sacrificed 16 weeks posttransplantation, and ETPs were sorted from the thymi of mice undergoing thymopoiesis. (A) ETPs (5 × 102) from WT and intrathymic-reconstituted (intrathymic-ETPs) mice were cultured in MethoCult media to assess myeloid potential. The total numbers of colonies derived from WT and intrathymic ETPs in a representative experiment are shown. (B) Colony morphologic features were assessed 7 days after culture, and representative photographs of granulocyte/macrophage and granulocyte colony-forming units as well as erythroid burst-forming units are shown. (C) The expression of myeloid, erythroid, and progenitor cell surface markers was assessed on WT- and intrathymic-ETP–derived colony-forming units. Representative plots showing expression of CD11b, Gr-1, c-Kit, CD25, and Ter119 are presented for cells derived from single colonies.
