Deficient T and B lymphopoiesis from adult bone marrow cells in the absence of IL-7Rα signaling and FL. Lethally irradiated 10- to 12-week-old CD45.1 WT and CD45.1 Fl^−/− mice received a transplant of 5 × 10⁶ BM cells from 10- to 11-week-old CD45.2 WT and Fl^−/−Il7r^−/− mice, respectively. At 3, 7, and 14 weeks after transplantation PB was analyzed for percentage of donor-derived T, B, and myeloid cells using monoclonal antibodies against CD45.1, CD45.2, CD4, CD8, B220, and Mac-1. (A) Representative FACS profiles of donor-derived (CD45.2⁺) lineage reconstitution in PB 14 weeks after transplantation. (B) Contribution of transplanted cells to total blood cells, and lineage distribution within total donor cells, 3, 7, and 14 weeks after transplantation (mean values of 5-7 mice). Double knock-out (2KO; Fl^−/−Il7r^−/−) B and T cells derived from Fl^−/−Il7r^−/− BM cells transplanted into Fl^−/− mice contributed 0.028% and 0.12%, respectively, to total PB cells at 14 weeks after transplantation. (C) At 14 weeks after transplantation, cellularities and total donor-derived T-cell (combined CD4⁺ and CD8⁺) numbers were established in the spleens. White bars show mean steady state T-cell numbers in the spleen of 10-week-old mice of each genotype (prior to irradiation and transplantation, 6-10 mice per genotype), whereas black bars represent mean values in WT and Fl^−/− mice that received a transplant of WT and Fl^−/−Il7r^−/− BM cells, respectively. All data represent mean (SD) values from a total of 5 to 7 recipient mice that underwent transplantation per group. (D,E) Nonirradiated 10- to 14-week-old Il7r^−/−, Fl^−/−, and Fl^−/−Il7r^−/− mice (all CD45.2) received a transplant of 10 × 10⁶ BM cells from 8- to 10-week-old WT CD45.1 mice. Four weeks after transplantation, thymic cellularities were enumerated and total number of donor-derived CD4⁺, CD8⁺, DP, as well as DN thymocytes were established by flow cytometry as previously described.³⁷  (D) Thymuses from typical Il7r^−/−, Fl^−/−Il7r^−/−, and Fl^−/− mice before and 4 weeks after transplantation of WT BM cells. Photographs taken with Olympus i720SW digital camera with 3 × optical zoom. (E) Total number of donor- and host-derived CD4⁺, CD8⁺, DP, and DN thymocytes. Data represent mean (SD) values of 4 recipients of each genotype.