TSLP sustains the differentiation of WT BM progenitors toward the B- and T-cell lineages in vivo. (A) Absolute cell number per 2 femurs 6 weeks after reconstitution of lethally irradiated IL-7^−/−, WT, and IL-7^−/− K14-TSLP Tg recipients with 10⁷ BM cells (CD45.1⁺) is shown. (B) FACS profiles were gated on CD45.1⁺ donor cells. Regions indicate the pro-B/pre-B-I (CD19⁺c-kit⁺), pre-B-II (CD19⁺CD25⁺), mature (CD19⁺B220^highIgM⁺), and immature (CD19⁺B220⁺IgM⁺) B cells. Numbers are mean and standard deviation of percentage (n = 3). (C) Absolute CD45.1⁺ thymocyte number and (D) percentages of donor-derived SP (CD4⁺CD8⁻, CD4⁻CD8⁺), DP (CD4⁺CD8⁺) thymocytes are shown. (E) Absolute CD45.1⁺ splenocyte number. Histograms represent the mean and standard deviation from analyzing 3 animals. (F) Regions indicate splenic CD4⁺, CD8⁺, and γδ⁺ T cells, and CD19⁺ B cells containing follicular (CD23⁺CD21⁺) and MZ (CD21^high CD23⁻) B cells. Numbers are mean and standard deviation of percentage (n = 3). (G) RAG2^−/− γc^−/−, WT, and RAG2^−/− γc^−/− K14-TSLP Tg mice were analyzed at 10 weeks of age. Regions indicate the committed (CD19⁺B220⁺) B cells in the BM. Representative FACS analyses of 1 of 3 mice.