Critical role of FLT3L but not TSLP in IL-7–independent B lymphopoiesis. (A) FACS profiles and mean (SD) numbers of pre-pro-B, pro-B, pre-B, and imm-B cells in BM of 10- to 11-week-old WT (n = 4), Flt3l^−/−Il7r^−/− (n = 7-8), and Flt3l^−/−Il7^−/−(n = 11) mice. (B) FACS profiles and mean (SD) numbers of B220IgM⁺ cells in spleens of 10- to 11-week-old WT (n = 4), Flt3l^−/−Il7r^−/− (n = 6), and Flt3l^−/−Il7^−/−(n = 9) mice. (C) Mean (SD) numbers of pre-pro-B, pro-B, pre-B, and imm-B cells in BM and (D) B220IgM⁺ cells in spleen of littermate Flt3l^−/−(n = 6, 3 litters) and Flt3l^−/−Tpte2^−/−(n = 6, 3 litters) mice. Numbers in FACS profiles show the mean percentages of cells in quadrants or gates as indicated of total BM and spleen cells (**P < .01, ***P < .001).